Two-dimensional FSI simulation of closing dynamics of a tilting disc mechanical heart valve.

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Govindarajan, V; Udaykumar, H S; Herbertson, L H; Deutsch, S; Manning, K B; Chandran, K B

2010-03-01

The fluid dynamics during valve closure resulting in high shear flows and large residence times of particles has been implicated in platelet activation and thrombus formation in mechanical heart valves. Our previous studies with bi-leaflet valves have shown that large shear stresses induced in the gap between the leaflet edge and the valve housing results in relatively high platelet activation levels whereas flow between the leaflets results in shed vortices not conducive to platelet damage. In this study we compare the result of closing dynamics of a tilting disc valve with that of a bi-leaflet valve. The two-dimensional fluid-structure interaction analysis of a tilting disc valve closure mechanics is performed with a fixed grid Cartesian mesh flow solver with local mesh refinement, and a Lagrangian particle dynamic analysis for computation of potential for platelet activation. Throughout the simulation the flow remains in the laminar regime and the flow through the gap width is marked by the development of a shear layer which separates from the leaflet downstream of the valve. Zones of re-circulation are observed in the gap between the leaflet edge and the valve housing on the major orifice region of the tilting disc valve and are seen to be migrating towards the minor orifice region. Jet flow is observed at the minor orifice region and a vortex is formed which sheds in the direction of fluid motion as observed in experiments using PIV measurements. The activation parameter computed for the tilting disc valve, at the time of closure was found to be 2.7 times greater than that of the bi-leaflet mechanical valve and was found to be in the vicinity of the minor orifice region mainly due to the migration of vortical structures from the major to the minor orifice region during the leaflet rebound of the closing phase.

Low radiation dose non-contrast cardiac CT: is it of value in the evaluation of mechanical aortic valve

International Nuclear Information System (INIS)

Bazeed, Mohamed Fayez; Moselhy, Mohamed Saleh; Rezk, Ahmad Ibrahim; Al-Murayeh, Mushabab Ayedh

2012-01-01

Background: Prosthetic bileaflet mechanical valve function has been traditionally evaluated using echocardiography and fluoroscopy. Multidetector computed tomography (MDCT) is a novel technique for cardiac evaluation. Purpose: To evaluate bileaflet mechanical aortic valves using a low-milliampere (mA), non-contrast MDCT protocol with a limited scan range. Material and Methods: Forty patients with a bileaflet mechanical aortic valve were evaluated using a non-contrast, low-mA, ECG-gated 64 MDCT protocol with a limited scan range. MDCT findings of opening and closing valve angles were correlated to fluoroscopy and echocardiography. Also, the valve visibility was evaluated on MDCT and fluoroscopy according to a 3-point grading scale. Results: The visualization score with the MDCT was significantly superior to the fluoroscopy (3 vs. 2.7). A strong correlation was noted between the opening (r = 0.82) and closing (r = 0.96) valve angles with MDCT and fluoroscopy without a statistically significant difference (P = 0.31 and 0.16, respectively). The mean effective radiation dose of the suggested protocol was 4 ± 0.5 mSv. Five valves were evaluated using transesophageal echocardiography because the valves were difficult to evaluate with transthoracic echocardiography, and all of these valves were evaluated optimally with MDCT. A high-pressure gradient was noted in nine valves, and the MDCT showed that seven of these valves inadequately opened, and two valves opened well, which resulted in patient valve mismatch. Incomplete valve closure was noted in five valves, and the echocardiography showed significant transvalvular regurgitation in all five valves. Conclusion: MDCT can provide a precise measurement of valve function and can potentially evaluate high-pressure gradients and transvalvular regurgitation

Low radiation dose non-contrast cardiac CT: is it of value in the evaluation of mechanical aortic valve

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Bazeed, Mohamed Fayez (Dept. of Diagnostic Radiology, Faculty of Medicine, Mansoura Univ. (Egypt)), email: m_bazeed@yahoo.com; Moselhy, Mohamed Saleh (Cardiology Dept. Faculty of Medicine, Suez Canal Univ. (Egypt)); Rezk, Ahmad Ibrahim (Dept. of Cardiac Surgery, Faculty of Medicine, Aim Shams Univ. (Egypt)); Al-Murayeh, Mushabab Ayedh (Dept. of Cardiac Services, Armed Forces Hospitals Southern Region (Saudi Arabia))

2012-05-15

Background: Prosthetic bileaflet mechanical valve function has been traditionally evaluated using echocardiography and fluoroscopy. Multidetector computed tomography (MDCT) is a novel technique for cardiac evaluation. Purpose: To evaluate bileaflet mechanical aortic valves using a low-milliampere (mA), non-contrast MDCT protocol with a limited scan range. Material and Methods: Forty patients with a bileaflet mechanical aortic valve were evaluated using a non-contrast, low-mA, ECG-gated 64 MDCT protocol with a limited scan range. MDCT findings of opening and closing valve angles were correlated to fluoroscopy and echocardiography. Also, the valve visibility was evaluated on MDCT and fluoroscopy according to a 3-point grading scale. Results: The visualization score with the MDCT was significantly superior to the fluoroscopy (3 vs. 2.7). A strong correlation was noted between the opening (r = 0.82) and closing (r = 0.96) valve angles with MDCT and fluoroscopy without a statistically significant difference (P = 0.31 and 0.16, respectively). The mean effective radiation dose of the suggested protocol was 4 +- 0.5 mSv. Five valves were evaluated using transesophageal echocardiography because the valves were difficult to evaluate with transthoracic echocardiography, and all of these valves were evaluated optimally with MDCT. A high-pressure gradient was noted in nine valves, and the MDCT showed that seven of these valves inadequately opened, and two valves opened well, which resulted in patient valve mismatch. Incomplete valve closure was noted in five valves, and the echocardiography showed significant transvalvular regurgitation in all five valves. Conclusion: MDCT can provide a precise measurement of valve function and can potentially evaluate high-pressure gradients and transvalvular regurgitation

Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves

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Ovandir Bazan

2013-12-01

Full Text Available INTRODUCTION: In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench. OBJECTIVE: To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models exposed to a steady flow regime, on four distinct sections, three downstream and one upstream. METHODS: To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements. RESULTS: It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found. CONCLUSIONS: Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM is superior to the 21 AJ - 501 model (Master Series. Based on the results, future studies can choose to focus on specific regions of the these valves.

Anatomic characteristics of bileaflet mitral valve prolapse--Barlow disease--in patients undergoing mitral valve repair.

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Rostagno, Carlo; Droandi, Ginevra; Rossi, Alessandra; Bevilacqua, Sergio; Romagnoli, Stefano; Montesi, Gian Franco; Stefàno, Pier Luigi

2014-01-01

Barlow disease is a still challenging pathology for the surgeon. Aim of the present study is to report anatomic abnormalities of mitral valve in patients undergoing mitral valve repair. Between January 1st, 2007, and December 31st, 2010, 85 consecutive patients (54 men and 31 women, mean age 59 +/- 14 years--range: 28-85 years) with the features of a Barlow mitral valve disease underwent mitral repair Forty seven percent of patients were in New York Heart Association functional class III or IV. Preoperative transesophageal echocardiography was compared with anatomical findings at the moment of surgery. Transthoracic echocardiography diagnosis of Barlow disease according to the criteria described by Carpentier was confirmed at anatomical inspection. Annular calcifications were found in 28 patients while 7 patients presented single or multiple clefts. A flail posterior mitral leaflet was detected in 32 subjects, while a flail anterior leaflet in 8. Elongation of chordae tendineae was demonstrated in 45 patients and chordal rupture in 31. All patients showed at trans esophageal echocardiography the typical features of Barlow disease. Seventy-seven (90.6%) patients had severe mitral valve regurgitation, in the remaining 9.4% it was moderate to severe. Transesophageal echocardiography failed to identify clefts in 2/7 and chordal rupture in 4/31. bileaflet prolapse > 2 mm, billowing valve with excess tissue and thickened leaflets > or = 3 mm, and severe annular dilatation, are characteristics of Barlow disease, however the identification of the associated and complex abnormalities of mitral valve is necessary to obtain optimal valve repair.

19 mm sized bileaflet valve prostheses' flow field investigated by bidimensional laser Doppler anemometry (part II: maximum turbulent shear stresses)

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Barbaro, V; Grigioni, M; Daniele, C; D'Avenio, G; Boccanera, G

1997-11-01

The investigation of the flow field generated by cardiac valve prostheses is a necessary task to gain knowledge on the possible relationship between turbulence-derived stresses and the hemolytic and thrombogenic complications in patients after valve replacement. The study of turbulence flows downstream of cardiac prostheses, in literature, especially concerns large-sized prostheses with a variable flow regime from very low up to 6 L/min. The Food and Drug Administration draft guidance requires the study of the minimum prosthetic size at a high cardiac output to reach the maximum Reynolds number conditions. Within the framework of a national research project regarding the characterization of cardiovascular endoprostheses, an in-depth study of turbulence generated downstream of bileaflet cardiac valves is currently under way at the Laboratory of Biomedical Engineering of the Istituto Superiore di Sanita. Four models of 19 mm bileaflet valve prostheses were used: St Jude Medical HP, Edwards Tekna, Sorin Bicarbon, and CarboMedics. The prostheses were selected for the nominal Tissue Annulus Diameter as reported by manufacturers without any assessment of valve sizing method, and were mounted in aortic position. The aortic geometry was scaled for 19 mm prostheses using angiographic data. The turbulence-derived shear stresses were investigated very close to the valve (0.35 D0), using a bidimensional Laser Doppler anemometry system and applying the Principal Stress Analysis. Results concern typical turbulence quantities during a 50 ms window at peak flow in the systolic phase. Conclusions are drawn regarding the turbulence associated to valve design features, as well as the possible damage to blood constituents.

Acute Mitral Valve Dysfunction Due to Escape of Prosthetic Mechanical Leaflet and Peripheral Leaftlet Embolization.

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Calik, Eyup Serhat; Limandal, Husnu Kamil; Arslan, Umit; Tort, Mehmet; Yildiz, Ziya; Bayram, Ednan; Dag, Ozgur; Kaygin, Mehmet Ali; Erkut, Bilgehan

2015-12-14

Leaflet escape of prosthetic valve is rare but potentially life threatening. Early diagnosis is essential on account of avoiding mortality, and emergency surgical correction is compulsory. This complication has previously been reported for both monoleaflet and bileaflet valve models. A 30-year-old man who had undergone mitral valve replacement with a bileaflet valve 8 years prior at another center was admitted with acute-onset with cardiogenic shock as an emergency case. Transthoracic echocardiograms showed acute-starting severe mitral regurgitation associated with prosthetic mitral valve. There was a suspicious finding of a single prosthetic mitral leaflet. But the problem related with the valve wasn't specifically determined. The patient underwent emergent surgery for replacement of the damaged prosthetic valves immediately. There was no tissue impingement and thrombosis, one of the two leaflets was absent, and there were no signs of endocarditis or pannus formation in the prosthetic valve. The missing leaflet could not be found within the cardiac cavity. The abdominal fluoroscopic study and plain radiography were unable to detect the escaped leaflet during surgery. The damaged valve was removed and a replacement 29 mm bileaflet mechanical valve was inserted by right lateral thoracotomy. After post-operative week one, the abdominal computed tomography scan and the ultrasound showed the escaped leaflet in the left femoral artery. Fifteen days after the surgery the escaped leaflet was removed safely from the left femoral artery and the patient made a complete recovery. The escaped leaflet showed a fracture of one of the pivot systems caused by structural failure. Early cardiac surgery should be applied because of life-threatening problems.

Mid- to long-term outcome comparison of the Medtronic Hancock II and bi-leaflet mechanical aortic valve replacement in patients younger than 60 years of age: a propensity-matched analysis.

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Wang, Yin; Chen, Si; Shi, Jiawei; Li, Geng; Dong, Nianguo

2016-03-01

This study aims to compare mid-long-term clinical outcomes between patients younger than 60 years of age undergoing bioprosthetic and mechanical aortic valve replacement. From January 2002 to December 2009, patients younger than 60 years of age who received Medtronic Hancock II porcine bioprostheses were selected and compared with those who received mechanical bi-leaflet valves in the aortic position. A stepwise logistic regression propensity score identified a subset of 112 evenly matched patient-pairs. Mid-long-term outcomes of survival, valve-related reoperations, thromboembolic events and bleeding events were assessed. The follow-up was only 95.1% complete. Fourteen measurable variables were statistically similar for the matched cohort. Postoperative in-hospital mortality was 3.6% (bioprosthetic valves) and 2.7% (mechanical valves) (P = 0.700). Survival at 5 and 10 years was 96.3 and 88.7% for patients receiving bioprosthetic valve replacement versus 96.3 and 87.9% for patients receiving mechanical valve replacement (P = 0.860), respectively. At 5 and 10 years after operations, freedom from valve-related reoperation was 97.2 and 94.8% for patients receiving mechanical valve replacement, and 96.3 and 90.2% for patients receiving bioprosthetic valve replacement (P = 0.296), respectively. There was no difference between freedom from thromboembolic events (P = 0.528) and bleeding events (P = 0.128) between the matched groups during the postoperative 10 years. In patients younger than 60 years of age undergoing aortic valve replacement, mid-long-term survival rate was similar for patients receiving bioprosthetic versus mechanical valve replacement. Bioprosthetic valves were associated with a trend for a lower risk of anticoagulation treatment and did not have significantly greater likelihood of a reoperation. These findings suggest that a bioprosthetic valve may be a reasonable choice for AVR in patients younger than 60 years of age. © The Author 2015. Published by

Monodimensional estimation of maximum Reynolds shear stress in the downstream flow field of bileaflet valves.

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Grigioni, Mauro; Daniele, Carla; D'Avenio, Giuseppe; Barbaro, Vincenzo

2002-05-01

Turbulent flow generated by prosthetic devices at the bloodstream level may cause mechanical stress on blood particles. Measurement of the Reynolds stress tensor and/or some of its components is a mandatory step to evaluate the mechanical load on blood components exerted by fluid stresses, as well as possible consequent blood damage (hemolysis or platelet activation). Because of the three-dimensional nature of turbulence, in general, a three-component anemometer should be used to measure all components of the Reynolds stress tensor, but this is difficult, especially in vivo. The present study aimed to derive the maximum Reynolds shear stress (RSS) in three commercially available prosthetic heart valves (PHVs) of wide diffusion, starting with monodimensional data provided in vivo by echo Doppler. Accurate measurement of PHV flow field was made using laser Doppler anemometry; this provided the principal turbulence quantities (mean velocity, root-mean-square value of velocity fluctuations, average value of cross-product of velocity fluctuations in orthogonal directions) needed to quantify the maximum turbulence-related shear stress. The recorded data enabled determination of the relationship, the Reynolds stresses ratio (RSR) between maximum RSS and Reynolds normal stress in the main flow direction. The RSR was found to be dependent upon the local structure of the flow field. The reported RSR profiles, which permit a simple calculation of maximum RSS, may prove valuable during the post-implantation phase, when an assessment of valve function is made echocardiographically. Hence, the risk of damage to blood constituents associated with bileaflet valve implantation may be accurately quantified in vivo.

A D-Shaped Bileaflet Bioprosthesis which Replicates Physiological Left Ventricular Flow Patterns.

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Sean Guo-Dong Tan

Full Text Available Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation.

A D-Shaped Bileaflet Bioprosthesis which Replicates Physiological Left Ventricular Flow Patterns

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Tan, Sean Guo-Dong; Kim, Sangho; Hon, Jimmy Kim Fatt; Leo, Hwa Liang

2016-01-01

Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve) has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation. PMID:27258099

Experimental study on the effect of an artificial cardiac valve on the left ventricular flow

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Wang, JiangSheng; Gao, Qi; Wei, RunJie; Wang, JinJun

2017-09-01

The use of artificial valves to replace diseased human heart valves is currently the main solution to address the malfunctioning of these valves. However, the effect of artificial valves on the ventricular flow still needs to be understood in flow physics. The left ventricular flow downstream of a St. Jude Medical (SJM) bileaflet mechanical heart valve (BMHV), which is a widely implanted mechanical bileaflet valve, is investigated with time-resolved particle image velocimetry in the current work. A tilting-disk valve is installed on the aortic orifice to guarantee unidirectional flow. Several post-processing tools are applied to provide combined analyses of the physics involved in the ventricular flow. The triple jet pattern that is closely related to the characteristics of the bileaflet valve is discussed in detail from both Eulerian and Lagrangian views. The effects of large-scale vortices on the transportation of blood are revealed by the combined analysis of the tracking of Lagrangian coherent structures, the Eulerian monitoring of the shear stresses, and virtual dye visualization. It is found that the utilization of the SJM BMHV complicates the ventricular flow and could reduce the efficiency of blood transportation. In addition, the kinematics of the bileaflets is presented to explore the effects of flow structures on their motion. These combined analyses could elucidate the properties of SJM BMHV. Furthermore, they could provide new insights into the understanding of other complex blood flows.

Time-resolved PIV technique for high temporal resolution measurement of mechanical prosthetic aortic valve fluid dynamics.

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Kaminsky, R; Morbiducci, U; Rossi, M; Scalise, L; Verdonck, P; Grigioni, M

2007-02-01

Prosthetic heart valves (PHVs) have been used to replace diseased native valves for more than five decades. Among these, mechanical PHVs are the most frequently implanted. Unfortunately, these devices still do not achieve ideal behavior and lead to many complications, many of which are related to fluid mechanics. The fluid dynamics of mechanical PHVs are particularly complex and the fine-scale characteristics of such flows call for very accurate experimental techniques. Adequate temporal resolution can be reached by applying time-resolved PIV, a high-resolution dynamic technique which is able to capture detailed chronological changes in the velocity field. The aim of this experimental study is to investigate the evolution of the flow field in a detailed time domain of a commercial bileaflet PHV in a mock-loop mimicking unsteady conditions, by means of time-resolved 2D Particle Image Velocimetry (PIV). The investigated flow field corresponded to the region immediately downstream of the valve plane. Spatial resolution as in "standard" PIV analysis of prosthetic valve fluid dynamics was used. The combination of a Nd:YLF high-repetition-rate double-cavity laser with a high frame rate CMOS camera allowed a detailed, highly temporally resolved acquisition (up to 10000 fps depending on the resolution) of the flow downstream of the PHV. Features that were observed include the non-homogeneity and unsteadiness of the phenomenon and the presence of large-scale vortices within the field, especially in the wake of the valve leaflets. Furthermore, we observed that highly temporally cycle-resolved analysis allowed the different behaviors exhibited by the bileaflet valve at closure to be captured in different acquired cardiac cycles. By accurately capturing hemodynamically relevant time scales of motion, time-resolved PIV characterization can realistically be expected to help designers in improving PHV performance and in furnishing comprehensive validation with experimental data

[History, present and future of biomaterials used for artificial heart valves].

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Kostrzewa, Benita; Rybak, Zbigniew

2013-01-01

Artificial heart valves can be classified into mechanical and biological. We have three types of mechanical heart valves: caged ball, tilting disc and bileaflet. Mechanical heart valves are made from various materials. They may be produced from metals, ceramics and polymers, e.g.: stainless steel, titanium, silicone, pyrolytic carbon. Biological valves are made from synthetic components (e.g.: PTFE, Dacron) and materials of biological origin (e.g.: cow pericardium, pig heart valve). We have also identified transcatheter aortic valve implantation (TAVI). TAVI may be produced from metals, ceramics and polymers (e.g.: stainless steel, titanium, Dacron) and biological material (e.g.: pig heart valve). This paper describes advantages and disadvantages of different types of artificial heart valves. The lifespan of mechanical valves is 20-30 years and they can be used for patients of any age. Mechanical valves have also disadvantages--anticoagulants are required to prevent thrombosis. Biological valves are made from natural materials, so they do not require prolonged anticoagulation. Their lifetime is 10-15 years, so they are offered to patients over 40 years. Another problem is the occurrence of calcification.

Rapid pannus formation after few months of obstructing aortic mechanical prosthesis.

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Al-Alao, Bassel; Simoniuk, Urszula; Heron, Brian; Parissis, Haralabos

2015-11-01

We report a rare case of a prosthetic aortic valve obstruction due to pannus formation only 3 months following aortic and mitral valve replacement. Fragments of asymmetrical pannus formation affected one of the leaflets of the bi-leaflet mechanical valve; the leaflet appeared immobile due to pannus ingrowth into the mechanical skeleton resulting in encroachment of the leaflet, which in turn became immobile. The patient successfully underwent emergency redo-aortic valve replacement.

Leaflet embolisation from Duromedics valves: a report of two cases.

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Kumar, N; Balasundaram, S; Rickard, M; al Halees, Z; Duran, C M

1991-12-01

Embolization of parts of mechanical valves has been reported since the inception of prosthetic valve implantation. We report here two cases of embolization of one hemileaflet of a Duromedic bileaflet prosthesis in the mitral position due to a pivot fracture. Both presented with moderately severe mitral regurgitation and pulmonary edema and were successfully managed by replacement of the malfunctioning prostheses. The embolised disc was located in the left common iliac artery by abdominal ultrasound and removed by an inguinal, retroperitoneal approach with low morbidity. Both patients left hospital and are doing well to-date.

Time-Resolved Micro PIV in the Pivoting Area of the Triflo Mechanical Heart Valve.

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Vennemann, Bernhard M; Rösgen, Thomas; Carrel, Thierry P; Obrist, Dominik

2016-09-01

The Lapeyre-Triflo FURTIVA valve aims at combining the favorable hemodynamics of bioprosthetic heart valves with the durability of mechanical heart valves (MHVs). The pivoting region of MHVs is hemodynamically of special interest as it may be a region of high shear stresses, combined with areas of flow stagnation. Here, platelets can be activated and may form a thrombus which in the most severe case can compromise leaflet mobility. In this study we set up an experiment to replicate the pulsatile flow in the aortic root and to study the flow in the pivoting region under physiological hemodynamic conditions (CO = 4.5 L/min / CO = 3.0 L/min, f = 60 BPM). It was found that the flow velocity in the pivoting region could reach values close to that of the bulk flow during systole. At the onset of diastole the three valve leaflets closed in a very synchronous manner within an average closing time of 55 ms which is much slower than what has been measured for traditional bileaflet MHVs. Hot spots for elevated viscous shear stresses were found at the flanges of the housing and the tips of the leaflet ears. Systolic VSS was maximal during mid-systole and reached levels of up to 40 Pa.

Rare early prosthesis obstruction after mitral valve replacement: a case report and literature review

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Shi Jun

2012-07-01

Full Text Available Abstract As a dreadful complication after the mechanical heart valve replacement, prosthetic valve obstruction caused by pannus formation occurs increasingly with time. The authors here present a case of 42-year-old woman who was urgently admitted to hospital with acute heart failure symptoms due to the mechanical mitral valve failure only 3 months after surgery. Transthoracic and transesophageal echocardiography demonstrated that the bileaflet of the mitral prosthesis were completely immobilized with only a small transvalvular jet remained. During the reoperation, the reason of the prosthetic valve obstruction was attributed to the noncircular pannus ingrowth extending from the atrioventricular side. For a better understanding of the prosthetic valve dysfunction caused by pannus formation, the authors then compile a literature review to briefly discuss the status quo of the clinical characteristics of this uncommon complication.

3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV.

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D'Avenio, Giuseppe; Grigioni, Mauro; Daniele, Carla; Morbiducci, Umberto; Hamilton, Kathrin

2015-01-01

Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs. The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis. A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry. The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

Curved butterfly bileaflet prosthetic cardiac valve

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McQueen, David M.; Peskin, Charles S.

1991-06-25

An annular valve body having a central passageway for the flow of blood therethrough with two curved leaflets each of which is pivotally supported on an accentric positioned axis in the central passageway for moving between a closed position and an open position. The leaflets are curved in a plane normal to the eccentric axis and positioned with the convex side of the leaflets facing each other when the leaflets are in the open position. Various parameters such as the curvature of the leaflets, the location of the eccentric axis, and the maximum opening angle of the leaflets are optimized according to the following performance criteria: maximize the minimum peak velocity through the valve, maximize the net stroke volume, and minimize the mean forward pressure difference, thereby reducing thrombosis and improving the hemodynamic performance.

Comparison of platelet activation through hinge vs bulk flow in mechanical heart valves

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Hedayat, Mohammadali; Borazjani, Iman

2017-11-01

Bileaflet mechanical heart valves increase the risk of thrombus formation in patients which is believed to be initiated by platelet activation. Platelets can be activated by the elevated shear stresses in the bulk flow during the systole phase or the flow through the hinge during the diastole. However, the importance of platelet activation by the bulk flow vs the hinge in MHVs has yet to be studied. Here, we investigate the contribution of each of the above mechanisms to the activation of platelets in MHs by performing simulation of the flow through a 25mm St. Jude Medical valve placed in a straight aorta. Two different gap sizes (250 and 150 micrometer) are used in this study. The simulations are done using a sharp interface curvilinear immersed boundary method along with a strong-coupling algorithm for FSI solver on overset grids. The platelet activation through the hinge for different gap sizes is compared to the activation in the bulk flow using two platelet activation models to ensure the consistency of the results. Our results for all gap sizes using different activation models show that the integration of platelet activation caused by the bulk flow is several times higher in comparison to the activation through the hinge. This work is supported by the American Heart Association Grant 13SDG17220022, and the computational resources were partly provided by Center for Computational Research (CCR) at University at Buffalo.

Statistical characteristics of mechanical heart valve cavitation in accelerated testing.

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Wu, Changfu; Hwang, Ned H C; Lin, Yu-Kweng M

2004-07-01

Cavitation damage has been observed on mechanical heart valves (MHVs) undergoing accelerated testing. Cavitation itself can be modeled as a stochastic process, as it varies from beat to beat of the testing machine. This in-vitro study was undertaken to investigate the statistical characteristics of MHV cavitation. A 25-mm St. Jude Medical bileaflet MHV (SJM 25) was tested in an accelerated tester at various pulse rates, ranging from 300 to 1,000 bpm, with stepwise increments of 100 bpm. A miniature pressure transducer was placed near a leaflet tip on the inflow side of the valve, to monitor regional transient pressure fluctuations at instants of valve closure. The pressure trace associated with each beat was passed through a 70 kHz high-pass digital filter to extract the high-frequency oscillation (HFO) components resulting from the collapse of cavitation bubbles. Three intensity-related measures were calculated for each HFO burst: its time span; its local root-mean-square (LRMS) value; and the area enveloped by the absolute value of the HFO pressure trace and the time axis, referred to as cavitation impulse. These were treated as stochastic processes, of which the first-order probability density functions (PDFs) were estimated for each test rate. Both the LRMS value and cavitation impulse were log-normal distributed, and the time span was normal distributed. These distribution laws were consistent at different test rates. The present investigation was directed at understanding MHV cavitation as a stochastic process. The results provide a basis for establishing further the statistical relationship between cavitation intensity and time-evolving cavitation damage on MHV surfaces. These data are required to assess and compare the performance of MHVs of different designs.

Flow visualization of a monoleaflet and bileaflet mechanical heart valve in a pneumatic ventricular assist device using a PIV system.

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Lee, Hwansung; Tatsumi, Eisuke; Taenaka, Yoshiyuki

2010-01-01

Our group is developing a new type of pulsatile pneumatic ventricular assist device (PVAD) that uses the Medtronic Hall tilting disc valve (M-H valve). Although tilting disc valves have good washout effect inside the blood pump, they are no longer in common clinical use and may be difficult to obtain in the future. To investigate the stability of the Sorin Bicarbon valve (S-B valve) in our PVAD, we constructed a model pump made of an acrylic resin with the same configuration as our PVAD and attempted to compare the flow visualization upstream and downstream of the outlet position valve between the M-H valve and the S-B valve using a particle image velocimetry (PIV) method. The outlet S-B valve had faster closure than the M-H valve. The maximum flow velocity was greater than with the M-H valve. The maximum Reynolds shear stress (RSS) of the M-H valve reached 150 N/m(2) and that of the S-B valve reached 300 N/m(2) upstream during the end-systolic and early-diastolic phases. In both valves, the maximum RSS upstream of the valve was higher than downstream of the valve because of the regurgitation flow during valve closure. In addition, the maximum viscous shear stress reached above 2 N/m(2), which occupied only about 1%-1.5% of the maximum RSS.

A finite element model on effects of impact load and cavitation on fatigue crack propagation in mechanical bileaflet aortic heart valve.

Science.gov (United States)

Mohammadi, H; Klassen, R J; Wan, W-K

2008-10-01

Pyrolytic carbon mechanical heart valves (MHVs) are widely used to replace dysfunctional and failed heart valves. As the human heart beats around 40 million times per year, fatigue is the prime mechanism of mechanical failure. In this study, a finite element approach is implemented to develop a model for fatigue analysis of MHVs due to the impact force between the leaflet and the stent and cavitation in the aortic position. A two-step method to predict crack propagation in the leaflets of MHVs has been developed. Stress intensity factors (SIFs) are computed at a small initiated crack located on the leaflet edge (the worst case) using the boundary element method (BEM). Static analysis of the crack is performed to analyse the stress distribution around the front crack zone when the crack is opened; this is followed by a dynamic crack analysis to consider crack propagation using the finite element approach. Two factors are taken into account in the calculation of the SIFs: first, the effect of microjet formation due to cavitation in the vicinity of leaflets, resulting in water hammer pressure; second, the effect of the impact force between the leaflet and the stent of the MHVs, both in the closing phase. The critical initial crack length, the SIFs, the water hammer pressure, and the maximum jet velocity due to cavitation have been calculated. With an initial crack length of 35 microm, the fatigue life of the heart valve is greater than 60 years (i.e. about 2.2 x 10(9) cycles) and, with an initial crack length of 170 microm, the fatigue life of the heart valve would be around 2.5 years (i.e. about 9.1 x 10(7) cycles). For an initial crack length greater than 170 microm, there is catastrophic failure and fatigue cracking no longer occurs. A finite element model of fatigue analysis using Patran command language (PCL custom code) in MSC software can be used to evaluate the useful lifespan of MHVs. Similar methodologies can be extended to other medical devices under cyclic

Mechanical versus bioprosthetic aortic valve replacement.

Science.gov (United States)

Head, Stuart J; Çelik, Mevlüt; Kappetein, A Pieter

2017-07-21

Mechanical valves used for aortic valve replacement (AVR) continue to be associated with bleeding risks because of anticoagulation therapy, while bioprosthetic valves are at risk of structural valve deterioration requiring reoperation. This risk/benefit ratio of mechanical and bioprosthetic valves has led American and European guidelines on valvular heart disease to be consistent in recommending the use of mechanical prostheses in patients younger than 60 years of age. Despite these recommendations, the use of bioprosthetic valves has significantly increased over the last decades in all age groups. A systematic review of manuscripts applying propensity-matching or multivariable analysis to compare the usage of mechanical vs. bioprosthetic valves found either similar outcomes between the two types of valves or favourable outcomes with mechanical prostheses, particularly in younger patients. The risk/benefit ratio and choice of valves will be impacted by developments in valve designs, anticoagulation therapy, reducing the required international normalized ratio, and transcatheter and minimally invasive procedures. However, there is currently no evidence to support lowering the age threshold for implanting a bioprosthesis. Physicians in the Heart Team and patients should be cautious in pursuing more bioprosthetic valve use until its benefit is clearly proven in middle-aged patients. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Evaluation of prosthetic valve obstruction on electrocardiographically gated multidetector-row computed tomography--identification of subprosthetic pannus in the aortic position.

Science.gov (United States)

Ueda, Tomohiro; Teshima, Hideki; Fukunaga, Shuji; Aoyagi, Shigeaki; Tanaka, Hiroyuki

2013-01-01

This study was performed to evaluate the diagnostic role of electrocardiographically gated multidetector-row computed tomography (MDCT) for prosthetic valve obstruction (PVO) in the aortic position. Between 2002 and 2006, 9 patients were diagnosed with PVO of an aortic bileaflet mechanical valve based on echocardiographic and cineradiographic criteria. These 9 patients were examined using MDCT before replacement of the mechanical valve, and intraoperative findings were compared to morphologic periprosthetic abnormalities observed on MDCT. CT attenuation (Hounsfield units; HU) of the periprosthetic abnormalities was measured to investigate the underlying cause of the PVO. MDCT showed subprosthetic masses extending beyond the prosthetic ring into the orifice of the valve. At reoperation, presence of subprosthetic pannus was confirmed in all of the 9 patients, but no periprosthetic thrombus was found. The mean CT attenuation of the subprosthetic pannus was 170 HU, and it was significantly greater than that obtained from the interventricular septum (108 HU; Ppannus causing PVO and the mean CT attenuation of subprosthetic pannus is significantly higher than that of the interventricular septum on MDCT.

Fracturing mechanics before valve-in-valve therapy of small aortic bioprosthetic heart valves.

Science.gov (United States)

Johansen, Peter; Engholt, Henrik; Tang, Mariann; Nybo, Rasmus F; Rasmussen, Per D; Nielsen-Kudsk, Jens Erik

2017-10-13

Patients with degraded bioprosthetic heart valves (BHV) who are not candidates for valve replacement may benefit from transcatheter valve-in-valve (VIV) therapy. However, in smaller-sized surgical BHV the resultant orifice may become too narrow. To overcome this, the valve frame can be fractured by a high-pressure balloon prior to VIV. However, knowledge on fracture pressures and mechanics are prerequisites. The aim of this study was to identify the fracture pressures needed in BHV, and to describe the fracture mechanics. Commonly used BHV of small sizes were mounted on a high-pressure balloon situated in a biplane fluoroscopic system with a high-speed camera. The instant of fracture was captured along with the balloon pressure. The valves were inspected for material protrusion and later dissected for fracture zone investigation and description. The valves with a polymer frame fractured at a lower pressure (8-10 atm) than those with a metal stent (19-26 atm). None of the fractured valves had elements protruding. VIV procedures in small-sized BHV may be performed after prior fracture of the valve frame by high-pressure balloon dilatation. This study provides tentative guidelines for expected balloon sizes and pressures for valve fracturing.

Advances in cardiovascular fluid mechanics: bench to bedside.

Science.gov (United States)

Dasi, Lakshmi P; Sucosky, Philippe; de Zelicourt, Diane; Sundareswaran, Kartik; Jimenez, Jorge; Yoganathan, Ajit P

2009-04-01

This paper presents recent advances in cardiovascular fluid mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the fluid mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex fluid mechanics associated with the cardiovascular system and have led to new translational technologies.

In vivo canine studies of a Sinkhole valve and vascular graft coated with biocompatible PU-PEO-SO3.

Science.gov (United States)

Han, D K; Lee, K B; Park, K D; Kim, C S; Jeong, S Y; Kim, Y H; Kim, H M; Min, B G

1993-01-01

PU-PEO-SO3 was applied as a coating material over a newly designed Sinkhole bileaflet PU heart valve and a porous PU vascular graft. Performance and biocompatibility were evaluated using an in vivo canine shunt system between the right ventricle and pulmonary artery. The survival periods in three implantations were 14, 24, and 39 days, during which no mechanical failure occurred in any Sinkhole valve or vascular graft. Scanning electron microscopy (SEM) studies demonstrated much less platelet adhesion and thrombus formation on PU-PEO-SO3 grafts than on PU vascular grafts. Cracks in the valve leaflet were occasionally observed on PU surfaces, but not on PU-PEO-SO3. After a 39 day implantation, calcium deposition on vascular grafts was decreased as compared with valve leaflets, and calcification on PU-PEO-SO3 was much lower than on PU. These results suggest that Sinkhole valves and vascular grafts are promising, and PU-PEO-SO3 as a coating material is more blood compatible, biostable, and calcification resistant in vivo than in untreated PU.

Mechanisms of mechanical heart valve cavitation: investigation using a tilting disk valve model.

Science.gov (United States)

He, Z; Xi, B; Zhu, K; Hwang, N H

2001-09-01

The induction of mechanical heart valve (MHV) cavitation was investigated using a 27 mm Medtronic Hall (MH27) tilting disk valve. The MH27 valve was mounted in the mitral position of a simulating pulse flow system, and stroboscopic lighting used to visualize cavitation bubbles on the occluder inflow surface at the instant of valve closure. MHV cavitation was monitored using a digital camera with 0.04 mm/pixel resolution sufficient to render the tiny bubbles clearly visible on the computer monitor screen. Cavitation on MH27 valve was classified as five types according to the time, site and shape of the cavitation bubbles. Valve cavitation occurred at the instant of occluder impact with the valve seat at closing. The impact motion was subdivided into three temporal phases: (i) squeezing flow; (ii) elastic collision; and (iii) leaflet rebound. MHV cavitation caused by vortices was found to be initiated by the squeezing jet and/or by the transvalvular leakage jets. By using a tension wave which swept across the occluder surface immediately upon elastic impact, nuclei in the vortex core were expanded to form cavitation bubbles. Analysis of the shape and location of the cavitation bubbles permitted a better understanding of MHV cavitation mechanisms, based on the fluid dynamics of jet vortex and tension wave propagations.

Mitral Prosthetic Valve Obstruction and Its Complications

Directory of Open Access Journals (Sweden)

Rajesh Rajan

2015-12-01

Full Text Available Prosthetic Valve Obstruction (PVO is a serious complication which is associated with increased morbidity and mortality. This could result from thrombus formation, development of pannus, or a combination of both. Patients with this complication often present with symptoms and signs of heart failure, systemic embolism, acute cardiovascular collapse, and sudden death. Transesophageal echocardiography and cine fluoroscopy play a vital role in diagnosis of this potentially lethal condition. Herein, we reported a 56-year-old male patient who presented with severe heart failure and was found to have obstructed ATS27 bileaflet mitral prosthetic valve. Thrombolysis and redo surgery are two important options for treating this condition although guidelines for choosing between the two are not very definite.

Development of Overflow-Prevention Valve with Trigger Mechanism.

Science.gov (United States)

Ishino, Yuji; Mizuno, Takeshi; Takasaki, Masaya

2016-09-01

A new overflow-prevention valve for combustible fluid is developed which uses a trigger mechanism. Loading arms for combustible fluid are used for transferring oil from a tanker to tanks and vice versa. The loading arm has a valve for preventing overflow. Overflow- prevention valves cannot use any electric component to avoid combustion. Therefore, the valve must be constructed only by mechanical parts. The conventional overflow-prevention valve uses fluid and pneumatic forces. It consists of a sensor probe, a cylinder, a main valve for shutting off the fluid and a locking mechanism for holding an open state of the main valve. The proposed overflow-prevention valve uses the pressure due to the height difference between the fluid level of the tank and the sensor probe. However, the force of the cylinder produced by the pressure is too small to release the locking mechanism. Therefore, a trigger mechanism is introduced between the cylinder and the locking mechanism. The trigger mechanism produces sufficient force to release the locking mechanism and close the main valve when the height of fluid exceeds a threshold value. A trigger mechanism is designed and fabricated. The operation necessary for closing the main valve is conformed experimentally.

Developments in mechanical heart valve prosthesis

Indian Academy of Sciences (India)

Artificial heart valves are engineered devices used for replacing diseased or damaged natural valves of the heart. Most commonly used for replacement are mechanical heart valves and biological valves. This paper briefly outlines the evolution, designs employed, materials being used,. and important factors that affect the ...

The prognosis of infective endocarditis treated with biological valves versus mechanical valves: A meta-analysis.

Science.gov (United States)

Tao, Ende; Wan, Li; Wang, WenJun; Luo, YunLong; Zeng, JinFu; Wu, Xia

2017-01-01

Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves. Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis. A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520). The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients

Transapical JenaValve in a patient with mechanical mitral valve prosthesis.

LENUS (Irish Health Repository)

O' Sullivan, Katie E

2014-01-29

We report the first case of transcatheter aortic valve replacement implantation using JenaValve™ in a patient with mechanical mitral valve prosthesis. We believe that the design features of this valve may be particularly suited for use in this setting. © 2014 Wiley Periodicals, Inc.

Obstructed bi-leaflet prosthetic mitral valve imaging with real-time three-dimensional transesophageal echocardiography.

Science.gov (United States)

Shimbo, Mai; Watanabe, Hiroyuki; Kimura, Shunsuke; Terada, Mai; Iino, Takako; Iino, Kenji; Ito, Hiroshi

2015-01-01

Real-time three-dimensional transesophageal echocardiography (RT3D-TEE) can provide unique visualization and better understanding of the relationship among cardiac structures. Here, we report the case of an 85-year-old woman with an obstructed mitral prosthetic valve diagnosed promptly by RT3D-TEE, which clearly showed a leaflet stuck in the closed position. The opening and closing angles of the valve leaflets measured by RT3D-TEE were compatible with those measured by fluoroscopy. Moreover, RT3D-TEE revealed, in the ring of the prosthetic valve, thrombi that were not visible on fluoroscopy. RT3D-TEE might be a valuable diagnostic technique for prosthetic mitral valve thrombosis. © 2014 Wiley Periodicals, Inc.

Perivalvular pannus and valve thrombosis: two concurrent mechanisms of mechanical valve prosthesis dysfunction.

Science.gov (United States)

Arnáiz-García, María Elena; González-Santos, Jose María; Bueno-Codoñer, María E; López-Rodríguez, Javier; Dalmau-Sorlí, María José; Arévalo-Abascal, Adolfo; Arribas-Jiménez, Antonio; Diego-Nieto, Alejandro; Rodríguez-Collado, Javier; Rodríguez-López, Jose María

2015-02-01

A 78-year-old woman was admitted to our institution with progressive dyspnea. She had previously been diagnosed with rheumatic heart disease and had undergone cardiac surgery for mechanical mitral valve replacement ten years previously. Transesophageal echocardiography revealed blockage of the mechanical prosthesis and the patient was scheduled for surgery, in which a thrombus was removed from the left atrial appendage. A partial thrombosis of the mechanical prosthesis and circumferential pannus overgrowth were concomitantly detected. Prosthetic heart valve blockage is a rare but life-threatening complication, the main causes of which are thrombosis and pannus formation. The two conditions are different but both are usually misdiagnosed. Two concurrent mechanisms of prosthesis blockage were found in this patient. Copyright © 2014 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

Doppler derived gradient of ST Jude Mechanical Prosthesis, early postoperative assessment

International Nuclear Information System (INIS)

Shaikh, A.H.; Hanif, B.; Adil, A.; Hashimi, S.; Qazi, H.A.; Mujtaba, I.

2010-01-01

Objective: To determine the doppler derived mean gradients of St Jude mechanical prosthesis in early postoperative period in patients undergoing valve replacement at a tertiary care cardiac centre. Methods: Medical records of 190 consecutive patients who underwent 233 mitral, aortic or dual (mitral and aortic) valve replacement by St Jude bileaflet mechanical prosthesis at Tabba Heart Institute, between March 2006 to December 2008 were reviewed. Doppler derived mean gradients were assessed predischarge and recorded. Results: There were 98 (51.5%) males and 92 (48.5%) females in the study cohort. The mean age was 40 +- 14 years. Of the total, 101 (53%) had mitral, 46 (24.2%) had aortic and 43 (22.6%) patients had dual valve replacement. Doppler derived mean gradient was assessed across 144 mitral and 89 aortic St Jude mechanical prosthesis. Doppler derived mean gradient for St Jude mitral prosthesis was 3.5 mm Hg and for St Jude aortic prosthesis was 10.2 mm Hg. Conclusions: The study determines baseline gradients across mitral and aortic St Jude mechanical prosthesis in our population. These can be used as reference gradients to assess St Jude prosthetic valve function in patients who did not have early postoperative doppler assessment. (author)

Clinical and echocardiographic assessment of the Medtronic Advantage aortic valve prosthesis: the Scandinavian multicentre, prospective study

DEFF Research Database (Denmark)

Haaverstad, Rune; Vitale, Nicola; Karevold, Asbjørn

2006-01-01

OBJECTIVE: The aim of this report is the prospective, multicentre evaluation of clinical results and haemodynamic performance of the Medtronic Advantage aortic valve prosthesis. METHODS: From April 2001 to June 2003, 166 patients (male:female 125:41; mean (SD) age 61.8 (11.8) years) received...... an aortic advantage valve prosthesis. Complete cumulative follow-up was 242.7 patient-years (maximum 3.2; mean 1.6 years). Postoperatively, patients underwent early (within 30 days) and 1 year transthoracic echocardiography. RESULTS: 30 day mortality was 2.4% (n = 4). Kaplan-Meier estimates of freedom from...... echocardiography. CONCLUSIONS: Haemodynamic performance and early clinical results of Medtronic advantage in the aortic position were satisfactory and comparable with those of other bileaflet valves in current clinical use....

Pannus-Related Mechanical Valve Dysfunction Leading to Hemodynamic Shock

Directory of Open Access Journals (Sweden)

Manabu Shiraishi

2012-02-01

Full Text Available Mechanical prosthetic valve dysfunction caused by pannus formation is rare. Pannus restricts movement of prosthetic valve leaflets, resulting in severe aortic regurgitation. We describe the case of a 77-year-old woman who presented to the emergency room with increasing dyspnea, ischemia, and shock secondary to mechanical aortic valve dysfunction. Transesophageal echocardiography showed a blockade of the leaflets of the mechanical aortic valve, with severe aortic regurgitation. She underwent emergent cardiac surgery for aortic valve replacement. Pannus formation should be considered as a potential cause of acute severe aortic regurgitation in a patient with a small-sized mechanical aortic prosthesis in the supra-annular position. On a pathological exam, extensive pannus was found on the ventricular side of the prosthetic valve, extending from the ring into the central orifice. [Arch Clin Exp Surg 2012; 1(1.000: 50-53

Long-term results of heart valve replacement with the Edwards Duromedics bileaflet prosthesis: a prospective ten-year clinical follow-up.

Science.gov (United States)

Podesser, B K; Khuenl-Brady, G; Eigenbauer, E; Roedler, S; Schmiedberger, A; Wolner, E; Moritz, A

1998-05-01

The Edwards Duromedics valve (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.) was designed with a self-irrigating hinge mechanism to reduce thromboembolic complications. After good initial clinical results, distribution was suspended in 1988 after reports of valve fracture after 20,000 valves had been implanted. The manufacturer conducted extensive studies to improve the Edwards Duromedics and reintroduced a modified version, which is available as Edwards Tekna. The purpose of the study was the evaluation of long-term results of the original Edwards Duromedics that might be important for the current version, the Edwards Tekna valve. A prospective clinical 10-year follow-up was performed of 508 patients who underwent valve replacement with the Edwards Duromedics valve in the aortic (n = 268), mitral (n = 183), and aortic and mitral (n = 56) position. The perioperative mortality rate was 6.9%; follow-up was 98% complete, comprising 3648 patient-years for a mean follow-up of 86 months (range: 33 to 144 months). The actuarial freedom from complications at the 10-year follow-up and the incidence rate (percent per patient-year) were as follows: late mortality rate, 69.2% +/- 2.4% (3.5% per patient-year); thromboembolism, 90.7% +/- 1.6% (0.96% per patient-year); anticoagulation-related hemorrhage, 87.7% +/- 1.7% (1.34% per patient-year); prosthetic valve endocarditis, 96.7% +/- 0.09% (0.38% per patient-year); valve-related mortality rate, 89.3% +/- 1.6% (1.21% per patient-year); valve failure, 86.2% +/- 1.85% (1.54% per patient-year); and valve-related morbidity and mortality rate, 71.1% +/- 2.3% (3.2% per patient-year). Three leaflet escapes were observed (one lethal, two successful reoperations; 99.1% +/- 0.05% freedom, 0.08% per patient-year). All patients functionally improved (86% in New York Heart Association classes I and II), and incidence of anemia was insignificant. These results confirm that the Edwards Duromedics valve shows excellent performance

Mechanical Aortic Valve Replacement in Octogenarian

Directory of Open Access Journals (Sweden)

Irfan Tasoglu

2013-10-01

Full Text Available Aim: This study analyzes the long-term outcomes of mechanical aortic valve replacement in octogenarian patients. Material and Method: A retrospective review was performed on 23 octogenarian patients who underwent mechanical aortic valve replacement. Hospital mortality, postoperative intensive care unit stay, hospital stay and long-term results was examined. Estimates of the cumulative event mortality rate were calculated by the Kaplan-Meier method. Results: The mean age of all patients was 82.9±2.3 years and most were men (65.22%. The median ejection fraction was 45%. 73.91% of patients were in New York Heart Association class III-IV. Thirteen patients (56.52% in this study underwent combined procedure, the remaining 10 (43.48% patients underwent isolated aortic valve replacement. The most common valve size was 23 mm. The mean intensive care unit stay was 1.76±1.14 days. The mean hospital stay was 9.33±5.06 days. No complications were observed in 56.52% patients during their hospital stay. The overall hospital mortality was 8.7%. Follow-up was completed for all 23 patients. Median follow-up time was 33 months (1-108 months. Actuarial survival among discharged from hospital was 59% at 5 years. Discussion: Mechanical aortic valve replacement is a safe procedure in octogenarian patients and can be performed safely even in combined procedure.

Characterization of a bioprosthetic bicuspid venous valve hemodynamics: implications for mechanism of valve dynamics.

Science.gov (United States)

Tien, W-H; Chen, H Y; Berwick, Z C; Krieger, J; Chambers, S; Dabiri, D; Kassab, G S

2014-10-01

Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential. A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid-structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD). Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the PIV measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven. The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve design optimizations that are needed for

Mitral valve surgery in the adult Marfan syndrome patient.

Science.gov (United States)

Bhudia, Sunil K; Troughton, Richard; Lam, Buu-Khanh; Rajeswaran, Jeevanantham; Mills, William R; Gillinov, A Marc; Griffin, Brian P; Blackstone, Eugene H; Lytle, Bruce W; Svensson, Lars G

2006-03-01

Because mitral valve dysfunction in adults with Marfan syndrome is poorly characterized, this study compares mitral valve pathophysiology and morphology with that of myxomatous mitral disease, documents types of mitral valve operations, and assesses long-term survival and durability of mitral valve surgery in Marfan patients. From May 1975 to June 2000, 27 adults with Marfan syndrome underwent mitral valve surgery. Their valve pathophysiology and morphology was compared with that of 119 patients with myxomatous mitral disease undergoing surgery from September 1995 to March 1999. Survival and repair durability were assessed at follow-up. Compared with myxomatous disease patients, Marfan patients had less posterior leaflet prolapse (44% versus 70%, p = 0.01), more bileaflet (44% versus 28%, p = 0.09) and anterior leaflet prolapse (11% versus 3%, p = 0.07), and presented earlier for surgery (age 41 +/- 12 years versus 57 +/- 13, p Marfan patients had longer and thinner leaflets. Mitral valve repair was performed less frequently in Marfan (16 of 27, 59%) than myxomatous disease patients (112 of 119, 94%). There were no hospital deaths; at 10 years, survival was 80% and freedom from reoperation 96%, with only 1 reoperation among the 16 repairs. Mitral valve pathophysiology and morphology differ between Marfan and myxomatous mitral valve diseases. Valve repair in Marfan patients is durable and gives acceptable long-term results, even in adults who present with advanced mitral valve pathology. With increasing use of the modified David reimplantation operation and sparing of the aortic valve, mitral valve repair is a greater imperative, particularly since we have not had to reoperate on any Marfan patients with reimplantations.

Afebrile Pannus-Induced Blood Culture-Negative Mechanical Valve Endocarditis.

Science.gov (United States)

Matsukuma, Seiji; Eishi, Kiyoyuki; Tanigawa, Kazuyoshi; Miura, Takashi; Matsumaru, Ichiro; Hisatomi, Kazuki; Tsuneto, Akira

2016-12-01

The diagnosis of prosthetic valve endocarditis may be challenging in patients with an atypical clinical presentation. Virtually all infections associated with mechanical prosthetic valves are localized to the prosthesis-tissue junction at the sewing ring and are accompanied by tissue destruction around the prosthesis. Because the orifice of the mechanical prosthetic valve is made of metal and pyrolytic carbon, which do not enable the adherence of microorganisms, any vegetation originating from the interior of the valve orifice is usually rare. Here we present a rare case of pannus-induced mechanical prosthetic valve endocarditis that was difficult to diagnose. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Influence of Tricuspid Bioprosthetic Mitral Valve Orientation Regarding the Flow Field Inside the Left Ventricle: In Vitro Hydrodynamic Characterization Based on 2D PIV Measurements.

Science.gov (United States)

Bazan, Ovandir; Ortiz, Jayme P; Fukumasu, Newton K; Pacifico, Antonio L; Yanagihara, Jurandir I

2016-02-01

The flow patterns of a prosthetic heart valve in the aortic or mitral position can change according to its type and orientation. This work describes the use of 2D particle image velocimetry (PIV) applied to the in vitro flow fields characterization inside the upper part of a left ventricular model at various heart rates and as a function of two orientations of stented tricuspid mitral bioprostheses. In the ventricular model, each mitral bioprosthesis (27 and 31 mm diameter) was installed in two orientations, rotated by 180°, while the aortic bileaflet mechanical valve (27 mm diameter) remained in a fixed orientation. The results (N = 50) showed changes in the intraventricular flow fields according to the mitral bioprostheses positioning. Also, changes in the aortic upstream velocity profiles were noticed as a function of mitral orientations. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Transcatheter Mitral Valve Devices - Functional Mechanical Designs.

Science.gov (United States)

Kliger, Chad

2014-03-01

Mitral regurgitation is a complex disorder involving a multitude of components of the mitral apparatus. With the desire for less invasive treatment approaches, transcatheter mitral valve therapies (TMVT) are directed at these components and available at varying stages of development. Therapeutic advancements and the potential to combine technologies may further improve their efficacy and safety. Transcatheter mitral valve replacement, while preserving the mitral apparatus, may emerge as an alternative or even a more suitable treatment option. In addition, early data on transcatheter mitral valve-in-valve and valve-in-ring implantation are encouraging and this approach may be an alternative to reoperation in the high-risk patient. This review details the expanding functional mechanical designs of current active TMVT.

Influence of type of aortic valve prosthesis on coronary blood flow velocity.

Science.gov (United States)

Jelenc, Matija; Juvan, Katja Ažman; Medvešček, Nadja Tatjana Ružič; Geršak, Borut

2013-02-01

Severe aortic valve stenosis is associated with high resting and reduced hyperemic coronary blood flow. Coronary blood flow increases after aortic valve replacement (AVR); however, the increase depends on the type of prosthesis used. The present study investigates the influence of type of aortic valve prosthesis on coronary blood flow velocity. The blood flow velocity in the left anterior descending coronary artery (LAD) and the right coronary artery (RCA) was measured intraoperatively before and after AVR with a stentless bioprosthesis (Sorin Freedom Solo; n = 11) or a bileaflet mechanical prosthesis (St. Jude Medical Regent; n = 11). Measurements were made with an X-Plore epicardial Doppler probe (Medistim, Oslo, Norway) following induction of hyperemia with an adenosine infusion. Preoperative and postoperative echocardiography evaluations were used to assess valvular and ventricular function. Velocity time integrals (VTI) were measured from the Doppler signals and used to calculate the proportion of systolic VTI (SF), diastolic VTI (DF), and normalized systolic coronary blood flow velocities (NSF) and normalized diastolic coronary blood flow velocities (NDF). The systolic proportion of the LAD VTI increased after AVR with the St. Jude Medical Regent prosthesis, which produced higher LAD SF and NSF values than the Sorin Freedom Solo prosthesis (SF, 0.41 ± 0.09 versus 0.29 ± 0.13 [P = .04]; NSF, 0.88 ± 0.24 versus 0.55 ± 0.17 [P = .01]). No significant changes in the LAD velocity profile were noted after valve replacement with the Sorin Freedom Solo, despite a significant reduction in transvalvular gradient and an increase in the effective orifice area. AVR had no effect on the RCA flow velocity profile. The coronary flow velocity profile in the LAD was significantly influenced by the type of aortic valve prosthesis used. The differences in the LAD velocity profile probably reflect differences in valve design and the systolic transvalvular flow pattern.

Validation of a numerical 3-D fluid-structure interaction model for a prosthetic valve based on experimental PIV measurements.

Science.gov (United States)

Guivier-Curien, Carine; Deplano, Valérie; Bertrand, Eric

2009-10-01

A numerical 3-D fluid-structure interaction (FSI) model of a prosthetic aortic valve was developed, based on a commercial computational fluid dynamics (CFD) software program using an Arbitrary Eulerian Lagrangian (ALE) formulation. To make sure of the validity of this numerical model, an equivalent experimental model accounting for both the geometrical features and the hydrodynamic conditions was also developed. The leaflet and the flow behaviours around the bileaflet valve were investigated numerically and experimentally by performing particle image velocimetry (PIV) measurements. Through quantitative and qualitative comparisons, it was shown that the leaflet behaviour and the velocity fields were similar in both models. The present study allows the validation of a fully coupled 3-D FSI numerical model. The promising numerical tool could be therefore used to investigate clinical issues involving the aortic valve.

Development of a micro-mechanical valve in a novel glaucoma implant.

Science.gov (United States)

Siewert, Stefan; Schultze, Christine; Schmidt, Wolfram; Hinze, Ulf; Chichkov, Boris; Wree, Andreas; Sternberg, Katrin; Allemann, Reto; Guthoff, Rudolf; Schmitz, Klaus-Peter

2012-10-01

This paper describes methods for design, manufacturing and characterization of a micro-mechanical valve for a novel glaucoma implant. The implant is designed to drain aqueous humour from the anterior chamber of the eye into the suprachoroidal space in case of an elevated intraocular pressure (IOP). In contrast to any existing glaucoma drainage device (GDD), the valve mechanism is located in the anterior chamber and there, surrounded by aqueous humour, immune to fibrosis induced failure. For the prevention of hypotony the micro-mechanical valve is designed to open if the physiological pressure difference between the anterior chamber and the suprachoroidal space in the range of 0.8 mmHg to 3.7 mmHg is exceeded. In particular the work includes: (i) manufacturing and morphological characterization of polymer tubing, (ii) mechanical material testing as basis for (iii) the design of micro-mechanical valves using finite element analysis (FEA), (iv) manufacturing of microstent prototypes including micro-mechanical valves by femtosecond laser micromachining and (v) the experimental fluid-mechanical characterization of the manufactured microstent prototypes with regard to valve opening pressure. The considered materials polyurethane (PUR) and silicone (SIL) exhibit low elastic modulus and high extensibility. The unique valve design enables a low opening pressure of micro-mechanical valves. An ideal valve design for PUR and SIL with an experimentally determined opening pressure of 2 mmHg and 3.7 mmHg is identified. The presented valve approach is suitable for the inhibition of hypotony as a major limitation of today's GDD and will potentially improve the minimally invasive treatment of glaucoma.

Analysis of aortic root surgery with composite mechanical aortic valve conduit and valve-sparing reconstruction.

Science.gov (United States)

Dias, Ricardo Ribeiro; Mejia, Omar Asdrubal Vilca; Fiorelli, Alfredo Inácio; Pomerantzeff, Pablo Maria Alberto; Dias, Altamiro Ribeiro; Mady, Charles; Stolf, Noedir Antonio Groppo

2010-01-01

Comparative analysis of early and late results of aortic root reconstruction with aortic valve sparing operations and the composite mechanical valve conduit replacement. From November 2002 to September 2009, 164 consecutive patients with mean age 54 ± 15 years, 115 male, underwent the aortic root reconstruction (125 mechanical valve conduit replacements and 39 valve sparing operations). Sixteen percent of patients had Marfan syndrome and 4.3% had bicuspid aortic valve. One hundred and forty-four patients (88%) were followed for a mean period of 41.1 ± 20.8 months. The hospital mortality was 4.9%, 5.6% in operations with valved conduits and 2.6% in the valve sparing procedures (P valve sparing operations, respectively (95% CI = 70% - 95%, P = 0.001), (95% CI = 82% - 95% P = 0.03) and (95% CI = 81% - 95%, P = 0.03). Multivariate analysis showed that creatinine greater than 1.4 mg/dl, Cabrol operation and renal dialysis were predictors of mortality, respectively, with occurrence chance of 6 (95% CI = 1.8 - 19.5, P = 0.003), 12 (95% CI = 3 - 49.7, P = 0.0004) and 16 (95% CI = 3.6 - 71.3, P = 0.0002). The aortic root reconstruction has a low early and late mortality, high survival free of complications and low need for reoperation. During the late follow-up, valve sparing aortic root reconstructions presented fewer incidences of bleeding, thromboembolic events and endocarditis.

Prevalence of pannus formation after aortic valve replacement: clinical aspects and surgical management.

Science.gov (United States)

Sakamoto, Yoshimasa; Hashimoto, Kazuhiro; Okuyama, Hiroshi; Ishii, Shinichi; Shingo, Taguchi; Kagawa, Hiroshi

2006-01-01

Pannus formation after aortic valve replacement is not common, but obstruction due to chronic pannus is one of the most serious complications of valve replacement. The causes of pannus formation are still unknown and effective preventive methods have not been fully elucidated. We reviewed our clinical experience of all patients who underwent reoperation for prosthetic aortic valve obstruction due to pannus formation between 1973 and 2004. We compared the initial 18-year period of surgery, when the Björk-Shiley tilting-disk valve was used, and the subsequent 13-year period of surgery, when the St. Jude Medical valve was used. Seven of a total of 390 patients (1.8%) required reoperation for prosthetic aortic valve obstruction due to pannus formation. All seven patients were women; four patients underwent resection of the pannus and three patients needed replacement of the valve. The frequency of pannus formation in the early group was 2.4% (6/253), whereas it was 0.73% (1/137) in the late group (P Pannus was localized at the minor orifice of the Björk-Shiley valve in the early group and turbulent transvalvular blood flow was considered to be one of the important factors triggering its growth. We also consider that small bileaflet valves have the possibility of promoting pannus formation and that the implantation of a larger prosthesis can contribute to reducing the occurrence of pannus.

Hemodynamic function of the standard St. Jude bileaflet disc valve has no clinical impact 10 years after aortic valve replacement

DEFF Research Database (Denmark)

Lund, Ole; Dorup, Inge; Emmertsen, Kristian

2005-01-01

in the survivors of a prospective series 10 years after AVR for aortic stenosis. DESIGN: Forty-three survivors aged 32-90 years from a prospective series attended a follow-up study with Doppler echo and radionuclide cardiography 10 years after AVR for aortic stenosis. Six patients with significant left sided valve...... to St. Jude valve geometric orifice area (GOA) indexed for either body surface area or left ventricular end-diastolic dimension (LVEDD). The gradients correlated directly with LVEDD but not with LVEF or LVMi. Eleven patients with hypertension had higher peak gradients (31+/-13 versus 22+/-8 mmHg, p

Optimal results of aortic valve replacement with small mechanical valves (< 19 mm).

Science.gov (United States)

Kato, Yasuyuki; Hattori, Koji; Motoki, Manabu; Takahashi, Yosuke; Kotani, Shinsuke; Nishimura, Shinsuke; Shibata, Toshihiko

2013-07-01

Controversy exists regarding the optimal operative method or type of prosthesis for patients with a small aortic root. The aim of this retrospective study was to investigate the early and mid-term outcomes of standard aortic valve replacement (AVR) using 16 mm or 18 mm ATS Advanced Performance (AP) or 17 mm St. Jude Medical (SJM) Regent valves for a small aortic root. Between April 2003 and August 2009, 78 patients (age range: 50-86 years; 86% aged > or = 65 years) underwent AVR with 16 mm or 18 mm ATS AP valves (16AP group: n = 21, 18AP group: n = 32), or a 17 mm SJM Regent valve (17Regent group: n = 25). Fifty-six patients (72%) had a body surface area (BSA) of regression was similar among the groups (-30%, -25% and -28% in the 16AP, 17Regent and 18AP groups, respectively; p = 0.844). The early and mid-term results of AVR with 16 mm or 18 mm ATS AP valves, or with a 17 mm SJM Regent valve, were satisfactory. Therefore, standard AVR using these small mechanical prostheses, which avoids the need to enlarge the annulus or to conduct stentless bioprosthesis implantation, might represent an acceptable method, especially in elderly patients with a small aortic root.

Comparison of magnetic resonance imaging and Laser Doppler Anemometry velocity measurements downstream of replacement heart valves: implications for in vivo assessment of prosthetic valve function.

Science.gov (United States)

Fontaine, A A; Heinrich, R S; Walker, P G; Pedersen, E M; Scheidegger, M B; Boesiger, P; Walton, S P; Yoganathan, A P

1996-01-01

The non-invasive, in-vivo assessment of prosthetic valve function is compromised by the lack of accurate measurements of the transvalvular flow fields or hemodynamics by current techniques. Short echo time magnetic resonance imaging (MRI) may provide a method for the non-invasive, in vivo assessment of prosthetic valve function by accurately measuring changes in the transvalvular flow fields associated with normal and dysfunctional prosthetic valves. The objectives of these in vitro experiments were to investigate the potential for using MRI as a tool to measure the complex flow fields distal to replacement heart valves, and to assess the accuracy of MRI velocity measurements by comparison with Laser Doppler Anemometry (LDA), a gold standard. The velocity fields downstream of tilting disc, bileaflet, ball and cage, and pericardial tissue valves were measured using both three-component LDA and MRI phase velocity encoding under a steady flow rate of 22.8 l/min, simulating peak systolic flow. The valves were tested under normal and stenotic conditions to assess the MRI capabilities under a wide range of local flow conditions, velocities and turbulence levels. A new short echo time MRI technique (FAcE), which allowed velocity measurements in stenotic jets with high turbulence, was tested. Good overall agreement was obtained between the MRI velocity measurements and the LDA data. The MRI velocity measurements adequately reproduced the spatial structure of the flow fields. In most cases peak velocities were accurately measured to within 15%. The results indicate that the FAcE MRI method has the potential to be used as a diagnostic tool to assess prosthetic valve function.

A Structural Analysis of a Mechanical Heart Valve Prosthesis with Flat Leaflet

Science.gov (United States)

Kwon, Young Joo

This paper addresses the basic concept of MDO methodology and the structural analysis that should be performed in the design process of a mechanical heart valve prosthesis with flat leaflet using MDO methodology. In the structural design of the mechanical heart valve (MHV) prosthesis, the fluid mechanics analysis is executed for the blood flow passing through the leaflets of a mechanical heart valve prosthesis. Thereafter, the rigid body dynamics analysis of the leaflet motion is performed to obtain the structural condition for the structural mechanics analysis of the deformed leaflet. Then the structural mechanics analysis of the deformed leaflet follows to confirm the minimum thickness of the leaflet for the structural durability of the mechanical heart valve prosthesis. This paper shows that the minimum leaflet thickness can be evaluated to be 0.6mm among the suggested thicknesses.

Mechanical valve obstruction: Review of diagnostic and treatment strategies

Science.gov (United States)

Salamon, Jason; Munoz-Mendoza, Jerson; Liebelt, Jared J; Taub, Cynthia C

2015-01-01

Prosthetic valve obstruction (PVO) is a rare but feared complication of mechanical valve replacement. Diagnostic evaluation should focus on differentiating prosthetic valve thrombosis (PVT) from pannus formation, as their treatment options differ. History of sub-optimal anti-coagulation and post-op time course to development of PVO are useful clinical characteristics in differentiating thrombus from pannus formation. Treatment of PVT is influenced by the patient’s symptoms, valve location, degree of obstruction and thrombus size and may include thrombolysis or surgical intervention. Alternatively, pannus formation requires surgical intervention. The purpose of this article is to review the pathophysiology, epidemiology, diagnostic approach and treatment options for aortic and mitral valve PVO. PMID:26730292

Missed aortic valve endocarditis resulting in complete atrioventricular block and redo mechanical valve replacement.

Science.gov (United States)

Harky, Amer; Garner, Megan; Popa, Miruna; Shipolini, Alex

2017-08-03

Infective endocarditis is a rare disease associated with high morbidity and mortality. As a result, early diagnosis and prompt antibiotic treatment with or without surgical intervention is crucial in the management of such condition.We report a case of missed infective endocarditis of the aortic valve. The patient underwent mechanical aortic valve replacement, with the native valve being sent for histopathological examination. On re-admission 16 months later, he presented with syncope, shortness of breathing and complete heart block. On review of the histopathology of native aortic valve, endocarditis was identified which had not been acted on. The patient underwent redo aortic valve replacement for severe aortic regurgitation.We highlight the importance of following up histopathological results as well as the need for multidisciplinary treatment of endocarditis with a combination of surgical and antibiotic therapy. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Dysfunction of mechanical heart valve prosthesis: experience with surgical management in 48 patients

Science.gov (United States)

Ma, Wei-Guo; Hou, Bin; Abdurusul, Adiljan; Gong, Ding-Xu; Tang, Yue; Chang, Qian; Xu, Jian-Ping

2015-01-01

Background Dysfunction of mechanical heart valve prostheses is an unusual but potentially lethal complication after mechanical prosthetic valve replacement. We seek to report our experience with mechanical valve dysfunction regarding etiology, surgical techniques and early outcomes. Methods Clinical data of 48 patients with mechanical valve dysfunction surgically treated between October 1996 and June 2011 were analyzed. Results Mean age was 43.7±10.9 years and 34 were female (70.8%). The median interval from primary valve implantation to dysfunction was 44.5 months (range, 1 hour to 20 years). There were 21 emergent and 27 elective reoperations. The etiology was thrombosis in 19 cases (39.6%), pannus in 12 (25%), thrombosis and pannus in 11 (22.9%), improper disc orientation in 2 (4.1%), missing leaflet in 1 (2.1%), excessively long knot end in 1 (2.1%), endogenous factor in 1 (2.1%) and unidentified in 1 (2.1%). Surgical procedure was mechanical valve replacement in 37 cases (77.1%), bioprosthetic valve replacement in 7 (14.9%), disc rotation in 2 (4.2%) and excision of excessive knot end in 1 (2.1%). Early deaths occurred in 7 patients (14.6%), due to low cardiac output in 3 (6.3%), multi-organ failure in 2 (4.2%) and refractory ventricular fibrillation in 2 (4.2%). Complications occurred in 10 patients (20.8%). Conclusions Surgical management of mechanical valve dysfunction is associated with significant mortality and morbidity. Earlier identification and prompt reoperation are vital to achieving better clinical outcomes. The high incidence of thrombosis in this series highlights the need for adequate anticoagulation and regular follow-up after mechanical valve replacement. PMID:26793354

Developments in mechanical heart valve prosthesis

Indian Academy of Sciences (India)

M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

BHUVANESHWAR. Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences. & Technology ... affect the performance of mechanical heart valves. The clinical performance of ... those who cannot be put under anticoagulant therapy, like women who may still wish to bear children, or hemolytic patients.

Biological and mechanical evaluation of a Bio-Hybrid scaffold for autologous valve tissue engineering

Energy Technology Data Exchange (ETDEWEB)

Jahnavi, S [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai, TN 600036 (India); Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Trivandrum, Kerala 695012 (India); Saravanan, U [Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, TN 600036 (India); Arthi, N [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai, TN 600036 (India); Bhuvaneshwar, G S [Department of Engineering Design, Indian Institute of Technology Madras, Chennai, TN 600036 (India); Kumary, T V [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Trivandrum, Kerala 695012 (India); Rajan, S [Madras Medical Mission, Institute of Cardio-Vascular Diseases, Mogappair, Chennai, Tamil Nadu 600037 (India); Verma, R S, E-mail: vermars@iitm.ac.in [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai, TN 600036 (India)

2017-04-01

Major challenge in heart valve tissue engineering for paediatric patients is the development of an autologous valve with regenerative capacity. Hybrid tissue engineering approach is recently gaining popularity to design scaffolds with desired biological and mechanical properties that can remodel post implantation. In this study, we fabricated aligned nanofibrous Bio-Hybrid scaffold made of decellularized bovine pericardium: polycaprolactone-chitosan with optimized polymer thickness to yield the desired biological and mechanical properties. CD44{sup +}, αSMA{sup +}, Vimentin{sup +} and CD105{sup −} human valve interstitial cells were isolated and seeded on these Bio-Hybrid scaffolds. Subsequent biological evaluation revealed interstitial cell proliferation with dense extra cellular matrix deposition that indicated the viability for growth and proliferation of seeded cells on the scaffolds. Uniaxial mechanical tests along axial direction showed that the Bio-Hybrid scaffolds has at least 20 times the strength of the native valves and its stiffness is nearly 3 times more than that of native valves. Biaxial and uniaxial mechanical studies on valve interstitial cells cultured Bio-Hybrid scaffolds revealed that the response along the axial and circumferential direction was different, similar to native valves. Overall, our findings suggest that Bio-Hybrid scaffold is a promising material for future development of regenerative heart valve constructs in children. - Highlights: • We report detailed biological and mechanical investigations of a Bio-Hybrid scaffold. • Optimized polymer thickness yielded desired biological and mechanical properties. • Bio-Hybrid scaffold revealed hVIC proliferation with dense ECM deposition. • Biaxial testing indicated that Bio-Hybrid scaffolds are mechanically stronger than native valves. • Bio-Hybrid scaffold is a promising material for autologous valve tissue engineering.

Deformation Differences between Tricuspid and Bicuspid Aortic Valves in Vitro

Science.gov (United States)

Szeto, Kai; Rodriguez-Rodriguez, Javier; Pastuszko, Peter; Nigam, Vishal; Lasheras, Juan C.

2011-11-01

It has been shown in clinical studies that patients with congenital bicuspid aortic valves (CBAVs) develop degenerative calcification of the leaflets at young ages compared to patients with the normal tricuspid aortic valves (TAVs). It has been hypothesized that the asymmetrical geometry of the leaflets in CBAVs, flow shear stresses (SS), disturbed flow, and excessive strain rate levels are possible causes for the early calcification and stenosis. Central to the validation of this hypothesis is the need to quantify the differences in strain rate levels between the BAVs and TAVs. We simulate the CBAVs by surgically stitching two of the leaflets of a porcine aortic valve together. To quantify strain differences, we performed in-vitro experiments in both trileaflet and bileaflet valves by tracking the motion of small ink dots marked on each leaflet surface. We then used phase-locked stereo photogrammetry to reconstruct at each instant of time the 3D surface of the leaflets and measure the strain rates in both radial and circumferential directions during the whole cardiac cycle. Our results indicate that the total strain rate of the simulated BAVs is about 15 to 20% higher than the normal leaflets of TAVs at systole. In the BAVs' case, the fused leaflet stretches radially up to 25% higher than the reference length. The excessive stretching in both directions in the fused leaflet results in large changes in the flow patterns and associated wall SS.

Design And Analysis Of A Camless Valve Mechanism For I.C Engines Using Rotary Disc Valves

Directory of Open Access Journals (Sweden)

Vivek Jitendra Panchal

2017-09-01

Full Text Available It is the object of the presented paper to provide an electromechanical rotary valve actuating system for opening and closing valves of an internal combustion engine capable of separately controlling both the inlet and exhaust valve operations of each individual cylinder in a multi-cylinder engine. This indicates that only one valve will be required for each cylinder of the engine. Previously published versions of this concept require a separate valve for intake and exhaust in each cylinder. The system provides an alternative to the camshaft assembly in an attempt to overcome the limitations and inadequacies inevitably posed by a fully mechanical system. The prototype development is approached in a theoretical manner beginning with the conceptualization and design of a rotating disk with a notches and corresponding closure surfaces to open and close the flow path. The actuated disk and notch design is then refined and followed by the design of an inlet and exhaust manifold to correspond to the valve design and the theorizing and design of a sealing gasket. The rotating speed of the valve is determined by a general idling speed and can be varied to provide variable valve timing with the motor. The final assembly eliminates a majority of the moving parts currently used in camshaft systems like the cam camshaft rocker arm push rod and springs and results in a significantly lighter valve actuation system. By eliminating the translatory motion of valves the problem of valves slamming on the valve seats at high velocities is eliminated thus greatly reducing engine wear.

Impact of bileaflet mitral valve prolapse on quantification of mitral regurgitation with cardiac magnetic resonance: a single-center study.

Science.gov (United States)

Vincenti, Gabriella; Masci, Pier Giorgio; Rutz, Tobias; De Blois, Jonathan; Prša, Milan; Jeanrenaud, Xavier; Schwitter, Juerg; Monney, Pierre

2017-07-27

To quantify mitral regurgitation (MR) with CMR, the regurgitant volume can be calculated as the difference between the left ventricular (LV) stroke volume (SV) measured with the Simpson's method and the reference SV, i.e. the right ventricular SV (RVSV) in patients without tricuspid regurgitation. However, for patients with prominent mitral valve prolapse (MVP), the Simpson's method may underestimate the LV end-systolic volume (LVESV) as it only considers the volume located between the apex and the mitral annulus, and neglects the ventricular volume that is displaced into the left atrium but contained within the prolapsed mitral leaflets at end systole. This may lead to an underestimation of LVESV, and resulting an over-estimation of LVSV, and an over-estimation of mitral regurgitation. The aim of the present study was to assess the impact of prominent MVP on MR quantification by CMR. In patients with MVP (and no more than trace tricuspid regurgitation) MR was quantified by calculating the regurgitant volume as the difference between LVSV and RVSV. LVSV uncorr was calculated conventionally as LV end-diastolic (LVEDV) minus LVESV. A corrected LVESV corr was calculated as the LVESV plus the prolapsed volume, i.e. the volume between the mitral annulus and the prolapsing mitral leaflets. The 2 methods were compared with respect to the MR grading. MR grades were defined as absent or trace, mild (5-29% regurgitant fraction (RF)), moderate (30-49% RF), or severe (≥50% RF). In 35 patients (44.0 ± 23.0y, 14 males, 20 patients with MR) the prolapsed volume was 16.5 ± 8.7 ml. The 2 methods were concordant in only 12 (34%) patients, as the uncorrected method indicated a 1-grade higher MR severity in 23 (66%) patients. For the uncorrected/corrected method, the distribution of the MR grades as absent-trace (0 vs 11, respectively), mild (20 vs 18, respectively), moderate (11 vs 5, respectively), and severe (4 vs 1, respectively) was significantly different (p�

Pulmonary Valve Replacement : Twenty-Six Years of Experience With Mechanical Valvar Prostheses

NARCIS (Netherlands)

Freling, Hendrik G.; van Slooten, Ymkje J.; van Melle, Joost P.; Ebels, Tjark; Hoendermis, Elke S.; Berger, Rolf M. F.; Hillege, Hans L.; Waterbolk, Tjalling W.; van Veldhuisen, Dirk J.; Willems, Tineke P.; Pieper, Petronella G.

BACKGROUND: Although the thromboembolic risk after pulmonary valve replacement (PVR) with mechanical valves is presumed to be high, recent studies suggest promising short-term and mid-term results. However, large studies reporting long-term mortality and valve-related complications are missing.

Cavitation behavior observed in three monoleaflet mechanical heart valves under accelerated testing conditions.

Science.gov (United States)

Lo, Chi-Wen; Liu, Jia-Shing; Li, Chi-Pei; Lu, Po-Chien; Hwang, Ned H

2008-01-01

Accelerated testing provides a substantial amount of data on mechanical heart valve durability in a short period of time, but such conditions may not accurately reflect in vivo performance. Cavitation, which occurs during mechanical heart valve closure when local flow field pressure decreases below vapor pressure, is thought to play a role in valve damage under accelerated conditions. The underlying flow dynamics and mechanisms behind cavitation bubble formation are poorly understood. Under physiologic conditions, random perivalvular cavitation is difficult to capture. We applied accelerated testing at a pulse rate of 600 bpm and transvalvular pressure of 120 mm Hg, with synchronized videographs and high-frequency pressure measurements, to study cavitation of the Medtronic Hall Standard (MHS), Medtronic Hall D-16 (MHD), and Omni Carbon (OC) valves. Results showed cavitation bubbles between 340 and 360 micros after leaflet/housing impact of the MHS, MHD, and OC valves, intensified by significant leaflet rebound. Squeeze flow, Venturi, and water hammer effects each contributed to cavitation, depending on valve design.

Risk-adjusted survival after tissue versus mechanical aortic valve replacement: a 23-year assessment.

Science.gov (United States)

Gaca, Jeffrey G; Clare, Robert M; Rankin, J Scott; Daneshmand, Mani A; Milano, Carmelo A; Hughes, G Chad; Wolfe, Walter G; Glower, Donald D; Smith, Peter K

2013-11-01

Detailed analyses of risk-adjusted outcomes after mitral valve surgery have documented significant survival decrements with tissue valves at any age. Several recent studies of prosthetic aortic valve replacement (AVR) also have suggested a poorer performance of tissue valves, although analyses have been limited to small matched series. The study aim was to test the hypothesis that AVR with tissue valves is associated with a lower risk-adjusted survival, as compared to mechanical valves. Between 1986 and 2009, primary isolated AVR, with or without coronary artery bypass grafting (CABG), was performed with currently available valve types in 2148 patients (1108 tissue valves, 1040 mechanical). Patients were selected for tissue valves to be used primarily in the elderly. Baseline and operative characteristics were documented prospectively with a consistent variable set over the entire 23-year period. Follow up was obtained with mailed questionnaires, supplemented by National Death Index searches. The average time to death or follow up was seven years, and follow up for survival was 96.2% complete. Risk-adjusted survival characteristics for the two groups were evaluated using a Cox proportional hazards model with stepwise selection of candidate variables. Differences in baseline characteristics between groups were (tissue versus mechanical): median age 73 versus 61 years; non-elective surgery 32% versus 28%; CABG 45% versus 35%; median ejection fraction 55% versus 55%; renal failure 6% versus 1%; diabetes 18% versus 7% (pvalves; however, after risk adjustment for the adverse profiles of tissue valve patients, no significant difference was observed in survival after tissue or mechanical AVR. Thus, the hypothesis did not hold, and risk-adjusted survival was equivalent, of course qualified by the fact that selection bias was evident. With selection criteria that employed tissue AVR more frequently in elderly patients, tissue and mechanical valves achieved similar survival

A Study on the Main Steam Safety Valve Opening Mechanism by Flashing on NPPs

International Nuclear Information System (INIS)

Kim, Bae Joo

2009-01-01

A safety injection event happened by opening of the Main Steam Safety Valve at Kori unit 1 on April 16, 2005. The safety valves were opened at the lower system pressure than the valve opening set point due to rapid system pressure drop by opening of the Power Operated Relief Valve installed at the upstream of the Main Steam System. But the opening mechanism of safety valve at the lower set point pressure was not explained exactly. So, it needs to be understood about the safety valve opening mechanism to prevent a recurrence of this kind of event at a similar system of Nuclear Power Plant. This study is aimed to suggest the hydrodynamic mechanism for the safety valve opening at the lower set point pressure and the possibility of the recurrence at similar system conditions through document reviewing for the related previous studies and Kori unit 1 event

Biological and mechanical evaluation of a Bio-Hybrid scaffold for autologous valve tissue engineering.

Science.gov (United States)

Jahnavi, S; Saravanan, U; Arthi, N; Bhuvaneshwar, G S; Kumary, T V; Rajan, S; Verma, R S

2017-04-01

Major challenge in heart valve tissue engineering for paediatric patients is the development of an autologous valve with regenerative capacity. Hybrid tissue engineering approach is recently gaining popularity to design scaffolds with desired biological and mechanical properties that can remodel post implantation. In this study, we fabricated aligned nanofibrous Bio-Hybrid scaffold made of decellularized bovine pericardium: polycaprolactone-chitosan with optimized polymer thickness to yield the desired biological and mechanical properties. CD44 + , αSMA + , Vimentin + and CD105 - human valve interstitial cells were isolated and seeded on these Bio-Hybrid scaffolds. Subsequent biological evaluation revealed interstitial cell proliferation with dense extra cellular matrix deposition that indicated the viability for growth and proliferation of seeded cells on the scaffolds. Uniaxial mechanical tests along axial direction showed that the Bio-Hybrid scaffolds has at least 20 times the strength of the native valves and its stiffness is nearly 3 times more than that of native valves. Biaxial and uniaxial mechanical studies on valve interstitial cells cultured Bio-Hybrid scaffolds revealed that the response along the axial and circumferential direction was different, similar to native valves. Overall, our findings suggest that Bio-Hybrid scaffold is a promising material for future development of regenerative heart valve constructs in children. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanical versus bioprosthetic mitral valve replacement in patients <65 years old.

Science.gov (United States)

Kaneko, Tsuyoshi; Aranki, Sary; Javed, Quratulain; McGurk, Siobhan; Shekar, Prem; Davidson, Michael; Cohn, Lawrence

2014-01-01

Because of its durability, the mechanical valve is typically chosen for young patients undergoing mitral valve replacement (MVR). However, a bioprosthetic valve might have the benefit of valve-in-valve transcatheter valve replacement when valve failure occurs. We examined the outcomes in patients who had undergone mechanical valve MVR (MVRm) versus bioprosthetic valve MVR (MVRb) in patients aged Security Death Index. The postoperative and long-term outcomes of interest included combined stroke and embolic events, reoperations, and mortality. Of 768 consecutive patients, 627 were in the MVRm and 141 in the MVRb group. Propensity score matching yielded a cohort of 125 MVRb (89%) and 125 control MVRm patients with similar etiology mixes. The groups were similar in age (MVRm, 53.2 ± 9.0 years; MVRb, 53.8 ± 10.6 years; P = .617) and other preoperative characteristics. The postoperative outcomes were also similar between the 2 groups, including reoperation for bleeding, stroke, deep sternal infection, sepsis, and length of hospital stay. The operative mortality was also similar (MVRm, 5.6%; MVRb, 8.0%; P = .617). However, Kaplan-Meier analysis showed the MVRb group had a greater reoperation rate (P = .001) and shorter estimated survival (11.3 vs 13.5 years, P = .004). The incidence of bleeding and stroke or embolic events between the 2 groups was similar. In the present report, MVRb for patients safety of mechanical valves in this group. Copyright © 2014 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

MITRAL VALVE PROLAPSE AND SUDDEN CARDIAC DEATH: WHO IS IN THE RISK GROUP?

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O. E. Shirobokikh

2016-01-01

Full Text Available Mitral valve prolapse (MVP is a congenital heart disease, fairly widespread in the population (2-8%. It rarely has complications, but they are serious and include sudden cardiac death (SCD, risk of which rises twofold from 0.2-0.4% cases by MVP. Most deaths are observed among young healthy women. This work is a review of literature dedicated to connection between MVP and SCD designed to explore possible predicts of SCD within patients suffering from MVP and to determine the subset of patients. A conclusion has been made that the connection between MVP and SCD is realized through life-threatening ventricular arrhythmias (VT, VF. The most common site of arrhythmias origin is the inferobasal left ventricular wall. A high-risk subset of patients is determined as young adult women with a midsystolic click at auscultation, bileaflet involvement of the mitral valve, T-wave abnormalities on inferior leads (II, III, aVF and frequent complex ventricular ectopic activity. Such patients require more intensive disease management of ventricular arrhythmias including consideration of surgical treatment.

Mitral Valve Disease

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... for mitral valve replacement—mechanical valves (metal) or biological valves (tissue). The principal advantage of mechanical valves ... small risk of stroke due to blood clotting. Biological valves usually are made from animal tissue. Biological ...

Mechanical performance of pyrolytic carbon in prosthetic heart valve applications.

Science.gov (United States)

Cao, H

1996-06-01

An experimental procedure has been developed for rigorous characterization of the fracture resistance and fatigue crack extension in pyrolytic carbon for prosthetic heart valve application. Experiments were conducted under sustained and cyclic loading in a simulated biological environment using Carbomedics Pyrolite carbon. While the material was shown to have modest fracture toughness, it exhibited excellent resistance to subcritical crack growth. The crack growth kinetics in pyrolytic carbon were formulated using a phenomenological description. A fatigue threshold was observed below which the crack growth rate diminishes. A damage tolerance concept based on fracture mechanics was used to develop an engineering design approach for mechanical heart valve prostheses. In particular, a new quantity, referred to as the safe-life index, was introduced to assess the design adequacy against subcritical crack growth in brittle materials. In addition, a weakest-link statistical description of the fracture strength is provided and used in the design of component proof-tests. It is shown that the structural reliability of mechanical heart valves can be assured by combining effective flaw detection and manufacturing quality control with adequate damage tolerance design.

Utility of cardiac computed tomography for evaluation of pannus in mechanical aortic valve.

Science.gov (United States)

Suh, Young Joo; Kim, Young Jin; Lee, Sak; Hong, Yoo Jin; Lee, Hye-Jeong; Hur, Jin; Choi, Byoung Wook; Chang, Byung-Chul

2015-08-01

The clinical significance of pannus detected on computed tomography (CT) has not yet been investigated. The purposes of this study were to investigate the clinical significance of pannus detected on cardiac CT in patients who underwent aortic valve replacement (AVR) with mechanical valves, and to determine predictors for pannus severity. A total of 92 patients who underwent cardiac CT and TTE and who had undergone mechanical AVR were included. The geometric orifice area (GOA), the presence of limitation of motion (LOM) and pannus were evaluated on CT. The GOA, presence of LOM, and presence and severity of pannus were compared with echocardiographic parameters. Logistic regression analysis was performed to determine the predictors for pannus severity. The GOA on CT positively correlated with effective orifice area on TTE (r = 0.733, P Pannus was found in 77.2% and LOM in 14.0%. With increasing pannus severity, mean transvalvular pressure gradient (PG) was significantly higher (P pannus, more severe pannus and LOM than patients with normal PG (P pannus (P pannus formation in patients with mechanical aortic valves. Moderate to severe pannus formation frequently occurred in patients with small mechanical valve size, Carbomedics valves, rheumatic heart disease and young age at AVR.

Nondestructive and noninvasive assessment of mechanical properties in heart valve tissue engineering

NARCIS (Netherlands)

Kortsmit, J.; Driessen, N.J.B.; Rutten, M.C.M.; Baaijens, F.P.T.

2009-01-01

Despite recent progress, mechanical behavior of tissue-engineered heart valves still needs improvement when native aortic valves are considered as a benchmark. Although it is known that cyclic straining enhances tissue formation, optimal loading protocols have not been defined yet. To obtain a

Heart valve surgery

Science.gov (United States)

... replacement; Valve repair; Heart valve prosthesis; Mechanical valves; Prosthetic valves ... surgery. Your heart valve has been damaged by infection ( endocarditis ). You have received a new heart valve ...

Experimental Study on Fracture Failure of BRW 250 Pump Liquid Valve Mechanical Spring Surface

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Rui Zeng

2017-01-01

Full Text Available In this paper, the singularity analysis method based on the continuous wave for the vibration signal of the plunger pump liquid valve under different conditions was studied, and the LMS based weighted least square method with good robustness and validity was proposed to calculate the LPZ index, which was the judgment criterion for fault of liquid valve mechanical spring. Fault diagnostic test results showed that the method could overcome the singularity of the binary discrete wave in the detection and quantitative accuracy problem, realize the accurate positioning of the singular point in the signal, identify the liquid valve disc in the spring break state to the liquid valve seat or lift limit the impact of the moment, and determine the fault of the liquid valve mechanical spring effectively.

Fatal association of mechanical valve thrombosis with dabigatran: a report of two cases.

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Atar, Shaul; Wishniak, Alice; Shturman, Alexander; Shtiwi, Sewaed; Brezins, Marc

2013-07-01

Several new oral anticoagulants have been approved for thromboembolism prevention in patients with nonvalvular atrial fibrillation. However, they are not yet approved for anticoagulation use in patients with prosthetic mechanical valves, and no randomized data have been published so far on their safety of use in these patients. We present two cases of patients with prosthetic mechanical mitral valves who were switched from warfarin and acenocoumarol to dabigatran and within 1 month experienced severe valve complications resulting in death. One patient experienced stroke and later cardiogenic shock and death, and the other experienced pulmonary edema, cardiogenic shock, and subsequent death.

Simple versus complex degenerative mitral valve disease.

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Javadikasgari, Hoda; Mihaljevic, Tomislav; Suri, Rakesh M; Svensson, Lars G; Navia, Jose L; Wang, Robert Z; Tappuni, Bassman; Lowry, Ashley M; McCurry, Kenneth R; Blackstone, Eugene H; Desai, Milind Y; Mick, Stephanie L; Gillinov, A Marc

2018-07-01

At a center where surgeons favor mitral valve (MV) repair for all subsets of leaflet prolapse, we compared results of patients undergoing repair for simple versus complex degenerative MV disease. From January 1985 to January 2016, 6153 patients underwent primary isolated MV repair for degenerative disease, 3101 patients underwent primary isolated MV repair for simple disease (posterior prolapse), and 3052 patients underwent primary isolated MV repair for complex disease (anterior or bileaflet prolapse), based on preoperative echocardiographic images. Logistic regression analysis was used to generate propensity scores for risk-adjusted comparisons (n = 2065 matched pairs). Durability was assessed by longitudinal recurrence of mitral regurgitation and reoperation. Compared with patients with simple disease, those undergoing repair of complex pathology were more likely to be younger and female (both P values < .0001) but with similar symptoms (P = .3). The most common repair technique was ring/band annuloplasty (3055/99% simple vs 3000/98% complex; P = .5), followed by leaflet resection (2802/90% simple vs 2249/74% complex; P < .0001). Among propensity-matched patients, recurrence of severe mitral regurgitation 10 years after repair was 6.2% for simple pathology versus 11% for complex pathology (P = .007), reoperation at 18 years was 6.3% for simple pathology versus 11% for complex pathology, and 20-year survival was 62% for simple pathology versus 61% for complex pathology (P = .6). Early surgical intervention has become more common in patients with degenerative MV disease, regardless of valve prolapse complexity or symptom status. Valve repair was associated with similarly low operative risk and time-related survival but less durability in complex disease. Lifelong annual echocardiographic surveillance after MV repair is recommended, particularly in patients with complex disease. Copyright © 2018 The American Association for Thoracic Surgery

Floppy mitral valve (FMV)/mitral valve prolapse (MVP) and the FMV/MVP syndrome: pathophysiologic mechanisms and pathogenesis of symptoms.

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Boudoulas, Konstantinos Dean; Boudoulas, Harisios

2013-01-01

Mitral valve prolapse (MVP) results from the systolic movement of a portion or segments of the mitral valve leaflets into the left atrium during left ventricular systole. It is well appreciated today that floppy mitral valve (FMV) is the central issue in the MVP and mitral valve regurgitation (MVR) story. The term FMV refers to the expansion of the area of the mitral valve leaflets with elongated chordae tendineae, chordae rupture and mitral annular dilation. FMV/MVP occurs in a heterogeneous group of patients with a wide spectrum of mitral valve involvement from mild to severe. Two types of symptoms can be defined in FMV/MVP patients. In one group of patients, symptoms are directly related to progressive MVR. In the other group, symptoms cannot be explained by the degree of MVR alone; activation of the autonomic nervous system has been implicated for the explanation of symptoms in this group of patients which is referred to as the FMV/MVP syndrome. In this brief review, the natural history, pathophysiologic mechanisms and management of patients with FMV/MVP/MVR and FMV/MVP syndrome are discussed. © 2013 S. Karger AG, Basel.

The Ross procedure offers excellent survival compared with mechanical aortic valve replacement in a real-world setting.

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Andreas, Martin; Wiedemann, Dominik; Seebacher, Gernot; Rath, Claus; Aref, Tandis; Rosenhek, Raphael; Heinze, Georg; Eigenbauer, Ernst; Simon, Paul; Ruetzler, Kurt; Hiesmayr, Joerg-Michael; Moritz, Anton; Laufer, Guenther; Kocher, Alfred

2014-09-01

The ideal prosthesis for young patients requiring aortic valve replacement has not been defined to date. Although the Ross procedure provides excellent survival, its application is still limited. We compared the long-term survival after the Ross procedure with mechanical aortic valve replacement. All consecutive Ross procedures and mechanical aortic valve replacements performed between 1991 and 2008 at a single centre were analysed. Only adult patients between 18 and 50 years of age were included in the study. Survival and valve-related complications were evaluated. Furthermore, survival was compared with the age- and sex-matched Austrian population. A total of 159 Ross patients and 173 mechanical valve patients were included. The cumulative survival for the Ross procedure was significantly better, with survival rates of 96, 94 and 93% at 5, 10 and 15 years, respectively, in comparison to 90, 84 and 75% (P Ross group but was significantly reduced in the mechanical valve group. In a real-world setting, the Ross procedure is associated with a long-term survival benefit in young adults in comparison to mechanical aortic valve replacement. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Mechanical valve at pulmonary site in adult TOF & absent pulmonary valve

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Aayush Goyal

2017-09-01

Full Text Available Absent pulmonary valve syndrome (APVS is a rare congenital heart disease. Tetralogy of Fallot (TOF with APVS is a rare variation of TOF. These patients are commonly cyanotic at birth. Respiratory complaints predominate due to airway compression by dilated pulmonary arteries. Commonest age of presentation is infancy with anecdotal adult case-reports. Surgical treatment requires establishing unobstructed competent right ventricular outflow tract (RVOT often with monocusp or conduits. We present a novel technique of rendering RVOT competent by implanting a tilting disc mechanical prosthesis in a rare adult TOF with APVS.

A global perspective on mechanical prosthetic heart valve thrombosis: Diagnostic and therapeutic challenges

Science.gov (United States)

Gürsoy, Mustafa Ozan; Kalçık, Macit; Yesin, Mahmut; Karakoyun, Süleyman; Bayam, Emrah; Gündüz, Sabahattin; Özkan, Mehmet

2016-01-01

Prosthetic valve thrombosis is one of the major causes of primary valve failure, which can be life-threatening. Multimodality imaging is necessary for determination of leaflet immobilization, cause of underlying pathology (thrombus versus pannus or both), and whether thrombolytic therapy attempt in the patient would be successful or surgery is needed. Current guidelines for the management of prosthetic valve thrombosis lack definitive class I recommendations due to lack of randomized controlled trials, and usually leave the choice of treatment to the clinician’s experience. In this review, we aimed to summarize the pathogenesis, diagnosis, and management of mechanical prosthetic valve thrombosis. PMID:28005024

Intro to Valve Guide Reconditioning. Automotive Mechanics. Valves. Instructor's Guide [and] Student Guide.

Science.gov (United States)

Horner, W.

This instructional package, one in a series of individualized instructional units on tools and techniques for repairing worn valve guides in motor vehicles, provides practical experience for students in working on cylinder heads. Covered in the module are reaming valve guides that are oversized to match a new oversized valve, reaming valve guides…

Mechanics of the pulmonary valve in the aortic position

NARCIS (Netherlands)

Soares, A.L.F.; Geemen, van D.; Bogaerdt, van den A.J.; Oomens, C.W.J.; Bouten, C.V.C.; Baaijens, F.P.T.

2014-01-01

Mathematical models can provide valuable information to assess and evaluate the mechanical behavior and remodeling of native tissue. A relevant example when studying collagen remodeling is the Ross procedure because it involves placing the pulmonary autograft in the more demanding aortic valve

Gasoline New Timing and Flux Adjustable Rotary Valve Design (Hereinafter: Rotary Valve

Directory of Open Access Journals (Sweden)

Du huiqi

2016-01-01

Full Text Available Conventional gasoline engine with an umbrella valve control cylinder intake and exhaust, in order to achieve sealing effect, the valve is driven by the spring force; at the same time, when the cam opens the valve to overcome the spring force acting. Sealing the better, the more power consumed in the engine mechanical losses, the valve mechanism consumes about 30%, which is not a small loss! This article describes a new type of rotary valve is to significantly reduce mechanical losses, so as to achieve energy saving purposes.

Clinical Implication of Transaortic Mitral Pannus Removal During Repeat Cardiac Surgery for Patients With Mechanical Mitral Valve.

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Park, Byungjoon; Sung, Kiick; Park, Pyo Won

2018-01-25

This study aimed to evaluate the safety and feasibility of transaortic mitral pannus removal (TMPR).Methods and Results:Between 2004 and 2016, 34 patients (median age, 57 years; 30 women) with rheumatic disease underwent pannus removal on the ventricular side of a mechanical mitral valve through the aortic valve during reoperation. The median time interval from the previous surgery was 14 years. TMPR was performed after removal of the mechanical aortic valve (n=21) or diseased native aortic valve (n=11). TMPR was performed in 2 patients through a normal aortic valve. The mitral transprosthetic mean pressure gradient (TMPG) was ≥5 mmHg in 11 patients, including 3 with prosthetic valve malfunction. Prophylactic TMPR was performed in 23 patients. There were no early deaths. Concomitant operations included 22 tricuspid valve surgeries (13 replacements, 15 repairs) and 32 aortic valve replacements (24 repeats, 8 primary). The mean gradient in patients who had mitral TMPG ≥5 mmHg was significantly decreased from 6.46±1.1 to 4.37±1.17 mmHg at discharge (Ppannus overgrowth in such valves.

MECHANICAL HEART-VALVE PROSTHESES - SOUND LEVEL AND RELATED COMPLAINTS

NARCIS (Netherlands)

LAURENS, RRP; WIT, HP; EBELS, T

In a randomised study, we investigated the sound production of mechanical heart valve prostheses and the complaints related to this sound. The CarboMedics, Bjork-Shiley monostrut and StJude Medical prostheses were compared. A-weighted levels of the pulse-like sound produced by the prosthesis were

Haemodynamic improvement of older, previously replaced mechanical mitral valves by removal of the subvalvular pannus in redo cardiac surgery.

Science.gov (United States)

Kim, Jong Hun; Kim, Tae Youn; Choi, Jong Bum; Kuh, Ja Hong

2017-01-01

Patients requiring redo cardiac surgery for diseased heart valves other than mitral valves may show increased pressure gradients and reduced valve areas of previously placed mechanical mitral valves due to subvalvular pannus formation. We treated four women who had mechanical mitral valves inserted greater than or equal to 20 years earlier and who presented with circular pannus that protruded into the lower margin of the valve ring but did not impede leaflet motion. Pannus removal improved the haemodynamic function of the mitral valve. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Time-resolved particle image velocimetry and laser doppler anemometry study of the turbulent flow field of bileaflet mechanical mitral prostheses.

Science.gov (United States)

Akutsu, Toshinosuke; Fukuda, Takamasa

2005-01-01

Dynamic particle image velocimetry (PIV) was applied to the study of the flow field associated with prosthetic heart valves. The results were compared with those of laser Doppler anemometry (LDA). Anatomically and antianatomically oriented Jyros (JR) and St. Jude Medical (SJM) valves were compared in the mitral position to study the effects of valve design on the downstream flow field. The experimental program used a dynamic PIV system utilizing high-speed, high-resolution video to map the true time-resolved velocity field inside the simulated ventricle. This system was complemented by a study using the more traditional LDA system for comparison. Based on the experimental data, the following general conclusions can be made. High-resolution dynamic PIV can capture true chronological changes in the velocity and turbulence fields. It also produces very detailed velocity and turbulence information comparable to the LDA results. In the vertical measuring plane that passes both the center of the aortic and mitral valves (A-A section), the two valves (the SJM and the JR) show distinct circulatory flow patterns when the valve is installed in the antianatomical orientation. Small differences in valve design can generate noticeable differences, particularly during the accelerating flow phase. The SJM valve maintains a relatively high velocity through the central orifice; the curved leaflets of the JR valve generate higher velocities with a divergent flow during the accelerating and peak flow phases. In the velocity field directly below the mitral valve and normal to the previous measuring plane (B-B section), where characteristic differences in valve design will be visible, symmetrical twin circulations were observed because of the divergent nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation. The SJM valve, with a central downward flow near the valve, is contrasted with the JR valve, which has a peripheral downward

Shelf-life of bioprosthetic heart valves: a structural and mechanical study.

Science.gov (United States)

Julien, M; Létouneau, D R; Marois, Y; Cardou, A; King, M W; Guidoin, R; Chachra, D; Lee, J M

1997-04-01

This study was undertaken to evaluate the influence of storage conditions on the shelf-life of porcine bioprosthetic valves. Fifty-five unimplanted porcine bioprostheses have been evaluated. The valves were stored in 0.5% buffered glutaraldehyde solution for different periods of time (7, 23 and 32 months). Twenty-eight valves were refrigerated while the remaining valves were stored at room temperature. The pH of the glutaraldehyde solution at room temperature decreased with time of storage, while that kept in the refrigerator remained stable over the course of the study. Macroscopic observations showed that the valve tissues kept at room temperature, especially for the periods of 23 and 32 months, became darker and more yellow in colour, whereas the refrigerated specimens exhibited no such changes in appearance. Scanning electron microscopy analysis revealed no noticeable differences on the surfaces of the leaflets stored under different conditions. Mechanical tests, including stress-strain response, stress relaxation and fracture behaviour, were carried out. Analysis of variance showed that the storage temperature, but not the length of storage, had a significant effect on some mechanical properties. The stress relaxation at 1000 s (P = 0.05), the ultimate tensile strength (P = 0.01) and the strain at fracture (P = 0.04) were all higher after storage at room temperature compared to the results after refrigeration. No statistically significant changes in the denaturation temperature of the collagen were observed between the different storage conditions. In conclusion, the storage temperature appears to have some influence on the bioprosthetic tissue. The bioprostheses stored under ambient conditions experience changes which may influence their longterm in vivo performance.

Consequence of patient substitution of nattokinase for warfarin after aortic valve replacement with a mechanical prosthesis.

Science.gov (United States)

Elahi, Maqsood M; Choi, Charles H; Konda, Subbareddy; Shake, Jay G

2015-01-01

This report describes a patient's self-substitution of nattokinase for the vitamin K antagonist warfarin after aortic valve replacement with a mechanical prosthesis. Nattokinase is an enzyme derived from a popular fermented soybean preparation in Japan (natto), which has fibrinolytic properties and is gaining popularity in nontraditional health journals and nonmedical health websites as an over-the-counter thrombolytic. After nearly a year of use of nattokinase without warfarin, the patient developed thrombus on the mechanical valve and underwent successful repeat valve replacement. We believe this is the first documented case of nattokinase being used as a substitute for warfarin after valve replacement, and we strongly discourage its use for this purpose.

Antiplatelet and anticoagulation regimen in patients with mechanical valve undergoing PCI - State-of-the-art review.

Science.gov (United States)

Gajanana, Deepakraj; Rogers, Toby; Iantorno, Micaela; Buchanan, Kyle D; Ben-Dor, Itsik; Pichard, Augusto D; Satler, Lowell F; Torguson, Rebecca; Okubagzi, Petros G; Waksman, Ron

2018-04-02

A common clinical dilemma regarding treatment of patients with a mechanical valve is the need for concomitant antiplatelet therapy for a variety of reasons, referred to as triple therapy. Triple therapy is when a patient is prescribed aspirin, a P2Y12 antagonist, and an oral anticoagulant. Based on the totality of the available evidence, best practice in 2017 for patients with mechanical valves undergoing percutaneous coronary intervention (PCI) is unclear. Furthermore, the optimal duration of dual antiplatelet therapy after PCI is evolving. With better valve designs that are less thrombogenic, the thromboembolic risks can be reduced at a lower international normalized ratio target, thus decreasing the bleeding risk. This review will offer an in-depth survey of current guidelines, current evidence, suggested approach for PCI in this cohort, and future studies regarding mechanical valve patients undergoing PCI. Copyright © 2017 Elsevier B.V. All rights reserved.

Aortic valve replacement and the stentless Freedom SOLO valve

NARCIS (Netherlands)

Wollersheim, L.W.L.M.

2016-01-01

Aortic valve stenosis has become the most prevalent valvular heart disease in Europe and North America, and is generally caused by age-related calcification of the aortic valve. For most patients, severe symptomatic aortic stenosis needs effective mechanical relief in the form of valve replacement

[Coupled Analysis of Fluid-Structure Interaction of a Micro-Mechanical Valve for Glaucoma Drainage Devices].

Science.gov (United States)

Siewert, S; Sämann, M; Schmidt, W; Stiehm, M; Falke, K; Grabow, N; Guthoff, R; Schmitz, K-P

2015-12-01

Glaucoma is the leading cause of irreversible blindness worldwide. In therapeutically refractory cases, alloplastic glaucoma drainage devices (GDD) are being increasingly used to decrease intraocular pressure. Current devices are mainly limited by fibrotic encapsulation and postoperative hypotension. Preliminary studies have described the development of a glaucoma microstent to control aqueous humour drainage from the anterior chamber into the suprachoroidal space. One focus of these studies was on the design of a micro-mechanical valve placed in the anterior chamber to inhibit postoperative hypotension. The present report describes the coupled analysis of fluid-structure interaction (FSI) as basis for future improvements in the design micro-mechanical valves. FSI analysis was carried out with ANSYS 14.5 software. Solid and fluid geometry were combined in a model, and the corresponding material properties of silicone (Silastic Rx-50) and water at room temperature were assigned. The meshing of the solid and fluid domains was carried out in accordance with the results of a convergence study with tetrahedron elements. Structural and fluid mechanical boundary conditions completed the model. The FSI analysis takes into account geometric non-linearity and adaptive remeshing to consider changing geometry. A valve opening pressure of 3.26 mmHg was derived from the FSI analysis and correlates well with the results of preliminary experimental fluid mechanical studies. Flow resistance was calculated from non-linear pressure-flow characteristics as 8.5 × 10(-3) mmHg/µl  · min(-1) and 2.7 × 10(-3) mmHg/µl  · min(-1), respectively before and after valve opening pressure is exceeded. FSI analysis indicated leakage flow before valve opening, which is due to the simplified model geometry. The presented bidirectional coupled FSI analysis is a powerful tool for the development of new designs of micro-mechanical valves for GDD and may help to minimise the time and cost

Björk-Shiley convexoconcave valves: susceptibility artifacts at brain MR imaging and mechanical valve fractures.

Science.gov (United States)

van Gorp, Maarten J; van der Graaf, Yolanda; de Mol, Bas A J M; Bakker, Chris J G; Witkamp, Theo D; Ramos, Lino M P; Mali, Willem P T M

2004-03-01

To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Björk-Shiley convexoconcave (BSCC) valves. MR images of the brain were obtained in 58 patients with prosthetic heart valves: 20 patients had BSCC valve replacements, and 38 had other types of heart valves. Two experienced neuroradiologists determined the presence or absence of susceptibility artifacts in a consensus reading. Artifacts were defined as characteristic black spots that were visible on T2*-weighted gradient-echo MR images. The statuses of the 20 explanted BSCC valves-specifically, whether they were intact or had an outlet strut fracture (OSF) or a single-leg fracture (SLF)-had been determined earlier. Number of artifacts seen at brain MR imaging was correlated with explanted valve status, and differences were analyzed with nonparametric statistical tests. Significantly more patients with BSCC valves (17 [85%] of 20 patients) than patients with other types of prosthetic valves (18 [47%] of 38 patients) had susceptibility artifacts at MR imaging (P =.005). BSCC valve OSFs were associated with a significantly higher number of artifacts than were intact BSCC valves (P =.01). No significant relationship between SLF and number of artifacts was observed. Susceptibility artifacts at brain MR imaging are not restricted to patients with BSCC valves. These artifacts can be seen on images obtained in patients with various other types of fractured and intact prosthetic heart valves. Copyright RSNA, 2004

Study on a new type variable valve lift timing mechanism with a three dimensional cam; Sanjigen cam ni yoru shinkahen valve lift timing kiko ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Ogura, M; Song, C [Nippon Institute of Technology, Saitama (Japan)

1997-10-01

The variable valve timing mechanism was invented to get a torque band at wide engine speed, and to reduce a compression job and pumping loss by a miler cycle at partial load. In this paper, the new type variable valve timing mechanism applying a three dimensional cam was proposed. Also, the feature of mechanism and the control system was done obviously. Further, about a miler cycle, a thermodynamics -like consideration was described. 5 refs., 8 figs.

Aortic valve insufficiency in the teenager and young adult: the role of prosthetic valve replacement.

Science.gov (United States)

Bradley, Scott M

2013-10-01

The contents of this article were presented in the session "Aortic insufficiency in the teenager" at the congenital parallel symposium of the 2013 Society of Thoracic Surgeons (STS) annual meeting. The accompanying articles detail the approaches of aortic valve repair and the Ross procedure.(1,2) The current article focuses on prosthetic valve replacement. For many young patients requiring aortic valve surgery, either aortic valve repair or a Ross procedure provides a good option. The advantages include avoidance of anticoagulation and potential for growth. In other patients, a prosthetic valve is an appropriate alternative. This article discusses the current state of knowledge regarding mechanical and bioprosthetic valve prostheses and their specific advantages relative to valve repair or a Ross procedure. In current practice, young patients requiring aortic valve surgery frequently undergo valve replacement with a prosthetic valve. In STS adult cardiac database, among patients ≤30 years of age undergoing aortic valve surgery, 34% had placement of a mechanical valve, 51% had placement of a bioprosthetic valve, 9% had aortic valve repair, and 2% had a Ross procedure. In the STS congenital database, among patients 12 to 30 years of age undergoing aortic valve surgery, 21% had placement of a mechanical valve, 18% had placement of a bioprosthetic valve, 30% had aortic valve repair, and 24% had a Ross procedure. In the future, the balance among these options may be altered by design improvements in prosthetic valves, alternatives to warfarin, the development of new patch materials for valve repair, and techniques to avoid Ross autograft failure.

The analysis of actuating mechanism and review of concepts for the vortex valve

International Nuclear Information System (INIS)

Park, Jong Kyun; Sim, Yun Seop; Joung, Sae Won; Lee, Ki Young; Lee, Jun; Kim, Young In

1995-12-01

To understand the basic features of the passive fluidic device, which is increasing available core cooling water from the safety injection tanks in the KNGR, review of the existing vortex valves concepts and analysis of the actuating mechanism of them have been performed and the results are as following: * Preliminary methodology development for parallel two water columns behavior, which is similar to the SIT valve actuation condition * Preliminary methodology for the vortex value actuation features * Analysis of the parallel water columns behavior and vortex valve actuation features using the results of above activities * Further works to be done in the analytical methodology. 16 figs., 2 refs. (Author) .new

Survival comparison of the Ross procedure and mechanical valve replacement with optimal self-management anticoagulation therapy: propensity-matched cohort study.

Science.gov (United States)

Mokhles, M Mostafa; Körtke, Heinrich; Stierle, Ulrich; Wagner, Otto; Charitos, Efstratios I; Bogers, Ad J J C; Gummert, Jan; Sievers, Hans-Hinrich; Takkenberg, Johanna J M

2011-01-04

It is suggested that in young adults the Ross procedure results in better late patient survival compared with mechanical prosthesis implantation. We performed a propensity score-matched study that assessed late survival in young adult patients after a Ross procedure versus that after mechanical aortic valve replacement with optimal self-management anticoagulation therapy. We selected 918 Ross patients and 406 mechanical valve patients 18 to 60 years of age without dissection, aneurysm, or mitral valve replacement who survived an elective procedure (1994 to 2008). With the use of propensity score matching, late survival was compared between the 2 groups. Two hundred fifty-three patients with a mechanical valve (mean follow-up, 6.3 years) could be propensity matched to a Ross patient (mean follow-up, 5.1 years). Mean age of the matched cohort was 47.3 years in the Ross procedure group and 48.0 years in the mechanical valve group (P=0.17); the ratio of male to female patients was 3.2 in the Ross procedure group and 2.7 in the mechanical valve group (P=0.46). Linearized all-cause mortality rate was 0.53% per patient-year in the Ross procedure group compared with 0.30% per patient-year in the mechanical valve group (matched hazard ratio, 1.86; 95% confidence interval, 0.58 to 5.91; P=0.32). Late survival was comparable to that of the general German population. In comparable patients, there is no late survival difference in the first postoperative decade between the Ross procedure and mechanical aortic valve implantation with optimal anticoagulation self-management. Survival in these selected young adult patients closely resembles that of the general population, possibly as a result of highly specialized anticoagulation self-management, better timing of surgery, and improved patient selection in recent years.

A study on the improvement of the load pressure feedback mechanism of the proportional pressure control valve

International Nuclear Information System (INIS)

Oh, In Ho; Jang, Ji Seong; Lee, Ill Yeong; Chung, Dai Jong; Cho, Sung Hyun

1999-01-01

The proportional pressure control valve having versatile functions and higher performance is an essential component in the open loop controlled rear wheel steering gear of the four wheel steering system on a passenger car. In this study, the authors suggest a new type of load pressure feedback mechanism which can make it easy change the control range of load pressure without changing the capacity of solenoid. The concept of the suggested mechanism, composed of the pressure chamber with throttles in series, was described. The mathematical model was derived from the rear wheel steering gear system consisting of a valve and a cylinder for the purpose of analyzing the valve characteristics. And the programme for computing the characteristic of the valve was developed. Experiments were carried out to confirm the performance of the valve and computations were performed to ascertain the usefulness of the developed programme. The results from the computations fairly coincide with those from the experiments. The results from the experiments and computations show that the performance of new valve is as good as that of the already developed one and the new valve has an advantage in the easiness in varying the control range of load pressure

Recommendations for the anticoagulation of pregnant patients with mechanical heart valves

NARCIS (Netherlands)

Schapkaitz, Elise; Jacobson, Barry Frank; Manga, Pravin; Chitsike, Rufaro Saeed; Benade, Estee; Haas, Sylvia; Buller, Harry R.

2015-01-01

The management of pregnant patients with mechanical heart valves remains challenging because there are no large randomised studies to provide guidelines for effective anticoagulant therapy. Both vitamin K antagonists and heparins may be associated with maternal and foetal adverse events. The

Anticoagulation in pregnant females with mechanical heart valves

International Nuclear Information System (INIS)

Shafique, H.; Chaudhry, A.; Ayyub, M.

2006-01-01

To evaluate the complications and outcome of anticoagulation therapy in pregnant females with valvular heart diseases. All pregnant females with prosthetic heart valves admitted in Armed Forces Institute of Cardiology from Jan 2004 to Dec 2004 were included in this study Basic demographic data including age, duration of pregnancy and complications observed were recorded. Warfarin was replaced with un-fractionated heparin (UFH) in first trimester and after that warfarin was continued with a targeted INR between 2.0-3.0. At 36 weeks warfarin was stopped and UFH was added; however, if patient went into spontaneous labour before this then immediate caesarian section was performed and UFH was restarted 4-6 hours after delivery along with oral warfarin. Out of 21 patients, sixteen (76.1%) had mitral valve diseases and five (23.9%) had both mitral and atrial. Majority (42.3%)of patients were in age group 26-30 years. Eleven (52.2%) reported in 9th month of gestation. Complications observed were hypertension (1), transient ischaemic attacks (1), pulmonary embolism (1), haemoptysis (1) and abortion (1). All patients, except one had successful completion of pregnancy. No case of foetal abnormality was seen. In 76% patients, daily dose of warfarin was <5 mg. Thrombo-prophylaxis in pregnancy with warfarin and UFH with an INR of 2.0-3.0 is effective in preventing thrombotic complications in females with mechanical valves without resulting in increase hemorrhagic complications. (author)

Rapid 3D printing of anatomically accurate and mechanically heterogeneous aortic valve hydrogel scaffolds

International Nuclear Information System (INIS)

Hockaday, L A; Kang, K H; Colangelo, N W; Cheung, P Y C; Duan, B; Wu, J; Bonassar, L J; Butcher, J T; Malone, E; Lipson, H; Girardi, L N; Chu, C C

2012-01-01

The aortic valve exhibits complex three-dimensional (3D) anatomy and heterogeneity essential for the long-term efficient biomechanical function. These are, however, challenging to mimic in de novo engineered living tissue valve strategies. We present a novel simultaneous 3D printing/photocrosslinking technique for rapidly engineering complex, heterogeneous aortic valve scaffolds. Native anatomic and axisymmetric aortic valve geometries (root wall and tri-leaflets) with 12–22 mm inner diameters (ID) were 3D printed with poly-ethylene glycol-diacrylate (PEG-DA) hydrogels (700 or 8000 MW) supplemented with alginate. 3D printing geometric accuracy was quantified and compared using Micro-CT. Porcine aortic valve interstitial cells (PAVIC) seeded scaffolds were cultured for up to 21 days. Results showed that blended PEG-DA scaffolds could achieve over tenfold range in elastic modulus (5.3±0.9 to 74.6±1.5 kPa). 3D printing times for valve conduits with mechanically contrasting hydrogels were optimized to 14 to 45 min, increasing linearly with conduit diameter. Larger printed valves had greater shape fidelity (93.3±2.6, 85.1±2.0 and 73.3±5.2% for 22, 17 and 12 mm ID porcine valves; 89.1±4.0, 84.1±5.6 and 66.6±5.2% for simplified valves). PAVIC seeded scaffolds maintained near 100% viability over 21 days. These results demonstrate that 3D hydrogel printing with controlled photocrosslinking can rapidly fabricate anatomical heterogeneous valve conduits that support cell engraftment. (paper)

Role of vortices in cavitation formation in the flow across a mechanical heart valve.

Science.gov (United States)

Li, Chi-Pei; Lu, Po-Chien; Liu, Jia-Shing; Lo, Chi-Wen; Hwang, Ned H

2008-07-01

Cavitation occurs during mechanical heart valve closure when the local pressure drops below vapor pressure. The formation of stable gas bubbles may result in gaseous emboli, and secondarily cause transient ischemic attacks or strokes. It is noted that instantaneous valve closure, occluder rebound and high-speed leakage flow generate vortices that promote low-pressure regions in favor of stable bubble formation; however, to date no studies have been conducted for the quantitative measurement and analysis of these vortices. A Björk-Shiley Monostrut (BSM) monoleaflet valve was placed in the mitral position of a pulsatile mock circulatory loop. Particle image velocimetry (PIV) and pico coulomb (PCB) pressure measurements were applied. Flow field measurements were carried out at t = -5, -3, -1, -0.5, 0 (valve closure), 0.3, 0.5, 0.75, 1.19, 1.44, 1.69, 1.94, 2, 2.19, 2.54, 2.79, 3.04, 3.29, 3.54, 5 and 10 ms. The vortices were quantitatively analyzed using the Rankine vortex model. A single counter-clockwise vortex was The instantaneous formation of cavitation bubbles at mechanical heart valve (MHV) closure, which subsequently damage blood cells and valve integrity, is a well-known and widely studied phenomenon (1-4). Contributing factors seem to include the water-hammer, squeeze flow and Venturi effects, all of which are short-lived. Both, Dauzat et al. (5) and Sliwka et al. (6) have detected high-intensity transient signals (HITS) with transcranial Doppler ultrasound in the carotid and cerebral arteries of MHV recipients, while Deklunder (7) observed clinical occurrences of cerebral gas emboli that were not seen with bioprosthetic valves. These detected over the major orifice, while a pair of counter-rotating vortices was found over the minor orifice. Velocity profiles were consistent with Rankine vortices. The vortex strength and magnitude of the pressure drop peaked shortly after initial occluder-housing impact and rapidly decreased after 0.5 ms, indicating viscous

Bioprinting a cardiac valve.

Science.gov (United States)

Jana, Soumen; Lerman, Amir

2015-12-01

Heart valve tissue engineering could be a possible solution for the limitations of mechanical and biological prostheses, which are commonly used for heart valve replacement. In tissue engineering, cells are seeded into a 3-dimensional platform, termed the scaffold, to make the engineered tissue construct. However, mimicking the mechanical and spatial heterogeneity of a heart valve structure in a fabricated scaffold with uniform cell distribution is daunting when approached conventionally. Bioprinting is an emerging technique that can produce biological products containing matrix and cells, together or separately with morphological, structural and mechanical diversity. This advance increases the possibility of fabricating the structure of a heart valve in vitro and using it as a functional tissue construct for implantation. This review describes the use of bioprinting technology in heart valve tissue engineering. Copyright © 2015 Elsevier Inc. All rights reserved.

Aortic root surgery in Marfan syndrome: Bentall procedure with the composite mechanical valved conduit versus aortic valve reimplantation with Valsalva graft.

Science.gov (United States)

Nardi, Paolo; Pellegrino, Antonio; Versaci, Francesco; Mantione, Ludmilla; Polisca, Patrizio; Iorio, Fiore S; Chiariello, Luigi

2010-09-01

The aim of the study is to compare mid-term results of Bentall aortic root replacement with composite mechanical valved conduit and aortic valve reimplantation procedure using the Valsalva graft for the treatment of aortic root aneurysm in patients with Marfan syndrome. We retrospectively compared data of 23 patients (mean age 38 + or - 14 years) who had undergone the Bentall procedure (group B) to those of 24 patients (mean age 36 + or - 12 years) who had undergone aortic valve reimplantation (group R) during a 14-year period. Follow-up (mean duration 65 + or - 44 months) was 100% complete. There were no operative deaths in either group. In group B, as compared with group R, preoperative aortic insufficiency (3.2 + or - 1.1/4 vs. 1.7 + or - 1.4/4, P Marfan patients, the Bentall procedure is associated with excellent mid-term outcome. The reimplantation technique, adopted for less dilated aortas, provides similarly satisfactory results. The Valsalva graft seems, with time, to allow a stable aortic valve function.

Mechanisms of valve competency after mitral valve annuloplasty for ischaemic mitral regurgitation using the Geoform ring: insights from three-dimensional echocardiography.

Science.gov (United States)

Armen, Todd A; Vandse, Rashmi; Crestanello, Juan A; Raman, Subha V; Bickle, Katherine M; Nathan, Nadia S

2009-01-01

Left ventricular remodelling leads to functional mitral regurgitation resulting from annular dilatation, leaflet tethering, tenting, and decreased leaflet coaptation. Mitral valve annuloplasty restores valve competency, improving the patient's functional status and ventricular function. This study was designed to evaluate the mechanisms underlying mitral valve competency after the implantation of a Geoform annuloplasty ring using three-dimensional (3D) echocardiography. Seven patients (mean age of 65 years) with ischaemic mitral regurgitation underwent mitral valve annuloplasty with the Geoform ring and coronary artery bypass surgery. Pre- and post-operative 3D echocardiograms were performed. Following mitral annuloplasty, mitral regurgitation decreased from 3.4+/-0.2 to 0.9+/-0.3 (P-value<0.0001), mitral valve tenting volume from 13+/-1.7 to 3.2+/-0.3 mL (P-value<0.001), annulus area from 12.6+/-1.0 to 3.3+/-0.2 cm2 (P-value<0.0001), valve circumference from 13+/-0.5 to 7.3+/-0.3 cm (P-value<0.0001), septolateral distance from 2.1+/-0.1 to 1.4+/-0.06 cm (P-value<0.01) and intercommissural distance from 3.4+/-0.1 to 2.7+/-0.03 cm (P-value<0.03). There was significant decrease in the septolateral distance at the level of A2-P2 with respect to other regions. These geometric changes were associated with the improvement in the NYHA class from 3.1+/-0.3 to 1.3+/-0.3 (P-value<0.002). The mitral valve annuloplasty with the Geoform ring restores leaflet coaptation and eliminates mitral regurgitation by effectively modifying the mitral annular geometry.

Study on Friction and Wear Characteristics of Aluminum Alloy Hydraulic Valve Body and Its Antiwear Mechanism

Directory of Open Access Journals (Sweden)

Rong Li

2017-03-01

Full Text Available In order for the working status of the aluminum alloyed hydraulic valve body to be controlled in actual conditions, a new friction and wear design device was designed for the cast iron and aluminum alloyed valve bodies comparison under the same conditions. The results displayed that: (1 The oil leakage of the aluminum alloyed hydraulic valve body was higher than the corresponding oil leakage of the iron body during the initial running stage. Besides during a later running stage, the oil leakage of the aluminum alloyed body was lower than corresponding oil leakage of the iron body; (2 The actual oil leakage of different materials consisted of two parts: the foundation leakage that was the leakage of the valve without wear and wear leakage that was caused by the worn valve body; (3 The aluminum alloyed valve could rely on the dust filling furrow and melting mechanism that led the body surface to retain dynamic balance, resulting in the valve leakage preservation at a low level. The aluminum alloy modified valve body can meet the requirements of hydraulic leakage under pressure, possibly constituting this alloy suitable for hydraulic valve body manufacturing.

Guide to prosthetic cardiac valves

International Nuclear Information System (INIS)

Morse, D.; Steiner, R.M.; Fernandez, J.

1985-01-01

This book contains 10 chapters. Some of the chapter titles are: The development of artificial heart valves: Introduction and historical perspective; The radiology of prosthetic heart valves; The evaluation of patients for prosthetic valve implantation; Pathology of cardiac valve replacement; and Bioengineering of mechanical and biological heart valve substitutes

Ventricular Pacing via the Coronary Sinus in a Patient with a Mechanical Tricuspid Valve Prosthesis

Directory of Open Access Journals (Sweden)

Janice Swampillai, MD

2011-01-01

Full Text Available Implantation of a transvenous endocardial pacing lead in the right ventricle is contra-indicated after mechanical tricuspid valve replacement; therefore a surgical approach to the epicardium is usually required. This case report describes ventricular pacing via a branch of the coronary sinus in a patient with mechanical mitral, aortic and tricuspid valve replacements. In conclusion, this approach is minimally invasive, provides effective ventricular stimulation with low pacing threshold and stable lead position, and is a feasible option when transvenous right ventricular pacing is not possible.

Mechanical valve assembly for xenon 133 gas delivery systems

Energy Technology Data Exchange (ETDEWEB)

Round, W.H. (Royal Brisbane Hospital, Herston (Australia))

Some gas delivery systems used in pulmonary ventilation scanning are unable to satisfactorily supply /sup 133/Xe gas to bed-ridden patients. A mechanical gas valve assembly to control the flow of gas in such systems was constructed. A commercially produced /sup 133/Xe gas delivery system when fitted with the new assembly was able to ventilate almost all patients whereas previously this could be achieved with approximately only 50% of patients.

Characteristic analysis of servo valve

International Nuclear Information System (INIS)

Ko, J. H.; Ryu, D. R.; Lee, J. H.; Kim, Y. S.; Na, J. C.; Kim, D. S.

2008-01-01

Electro-pneumatic servo valve is an electro-mechanical device which converts electric signals into a proper pneumatic flow rate or pressure. In order to improve the overall performance of pneumatic servo systems, electro-pneumatic servo valves are required, which have fast dynamic characteristics, no air leakage at a null point, and can be fabricated at a low-cost. The first objective of this research is to design and to fabricate a new electro-pneumatic servo valve which satisfies the above-mentioned requirements. In order to design the mechanism of the servo valve optimally, the flow inside the valve depending upon the position of spool was analyzed variously, and on the basis of such analysis results, the valve mechanism, which was formed by combination of the spool and the sleeve, was designed and manufactured. And a tester for conducting an overall performance test was designed and manufactured, and as a result of conducting the flow rate test, the pressure test and the frequency test on the developed pneumatic servo valve

Small valve area index: its influence on early mortality after mitral valve replacement

NARCIS (Netherlands)

Yazdanbakhsh, A. P.; van den Brink, R. B.; Dekker, Egbert; de Mol, B. A.

2000-01-01

OBJECTIVE: To test the hypothesis that mitral valve prosthesis-patient mismatch increases postoperative mortality. METHODS AND RESULTS: The effect of mitral valve prosthesis-patient mismatch on survival in a cohort of consecutive patients after mitral valve replacement with a mechanical prosthesis

Coronary Emboli in a Young Patient with Mechanical Aortic Valve: A Rare Cause of Acute Myocardial Infarction

Directory of Open Access Journals (Sweden)

Arash Gholoobi

2016-03-01

Full Text Available Coronary artery embolism is an uncommon cause of Acute Myocardial Infarction (AMI. Herein, we reported a 24-year-old male who was admitted with acute infero-posterior myocardial infarction and cerebral Transient Ischemic Attack (TIA. He had undergone mechanical Aortic Valve Replacement (AVR surgery 6 years ago. Surprisingly, the patient had decided to stop taking his medication (warfarin 20 days earlier without any medical advice. Coronary angiography revealed a thrombus located at the distal part of the left circumflex artery. Discontinuation of anticoagulant therapy in the presence of mechanical valve prosthesis, clinical evidence of coincidental TIA, and lack of atherosclerotic risk factors were highly suggestive of coronary thromboembolism as the cause of AMI. Overall, this case report emphasized the necessity of continuous education in patients with mechanical heart valves to prevent such undesired events.

Velocity and shear stress distribution downstream of mechanical heart valves in pulsatile flow.

Science.gov (United States)

Giersiepen, M; Krause, U; Knott, E; Reul, H; Rau, G

1989-04-01

Ten mechanical valves (TAD 27 mm): Starr-Edwards Silastic Ball, Björk-Shiley Standard, Björk-Shiley Concave-Convex, Björk-Shiley Monostrut, Hall-Kaster (Medtronic-Hall), OmniCarbon, Bicer Val, Sorin, Saint-Jude Medical and Hemex (Duromedics) are investigated in a comparative in vitro study. The velocity and turbulent shear stress profiles of the valves were determined by Laser Doppler anemometry in two different downstream axes within a model aortic root. Depending on the individual valve design, velocity peaks up to 1.5 m/s and turbulent shear stress peaks up to 150 N/m2 were measured during the systolic phase. These shear stress peaks mainly occurred in areas of flow separation and intense momentum exchange. Directly downstream of the valves (measuring axis 0.55.dAorta) turbulent shear stress peaks occurred at peak systole and during the deceleration phase, while in the second measuring axis (1.5.dAorta) turbulence levels were lower. Shear stress levels were high at the borders of the fluid jets. The results are discussed from a fluid-dynamic point of view.

A rare case of prosthetic endocarditis and dehiscence in a mechanical valved conduit.

Science.gov (United States)

Kannan, Arun; Smith, Cristy; Subramanian, Sreekumar; Janardhanan, Rajesh

2014-02-07

A middle-aged adult patient with a history of aortic root replacement with a mechanical valved conduit and remote chest trauma was referred to our institution with prosthetic endocarditis. Transoesophageal echocardiogram at our institution confirmed a near-complete dehiscence of the prosthetic aortic valve from the conduit, with significant perivalvular flow forming a pseudoaneurysm. The patient underwent a high-risk re-operation, involving redo aortic root replacement with a homograft after extensive debridement of the infected tissue. The patient was discharged to an outside facility after an uncomplicated hospital course, and remains stable.

Experimental investigations on the fluid-mechanics of an electrospun heart valve by means of particle image velocimetry.

Science.gov (United States)

Del Gaudio, Costantino; Gasbarroni, Pier Luca; Romano, Giovanni Paolo

2016-12-01

End-stage failing heart valves are currently replaced by mechanical or biological prostheses. Both types positively contribute to restore the physiological function of native valves, but a number of drawbacks limits the expected performances. In order to improve the outcome, tissue engineering can offer an alternative approach to design and fabricate innovative heart valves capable to support the requested function and to promote the formation of a novel, viable and correctly operating physiological structure. This potential result is particularly critical if referred to the aortic valve, being the one mainly exposed to structural and functional degeneration. In this regard, the here proposed study presents the fabrication and in vitro characterization of a bioresorbable electrospun heart valve prosthesis using the particle image velocimetry technique either in physiological and pathological fluid dynamic conditions. The scaffold was designed to reproduce the aortic valve geometry, also mimicking the fibrous structure of the natural extracellular matrix. To evaluate its performances for possible implantation, the flow fields downstream the valve were accurately investigated and compared. The experimental results showed a correct functionality of the device, supported by the formation of vortex structures at the edge of the three cusps, with Reynolds stress values below the threshold for the risk of hemolysis (which can be comprised in the range 400-4000N/m(2) depending on the exposure period), and a good structural resistance to the mechanical loads generated by the driving pressure difference. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pregnancy follow-up in a patient with mechanical valve: possible in ...

African Journals Online (AJOL)

Pregnancy follow-up in a patient with mechanical valve: possible in sub-Saharan Africa? ... Background: In Africa in general and in Cameroon in particular, post rheumatic cardiopathies are a health care problem, one of the causes of infertility in the women population and a major cause of death among children and adults.

Use of multidetector-row computed tomography scan to detect pannus formation in prosthetic mechanical aortic valves.

Science.gov (United States)

Aladmawi, Mohamed A; Pragliola, Claudio; Vriz, Olga; Galzerano, Domenico

2017-04-01

Obstruction of a mechanical aortic valve by pannus formation at the subvalvular level is a major long-term complication of aortic valve replacement (AVR). In fact, pannus is sometime difficult to differentiate from patient-prosthesis mismatch or valve thrombosis. In most cases cine-angiography and echocardiography, either transthoracic or transesophageal, cannot correctly visualize the complication when the leaflets show a normal mobility. Recent technological refinements made this difficult diagnosis possible by ECG-gated computed tomography (CT) scan which shows adequate images in 90% of the cases and can differentiate pannus from fresh and organized thrombus.

Bjork-Shiley convexoconcave valves: Susceptibility artifacts at brain MR imaging and mechanical valve fractures

NARCIS (Netherlands)

van Gorp, Maarten J.; van der Graaf, Yolanda; de Mol, Bas A. J. M.; Bakker, Chris J. G.; Witkamp, Theo D.; Ramos, Lino M. P.; Mali, Willem P. T. M.

2004-01-01

PURPOSE: To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Bjork-Shiley convexoconcave (BSCC) valves. MATERIALS AND METHODS: MR images of the brain were obtained in 58 patients with prosthetic heart

Mechanism study of freeze-valve for molten salt reactor (MSR)

International Nuclear Information System (INIS)

Qinhua, Zhang

2014-01-01

Molten salt reactor (MSR) is one of the fourth generation nuclear reactor, ordinary nuclear grade valve is unsuitable for MSR due to its special coolant and extraordinary working temperature. Freeze-valve is proposed as the most appropriate valve for MSR, but the technology issue about freeze-valve has not been report in recent decades. Its significance to test the comprehensive property of freeze-valve for the application in MSR. A high temperature molten salt test loop was built which the physics property of salt is similar to the coolant of MSR. The results indicate that freeze-valve has a good performance use in the molten salt circumstances of high temperature (max 700 deg. C) and strong corrosion (authors)

A New Type of Non-Mechanical Valves for Recirculation of Fine Particles

DEFF Research Database (Denmark)

Azizaddini, Seyednezamaddin

of the thesis is to design a new version of a non-mechanical valve for transportation of the particles and closing the loop in circulating or interconnected fluidized bed systems. As the primary proposal, combination of three assistive methods (tapered fluidized bed, mixture of coarse and fine particles...

Valve system incorporating single failure protection logic

Science.gov (United States)

Ryan, Rodger; Timmerman, Walter J. H.

1980-01-01

A valve system incorporating single failure protective logic. The system consists of a valve combination or composite valve which allows actuation or de-actuation of a device such as a hydraulic cylinder or other mechanism, integral with or separate from the valve assembly, by means of three independent input signals combined in a function commonly known as two-out-of-three logic. Using the input signals as independent and redundant actuation/de-actuation signals, a single signal failure, or failure of the corresponding valve or valve set, will neither prevent the desired action, nor cause the undesired action of the mechanism.

Pannus Formation Leads to Valve Malfunction in the Tricuspid Position 19 Years after Triple Valve Replacement.

Science.gov (United States)

Alskaf, Ebraham; McConkey, Hannah; Laskar, Nabila; Kardos, Attila

2016-06-20

The Medtronic ATS Open Pivot mechanical valve has been successfully used in heart valve surgery for more than two decades. We present the case of a patient who, 19 years following a tricuspid valve replacement with an ATS prosthesis as part of a triple valve operation following infective endocarditis, developed severe tricuspid regurgitation due to pannus formation.

Long-Term Outcomes of the Ross Procedure Versus Mechanical Aortic Valve Replacement: Propensity-Matched Cohort Study.

Science.gov (United States)

Mazine, Amine; David, Tirone E; Rao, Vivek; Hickey, Edward J; Christie, Shakira; Manlhiot, Cedric; Ouzounian, Maral

2016-08-23

The ideal aortic valve substitute in young and middle-aged adults remains unknown. We sought to compare the long-term outcomes of patients undergoing the Ross procedure and those receiving a mechanical aortic valve replacement (AVR). From 1990 to 2014, 258 patients underwent a Ross procedure and 1444 had a mechanical AVR at a single institution. Patients were matched into 208 pairs through the use of a propensity score. Mean age was 37.2±10.2 years, and 63% were male. Mean follow-up was 14.2±6.5 years. Overall survival was equivalent (Ross versus AVR: hazard ratio, 0.91, 95% confidence interval, 0.38-2.16; P=0.83), although freedom from cardiac- and valve-related mortality was improved in the Ross group (Ross versus AVR: hazard ratio, 0.22; 95% confidence interval, 0.034-0.86; P=0.03). Freedom from reintervention was equivalent after both procedures (Ross versus AVR: hazard ratio, 1.86; 95% confidence interval, 0.76-4.94; P=0.18). Long-term freedom from stroke or major bleeding was superior after the Ross procedure (Ross versus AVR: hazard ratio, 0.09; 95% confidence interval, 0.02-0.31; PRoss procedure and mechanical AVR. However, the Ross procedure was associated with improved freedom from cardiac- and valve-related mortality and a significant reduction in the incidence of stroke and major bleeding. In specialized centers, the Ross procedure represents an excellent option and should be considered for young and middle-aged adults undergoing AVR. © 2016 American Heart Association, Inc.

Morphological and mechanical properties of the posterior leaflet chordae tendineae in the mitral valve

NARCIS (Netherlands)

Lodder, J.; Verkerke, Gijsbertus Jacob; Delemarre, B.J.M.; Dodou, D.

2016-01-01

A number of studies have investigated the morphological and mechanical properties of the chordae tendineae of the mitral valve, providing comparisons between basal, marginal, and strut chordae and between chordae at the anterior and posterior leaflets. This study contributes to the literature by

Morphological and mechanical properties of the posterior leaflet chordae tendineae in the mitral valve

NARCIS (Netherlands)

Lodder, Joost; Verkerke, Gijsbertus J.; Delemarre, Ben J. M.; Dodou, Dimitra

A number of studies have investigated the morphological and mechanical properties of the chordae tendineae of the mitral valve, providing comparisons between basal, marginal, and strut chordae and between chordae at the anterior and posterior leaflets. This study contributes to the literature by

Self-management of oral anticoagulant therapy for mechanical heart valve patients

DEFF Research Database (Denmark)

Christensen, Thomas D; Attermann, Jørn; Pilegaard, Hans K

2001-01-01

.4%–2.9%) for the control group. Conclusion: Self-management of OAT is a feasible and safe concept for selected patients with mechanical heart valve prostheses also on a long-term basis. It provides at least as good and most likely better quality of anticoagulant therapy than conventional management assessed by time within......Objective: Self-management of oral anticoagulant therapy (OAT) has shown good results on a short-term basis. We hypothesize that self-management of OAT provides a better quality of treatment than conventional management also on a long-term basis. The aim of this study was to assess the quality...... of conventionally managed heart valve patients (control group) was used as reference. Results: The median observation time was 1175 days (range: 174–1428 days). The self-managed patients were within therapeutic INR target range for a mean of 78.0% (range: 36.1%–93.9%) of the time compared with 61.0% (range 37...

Echocardiographic Assessment of Heart Valve Prostheses

Science.gov (United States)

Sordelli, Chiara; Severino, Sergio; Ascione, Luigi; Coppolino, Pasquale; Caso, Pio

2014-01-01

Patients submitted to valve replacement with mechanical or biological prosthesis, may present symptoms related either to valvular malfunction or ventricular dysfunction from other causes. Because a clinical examination is not sufficient to evaluate a prosthetic valve, several diagnostic methods have been proposed to assess the functional status of a prosthetic valve. This review provides an overview of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. Compared to native valves, echocardiographic evaluation of prosthetic valves is certainly more complex, both for the examination and the interpretation. Echocardiography also allows discriminating between intra- and/or peri-prosthetic regurgitation, present in the majority of mechanical valves. Transthoracic echocardiography (TTE) requires different angles of the probe with unconventional views. Transesophageal echocardiography (TEE) is the method of choice in presence of technical difficulties. Three-dimensional (3D)-TEE seems to be superior to 2D-TEE, especially in the assessment of paravalvular leak regurgitation (PVL) that it provides improved localization and analysis of the PVL size and shape. PMID:28465917

Bioprosthetic Valve Fracture to Facilitate Transcatheter Valve-in-Valve Implantation.

Science.gov (United States)

Allen, Keith B; Chhatriwalla, Adnan K; Cohen, David J; Saxon, John T; Aggarwal, Sanjeev; Hart, Anthony; Baron, Suzanne; Davis, J Russell; Pak, Alex F; Dvir, Danny; Borkon, A Michael

2017-11-01

Valve-in-valve transcatheter aortic valve replacement is less effective in small surgical bioprostheses. We evaluated the feasibility of bioprosthetic valve fracture with a high-pressure balloon to facilitate valve-in-valve transcatheter aortic valve replacement. In vitro bench testing on aortic tissue valves was performed on 19-mm and 21-mm Mitroflow (Sorin, Milan, Italy), Magna and Magna Ease (Edwards Lifesciences, Irvine, CA), Trifecta and Biocor Epic (St. Jude Medical, Minneapolis, MN), and Hancock II and Mosaic (Medtronic, Minneapolis, MN). High-pressure balloons Tru Dilation, Atlas Gold, and Dorado (C.R. Bard, Murray Hill, NJ) were used to determine which valves could be fractured and at what pressure fracture occurred. Mitroflow, Magna, Magna Ease, Mosaic, and Biocor Epic surgical valves were successfully fractured using high-pressures balloon 1 mm larger than the labeled valve size whereas Trifecta and Hancock II surgical valves could not be fractured. Only the internal valve frame was fractured, and the sewing cuff was never disrupted. Manufacturer's rated burst pressures for balloons were exceeded, with fracture pressures ranging from 8 to 24 atmospheres depending on the surgical valve. Testing further demonstrated that fracture facilitated the expansion of previously constrained, underexpanded transcatheter valves (both balloon and self-expanding) to the manufacturer's recommended size. Bench testing demonstrates that the frame of most, but not all, bioprosthetic surgical aortic valves can be fractured using high-pressure balloons. The safety of bioprosthetic valve fracture to optimize valve-in-valve transcatheter aortic valve replacement in small surgical valves requires further clinical investigation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Surge-damping vacuum valve

International Nuclear Information System (INIS)

Bullock, J.C.; Kelley, B.E.

1977-01-01

A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve

Miniature piezo electric vacuum inlet valve

Science.gov (United States)

Keville, Robert F.; Dietrich, Daniel D.

1998-03-24

A miniature piezo electric vacuum inlet valve having a fast pulse rate and is battery operated with variable flow capability. The low power (piezo electric valves which require preloading of the crystal drive mechanism and 120 Vac, thus the valve of the present invention is smaller by a factor of three.

Characteristic analysis and experiment of pneumatic servo valve

International Nuclear Information System (INIS)

Kim, Dong Soo; Lee, Won Hee; Choi, Byung Oh

2004-01-01

Electro-pneumatic servo valve is an electro-mechanical device which converts electric signals into a proper pneumatic flow rate or pressure. In order to improve the overall performance of pneumatic servo systems, electro-pneumatic servo valves are required, which have fast dynamic characteristics, no air leakage at a null point, and can be fabricated at a low-cost. The first objective of this research is to design and to fabricate a new electro-pneumatic servo valve which satisfies the above-mentioned requirements. In order to design the mechanism of the servo valve optimally, the flow inside the valve depending upon the position of spool was analyzed variously, and on the basis of such analysis results, the valve mechanism, which was formed by combination of the spool and the sleeve, was designed and manufactured. And a tester for conducting an overall performance test was designed and manufactured, and as a result of conducting the flow rate test, the pressure test and the frequency test on the developed pneumatic servo valve

Successful thrombectomy of a stuck mechanical prosthetic mitral valve guided by perioperative transesophageal echocardiography and cinefluoroscopy

Directory of Open Access Journals (Sweden)

Paulo César Gobert Damasceno Campos

2009-03-01

Full Text Available We describe the case of a 53-year-old man with past history of rheumatic valvular disease who developed acute decompensated heart failure due to thrombosis of his mechanical mitral valve prosthesis. The diagnosis was established after a combined and complementary approach of echocardiography and cinefluoroscopy. Because of the severe heart failure at presentation, the patient was taken to surgery. The intraoperative transesophageal echocardiography was critical to guide a successful thrombectomy procedure. Postoperative pathological findings revealed the presence of thrombus and fibrotic tissue (pannus in the surgical specimens removed from the valve. The success of this case and the treatment choice are supported by the most recent literature data on prosthetic valve thrombosis. We highlight the use of three diagnostic approaches in our patient: echocardiography, cinefluoroscopy and pathology.

Modeling valve leakage

International Nuclear Information System (INIS)

Bell, S.R.; Rohrscheib, R.

1994-01-01

The American Society of Mechanical Engineers (ASME) Code requires individual valve leakage testing for Category A valves. Although the U.S. Nuclear Regulatory Commission (USNRC) has recognized that it is more appropriate to test containment isolation valves in groups, as allowed by 10 CFR 50, Appendix J, a utility seeking relief from these Code requirements must provide technical justification for the relief and establish a conservative alternate acceptance criteria. In order to provide technical justification for group testing of containment isolation valves, Illinois Power developed a calculation (model) for determining the size of a leakage pathway in a valve disc or seat for a given leakage rate. The model was verified experimentally by machining leakage pathways of known size and then measuring the leakage and comparing this value to the calculated value. For the range of values typical of leakage rate testing, the correlation between the experimental values and calculated values was quote good. Based upon these results, Illinois Power established a conservative acceptance criteria for all valves in the inservice testing (IST) program and was granted relief by the USNRC from the individual leakage testing requirements of the ASME Code. This paper presents the results of Illinois Power's work in the area of valve leakage rate testing

Guidelines for valves in tritium service

International Nuclear Information System (INIS)

Weaver, W.W.

1994-01-01

Some undesirable practices and misapplications that caused valve-related failures are examined, and future courses of action are recommended to avoid repetition of these events. Desirable valve characteristics and practices that should be considered when selecting valves for use in tritium service are also discussed. Supporting logic for the desirability of these features is presented by discussing the mechanisms of valve degradation followed by examples of related events. Desirable valve and system features and operational actions are grouped into two categories: strongly recommended and recommended. 13 refs., 1 fig

Engineering of a polymer layered bio-hybrid heart valve scaffold

Energy Technology Data Exchange (ETDEWEB)

Jahnavi, S., E-mail: jani84@gmail.com [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036, TN (India); Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Trivandrum, Kerala 695012 (India); Kumary, T.V., E-mail: tvkumary@yahoo.com [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Trivandrum, Kerala 695012 (India); Bhuvaneshwar, G.S., E-mail: gs.bhuvnesh@gmail.com [Trivitron Innovation Centre, Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, TN (India); Natarajan, T.S., E-mail: tsniit@gmail.com [Conducting Polymer laboratory, Department of Physics, Indian Institute of Technology, Madras, Chennai 600036, TN (India); Verma, R.S., E-mail: vermars@iitm.ac.in [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036, TN (India)

2015-06-01

Current treatment strategy for end stage valve disease involves either valvular repair or replacement with homograft/mechanical/bioprosthetic valves. In cases of recurrent stenosis/ regurgitation, valve replacement is preferred choice of treatment over valvular repair. Currently available mechanical valves primarily provide durability whereas bioprosthetic valves have superior tissue compatibility but both lack remodelling and regenerative properties making their utility limited in paediatric patients. With advances in tissue engineering, attempts have been made to fabricate valves with regenerative potential using various polymers, decellularized tissues and hybrid scaffolds. To engineer an ideal heart valve, decellularized bovine pericardium extracellular matrix (DBPECM) is an attractive biocompatible scaffold but has weak mechanical properties and rapid degradation. However, DBPECM can be modified with synthetic polymers to enhance its mechanical properties. In this study, we developed a Bio-Hybrid scaffold with non-cross linked DBPECM in its native structure coated with a layer of Polycaprolactone-Chitosan (PCL-CH) nanofibers that displayed superior mechanical properties. Surface and functional studies demonstrated integration of PCL-CH to the DBPECM with enhanced bio and hemocompatibility. This engineered Bio-Hybrid scaffold exhibited most of the physical, biochemical and functional properties of the native valve that makes it an ideal scaffold for fabrication of cardiac valve with regenerative potential. - Highlights: • A Bio-Hybrid scaffold was fabricated with PCL-CH blend and DBPECM. • PCL-CH functionally interacted with decellularized matrix without cross linking. • Modified scaffold exhibited mechanical properties similar to native heart valve. • Supported better fibroblast and endothelial cell adhesion and proliferation. • The developed scaffold can be utilized for tissue engineering of heart valve.

Redo mitral valve surgery

Directory of Open Access Journals (Sweden)

Redoy Ranjan

2018-03-01

Full Text Available This study is based on the findings of a single surgeon’s practice of mitral valve replacement of 167 patients from April 2005 to June 2017 who developed symptomatic mitral restenosis after closed or open mitral commisurotomy. Both clinical and color doppler echocardiographic data of peri-operative and six months follow-up period were evaluated and compared to assess the early outcome of the redo mitral valve surgery. With male-female ratio of 1: 2.2 and after a duration of 6 to 22 years symptom free interval between the redo procedures, the selected patients with mitral valve restenosis undergone valve replacement with either mechanical valve in 62% cases and also tissue valve in 38% cases. Particular emphasis was given to separate the adhered pericardium from the heart completely to ameliorate base to apex and global contraction of the heart. Besides favorable post-operative clinical outcome, the echocardiographic findings were also encouraging as there was statistically significant increase in the mitral valve area and ejection fraction with significant decrease in the left atrial diameter, pressure gradient across the mitral valve and pulmonary artery systolic pressure. Therefore, in case of inevitable mitral restenosis after closed or open commisurotomy, mitral valve replacement is a promising treatment modality.

[Tricuspid valve insufficiency: what should be done?].

Science.gov (United States)

von Segesser, L K; Stauffer, J C; Delabays, A; Chassot, P G

1998-12-01

Tricuspid regurgitation is relatively common. Due to the progress made in echocardiography, its diagnosis is in general made readily and in reliable fashion. Basically one has to distinguish between functional tricuspid valve regurgitation due to volume and/or pressure overload of the right ventricle with intact valve structures versus tricuspid valve regurgitation due to pathologic valve structures. The clear identification of the regurgitation mechanism is of prime importance for the treatment. Functional tricuspid valve regurgitation can often be improved by medical treatment of heart failure, and eventually a tricuspid valve plasty can solve the problem. However, the presence of pathologic tricuspid valve structures makes in general more specific plastic surgical procedures and even prosthetic valve replacements necessary. A typical example for a structural tricuspid valve regurgitation is the case of a traumatic papillary muscle rupture. Due to the sudden onset, this pathology is not well tolerated and requires in general surgical reinsertion of the papillary muscle. In contrast, tricuspid valve regurgitation resulting from chronic pulmonary embolism with pulmonary artery hypertension, can be improved by pulmonary artery thrombendarteriectomy and even completely cured with an additional tricuspid annuloplasty. However, tricuspid regurgitations due to terminal heart failure are not be addressed with surgery directed to tricuspid valve repair or replacement. Heart transplantation, dynamic cardiomyoplasty or mechanical circulatory support should be evaluated instead.

Use of a valve operation test and evaluation system to enhance valve reliability

International Nuclear Information System (INIS)

Lowry, D.A.

1990-01-01

Power plant owners have emphasized the need for assuring safe, reliable operation of valves. While most valves must simply open or close, the mechanisms involved can be quite complex. Motor operated valves (MOVs) must be properly adjusted to assure operability. Individual operator components determine the performance of the entire MOV. Failure in MOVs could cripple or shut down a unit. Thus, a complete valve program consisting of design reviews, operational testing, and preventive and predictive maintenance activities will enhance an owner's confidence level that his valves win operate as expected. Liberty's Valve Operation Test and Evaluation System (VOTES) accurately measures stein thrust without intruding on valve operation. Since mounting a strain gage to a valve stem is a desirable but impractical way of obtaining precise stem thrust, Liberty developed a method to obtain identical data by placing a strain gage sensor on the valve yoke. VOTES provides information which effectively eliminates costly, unscheduled downtime. This paper presents the results of infield VOTES testing. The system's proven ability to identify and characterize actuator and valve performance is demonstrated. Specific topics of discussion include the ability of VOTES to ease a utility's IE Bulletin 8543 concerns and conclusively diagnose MOV components. Data from static and differential pressure testing are presented. Technical, operational, and financial advantages resulting from VOTES technology are explored in detail

Cyclic Mechanical Loading Is Essential for Rac1-Mediated Elongation and Remodeling of the Embryonic Mitral Valve.

Science.gov (United States)

Gould, Russell A; Yalcin, Huseyin C; MacKay, Joanna L; Sauls, Kimberly; Norris, Russell; Kumar, Sanjay; Butcher, Jonathan T

2016-01-11

During valvulogenesis, globular endocardial cushions elongate and remodel into highly organized thin fibrous leaflets. Proper regulation of this dynamic process is essential to maintain unidirectional blood flow as the embryonic heart matures. In this study, we tested how mechanosensitive small GTPases, RhoA and Rac1, coordinate atrioventricular valve (AV) differentiation and morphogenesis. RhoA activity and its regulated GTPase-activating protein FilGAP are elevated during early cushion formation but decreased considerably during valve remodeling. In contrast, Rac1 activity was nearly absent in the early cushions but increased substantially as the valve matured. Using gain- and loss-of-function assays, we determined that the RhoA pathway was essential for the contractile myofibroblastic phenotype present in early cushion formation but was surprisingly insufficient to drive matrix compaction during valve maturation. The Rac1 pathway was necessary to induce matrix compaction in vitro through increased cell adhesion, elongation, and stress fiber alignment. Facilitating this process, we found that acute cyclic stretch was a potent activator of RhoA and subsequently downregulated Rac1 activity via FilGAP. On the other hand, chronic cyclic stretch reduced active RhoA and downstream FilGAP, which enabled Rac1 activation. Finally, we used partial atrial ligation experiments to confirm in vivo that altered cyclic mechanical loading augmented or restricted cushion elongation and thinning, directly through potentiation of active Rac1 and active RhoA, respectively. Together, these results demonstrate that cyclic mechanical signaling coordinates the RhoA to Rac1 signaling transition essential for proper embryonic mitral valve remodeling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mitral valve prolapse: an underestimated cause of sudden cardiac death-a current review of the literature.

Science.gov (United States)

Spartalis, Michael; Tzatzaki, Eleni; Spartalis, Eleftherios; Athanasiou, Antonios; Moris, Demetrios; Damaskos, Christos; Garmpis, Nikolaos; Voudris, Vassilis

2017-12-01

Mitral valve prolapse (MVP) is a common valve abnormality in general population. Despite the general belief of a benign disorder, several articles since the 1980s report sudden cardiac death (SCD) in MVP patients, with a substantial percentage of asymptomatic young individuals. The problem is to detect those patients at increased risk and implement methods that are suitable to prevent cardiac arrest. This review investigates the correlation between MVP and SCD, the understanding of the pathophysiology, the strategies for detecting those at risk and treatment options. A complete literature survey was performed using PubMed database search to gather available information regarding MVP and SCD. A total of 33 studies met selection criteria for inclusion in the review. MVP is an underrated cause of arrhythmic SCD. The subset of patients with malignant MVP who may be at greater risk for SCD is characterized by young women with bileaflet MVP, biphasic or inverted T waves in the inferior leads, and frequent complex ventricular ectopic activity with documented ventricular bigeminy or ventricular tachycardia (VT) and premature ventricular contractions (PVCs) configurations of outflow tract alternating with fascicular origin or papillary muscle. MVP is a common condition in the general population and is often encountered in asymptomatic individuals. The existing literature continues to generate significant controversy regarding the association of MVP with ventricular arrhythmias and SCD. Early echocardiography and cardiac magnetic resonance (CMR) are essential, as is a greater understanding of the potential electrophysiological processes of primary arrhythmogenesis and the evaluation of the genetic substrate.

Cellular regulation of the structure and function of aortic valves

Directory of Open Access Journals (Sweden)

Ismail El-Hamamsy

2010-01-01

Full Text Available The aortic valve was long considered a passive structure that opens and closes in response to changes in transvalvular pressure. Recent evidence suggests that the aortic valve performs highly sophisticated functions as a result of its unique microscopic structure. These functions allow it to adapt to its hemodynamic and mechanical environment. Understanding the cellular and molecular mechanisms involved in normal valve physiology is essential to elucidate the mechanisms behind valve disease. We here review the structure and developmental biology of aortic valves; we examine the role of its cellular parts in regulating its function and describe potential pathophysiological and clinical implications.

Mechanical Designs for Relief Valves for Cryogenic Apparatuses and Installations

CERN Multimedia

CERN. Geneva

2016-01-01

There are also pressure relief valves with warm seat available on which the set pressure is based on an adjustment of forces by permanent magnets. Pressure vessel rules allows also the choice for an active triggered pressure relief valve (Cont...

Hemodynamic Evaluation of a Biological and Mechanical Aortic Valve Prosthesis Using Patient-Specific MRI-Based CFD.

Science.gov (United States)

Hellmeier, Florian; Nordmeyer, Sarah; Yevtushenko, Pavlo; Bruening, Jan; Berger, Felix; Kuehne, Titus; Goubergrits, Leonid; Kelm, Marcus

2018-01-01

Modeling different treatment options before a procedure is performed is a promising approach for surgical decision making and patient care in heart valve disease. This study investigated the hemodynamic impact of different prostheses through patient-specific MRI-based CFD simulations. Ten time-resolved MRI data sets with and without velocity encoding were obtained to reconstruct the aorta and set hemodynamic boundary conditions for simulations. Aortic hemodynamics after virtual valve replacement with a biological and mechanical valve prosthesis were investigated. Wall shear stress (WSS), secondary flow degree (SFD), transvalvular pressure drop (TPD), turbulent kinetic energy (TKE), and normalized flow displacement (NFD) were evaluated to characterize valve-induced hemodynamics. The biological prostheses induced significantly higher WSS (medians: 9.3 vs. 8.6 Pa, P = 0.027) and SFD (means: 0.78 vs. 0.49, P = 0.002) in the ascending aorta, TPD (medians: 11.4 vs. 2.7 mm Hg, P = 0.002), TKE (means: 400 vs. 283 cm 2 /s 2 , P = 0.037), and NFD (means: 0.0994 vs. 0.0607, P = 0.020) than the mechanical prostheses. The differences between the prosthesis types showed great inter-patient variability, however. Given this variability, a patient-specific evaluation is warranted. In conclusion, MRI-based CFD offers an opportunity to assess the interactions between prosthesis and patient-specific boundary conditions, which may help in optimizing surgical decision making and providing additional guidance to clinicians. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Bioprosthetic Valve Fracture Improves the Hemodynamic Results of Valve-in-Valve Transcatheter Aortic Valve Replacement.

Science.gov (United States)

Chhatriwalla, Adnan K; Allen, Keith B; Saxon, John T; Cohen, David J; Aggarwal, Sanjeev; Hart, Anthony J; Baron, Suzanne J; Dvir, Danny; Borkon, A Michael

2017-07-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) may be less effective in small surgical valves because of patient/prosthesis mismatch. Bioprosthetic valve fracture (BVF) using a high-pressure balloon can be performed to facilitate VIV TAVR. We report data from 20 consecutive clinical cases in which BVF was successfully performed before or after VIV TAVR by inflation of a high-pressure balloon positioned across the valve ring during rapid ventricular pacing. Hemodynamic measurements and calculation of the valve effective orifice area were performed at baseline, immediately after VIV TAVR, and after BVF. BVF was successfully performed in 20 patients undergoing VIV TAVR with balloon-expandable (n=8) or self-expanding (n=12) transcatheter valves in Mitroflow, Carpentier-Edwards Perimount, Magna and Magna Ease, Biocor Epic and Biocor Epic Supra, and Mosaic surgical valves. Successful fracture was noted fluoroscopically when the waist of the balloon released and by a sudden drop in inflation pressure, often accompanied by an audible snap. BVF resulted in a reduction in the mean transvalvular gradient (from 20.5±7.4 to 6.7±3.7 mm Hg, P valve effective orifice area (from 1.0±0.4 to 1.8±0.6 cm 2 , P valves to facilitate VIV TAVR with either balloon-expandable or self-expanding transcatheter valves and results in reduced residual transvalvular gradients and increased valve effective orifice area. © 2017 American Heart Association, Inc.

Supercharged two-cycle engines employing novel single element reciprocating shuttle inlet valve mechanisms and with a variable compression ratio

Science.gov (United States)

Wiesen, Bernard (Inventor)

2008-01-01

This invention relates to novel reciprocating shuttle inlet valves, effective with every type of two-cycle engine, from small high-speed single cylinder model engines, to large low-speed multiple cylinder engines, employing spark or compression ignition. Also permitting the elimination of out-of-phase piston arrangements to control scavenging and supercharging of opposed-piston engines. The reciprocating shuttle inlet valve (32) and its operating mechanism (34) is constructed as a single and simple uncomplicated member, in combination with the lost-motion abutments, (46) and (48), formed in a piston skirt, obviating the need for any complex mechanisms or auxiliary drives, unaffected by heat, friction, wear or inertial forces. The reciprocating shuttle inlet valve retains the simplicity and advantages of two-cycle engines, while permitting an increase in volumetric efficiency and performance, thereby increasing the range of usefulness of two-cycle engines into many areas that are now dominated by the four-cycle engine.

Impact of Prosthesis-Patient Mismatch on Long-term Functional Capacity After Mechanical Aortic Valve Replacement

NARCIS (Netherlands)

Petit-Eisenmann, H.; Epailly, E.; Velten, M.; Radojevic, J.; Eisenmann, B.; Kremer, H.; Kindo, M.

2016-01-01

BACKGROUND: The impact of prosthesis-patient mismatch (PPM) after aortic valve replacement (AVR) for aortic stenosis on exercise capacity remains controversial. The aim of this study was to analyze the long-term impact of PPM after mechanical AVR on maximal oxygen uptake (VO2max). METHODS: The study

GIANT PROSTHETIC VALVE THROMBUS

Directory of Open Access Journals (Sweden)

Prashanth Kumar

2015-04-01

Full Text Available Mechanical prosthetic valves are predisposed to bleeding, thrombosis & thromboembolic complications. Overall incidence of thromboembolic complications is 1% per year who are on oral anticoagulants, whereas bleeding complications incidence is 0.5% to 6.6% per year. 1, 2 Minimization of Scylla of thromboembolic & Charybdis of bleeding complication needs a balancing act of optimal antithrombotic therapy. We are reporting a case of middle aged male patient with prosthetic mitral valve presenting in heart failure. Patient had discontinued anticoagulants, as he had subdural hematoma in the past. He presented to our institute with a giant prosthetic valve thrombus.

Restoration of Tricuspid Valve Mechanism at the Level of Displaced Septal and Posterior Leaflets in Ebstein's Anomaly.

Science.gov (United States)

Im, Yu-Mi; Park, Chun Soo; Park, Jeong-Jun; Yun, Tae-Jin

2016-03-01

Surgical techniques currently used for the repair of Ebstein's anomaly comprise reconstruction of the tricuspid valve mechanism at the level of the true annulus with or without plication of the atrialized right ventricle. However, performing this procedure for patients with a dysmorphic anterior leaflet (i.e., insufficient leaflet tissue and decreased mobility due to tethering) may necessitate technical modifications. A retrospective review was performed of 31 patients (seven males and 24 females, median age at operation 31 years) with Ebstein's anomaly, who underwent tricuspid valve repair between March 2002 and December 2014. The original Hetzer technique (annulus to annulus approximation) was employed for six patients with a well-formed anterior leaflet. In 25 patients, the tricuspid valve mechanism was restored at the displaced septal leaflet by approximating the anterior leaflet attachment in the true annulus to the displaced septal leaflet attachment in the mid-septum. A bidirectional superior cavopulmonary anastomosis was added in 27 of 31 (87%) patients. No early or late death occurred during the median follow-up of 66 months (1-138 months). Immediate postoperative tricuspid regurgitation was trivial to mild in 22 patients, and the median preoperative, immediate postoperative, and last follow-up tricuspid regurgitation jet areas in 21 adult patients were 23.3 cm2, 10.4 cm2, and 7.0 cm2, respectively. Two patients underwent reoperation at 81 and 119 months postoperatively. Five-year freedom from severe tricuspid regurgitation or reoperation was 93.2%. Restoration of the tricuspid valve mechanism at the level of displaced septal leaflet leads to excellent long-term outcomes. The addition of the bidirectional superior cavopulmonary anastomosis has contributed to the success of this technique. © 2016 Wiley Periodicals, Inc.

Next-generation nozzle check valve significantly reduces operating costs

Energy Technology Data Exchange (ETDEWEB)

Roorda, O. [SMX International, Toronto, ON (Canada)

2009-01-15

Check valves perform an important function in preventing reverse flow and protecting plant and mechanical equipment. However, the variety of different types of valves and extreme differences in performance even within one type can change maintenance requirements and life cycle costs, amounting to millions of dollars over the typical 15-year design life of piping components. A next-generation non-slam nozzle check valve which prevents return flow has greatly reduced operating costs by protecting the mechanical equipment in a piping system. This article described the check valve varieties such as the swing check valve, a dual-plate check valve, and nozzle check valves. Advancements in optimized design of a non-slam nozzle check valve were also discussed, with particular reference to computer flow modelling such as computational fluid dynamics; computer stress modelling such as finite element analysis; and flow testing (using rapid prototype development and flow loop testing), both to improve dynamic performance and reduce hydraulic losses. The benefits of maximized dynamic performance and minimized pressure loss from the new designed valve were also outlined. It was concluded that this latest non-slam nozzle check valve design has potential applications in natural gas, liquefied natural gas, and oil pipelines, including subsea applications, as well as refineries, and petrochemical plants among others, and is suitable for horizontal and vertical installation. The result of this next-generation nozzle check valve design is not only superior performance, and effective protection of mechanical equipment but also minimized life cycle costs. 1 fig.

Gate valve performance prediction

International Nuclear Information System (INIS)

Harrison, D.H.; Damerell, P.S.; Wang, J.K.; Kalsi, M.S.; Wolfe, K.J.

1994-01-01

The Electric Power Research Institute is carrying out a program to improve the performance prediction methods for motor-operated valves. As part of this program, an analytical method to predict the stem thrust required to stroke a gate valve has been developed and has been assessed against data from gate valve tests. The method accounts for the loads applied to the disc by fluid flow and for the detailed mechanical interaction of the stem, disc, guides, and seats. To support development of the method, two separate-effects test programs were carried out. One test program determined friction coefficients for contacts between gate valve parts by using material specimens in controlled environments. The other test program investigated the interaction of the stem, disc, guides, and seat using a special fixture with full-sized gate valve parts. The method has been assessed against flow-loop and in-plant test data. These tests include valve sizes from 3 to 18 in. and cover a considerable range of flow, temperature, and differential pressure. Stem thrust predictions for the method bound measured results. In some cases, the bounding predictions are substantially higher than the stem loads required for valve operation, as a result of the bounding nature of the friction coefficients in the method

Effects of suture position on left ventricular fluid mechanics under mitral valve edge-to-edge repair.

Science.gov (United States)

Du, Dongxing; Jiang, Song; Wang, Ze; Hu, Yingying; He, Zhaoming

2014-01-01

Mitral valve (MV) edge-to-edge repair (ETER) is a surgical procedure for the correction of mitral valve regurgitation by suturing the free edge of the leaflets. The leaflets are often sutured at three different positions: central, lateral and commissural portions. To study the effects of position of suture on left ventricular (LV) fluid mechanics under mitral valve ETER, a parametric model of MV-LV system during diastole was developed. The distribution and development of vortex and atrio-ventricular pressure under different suture position were investigated. Results show that the MV sutured at central and lateral in ETER creates two vortex rings around two jets, compared with single vortex ring around one jet of the MV sutured at commissure. Smaller total orifices lead to a higher pressure difference across the atrio-ventricular leaflets in diastole. The central suture generates smaller wall shear stresses than the lateral suture, while the commissural suture generated the minimum wall shear stresses in ETER.

Flow oscillations on the steam control valve in the middle opening condition. Clarification of the effects of valve body and valve seat by steam experiments

International Nuclear Information System (INIS)

Morita, Ryo; Inada, Fumio

2007-01-01

A steam control valve might cause vibrations of piping when the valve opening is in a middle condition. For rationalization of maintenance and management of the plant, the valve should be improved, but it is difficult to understand flow characteristics in detail by experiment because flow around the valve is complex 3D structure and becomes supersonic (M>1). Therefore, it is necessary to clarify the cause of the vibrations and to develop the countermeasures by CFD (Computational Fluid Dynamics) technology. In previous researches, we clarified a mechanism of the pressure fluctuations in the middle opening condition and suggested the new valve shape (named 'Extended Valve') that can suppress the pressure fluctuations by air experiments and CFD calculations. Then, we also conducted steam experiments and CFD calculations to understand the differences between air and the steam, and found that the pressure fluctuations in the middle opening condition also occurred in the steam tests and the differences between the air and steam were not remarkable. In this report, to clarify the effects of valve and valve seat shape in steam flow condition, we conduct the steam experiments with various valve and seat shape. As a result, we find the change of the valve seat can decrease the amplitude of pressure fluctuations, but can not quite suppress the pressure fluctuations in the middle opening condition. Then, we apply the 'Extended Valve' to clarify the valve shape effect, and find that the extended valve suppresses the pressure fluctuations in the middle opening condition completely and decreases the pressure amplitude drastically. (author)

Radiological visualization of prosthetic heart valves in situ

International Nuclear Information System (INIS)

Hoffmeister, H.M.; Pirschel, J.

1986-01-01

To determine the radiographic appearance of prosthetic heart valves 15 different models were investigated in situ. Fluoroscopy with detail radiographs and standard chest-radiographs were used for identification of the specific type of the prosthesis, for determination of details of the valve apparatus and for evaluation of the motion of the valve disc/ball. - Fluoroscopy and routine radiographs provided sufficient information to identify all prosthetic heart valves with exception of the Xenomedica bioprosthesis. If radiopaque material was used for the valve disc/ball, fluoroscopic assessment of the function of the valve was possible. Thus, in most types of disc or ball valves the opening/closing of the valve can be visualized, whereas in bioprosthesis a radiological determination of the mechanical function is not possible. (orig.) [de

Successful Management of Prosthetic Valve Brucella Endocarditis with Antibiotherapy Alone

Directory of Open Access Journals (Sweden)

José Pedro Fonseca

2018-01-01

Full Text Available Objectives: To report a case of mechanical aortic prosthesis Brucella endocarditis successfully treated with antibiotics alone. Materials and methods: We describe a clinical case and present a review of the literature. Results: A 60-year-old female farmer with a mechanical aortic prosthetic valve presented with low back pain and fever. She was diagnosed with prosthetic valve Brucella mellitensis endocarditis and was cured with antibiotic therapy alone. Few cases of successfully treated prosthetic valve Brucella endocarditis without surgery have been reported. Conclusion: Prosthetic valve Brucella endocarditis usually requires surgical valve replacement. However, selected patients may be successfully treated with antibiotic therapy alone.

Verification of pharmacogenetics-based warfarin dosing algorithms in Han-Chinese patients undertaking mechanic heart valve replacement.

Science.gov (United States)

Zhao, Li; Chen, Chunxia; Li, Bei; Dong, Li; Guo, Yingqiang; Xiao, Xijun; Zhang, Eryong; Qin, Li

2014-01-01

To study the performance of pharmacogenetics-based warfarin dosing algorithms in the initial and the stable warfarin treatment phases in a cohort of Han-Chinese patients undertaking mechanic heart valve replacement. We searched PubMed, Chinese National Knowledge Infrastructure and Wanfang databases for selecting pharmacogenetics-based warfarin dosing models. Patients with mechanic heart valve replacement were consecutively recruited between March 2012 and July 2012. The predicted warfarin dose of each patient was calculated and compared with the observed initial and stable warfarin doses. The percentage of patients whose predicted dose fell within 20% of their actual therapeutic dose (percentage within 20%), and the mean absolute error (MAE) were utilized to evaluate the predictive accuracy of all the selected algorithms. A total of 8 algorithms including Du, Huang, Miao, Wei, Zhang, Lou, Gage, and International Warfarin Pharmacogenetics Consortium (IWPC) model, were tested in 181 patients. The MAE of the Gage, IWPC and 6 Han-Chinese pharmacogenetics-based warfarin dosing algorithms was less than 0.6 mg/day in accuracy and the percentage within 20% exceeded 45% in all of the selected models in both the initial and the stable treatment stages. When patients were stratified according to the warfarin dose range, all of the equations demonstrated better performance in the ideal-dose range (1.88-4.38 mg/day) than the low-dose range (pharmacogenetics-based warfarin dosing regimens performed similarly in our cohort. However, the algorithms of Wei, Huang, and Miao showed a better potential for warfarin prediction in the initial and the stable treatment phases in Han-Chinese patients undertaking mechanic heart valve replacement.

Device for the simultaneous operation of the closing valve of a vessel and the closing valve of a transport container

International Nuclear Information System (INIS)

Tellier, Claude; Surriray, Michel.

1982-01-01

This device includes mechanisms for unlatching the closing valve of the vessel and securing it to the closing valve of the transport container and other mechanisms for vertically raising the assembly of valves, pivoting it and bringing it into a vertical position in a bulge provided in the bottom of the transport container. For example the first containment is a nuclear reactor vessel and the transport container is used for carrying an item from the vessel to an external area (for instance, a defective pump to the repair area) and for the return transport operation [fr

Factors Influencing Mortality after Bioprosthetic Valve Replacement; A Midterm Outcome

OpenAIRE

Hassan Javadzadegan; Amir Javadzadegan; Jafar Mehdizadeh Baghbani

2013-01-01

Introduction: Although valve repair is applied routinely nowadays, particularly for mitral regurgitation (MR) or tricuspid regurgitation (TR), valve replacement using prosthetic valves is also common especially in adults. Unfortunately the valve with ideal hemodynamic performance and long-term durability without increasing the risk of bleeding due to long-term anticoagulant therapy has not been introduced. Therefore, patients and physicians must choose either bioprosthetic or mechanical valve...

Detection circuit of solenoid valve operation and control rod drive mechanism utilizing the circuit

International Nuclear Information System (INIS)

Ono, Takehiko.

1976-01-01

Object: To detect the operation of a plunger and detect opening and closing operations of a solenoid valve driving device due to change in impedance of a coil for driving the solenoid valve to judge normality and abnormality of the solenoid valve, thereby increasing reliance and safety of drive and control apparatus of control rods. Structure: An arrangement comprises a drive and operation detector section wherein the operation of a solenoid driving device for controlling power supply to a coil for driving the solenoid valve to control opening and closing of the solenoid valve, and a plunger operation detector section for detecting change in impedance of the drive coil to detect that the plunger of the solenoid valve is either in the opening direction or closing direction, whereby a predetermined low voltage such as not to activate the solenoid valve even when the solenoid valve is open or closed is applied to detect a current flowing into the coil at that time, thus detecting an operating state of the plunger. (Yoshino, Y.)

A novel left heart simulator for the multi-modality characterization of native mitral valve geometry and fluid mechanics.

Science.gov (United States)

Rabbah, Jean-Pierre; Saikrishnan, Neelakantan; Yoganathan, Ajit P

2013-02-01

Numerical models of the mitral valve have been used to elucidate mitral valve function and mechanics. These models have evolved from simple two-dimensional approximations to complex three-dimensional fully coupled fluid structure interaction models. However, to date these models lack direct one-to-one experimental validation. As computational solvers vary considerably, experimental benchmark data are critically important to ensure model accuracy. In this study, a novel left heart simulator was designed specifically for the validation of numerical mitral valve models. Several distinct experimental techniques were collectively performed to resolve mitral valve geometry and hemodynamics. In particular, micro-computed tomography was used to obtain accurate and high-resolution (39 μm voxel) native valvular anatomy, which included the mitral leaflets, chordae tendinae, and papillary muscles. Three-dimensional echocardiography was used to obtain systolic leaflet geometry. Stereoscopic digital particle image velocimetry provided all three components of fluid velocity through the mitral valve, resolved every 25 ms in the cardiac cycle. A strong central filling jet (V ~ 0.6 m/s) was observed during peak systole with minimal out-of-plane velocities. In addition, physiologic hemodynamic boundary conditions were defined and all data were synchronously acquired through a central trigger. Finally, the simulator is a precisely controlled environment, in which flow conditions and geometry can be systematically prescribed and resultant valvular function and hemodynamics assessed. Thus, this work represents the first comprehensive database of high fidelity experimental data, critical for extensive validation of mitral valve fluid structure interaction simulations.

MEMS Micro-Valve for Space Applications

Science.gov (United States)

Chakraborty, I.; Tang, W. C.; Bame, D. P.; Tang, T. K.

1998-01-01

We report on the development of a Micro-ElectroMechanical Systems (MEMS) valve that is designed to meet the rigorous performance requirements for a variety of space applications, such as micropropulsion, in-situ chemical analysis of other planets, or micro-fluidics experiments in micro-gravity. These systems often require very small yet reliable silicon valves with extremely low leak rates and long shelf lives. Also, they must survive the perils of space travel, which include unstoppable radiation, monumental shock and vibration forces, as well as extreme variations in temperature. Currently, no commercial MEMS valve meets these requirements. We at JPL are developing a piezoelectric MEMS valve that attempts to address the unique problem of space. We begin with proven configurations that may seem familiar. However, we have implemented some major design innovations that should produce a superior valve. The JPL micro-valve is expected to have an extremely low leak rate, limited susceptibility to particulates, vibration or radiation, as well as a wide operational temperature range.

Single calibration multiplane stereo-PIV: the effect of mitral valve orientation on three-dimensional flow in a left ventricle model

Science.gov (United States)

Saaid, Hicham; Segers, Patrick; Novara, Matteo; Claessens, Tom; Verdonck, Pascal

2018-03-01

The characterization of flow patterns in the left ventricle may help the development and interpretation of flow-based parameters of cardiac function and (patho-)physiology. Yet, in vivo visualization of highly dynamic three-dimensional flow patterns in an opaque and moving chamber is a challenging task. This has been shown in several recent multidisciplinary studies where in vivo imaging methods are often complemented by in silico solutions, or by in vitro methods. Because of its distinctive features, particle image velocimetry (PIV) has been extensively used to investigate flow dynamics in the cardiovascular field. However, full volumetric PIV data in a dynamically changing geometry such as the left ventricle remain extremely scarce, which justifies the present study. An investigation of the left ventricle flow making use of a customized cardiovascular simulator is presented; a multiplane scanning-stereoscopic PIV setup is used, which allows for the measurement of independent planes across the measurement volume. Due to the accuracy in traversing the illumination and imaging systems, the present setup allows to reconstruct the flow in a 3D volume performing only one single calibration. The effects of the orientation of a prosthetic mitral valve in anatomical and anti-anatomical configurations have been investigated during the diastolic filling time. The measurement is performed in a phase-locked manner; the mean velocity components are presented together with the vorticity and turbulent kinetic energy maps. The reconstructed 3D flow structures downstream the bileaflet mitral valve are shown, which provides additional insight of the highly three-dimensional flow.

High-resolution measurement of the unsteady velocity field to evaluate blood damage induced by a mechanical heart valve.

Science.gov (United States)

Bellofiore, Alessandro; Quinlan, Nathan J

2011-09-01

We investigate the potential of prosthetic heart valves to generate abnormal flow and stress patterns, which can contribute to platelet activation and lysis according to blood damage accumulation mechanisms. High-resolution velocity measurements of the unsteady flow field, obtained with a standard particle image velocimetry system and a scaled-up model valve, are used to estimate the shear stresses arising downstream of the valve, accounting for flow features at scales less than one order of magnitude larger than blood cells. Velocity data at effective spatial and temporal resolution of 60 μm and 1.75 kHz, respectively, enabled accurate extraction of Lagrangian trajectories and loading histories experienced by blood cells. Non-physiological stresses up to 10 Pa were detected, while the development of vortex flow in the wake of the valve was observed to significantly increase the exposure time, favouring platelet activation. The loading histories, combined with empirical models for blood damage, reveal that platelet activation and lysis are promoted at different stages of the heart cycle. Shear stress and blood damage estimates are shown to be sensitive to measurement resolution.

Verification of Pharmacogenetics-Based Warfarin Dosing Algorithms in Han-Chinese Patients Undertaking Mechanic Heart Valve Replacement

Science.gov (United States)

Zhao, Li; Chen, Chunxia; Li, Bei; Dong, Li; Guo, Yingqiang; Xiao, Xijun; Zhang, Eryong; Qin, Li

2014-01-01

Objective To study the performance of pharmacogenetics-based warfarin dosing algorithms in the initial and the stable warfarin treatment phases in a cohort of Han-Chinese patients undertaking mechanic heart valve replacement. Methods We searched PubMed, Chinese National Knowledge Infrastructure and Wanfang databases for selecting pharmacogenetics-based warfarin dosing models. Patients with mechanic heart valve replacement were consecutively recruited between March 2012 and July 2012. The predicted warfarin dose of each patient was calculated and compared with the observed initial and stable warfarin doses. The percentage of patients whose predicted dose fell within 20% of their actual therapeutic dose (percentage within 20%), and the mean absolute error (MAE) were utilized to evaluate the predictive accuracy of all the selected algorithms. Results A total of 8 algorithms including Du, Huang, Miao, Wei, Zhang, Lou, Gage, and International Warfarin Pharmacogenetics Consortium (IWPC) model, were tested in 181 patients. The MAE of the Gage, IWPC and 6 Han-Chinese pharmacogenetics-based warfarin dosing algorithms was less than 0.6 mg/day in accuracy and the percentage within 20% exceeded 45% in all of the selected models in both the initial and the stable treatment stages. When patients were stratified according to the warfarin dose range, all of the equations demonstrated better performance in the ideal-dose range (1.88–4.38 mg/day) than the low-dose range (warfarin dose prediction and in the low-dose and the ideal-dose ranges. Conclusions All of the selected pharmacogenetics-based warfarin dosing regimens performed similarly in our cohort. However, the algorithms of Wei, Huang, and Miao showed a better potential for warfarin prediction in the initial and the stable treatment phases in Han-Chinese patients undertaking mechanic heart valve replacement. PMID:24728385

Function analysis of steam isolation valves

International Nuclear Information System (INIS)

Persson, R.; Sjoeberg, A.; Aakesson, H.; Kilpi, K.; Noro, H.; Siikonen, T.; Wallen, G.

1981-01-01

Function analysis of system-medium-operated steam isolation valves has been the objective of the Swedish-Finnish IVLS project, the results of which are presented in this report. Theoretical models were to be verified against available experimental data, to some extent from the HDR blowdown experiments, which are part of a German reactor safety program. Finnish hydraulic measurements on a valve model (scale 1:2.15) have been performed to give complementary data. The analysis work has covered the thermal-hydraulic behaviour of steam isolation valves as well as phenomena related to structural mechanics. (Auth.)

Dysfunction of an On-X Heart Valve by Pannus.

Science.gov (United States)

Abad, Cipriano; Urso, Stefano; Gomez, Elsa; De la Vega, Maria

2016-09-01

A 68-year-old woman with a history of previous double-valve replacement with On-X mechanical heart valves presented with clinical, echocardiographic and cardiac catheterization signs of obstruction of the On-X tricuspid heart valve prosthesis. The patient was successfully reoperated, but at surgery the valve was seen to be invaded by an abnormal overgrowth of pannus that blocked one of the leaflets. A small amount of non-obstructive fresh thrombus was also observed. The valve was successfully replaced with a biological heart valve prosthesis. The patient was discharged home, and is doing well four months after the operation, when echocardiography demonstrated normal function in the tricuspid valve. The present case represents the first ever report of pannus formation and subsequent dysfunction in an On-X heart valve, and also the first case of tricuspid valve malfunction and obstruction using this type of heart valve substitute.

MECHANISMS OF COUNTERACTING FLAP-VALVE BRONCHIAL OBSTRUCTION IN CASE OF OBSTRUCTIVE PULMONARY EMPHYSEMA

Directory of Open Access Journals (Sweden)

K. F. Tetenev

2015-01-01

Full Text Available The research goal was to formulate and substantiate the hypothesis explaining support for an expiratory air flow in case of pulmonary emphysema. The research method consisted in comparing the mechanical properties of lungs in practically healthy individuals (37 individuals, mean age – (30.4 ± 1.7 y.o. and COPD patients with pronounced lung emphysema (30 patients, mean age – (52.1 ± 2.3 y.o. as well as those of isolated normal lungs (n = 14 and isolated lungs of patients who died of COPD (n = 5. Pulmo-nary mechanics was studied via the simultaneous measurement of transpulmonary pressure and lung ven-tilation volume. General lung hysteresis and elastic lung hysteresis were calculated. The mechanical properties of isolated lungs were studied using passive ventilation under the Donders bell. The air flow was interrupted in order to measure alveolar pressure and develop an elastic lung hysteresis curve. Pres-sure in the Donders bell was changed by means of a special pump in automatic and manual modes. The research has not revealed any fundamental differences between the mechanical properties of the normal and emphysematous lungs. A minimum increase in the pressure inside the Donders bell over atmospheric pressure used to stop air ejection in both normal and the emphysematous lungs as the result of flap-valve bronchial obstruction. In living beings, air is ejected from lungs with an increase in pressure under the conditions of forced expiration. Pressure increases up to (38.6 ± 2.71 cm H2O in healthy individuals and up to (20.5 ± 1.86 cm H2O in COPD patients. Probably, an expiratory air flow is supported by active expiratory bronchial dilatation that counteracts flap-valve bronchial obstruction. The hypothesis is based on the confirmed ability of the lungs to perform inspiratory actions (in addition to the action of respiratory muscles and the theory of mechanical lung activity.

Radial Force: An Underestimated Parameter in Oversizing Transcatheter Aortic Valve Replacement Prostheses: In Vitro Analysis with Five Commercialized Valves.

Science.gov (United States)

Egron, Sandrine; Fujita, Buntaro; Gullón, Lucía; Désirée, Pott; Schmitz-Rode, Thomas; Ensminger, Stephan; Steinseifer, Ulrich

2017-09-05

The goal is to inform in depth on transcatheter aortic valve replacement (TAVR) prosthesis mechanical behavior, depending on frame type, design, and size, and how it crucially impacts the oversizing issue in clinical use, and ultimately the procedure outcome. Transcatheter aortic valve replacement is an established therapy for high-risk patients suffering from aortic stenosis, and the indication for TAVR is progressively expanding to intermediate-risk patients. Choosing the optimal oversizing degree is crucial to safely anchor the TAVR valve-which involves limiting the risks for embolism, aortic regurgitation, conductance disturbance, or annulus rupture-and to increase the valve prosthesis performance. The radial force (RF) profiles of five TAVR prostheses were measured in vitro: the CoreValve 23 and 26 (Medtronic, MN), the Acurate neo S (Symetis, Switzerland), and the SAPIEN XT 23 and 26 (Edwards Lifesciences, CA). Measurements were run with the RX Machine equipment (Machine Solutions Inc., AZ), which is used in ISO standard tests for intravascular stents. Test protocols were adapted for TAVR prostheses. With the prostheses RF profiles' results, mechanical behavior differences could be described and discussed in terms of oversizing strategy and clinical impact for all five valves. Besides, crossing the prostheses' RF profiles with their recommended size windows made the assessment of borderline size cases possible and helped analyze the risks when accurate measurement of patient aortic annulus proves difficult. The prostheses' RF profiles bring new support in clinical decision-making for valve type and size in patients.

Mechanism of Microbubble Growth at Mitral Mechanical Heart Valve (MHV) Closure

Science.gov (United States)

Rambod, Edmond; Beizaie, Masoud; Shusser, Michael; Gharib, Morteza

1999-11-01

The growth mechanism of microbubbles at mitral MHV closure has been experimentally studied. In the heart, some of the tiny bubbles grow explosively and form larger and persistent bubbles. An experimental set-up was designed to allow the passage of micron-size bubbles through an 80 micron-wide slot, simulating a typical gap between the housing ring and the occluders in MHV. The bubbles were generated using an air-liquid dispenser and were delivered to the system via a 250 micron-diameter hypedermic needle positioned vertically near the slot. A solenoid valve was used to deliver a 10cc volume of liquid in 25ms time through the slot. High-speed imaging was used to study the impact of flow through the slot on bubble growth. The velocity of liquid through the slot was assessed to be in the range of 12-15 m/s. Our observations confirmed the rapid and drastic growth of microbubbles following their passage through the narrow slot, due to pressure drop. Vortices, which were induced by flow separation on the downstream of the slot, caused the grown bubbles to shatter and form more stable bubbles.

Strut fracture in a Bjork-Shiley aortic valve prosthesis.

Science.gov (United States)

Lifschultz, B D; Donoghue, E R

1985-10-01

Strut fracture can be a life-threatening adverse effect of mechanical prosthetic heart valves. This complication has occurred in the DeBakey, the Beall, the Cooley-Cutter and, most recently, the Bjork-Shiley valves. We report the case of a 35-year-old man who died suddenly 16 months after a 60 degree Bjork-Shiley Convexo-Concave heart valve prosthesis was inserted in the aortic position. At autopsy, the two welded attachments of the valve's outlet strut had fractured. The valve's tilting disc was found in his abdominal aorta.

The Fluid Mechanics of Transcatheter Heart Valve Leaflet Thrombosis in the Neosinus.

Science.gov (United States)

Midha, Prem A; Raghav, Vrishank; Sharma, Rahul; Condado, Jose F; Okafor, Ikechukwu U; Rami, Tanya; Kumar, Gautam; Thourani, Vinod H; Jilaihawi, Hasan; Babaliaros, Vasilis; Makkar, Raj R; Yoganathan, Ajit P

2017-10-24

Transcatheter heart valve (THV) thrombosis has been increasingly reported. In these studies, thrombus quantification has been based on a 2-dimensional assessment of a 3-dimensional phenomenon. Postprocedural, 4-dimensional, volume-rendered CT data of patients with CoreValve, Evolut R, and SAPIEN 3 transcatheter aortic valve replacement enrolled in the RESOLVE study (Assessment of Transcatheter and Surgical Aortic Bioprosthetic Valve Dysfunction With Multimodality Imaging and Its Treatment with Anticoagulation) were included in this analysis. Patients on anticoagulation were excluded. SAPIEN 3 and CoreValve/Evolut R patients with and without hypoattenuated leaflet thickening were included to study differences between groups. Patients were classified as having THV thrombosis if there was any evidence of hypoattenuated leaflet thickening. Anatomic and THV deployment geometries were analyzed, and thrombus volumes were computed through manual 3-dimensional reconstruction. We aimed to identify and evaluate risk factors that contribute to THV thrombosis through the combination of retrospective clinical data analysis and in vitro imaging in the space between the native and THV leaflets (neosinus). SAPIEN 3 valves with leaflet thrombosis were on average 10% further expanded (by diameter) than those without (95.5±5.2% versus 85.4±3.9%; P <0.001). However, this relationship was not evident with the CoreValve/Evolut R. In CoreValve/Evolut Rs with thrombosis, the thrombus volume increased linearly with implant depth ( R 2 =0.7, P <0.001). This finding was not seen in the SAPIEN 3. The in vitro analysis showed that a supraannular THV deployment resulted in a nearly 7-fold decrease in stagnation zone size (velocities <0.1 m/s) when compared with an intraannular deployment. In addition, the in vitro model indicated that the size of the stagnation zone increased as cardiac output decreased. Although transcatheter aortic valve replacement thrombosis is a multifactorial process

Resurgery for recurrent heart valve diseases

Directory of Open Access Journals (Sweden)

Chong-lei REN

2017-02-01

Full Text Available Objective　To summarize the experience with resurgery for recurrent valvular heart diseases. Methods　From June 2004 to June 2015, 28 patients (15 males and 13 females with ages ranging from 44 to 67 years (55.6±6.5 years with recurrent heart valve disease underwent resurgery. The reasons for resurgery included perivalvular leakage (7 cases, bioprosthetic valve decline (6 cases in mitral valve and 3 in tricuspid valve, mechanical prostheses dysfunction (2cases, infective endocarditis after valve replacement (2 cases, restenosis of repaired native valve (1 case, and severe tricuspid insufficiency after left-side valve surgery (7 cases. Resurgery included mitral valve replacement in 18 patients and tricuspid valve replacement in 10. All the patients underwent third or fourth or even fifth cardiac surgery for valve replacement. Results　There were 2 hospital deaths with a mortality of 7.1% (2/28. The main causes of early-stage deaths were low cardiac output syndrome. The main postoperative complications were respiratory failure in 3, low cardiac output syndrome in 2, reexploration for bleeding in 2 and serious infectious shock in 1. All the patients were found with the great improvement in heart function and the re-implanted prostheses worked well during follow-up. Conclusions　Although resurgery for recurrent heart valve disease poses a continuing challenge to cardiac surgeon, it could be performed with the satisfactory results. The keys to a successful cardiac resurgery include appropriate operational timing, refined surgical technique and reasonable perioperative managements. DOI: 10.11855/j.issn.0577-7402.2017.01.11

BWR control rod drive scram pilot valve monitoring program

International Nuclear Information System (INIS)

Soden, R.A.; Kelly, V.

1986-01-01

The control rod drive system in a Boiling Water Reactor is the most important safety system in the power plant. All components of the system can be verified except the solenoid operated, scram pilot valves without scramming a rod. The pilot valve mechanical works is the weak link to the control rod drive system. These pilot valves control the hydraulic system which applies pressure to the insert side of the control rod piston and vents the withdraw side of the piston causing the rods to insert during a scram. The only verification that the valve is operating properly is to scram the rod. The concern for this portion of the system is demonstrated by the high number of redundant components and complete periodic testing of the electrical circuits. The pilot valve can become hung-up through wear, fracture of internal components, mechanical binding, foreign material or chemicals left in the valve during maintenance, etc. If the valve becomes hung-up the electrical tests performed will not indicate this condition and scramming the rod is in jeopardy. Only an attempt to scram a rod will indicate the hung-up valve. While this condition exists the rod is considered inoperative. This paper describes a system developed at a nuclear power plant that monitors the pilot valves on the control rod drive system. This system utilizes pattern recognition to assure proper internal workings of the scram pilot valves to plant operators. The system is totally automatic such that each time the valve is operated on a half scram, a printout is available to the operator along with light indication that each of the 370 valves (on one unit of a BWR) is operating properly. With this monitoring system installed, all components of the control rod drive system including the solenoid pilot valves can be verified as operational without scramming any rods

Classification of heart valve condition using acoustic measurements

Energy Technology Data Exchange (ETDEWEB)

Clark, G. [Lawrence Livermore National Lab., CA (United States)

1994-11-15

Prosthetic heart valves and the many great strides in valve design have been responsible for extending the life spans of many people with serious heart conditions. Even though the prosthetic valves are extremely reliable, they are eventually susceptible to long-term fatigue and structural failure effects expected from mechanical devices operating over long periods of time. The purpose of our work is to classify the condition of in vivo Bjork-Shiley Convexo-Concave (BSCC) heart valves by processing acoustic measurements of heart valve sounds. The structural failures of interest for Bscc valves is called single leg separation (SLS). SLS can occur if the outlet strut cracks and separates from the main structure of the valve. We measure acoustic opening and closing sounds (waveforms) using high sensitivity contact microphones on the patient`s thorax. For our analysis, we focus our processing and classification efforts on the opening sounds because they yield direct information about outlet strut condition with minimal distortion caused by energy radiated from the valve disc.

Preliminary assessment of valve IST effectiveness

International Nuclear Information System (INIS)

Grove, E.; DiBiasio, A.; Carbonaro, J.

1994-01-01

A preliminary review of inservice testing effectiveness for Code Class 1,2, and 3 valves at nuclear power plants was performed. These requirements are specified by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI, and the Operations and Maintenance Standard. The Institute of Nuclear Power Operations Nuclear Plant Reliability Data System (NPRDS) database was used to provide failure reports for these components for 1988 to 1992. This time period coincides with the issuance of Generic Letter 89-04, which resulted in a more consistent application of the requirements by the licensees. For this time period, 8,593 valve failures were identified. From the review of the NPRDS database, the primary failure causes and failure modes for motor-operated valves (MOV), air-operated valves (AOV), and check valves (CV) were identified. Solenoid-operated valves were not reviewed in this study. Plant testing programs were effective in identifying approximately 60% of the CV failures, 46% of the AOV failures, and 44% of the MOV failures

Valve-sparing and valve-replacing techniques for aortic root replacement in patients with Marfan syndrome: Analysis of early outcome.

Science.gov (United States)

Volguina, Irina V; Miller, D Craig; LeMaire, Scott A; Palmero, Laura C; Wang, Xing Li; Connolly, Heidi M; Sundt, Thoralf M; Bavaria, Joseph E; Dietz, Harry C; Milewicz, Dianna M; Coselli, Joseph S

2009-05-01

A prospective, international registry study was initiated to provide contemporary comparative data on short-term clinical outcomes after aortic valve-sparing and aortic valve-replacing root operations in patients with Marfan syndrome. The purpose of this initial report is to describe the study design and to compare early outcomes in the first 151 enrolled patients. We assessed 30-day outcomes in 151 patients who met strict Ghent diagnostic criteria for Marfan syndrome and underwent aortic root replacement with either valve-replacing (n = 46) or valve-sparing techniques (n = 105) at one of 18 participating centers. In the valve replacement group, a mechanical composite valve graft was used in 39 (85%) patients and a bioprosthetic valve in 7 (15%). In the valve-sparing group, David V procedures were performed in 57 (54%) patients, David I in 38 (36%), David IV in 8 (8%), Florida sleeve in 1 (1%), and Yacoub remodeling in 1 (1%). No in-hospital or 30-day deaths occurred. Despite longer crossclamp and cardiopulmonary bypass times in the valve-sparing group, there were no significant between-group differences in postoperative complications. Thirty-day valve-related complications occurred in 2 (4%) patients undergoing valve replacement and in 3 (3%) undergoing valve-sparing procedures (P = .6). The analysis of early outcomes revealed that valve-sparing techniques were the most common approach to root replacement in patients with Marfan syndrome in these centers. The complexity of valve-sparing root replacement did not translate into any demonstrable adverse early outcomes. Subsequent analysis will compare the 3-year durability of these two surgical approaches.

Neurotrophin 3 upregulates proliferation and collagen production in human aortic valve interstitial cells: a potential role in aortic valve sclerosis.

Science.gov (United States)

Yao, Qingzhou; Song, Rui; Ao, Lihua; Cleveland, Joseph C; Fullerton, David A; Meng, Xianzhong

2017-06-01

Calcific aortic valve disease (CAVD) is a leading cardiovascular disorder in the elderly. Diseased aortic valves are characterized by sclerosis (fibrosis) and nodular calcification. Sclerosis, an early pathological change, is caused by aortic valve interstitial cell (AVIC) proliferation and overproduction of extracellular matrix (ECM) proteins. However, the mechanism of aortic valve sclerosis remains unclear. Recently, we observed that diseased human aortic valves overexpress growth factor neurotrophin 3 (NT3). In the present study, we tested the hypothesis that NT3 is a profibrogenic factor to human AVICs. AVICs isolated from normal human aortic valves were cultured in M199 growth medium and treated with recombinant human NT3 (0.10 µg/ml). An exposure to NT3 induced AVIC proliferation, upregulated the production of collagen and matrix metalloproteinase (MMP), and augmented collagen deposition. These changes were abolished by inhibition of the Trk receptors. NT3 induced Akt phosphorylation and increased cyclin D1 protein levels in a Trk receptor-dependent fashion. Inhibition of Akt abrogated the effect of NT3 on cyclin D1 production. Furthermore, inhibition of either Akt or cyclin D1 suppressed NT3-induced cellular proliferation and MMP-9 and collagen production, as well as collagen deposition. Thus, NT3 upregulates cellular proliferation, ECM protein production, and collagen deposition in human AVICs. It exerts these effects through the Trk-Akt-cyclin D1 cascade. NT3 is a profibrogenic mediator in human aortic valve, and overproduction of NT3 by aortic valve tissue may contribute to the mechanism of valvular sclerosis. Copyright © 2017 the American Physiological Society.

46 CFR 78.47-38 - Valves and closing appliances.

Science.gov (United States)

2010-10-01

... 46 Shipping 3 2010-10-01 2010-10-01 false Valves and closing appliances. 78.47-38 Section 78.47-38... Fire and Emergency Equipment, Etc. § 78.47-38 Valves and closing appliances. (a) All valves and closing appliances, or other mechanisms which may be required to be operated for damage control purposes in case of...

Check valve

Science.gov (United States)

Upton, H.A.; Garcia, P.

1999-08-24

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs.

Check valve

International Nuclear Information System (INIS)

Upton, H.A.; Garcia, P.

1999-01-01

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs

Factors influencing mortality after bioprosthetic valve replacement; a midterm outcome.

Science.gov (United States)

Javadzadegan, Hassan; Javadzadegan, Amir; Mehdizadeh Baghbani, Jafar

2013-01-01

Although valve repair is applied routinely nowadays, particularly for mitral regurgitation (MR) or tricuspid regurgitation (TR), valve replacement using prosthetic valves is also common especially in adults. Unfortunately the valve with ideal hemodynamic performance and long-term durability without increasing the risk of bleeding due to long-term anticoagulant therapy has not been introduced. Therefore, patients and physicians must choose either bioprosthetic or mechanical valves. Currently, there is an increasing clinical trend of using bioprosthetic valves instead of mechanical valves even in young patients apparently because of their advantages. Seventy patients undergone valvular replacement using bioprosthetic valves were evaluated by ECG and Echocardiography to assess the rhythm and ejection fracture. Mean follow-up time was 33 months (min 9, max 92). Mortality rate was 25.9% (n=18) within 8 years of follow-up. Statistical analysis showed a significant relation between atrial fibrillation rhythm and mortality (P=0.02). Morbidities occurred in 30 patients (42.8%). Significant statistical relation was found between the morbidities and age over 65 years old (P=0.005). In follow-up period, 4 cases (5.7%) underwent re-operation due to global valve dysfunction. Our study shows that using biprosthetic valve could reduce the risk of morbidity occurrence in patient who needs valve replacement. However, if medical treatments fail, patients should be referred for surgery. This would reduce the risk of mortality because of lower incident of complications such as atrial fibrillation and morbidities due to younger patients' population.

Decreased mechanical properties of heart valve tissue constructs cultured in platelet lysate as compared to fetal bovine serum

NARCIS (Netherlands)

Geemen, van D.; Riem Vis, P.W.; Soekhradj - Soechit, R.S.; Sluijter, J.P.G.; Liefde - van Beest, de M.; Kluin, J.; Bouten, C.V.C.

2011-01-01

In autologous heart valve tissue engineering, there is an ongoing search for alternatives of fetal bovine serum (FBS). Human platelet-lysate (PL) might be a promising substitute. In the present article, we aimed to examine the tissue formation, functionality, and mechanical properties of engineered

Actuation and Control of a Micro Electrohydraulic Digital Servo Valve

Energy Technology Data Exchange (ETDEWEB)

Yu, Z Q; Hu, M J; Pei, X; Ruan, J [MOE Key Laboratory of Mechanical Manufacture and Automation Zhejiang University of Technology, 310014 (China)

2006-10-15

Structure of the micro digital servo valve is given. A micro stepper motor is used as electrical-to-mechanical interface of the valve. A special mechanical device is designed to convert the rotation of the stepper motor into the linear motion of the spool. This moving conversion device functions through an eccentric ball head rigidly connected to the axis of the stepper motor and plugged into a slot at the central spool land. While the stepper motor rotates, the eccentric ball head will actuate the spool to make a linear motion. Unlike conventional servo or proportional valves, in which the spool is forced to central position by a spring force, when the current supply is switched off, the digital valve has a program to control the spool to its central position each time the electrical power supply is switched on or off. The two end screws are used to adjust the position of the sleeve to sustain a mechanical central position coincided with electrical central position given by the stepper motor after initialization. The adjustment has to be carried once before the first time the servo valve is put into service. This paper presents theoretical analysis and experimental study of dynamic characteristics of the proposed micro digital servo valve. Experimental results demonstrated that the valve takes the advantage of high accuracy and fast response.

Actuation and Control of a Micro Electrohydraulic Digital Servo Valve

International Nuclear Information System (INIS)

Yu, Z Q; Hu, M J; Pei, X; Ruan, J

2006-01-01

Structure of the micro digital servo valve is given. A micro stepper motor is used as electrical-to-mechanical interface of the valve. A special mechanical device is designed to convert the rotation of the stepper motor into the linear motion of the spool. This moving conversion device functions through an eccentric ball head rigidly connected to the axis of the stepper motor and plugged into a slot at the central spool land. While the stepper motor rotates, the eccentric ball head will actuate the spool to make a linear motion. Unlike conventional servo or proportional valves, in which the spool is forced to central position by a spring force, when the current supply is switched off, the digital valve has a program to control the spool to its central position each time the electrical power supply is switched on or off. The two end screws are used to adjust the position of the sleeve to sustain a mechanical central position coincided with electrical central position given by the stepper motor after initialization. The adjustment has to be carried once before the first time the servo valve is put into service. This paper presents theoretical analysis and experimental study of dynamic characteristics of the proposed micro digital servo valve. Experimental results demonstrated that the valve takes the advantage of high accuracy and fast response

NRC valve performance test program - check valve testing

International Nuclear Information System (INIS)

Jeanmougin, N.M.

1987-01-01

The Valve Performance Test Program addresses the current requirements for testing of pressure isolation valves (PIVs) in light water reactors. Leak rate monitoring is the current method used by operating commercial power plants to survey the condition of their PIVs. ETEC testing of three check valves (4-inch, 6-inch, and 12-inch nominal diameters) indicates that leak rate testing is not a reliable method for detecting impending valve failure. Acoustic emission monitoring of check valves shows promise as a method of detecting loosened internals damage. Future efforts will focus on evaluation of acoustic emission monitoring as a technique for determining check valve condition. Three gate valves also will be tested to evaluate whether the check valve results are applicable to gate type PIVs

Transcatheter, valve-in-valve transapical aortic and mitral valve implantation, in a high risk patient with aortic and mitral prosthetic valve stenoses

Directory of Open Access Journals (Sweden)

Harish Ramakrishna

2015-01-01

Full Text Available Transcatheter valve implantation continues to grow worldwide and has been used principally for the nonsurgical management of native aortic valvular disease-as a potentially less invasive method of valve replacement in high-risk and inoperable patients with severe aortic valve stenosis. Given the burden of valvular heart disease in the general population and the increasing numbers of patients who have had previous valve operations, we are now seeing a growing number of high-risk patients presenting with prosthetic valve stenosis, who are not potential surgical candidates. For this high-risk subset transcatheter valve delivery may be the only option. Here, we present an inoperable patient with severe, prosthetic valve aortic and mitral stenosis who was successfully treated with a trans catheter based approach, with a valve-in-valve implantation procedure of both aortic and mitral valves.

Stent valve implantation in conventional redo aortic valve surgery to prevent patient-prosthesis mismatch.

Science.gov (United States)

Ferrari, Enrico; Franciosi, Giorgio; Clivio, Sara; Faletra, Francesco; Moccetti, Marco; Moccetti, Tiziano; Pedrazzini, Giovanni; Demertzis, Stefanos

2017-03-01

The goal was to show the technical details, feasibility and clinical results of balloon-expandable stent valve implantation in the aortic position during conventional redo open-heart surgery in selected obese patients with a small aortic prosthesis and severe patient-prosthesis mismatch. Two symptomatic overweight patients (body mass index of 31 and 38), each with a small aortic prosthesis (a 4-year-old, 21-mm Hancock II biological valve and a 29-year-old, 23-mm Duromedic mechanical valve), increased transvalvular gradients (59/31 and 74/44 mmHg) and a reduced indexed effective orifice area (0.50 and 0.43 cm 2 /m 2 ) underwent implantation of two 26-mm balloon-expandable Sapien 3 valves during standard on-pump redo valve surgery. Using full re-sternotomy, cardiopulmonary bypass and cardioplegic arrest, the two balloon-expandable stent valves were implanted under direct view using a standard aortotomy, after prosthesis removal and without annulus enlargement. Aortic cross-clamp times were 162 and 126 min; cardiopulmonary bypass times were 178 and 180 min; total surgical times were 360 and 318 min. At discharge, echocardiograms showed transvalvular peak and mean gradients of 13/9 and 23/13 mmHg and indexed effective orifice areas of 0.64 and 1.08 cm 2 /m 2 . The 3-month echocardiographic follow-up showed transvalvular peak and mean gradients of 18/9 and 19/11 mmHg and indexed effective orifice areas of 0.78 cm 2 /m 2 and 0.84 cm 2 /m 2 , with improved symptoms (New York Heart Association class 1). Implantation of a balloon-expandable stent valve during redo aortic valve surgery is feasible in selected cases and prevents patient-prosthesis mismatch in obese patients without need for aortic annulus enlargement. Moreover, in the case of stent valve degeneration, this approach permits additional valve-in-valve procedures with large stent valves and prevents re-redo surgery. © The Author 2016. Published by Oxford University Press on behalf of the

Surgery for rheumatic mitral valve disease in sub-saharan African countries: why valve repair is still the best surgical option.

Science.gov (United States)

Mvondo, Charles Mve; Pugliese, Marta; Giamberti, Alessandro; Chelo, David; Kuate, Liliane Mfeukeu; Boombhi, Jerome; Dailor, Ellen Marie

2016-01-01

Rheumatic valve disease, a consequence of acute rheumatic fever, remains endemic in developing countries in the sub-Saharan region where it is the leading cause of heart failure and cardiovascular death, involving predominantly a young population. The involvement of the mitral valve is pathognomonic and mitral surgery has become the lone therapeutic option for the majority of these patients. However, controversies exist on the choice between valve repair or prosthetic valve replacement. Although the advantages of mitral valve repair over prosthetic valve replacement in degenerative mitral disease are well established, this has not been the case for rheumatic lesions, where the use of prosthetic valves, specifically mechanical devices, even in poorly compliant populations remains very common. These patients deserve more accurate evaluation in the choice of the surgical strategy which strongly impacts the post-operative outcomes. This report discusses the factors supporting mitral repair surgery in rheumatic disease, according to the patients' characteristics and the effectiveness of the current repair techniques compared to prosthetic valve replacement in developing countries.

Magnon Valve Effect between Two Magnetic Insulators

Science.gov (United States)

Wu, H.; Huang, L.; Fang, C.; Yang, B. S.; Wan, C. H.; Yu, G. Q.; Feng, J. F.; Wei, H. X.; Han, X. F.

2018-03-01

The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by the spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of the magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.

D-dimer to guide the intensity of anticoagulation in Chinese patients after mechanical heart valve replacement: a randomized controlled trial.

Science.gov (United States)

Zhang, L; Zheng, X; Long, Y; Wu, M; Chen, Y; Yang, J; Liu, Z; Zhang, Z

2017-10-01

Essentials Low anticoagulation intensity reduces bleeding but increases thrombosis during warfarin therapy. Elevated D-dimer level is associated with increased thrombosis events. D-dimer can be used to find potential thrombosis in those receiving low intensity therapy. D-dimer-guided therapy may be the optimal strategy for those with mechanical heart valve replacement. Background Controversies remain regarding the optimal anticoagulation intensity for Chinese patients after mechanical heart valve replacement despite guidelines having recommended a standard anticoagulation intensity. Objectives To investigate whether D-dimer could be used to determine the optimal anticoagulation intensity in Chinese patients after mechanical heart valve replacement. Patients/Methods This was a prospective, randomized controlled clinical study. A total of 748 patients following mechanical heart valve replacement in Wuhan Asia Heart Hospital were randomized to three groups at a ratio of 1 : 1 : 1. Patients in two control groups received warfarin therapy based on constant standard intensity (international normalized ratio [INR], 2.5-3.5; n = 250) and low intensity (INR, 1.8-2.6; n = 248), respectively. In the experimental group (n = 250), warfarin therapy was initiated at low intensity, then those with elevated D-dimer levels were adjusted to standard intensity. All patients were followed-up for 24 months until the occurrence of endpoints, including bleeding events, thrombotic events and all-cause mortality. Results A total of 718 patients were included in the analysis. Fifty-three events occurred during follow-up. There was less hemorrhage (3/240 vs. 16/241; hazard ratio [HR], 0.18; 95% confidence interval [CI], 0.07-0.45) and all-cause mortality (4/240 vs. 12/241; HR, 0.33; 95% CI, 0.12-0.87) observed in the D-dimer-guided group than in the standard-intensity group. A lower incidence of thrombotic events was also observed in the D-dimer-guided group when compared with the

Inhibitory role of Notch1 in calcific aortic valve disease.

Directory of Open Access Journals (Sweden)

Asha Acharya

Full Text Available Aortic valve calcification is the most common form of valvular heart disease, but the mechanisms of calcific aortic valve disease (CAVD are unknown. NOTCH1 mutations are associated with aortic valve malformations and adult-onset calcification in families with inherited disease. The Notch signaling pathway is critical for multiple cell differentiation processes, but its role in the development of CAVD is not well understood. The aim of this study was to investigate the molecular changes that occur with inhibition of Notch signaling in the aortic valve. Notch signaling pathway members are expressed in adult aortic valve cusps, and examination of diseased human aortic valves revealed decreased expression of NOTCH1 in areas of calcium deposition. To identify downstream mediators of Notch1, we examined gene expression changes that occur with chemical inhibition of Notch signaling in rat aortic valve interstitial cells (AVICs. We found significant downregulation of Sox9 along with several cartilage-specific genes that were direct targets of the transcription factor, Sox9. Loss of Sox9 expression has been published to be associated with aortic valve calcification. Utilizing an in vitro porcine aortic valve calcification model system, inhibition of Notch activity resulted in accelerated calcification while stimulation of Notch signaling attenuated the calcific process. Finally, the addition of Sox9 was able to prevent the calcification of porcine AVICs that occurs with Notch inhibition. In conclusion, loss of Notch signaling contributes to aortic valve calcification via a Sox9-dependent mechanism.

Extrinsic mechanism obstructing the opening of a prosthetic mitral valve: an unusual case of suture entrapment.

Science.gov (United States)

Ozkan, Mehmet; Astarcioglu, Mehmet Ali; Karakoyun, Suleyman; Balkanay, Mehmet

2012-02-01

Obstruction to a prosthetic cardiac valve is a well-recognized complication of cardiac valve replacement. Malfunction of the mobile component of a prosthetic valve to open or close correctly may occur in consequence of intrinsic or extrinsic causes (thrombus, vegetation, entrapment of left ventricular myocardium, suture entanglement, and pannus formation) that may result prosthetic valve stenosis and/or insufficiency. In the case we report a 48-year-old female with valve dysfunction occurred early after surgery, as one valve leaflet was only able to partially open due to suture entrapment. © 2011, Wiley Periodicals, Inc.

Energy dynamics of the intraventricular vortex after mitral valve surgery.

Science.gov (United States)

Nakashima, Kouki; Itatani, Keiichi; Kitamura, Tadashi; Oka, Norihiko; Horai, Tetsuya; Miyazaki, Shohei; Nie, Masaki; Miyaji, Kagami

2017-09-01

Mitral valve morphology after mitral valve surgery affects postoperative intraventricular flow patterns and long-term cardiac performance. We visualized ventricular flow by echocardiography vector flow mapping (VFM) to reveal the impact of different mitral valve procedures. Eleven cases of mechanical mitral valve replacement (nine in the anti-anatomical and two in the anatomical position), three bioprosthetic mitral valve replacements, and four mitral valve repairs were evaluated. The mean age at the procedure was 57.4 ± 17.8 year, and the echocardiography VFM in the apical long-axis view was performed 119.9 ± 126.7 months later. Flow energy loss (EL), kinetic pressure (KP), and the flow energy efficiency ratio (EL/KP) were measured. The cases with MVR in the anatomical position and with valve repair had normal vortex directionality ("Clockwise"; N = 6), whereas those with MVR in the anti-anatomical position and with a bioprosthetic mitral valve had the vortex in the opposite direction ("Counterclockwise"; N = 12). During diastole, vortex direction had no effect on EL ("Clockwise": 0.080 ± 0.025 W/m; "Counterclockwise": 0.083 ± 0.048 W/m; P = 0.31) or KP ("Clockwise": 0.117 ± 0.021 N; "Counterclockwise": 0.099 ± 0.057 N; P = 0.023). However, during systole, the EL/KP ratio was significantly higher in the "Counterclockwise" vortex than that in the "Clockwise" vortex (1.056 ± 0.463 vs. 0.617 ± 0.158; P = 0.009). MVP and MVR with a mechanical valve in the anatomical position preserve the physiological vortex, whereas MVR with a mechanical valve in the anti-anatomical position and a bioprosthetic mitral valve generate inefficient vortex flow patterns, resulting in a potential increase in excessive cardiac workload.

Antithrombotic Therapy in Patients with Prosthetic Heart Valves

Directory of Open Access Journals (Sweden)

Mohamed HA

2009-01-01

Full Text Available Patients with mechanical valve prostheses require a lifelong anticoagulant treatment. The combined use of Warfarin and low-dose aspirin appears to reduce the risk of valve thrombosis and systemic embolism at a low risk of bleeding. The management of women with prosthetic heart valves during pregnancy poses a particular challenge, as there are no available controlled clinical trials to provide guidelines for effective antithrombotic therapy. Oral anticoagulants, such as Warfarin, cause foetal embryopathy; unfractionated heparin and low-molecular-weight heparin have been reported to be ineffective in preventing thromboembolic complications.This article discusses the available data and the most recent guidelines in the antithrombotic management of patients with prosthetic valves, and antithrombotic therapy in various clinical situations such as pregnant women with prosthetic heart valves, and patients with prosthetic heart valves undergoing noncardiac surgery.

Mechanical stress is associated with right ventricular response to pulmonary valve replacement in patients with repaired tetralogy of Fallot.

Science.gov (United States)

Tang, Dalin; Yang, Chun; Del Nido, Pedro J; Zuo, Heng; Rathod, Rahul H; Huang, Xueying; Gooty, Vasu; Tang, Alexander; Billiar, Kristen L; Wu, Zheyang; Geva, Tal

2016-03-01

Patients with repaired tetralogy of Fallot account for a substantial proportion of cases with late-onset right ventricular failure. The current surgical approach, which includes pulmonary valve replacement/insertion, has yielded mixed results. Therefore, it may be clinically useful to identify parameters that can be used to predict right ventricular function response to pulmonary valve replacement. Cardiac magnetic resonance data before and 6 months after pulmonary valve replacement were obtained from 16 patients with repaired tetralogy of Fallot (8 male, 8 female; median age, 42.75 years). Right ventricular ejection fraction change from pre- to postpulmonary valve replacement was used as the outcome. The patients were divided into group 1 (n = 8, better outcome) and group 2 (n = 8, worst outcome). Cardiac magnetic resonance-based patient-specific computational right ventricular/left ventricular models were constructed, and right ventricular mechanical stress and strain, wall thickness, curvature, and volumes were obtained for analysis. Our results indicated that right ventricular wall stress was the best single predictor for postpulmonary valve replacement outcome with an area under the receiver operating characteristic curve of 0.819. Mean values of stress, strain, wall thickness, and longitudinal curvature differed significantly between the 2 groups with right ventricular wall stress showing the largest difference. Mean right ventricular stress in group 2 was 103% higher than in group 1. Computational modeling and right ventricular stress may be used as tools to identify right ventricular function response to pulmonary valve replacement. Large-scale clinical studies are needed to validate these preliminary findings. Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Aortic valve replacement for Libman-Sacks endocarditis.

Science.gov (United States)

Keenan, Jack B; Janardhanan, Rajesh; Larsen, Brandon T; Khalpey, Zain

2016-10-04

A 24-year-old man with systemic lupus erythematosus and antiphospholipid syndrome complicated by lupus nephritis presented with acute limb ischaemia secondary to an embolus. Following embolectomy, the patient underwent a transthoracic echocardiogram which revealed a large vegetation on all three cusps of the aortic valve. The patient was taken for an urgent aortic valve replacement with a mechanical valve. Cultures of one cusp remained sterile. Histopathological examination of the remaining two cusps revealed sterile fibrin-rich thrombotic vegetations characteristic of non-bacterial thrombotic endocarditis. 2016 BMJ Publishing Group Ltd.

Thrombocytopenia following implantation of the stentless biological sorin freedom SOLO valve.

Science.gov (United States)

Gersak, Borut; Gartner, Urska; Antonic, Miha

2011-07-01

Stentless biological valves have proven advantages in hemodynamic performance and left ventricular function compared to stented biological valves. Following a marked postoperative fall in the platelet count of patients after implantation of the Freedom SOLO valve, the study aim was to confirm clinical observations that this effect was more severe in patients receiving Freedom SOLO valves than in those receiving St. Jude Medical (SJM) mechanical aortic valves. Preoperative and postoperative platelet counts were compared in two groups of patients who underwent aortic valve replacement (AVR) without any concomitant procedures between January and December 2007. Patients received either a Freedom SOLO valve (n = 28) or a SJM mechanical valve (n = 41). Mean values of platelet counts were compared using three multiple linear regression models. Platelet counts were significantly lower in the Freedom SOLO group than in the SJM group from the first postoperative day (POD 1) up to POD 6 (p SOLO group the platelet count fell below 30x10(9)/l, while the lowest level in the SJM group was 75x10(9)/l. Based on multiple linear regression models, the type of valve implanted had a statistically significant influence on postoperative platelet counts on POD 1, POD 3, and POD 5 (p SOLO group.

Function analysis of steam isolation valves

International Nuclear Information System (INIS)

Persson, R.; Kilpi, K.; Noro, H.; Siikonen, T.; Sjoeberg, A.; Wallen, G.; Aakesson, H.

1981-01-01

Function analysis of system-medium-operated steam isolation valves has been the objective of the Swedish-Finnish IVLS project, the results of which are presented in this report. Theoretical models were to be verified against available experimental data, to some extent from the HDR blowdown experiments, which are part of a German reactor safety program. Finnish hydraulic measurements on a valve model (scale 1:2.15) have been performed to give complementary data. The analysis work has covered the thermal-hydraulic behaviour of steam isolation valves as well as phenomena related to structural mechanics. Work performed under contract with the Swedish Nuclear Power Inspectorate. (Author)

Three-dimentional simulation of flow-induced platelet activation in artificial heart valves

Science.gov (United States)

Hedayat, Mohammadali; Asgharzadeh, Hafez; Borazjani, Iman

2015-11-01

Since the advent of heart valve, several valve types such as mechanical and bio-prosthetic valves have been designed. Mechanical Heart Valves (MHV) are durable but suffer from thromboembolic complications that caused by shear-induced platelet activation near the valve region. Bio-prosthetic Heart Valves (BHV) are known for better hemodynamics. However, they usually have a short average life time. Realistic simulations of heart valves in combination with platelet activation models can lead to a better understanding of the potential risk of thrombus formation in such devices. In this study, an Eulerian approach is developed to calculate the platelet activation in three-dimensional simulations of flow through MHV and BHV using a parallel overset-curvilinear immersed boundary technique. A curvilinear body-fitted grid is used for the flow simulation through the anatomic aorta, while the sharp-interface immersed boundary method is used for simulation of the Left Ventricle (LV) with prescribed motion. In addition, dynamics of valves were calculated numerically using under-relaxed strong-coupling algorithm. Finally, the platelet activation results for BMV and MHV are compared with each other.

Mechanisms of recurrent aortic regurgitation after aortic valve repair: predictive value of intraoperative transesophageal echocardiography.

Science.gov (United States)

le Polain de Waroux, Jean-Benoît; Pouleur, Anne-Catherine; Robert, Annie; Pasquet, Agnès; Gerber, Bernhard L; Noirhomme, Philippe; El Khoury, Gébrine; Vanoverschelde, Jean-Louis J

2009-08-01

The aim of the present study was to examine the intraoperative echocardiographic features associated with recurrent severe aortic regurgitation (AR) after an aortic valve repair surgery. Surgical valve repair for AR has significant advantages over valve replacement, but little is known about the predictors and mechanisms of its failure. We blindly reviewed all clinical, pre-operative, intraoperative, and follow-up transesophageal echocardiographic data of 186 consecutive patients who underwent valve repair for AR during a 10-year period and in whom intraoperative and follow-up echo data were available. After a median follow-up duration of 18 months, 41 patients had recurrent 3+ AR, 23 patients presented with residual 1+ to 2+ AR, and 122 had no or trivial AR. In patients with recurrent 3+ AR, the cause of recurrent AR was the rupture of a pericardial patch in 3 patients, a residual cusp prolapse in 26 patients, a restrictive cusp motion in 9 patients, an aortic dissection in 2 patients, and an infective endocarditis in 1 patient. Pre-operatively, all 3 groups were similar for aortic root dimensions and prevalence of bicuspid valve (overall 37%). Patients with recurrent AR were more likely to display Marfan syndrome or type 3 dysfunction pre-operatively. At the opposite end, patients with continent AR repair at follow-up were more likely to have type 2 dysfunction pre-operatively. After cardiopulmonary bypass, a shorter coaptation length, the degree of cusp billowing, a lower level of coaptation (relative to the annulus), a larger diameter of the aortic annulus and the sino-tubular junction, the presence of a residual AR, and the width of its vena contracta were associated with the presence of AR at follow-up. Multivariate Cox analysis identified a shorter coaptation length (odds ratio [OR]: 0.8, p = 0.05), a coaptation occurring below the level of the aortic annulus (OR: 7.9, p < 0.01), a larger aortic annulus (OR: 1.2, p = 0.01), and residual aortic regurgitation

SAFETY SHUTOFF VALVE

DEFF Research Database (Denmark)

2010-01-01

It is disclosed a shut-off valve which acts automatically and has a fully mechanical performance with respect to the loosing of the tower-shape part balance under the effect of the special acceleration Which is arisen from the quakes waves or serious vibrations, while such vibrations are mainly r...

Bioprosthetic Valve Fracture During Valve-in-valve TAVR: Bench to Bedside.

Science.gov (United States)

Saxon, John T; Allen, Keith B; Cohen, David J; Chhatriwalla, Adnan K

2018-01-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) has been established as a safe and effective means of treating failed surgical bioprosthetic valves (BPVs) in patients at high risk for complications related to reoperation. Patients who undergo VIV TAVR are at risk of patient-prosthesis mismatch, as the transcatheter heart valve (THV) is implanted within the ring of the existing BPV, limiting full expansion and reducing the maximum achievable effective orifice area of the THV. Importantly, patient-prosthesis mismatch and high residual transvalvular gradients are associated with reduced survival following VIV TAVR. Bioprosthetic valve fracture (BVF) is as a novel technique to address this problem. During BPV, a non-compliant valvuloplasty balloon is positioned within the BPV frame, and a highpressure balloon inflation is performed to fracture the surgical sewing ring of the BPV. This allows for further expansion of the BPV as well as the implanted THV, thus increasing the maximum effective orifice area that can be achieved after VIV TAVR. This review focuses on the current evidence base for BVF to facilitate VIV TAVR, including initial bench testing, procedural technique, clinical experience and future directions.

Multifunctional four-port directional control valve constructed from logic valves

International Nuclear Information System (INIS)

Lisowski, E.; Czyżycki, W.; Rajda, J.

2014-01-01

Highlights: • Directional valve with standard ISO 440-08 has been constructed from logic valves. • Only one innovative valve may replace whole family of the standard valves. • CFD analysis and bench tests of the innovative valve has been carried. • Parameters of the innovative valve are equaling or surpassing the standard ones. • The innovative valve has additional possibilities of pressure and flow control. - Abstract: The paper refers to four-port solenoid pilot operated valves, which are subplate mounted in a hydraulic system in accordance with the ISO 4401 standard. Their widespread use in many machines and devices causes a continuing interest in the development of their design by both the scientific centers and the industry. This paper presents an innovative directional control valve based on the use of logic valves and a methodology followed for the design of it by using Solid Edge CAD and ANSYS/Fluent CFD software. The valve design methodology takes into account the need to seek solutions that minimize flow resistance through the valve. For this purpose, the flow paths are prepared by means of CAD software and pressure-flow curves are determined as a result of CFD analysis. The obtained curves are compared with the curves available in the catalogs of spool type directional control valves. The new solution allows to replace the whole family of spool type four-port directional control valves by one valve built of logic valves. In addition, the innovative directional control valve provides leak-proof shutting the flow paths off and also it can control flow rate and even pressure of working liquid. A prototype of the valve designed by the presented method has been made and tested on the test bench. The results quoted in the paper confirm that the developed logic type directional control valve is able to meet all designed connection configurations, and the obtained pressure-flow curves show very good conformity with the results of CFD analysis

Control Valve

Energy Technology Data Exchange (ETDEWEB)

Moore, Wayne R.

2018-03-20

A control valve includes a first conduit having a first inlet and a first outlet and defining a first passage; a second conduit having a second inlet and a second outlet and defining a second passage, the second conduit extending into the first passage such that the second inlet is located within the first passage; and a valve plate disposed pivotably within the first passage, the valve plate defining a valve plate surface. Pivoting of the valve plate within the first passage varies flow from the first inlet to the first outlet and the valve plate is pivotal between a first position and a second position such that in the first position the valve plate substantially prevents fluid communication between the first passage and the second passage and such that in the second position the valve plate permits fluid communication between the first passage and the second passage.

Prosthetic Mitral Valve Leaflet Escape

Science.gov (United States)

Kim, Darae; Hun, Sin Sang; Cho, In-Jeong; Shim, Chi-Young; Ha, Jong-Won; Chung, Namsik; Ju, Hyun Chul; Sohn, Jang Won

2013-01-01

Leaflet escape of prosthetic valve is rare but potentially life threatening. It is essential to make timely diagnosis in order to avoid mortality. Transesophageal echocardiography and cinefluoroscopy is usually diagnostic and the location of the missing leaflet can be identified by computed tomography (CT). Emergent surgical correction is mandatory. We report a case of fractured escape of Edward-Duromedics mitral valve 27 years after the surgery. The patient presented with symptoms of acute decompensated heart failure and cardiogenic shock. She was instantly intubated and mechanically ventilated. After prompt evaluation including transthoracic echocardiography and CT, the escape of the leaflet was confirmed. The patient underwent emergent surgery for replacement of the damaged prosthetic valves immediately. Eleven days after the surgery, the dislodged leaflet in iliac artery was removed safely and the patient recovered well. PMID:23837121

Valving for controlling a fluid-driven reciprocating apparatus

Science.gov (United States)

Whitehead, John C.

1995-01-01

A pair of control valve assemblies for alternately actuating a pair of fluid-driven free-piston devices by using fluid pressure communication therebetween. Each control valve assembly is switched by a pressure signal depending on the state of its counterpart's piston. The communication logic is arranged to provide overlap of the forward strokes of the pistons, so that at least one of the pair will always be pressurized. Thus, uninterrupted pumping of liquid is made possible from a pair of free-piston pumps. In addition, the speed and frequency of piston stroking is entirely dependent on the mechanical power load applied. In the case of a pair of pumps, this enables liquid delivery at a substantially constant pressure over the full range of flow rates, from zero to maximum flow. Each of the valve assemblies uses an intake-exhaust valve and a signal valve with the signal valve of one pump being connected to be pressure responsive to the piston of the opposite cylinder or pump.

Review and analysis of check valve failure data

International Nuclear Information System (INIS)

Todd, M.D.; Casada, D.A.

1992-01-01

Check valve operating problems in recent years have resulted in significant operating transients, increased cost and decreased system availability. There has been, in response, additional attention given to check valves by utilities, as well as the US Nuclear Regulatory Commission and the American Society of Mechanical Engineers Operation and Maintenance Committee. All these organizations have the fundamental goal of ensuring reliable operation of check valves. A key ingredient to an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. Oak Ridge National Laboratory is currently conducting a detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System. The focus of the review is on check valve failures that have involved significant degradation of the valve internal parts. A variety of parameters are being considered during the review, including size, age, system of service, method of failure discovery, the affected valve parts, attributed causes, and corrective actions

Fluid mechanics of needle valves with rounded components Part I: Configurations and models

Czech Academy of Sciences Publication Activity Database

Tesař, Václav

2017-01-01

Roč. 254, February (2017), s. 101-108 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * valve with rounded inlet * valve Subject RIV: BK - Fluid Dynamics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.499, year: 2016 http://ac.els-cdn.com/S0924424716310226/1-s2.0-S0924424716310226-main.pdf?_tid=f1570ee0-2f46-11e7-b057-00000aab0f26&acdnat=1493736920_595bfaae6a6922d4213225a968d5d74c

Analysis of Mitral Valve Replacement Outcomes is Enhanced by Meaningful Clinical Use of Electronic Health Records

Science.gov (United States)

Chen, John C; Pfeffer, Thomas; Johnstone, Shelley; Chen, Yuexin; Kiley, Mary-Lou; Richter, Richard; Lee, Hon

2013-01-01

Objective: Cardiac surgical mortality has improved during the last decade despite the aging of the population. An integrated US health plan developed a heart valve registry to track outcomes and complications of heart valve operations. This database was used for longitudinal evaluation of mitral valve (MV) outcomes from 1999 to 2008 at four affiliated hospitals. Methods: We identified 3130 patients in the Apollo database who underwent 3180 initial MV procedures. Internal administrative and Social Security Administration databases were merged to determine survival rates. Electronic health records were searched to ascertain demographics, comorbidities, and postoperative complications. Cox regression was used to evaluate mean survival and identify risk factors. Results: The procedures included 1160 mechanical valve replacements, 1159 tissue valve replacements, and 861 annuloplasties. The mean age of patients undergoing these procedures was 58 ± 11 years, 69 ± 12 years, and 62 ± 12 years, respectively. Mean survival was 8.9 ± 0.1 years for mechanical valve replacement, 7.0 ± 0.1 years for tissue valve replacement, and 7.7 ± 0.1 years for annuloplasty. Early in the study, there was a preference for implanting mechanical MVs. Beginning in 2003, more patients received tissue valve replacements rather than mechanical valves. Over time, there was an increasing trend of annuloplasty. Cox regression analysis identified the following risk factors for increased ten-year mortality: tissue valve implantation; advanced age; female sex; nonelective, nonisolated procedure; diabetes; postoperative use of banked blood products; previous cardiovascular intervention; dialysis; and longer perfusion time. Hospital location, reoperation, preoperative anticoagulation, and cardiogenic shock were not statistically significant risk factors. Conclusions: When controlling for other risk factors, we observed a lower long-term survival rate for tissue valve replacement compared with

Valve packing manual. A maintenance application guide

International Nuclear Information System (INIS)

Aikin, J.A.; McCutcheon, R.G.; Cumming, D.

1997-01-01

Since 1970, AECL Chalk River Mechanical Equipment Development (MED) branch has invested over 175 person years in testing related to improving valve packing performance. Successful developments, including, 'live-loading', reduced packing heights, and performance-based packing qualification testing have been implemented. Since 1986, MED and the Integrated Valve Actuator Program Task Force - Valve Packing Steering Committee (IVAP-VPSC) have been involved in the development of combination die-formed graphite packing for use in CANDU plants. Many reports, articles, and specifications have been issued. Due to the large amount of test data and reports, a more user-friendly document has been prepared for everyday use. The Valve Packing Manual is based on many years of MED research and testing, as well as operating experience from CANDU nuclear generating stations (NGS). Since 1986, packing research and testing has been funded by the CANDU Owners Group (COG), the Electric Power Research Institute (EPRI), and participating valve packing manufacturers. The Valve Packing Manual (VPM) provides topical summaries of all work related to valve packing done since 1985. It includes advances in configuration design, stem packing friction, materials specifications, and installation procedures. This paper provides an overview on the application of the VPM with a focus on qualification testing, packing configuration, and stem packing friction. (author)

Non-cardiac surgery in patients with prosthetic heart valves: a 12 years experience

International Nuclear Information System (INIS)

Akhtar, R.P.; Khan, J.S.; Abid, A.R.; Gardezi, S.J.R.

2007-01-01

To study patients with mechanical heart valves undergoing non-cardiac surgery and their anticoagulation management during these procedures. Patients with mechanical heart valves undergoing non-cardiac surgical operation during this period, were included. Their anticoagulation was monitored and anticoagulation related complications were recorded. In this study, 507 consecutive patients with a mechanical heart valve replacement were followed-up. Forty two (8.28%) patients underwent non-cardiac surgical operations of which 24 (57.1%) were for abdominal and non-abdominal surgeries, 5 (20.8%) were emergency and 19 (79.2%) were planned. There were 18 (42.9%) caesarean sections for pregnancies. Among the 24 procedures, there were 7(29.1%) laparotomies, 7(29.1%) hernia repairs, 2 (8.3%) cholecystectomies, 2 (8.3%) hysterectomies, 1(4.1%) craniotomy, 1(4.1%) spinal surgery for neuroblastoma, 1(4.1%) ankle fracture and 1(4.1%) carbuncle. No untoward valve or anticoagulation related complication was seen during this period. Patients with mechanical valve prosthesis on life-long anticoagulation, if managed properly, can undergo any type of noncardiac surgical operation with minimal risk. (author)

Consequence of patient substitution of nattokinase for warfarin after aortic valve replacement with a mechanical prosthesis

OpenAIRE

Elahi, Maqsood M.; Choi, Charles H.; Konda, Subbareddy; Shake, Jay G.

2015-01-01

This report describes a patient's self-substitution of nattokinase for the vitamin K antagonist warfarin after aortic valve replacement with a mechanical prosthesis. Nattokinase is an enzyme derived from a popular fermented soybean preparation in Japan (natto), which has fibrinolytic properties and is gaining popularity in nontraditional health journals and nonmedical health websites as an over-the-counter thrombolytic. After nearly a year of use of nattokinase without warfarin, the patient d...

Thromboembolism and mechanical heart valves : A randomized study revisited

NARCIS (Netherlands)

Kuntze, CEE; Blackstone, EH; Ebels, T

Background. This study was designed to revise and substantiate previous inferences, based on short-term follow-up, about differences in the incidence of anticoagulant-related events after heart valve replacement among patients who had been randomly assigned to receive either a Bjork-Shiley,

A new approach to heart valve tissue engineering

DEFF Research Database (Denmark)

Kaasi, Andreas; Cestari, Idágene A.; Stolf, Noedir A G.

2011-01-01

The 'biomimetic' approach to tissue engineering usually involves the use of a bioreactor mimicking physiological parameters whilst supplying nutrients to the developing tissue. Here we present a new heart valve bioreactor, having as its centrepiece a ventricular assist device (VAD), which exposes...... chamber. Subsequently, applied vacuum to the pneumatic chamber causes the blood chamber to fill. A mechanical heart valve was placed in the VAD's inflow position. The tissue engineered (TE) valve was placed in the outflow position. The VAD was coupled in series with a Windkessel compliance chamber...

Valve thrombosis following transcatheter aortic valve implantation: a systematic review.

Science.gov (United States)

Córdoba-Soriano, Juan G; Puri, Rishi; Amat-Santos, Ignacio; Ribeiro, Henrique B; Abdul-Jawad Altisent, Omar; del Trigo, María; Paradis, Jean-Michel; Dumont, Eric; Urena, Marina; Rodés-Cabau, Josep

2015-03-01

Despite the rapid global uptake of transcatheter aortic valve implantation, valve trombosis has yet to be systematically evaluated in this field. The aim of this study was to determine the clinical characteristics, diagnostic criteria, and treatment outcomes of patients diagnosed with valve thrombosis following transcatheter aortic valve implantation through a systematic review of published data. Literature published between 2002 and 2012 on valve thrombosis as a complication of transcatheter aortic valve implantation was identified through a systematic electronic search. A total of 11 publications were identified, describing 16 patients (mean age, 80 [5] years, 65% men). All but 1 patient (94%) received a balloon-expandable valve. All patients received dual antiplatelet therapy immediately following the procedure and continued to take either mono- or dual antiplatelet therapy at the time of valve thrombosis diagnosis. Valve thrombosis was diagnosed at a median of 6 months post-procedure, with progressive dyspnea being the most common symptom. A significant increase in transvalvular gradient (from 10 [4] to 40 [12] mmHg) was the most common echocardiographic feature, in addition to leaflet thickening. Thrombus was not directly visualized with echocardiography. Three patients underwent valve explantation, and the remaining received warfarin, which effectively restored the mean transvalvular gradient to baseline within 2 months. Systemic embolism was not a feature of valve thrombosis post-transcatheter aortic valve implantation. Although a rare, yet likely under-reported complication of post-transcatheter aortic valve implantation, progressive dyspnea coupled with an increasing transvalvular gradient on echocardiography within the months following the intervention likely signifies valve thrombosis. While direct thrombus visualization appears difficult, prompt initiation of oral anticoagulation therapy effectively restores baseline valve function. Copyright © 2014

Aortic root surgery in Marfan syndrome: Comparison of aortic valve-sparing reimplantation versus composite grafting.

Science.gov (United States)

Karck, Matthias; Kallenbach, Klaus; Hagl, Christian; Rhein, Christine; Leyh, Rainer; Haverich, Axel

2004-02-01

The objective of this study was to compare the results of aortic valve-sparing reimplantation and aortic root replacement with mechanical valve conduits in patients with Marfan syndrome undergoing operation for aortic root aneurysms. Patients and methods Between March 1979 and April 2002, 119 patients with clinical evidence of Marfan syndrome underwent composite graft replacement with mechanical valve conduits (n = 74) or aortic valve-sparing reimplantation according to David (n = 45). The underlying causes were aortic dissection type A (43 patients) and aneurysms (76 patients). Patients undergoing aortic valve reimplantation were younger compared with patients undergoing composite grafting (28 vs 35 years, P =.002) and had longer intraoperative aortic crossclamp times (125 vs 78 minutes, P valve reimplantation (P =.15). Mean follow-up was 30 months for patients undergoing aortic valve reimplantation and 114 months for patients undergoing composite grafting. Freedom from reoperation and death after 5 years postoperatively was 92% and 89% in patients undergoing composite grafting and 84% and 96% in patients undergoing aortic valve reimplantation (P =.31; P =.54), respectively. Thromboembolic complications or late postoperative bleeding occurred in 17 patients undergoing composite grafting, and an early postoperative event occurred in 1 patient undergoing aortic valve reimplantation. The results of aortic valve reimplantation and composite grafting of the aortic valve and ascending aorta with mechanical valve conduits are similar with regard to early and mid-term postoperative mortality and to the incidence of late reoperations in patients with Marfan syndrome. The low risk of thromboembolic or bleeding complications favors aortic valve reimplantation in these patients.

Platelet thrombosis in cardiac-valve prostheses

International Nuclear Information System (INIS)

Dewanjee, M.K.

1989-01-01

The contribution of platelets and clotting factors in thrombosis on cardiovascular prostheses had been quantified with several tracers. Thrombus formation in vivo could be measured semiquantitatively in animal models and patients with indium-111, Technetium-99m labeled platelets, iodine-123, iodine-131 labeled fibrinogen, and In-111 and Tc-99m labeled antibody to the fibrinogen-receptor on the platelet- membrane, or fibrin. The early studies demonstrated that certain platelet-inhibitors, e.g. sulfinpyrazone, aspirin or aspirin- persantine increased platelet survival time with mechanical valves implanted in the baboon model and patients. Thrombus localization by imaging is possible for large thrombus on thrombogenic surface of prosthesis in the acute phase. The majority of thrombus was found in the sewing ring (Dacron) in the acute phase in both the mechanical and tissue valves. The amount of retained thrombus in both mechanical and tissue valves in our one-day study in the dog model was similar (< 1% if injected In-111 platelets = 5 billion platelets). As the fibrous ingrowth covered the sewing ring, the thrombus formation decreased significantly. Only a small amount of thrombus was found on the leaflets at one month in both the dog and calf models. 38 refs., 9 figs., 5 tabs

Platelet thrombosis in cardiac-valve prostheses

Energy Technology Data Exchange (ETDEWEB)

Dewanjee, M.K.

1989-01-01

The contribution of platelets and clotting factors in thrombosis on cardiovascular prostheses had been quantified with several tracers. Thrombus formation in vivo could be measured semiquantitatively in animal models and patients with indium-111, Technetium-99m labeled platelets, iodine-123, iodine-131 labeled fibrinogen, and In-111 and Tc-99m labeled antibody to the fibrinogen-receptor on the platelet- membrane, or fibrin. The early studies demonstrated that certain platelet-inhibitors, e.g. sulfinpyrazone, aspirin or aspirin- persantine increased platelet survival time with mechanical valves implanted in the baboon model and patients. Thrombus localization by imaging is possible for large thrombus on thrombogenic surface of prosthesis in the acute phase. The majority of thrombus was found in the sewing ring (Dacron) in the acute phase in both the mechanical and tissue valves. The amount of retained thrombus in both mechanical and tissue valves in our one-day study in the dog model was similar (< 1% if injected In-111 platelets = 5 billion platelets). As the fibrous ingrowth covered the sewing ring, the thrombus formation decreased significantly. Only a small amount of thrombus was found on the leaflets at one month in both the dog and calf models. 38 refs., 9 figs., 5 tabs.

Tight valve

International Nuclear Information System (INIS)

Guedj, F.

1987-01-01

This sealed valve is made with a valve seat, an axial valve with a rod fixed to its upper end, a thick bell surrounding the rod and welded by a thin join on the valve casing, a threated ring screwed onto the upper end of the rod and a magnet or electromagnet rotating the ring outside the bell [fr

The JUPITER registry: One-year outcomes of transapical aortic valve implantation using a second generation transcatheter heart valve for aortic regurgitation.

Science.gov (United States)

Silaschi, Miriam; Conradi, Lenard; Wendler, Olaf; Schlingloff, Friederike; Kappert, Utz; Rastan, Ardawan J; Baumbach, Hardy; Holzhey, David; Eichinger, Walter; Bader, Ralf; Treede, Hendrik

2018-06-01

We present 1-year outcomes of the post-market registry of a next-generation transcatheter heart valve used for aortic regurgitation (AR). Transcatheter aortic valve replacement (TAVR) is routine in high-risk patients with aortic stenosis but is not recommended for AR. The JenaValve™ (JenaValve Technology GmbH, Munich, Germany) overcomes technical challenges in AR patients through a leaflet clipping mechanism. The JenaValve EvalUation of Long Term Performance and Safety In PaTients with SEvere Aortic Stenosis oR Aortic Insufficiency (JUPITER) Registry is a European study to evaluate safety and effectiveness of this THV. From 2012-2015, 30 patients with AR were enrolled. Mean age was 74.4 ± 9.3 years. Procedural success was 96.7% (29/30). One patient was converted to open surgery. No annular rupture or coronary ostia obstruction occurred. Mortality at 30 days was 10.0% (3/30). Combined safety endpoint was met in 13.3% (4/30). Paravalvular regurgitation was not present/trivial in 84.6% (22/26) and mild in 15.4% (4/26). Rate of permanent pacemaker implantation was 3.8% (1/26). One-year Kaplan-Meier survival was 79.9%, one-year combined efficacy was 73.1% (19/30). No further strokes were observed during 1 year of follow-up. The JenaValve overcomes technical challenges of TAVR in AR through a clipping mechanism. We report satisfactory outcomes of a multicenter registry using the JenaValve for predominant AR, as rate of THV embolization, residual AR and permanent pacemaker implantation was low. One-year results using the JenaValve for AR encourage its use for this indication. © 2017 Wiley Periodicals, Inc.

Intermittent acute aortic valve regurgitation: A case report of a prosthetic valve dysfunction

NARCIS (Netherlands)

S.E. Karagiannis (Stefanos); G. Karatasakis (George); K. Spargias (Konstantinos); L. Louka; D. Poldermans (Don); D.V. Cokkinos (Dennis)

2008-01-01

textabstractComplications of any mechanical prosthesis include thrombus or pannus formation. In our case report we demonstrate that prosthetic aortic valve regurgitation due to pannus formation may be intermittent and non-cyclic in pattern and therefore not obvious at the time of original clinical

Aortic valve bypass

DEFF Research Database (Denmark)

Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik

2013-01-01

In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). ...

Bentall Procedure Using Cryopreserved Valved Aortic Homografts

Science.gov (United States)

Christenson, Jan T.; Sierra, Jorge; Trindade, Pedro T.; Didier, Dominique; Kalangos, Afksendiyos

2004-01-01

The Bentall procedure is the standard operation for patients who have lesions of the ascending aorta associated with aortic valve disease. In many cases, however, mechanical prosthetic conduits are not suitable. There are few reports in the English-language medical literature concerning the mid- to long-term outcome of Bentall operations with cryopreserved homografts. Therefore, we reviewed our experience with this procedure and valved homografts. From January 1997 through December 2002, 21 patients underwent a Bentall operation with cryopreserved homografts at our institution. There were 14 males and 7 females; the mean age was 36 ± 21 years (range, 15–74 years). Eleven patients had undergone previous aortic valve surgery. All patients had aortic dilatation or aneurysms involving the ascending aorta. Indications for surgery included aortic valve stenosis or insufficiency, and aortic valve endocarditis (native valve or prosthetic). One patient had Takayasu's arteritis and 3 had Marfan syndrome. There was 1 hospital death (due to sepsis), but no other major postoperative complications. The mean hospital stay was 14 ± 7 days. Follow-up echocardiographic and computed tomographic scans were performed yearly. The mean follow-up was 34 months (6–72 months). Follow-up imaging revealed no calcifications or degenerative processes related to the homograft. Four patients had minimal valve regurgitation. Two patients died during follow-up. The 3-year actuarial survival rate was 85.7%. Our data suggest that the Bentall procedure with a valved homograft conduit is a safe procedure with excellent mid- to long-term results, comparable to results reported with aortic valve replacement with a homograft. PMID:15745290

Aorta-atria-septum combined incision for aortic valve re-replacement

Science.gov (United States)

Xu, Yiwei; Ye, Xiaofeng; Li, Zhaolong

2018-01-01

This case report illustrates a patient who underwent supra-annular mechanical aortic valve replacement then suffered from prosthesis dysfunction, increasing pressure gradient with aortic valve. She was successfully underwent aortic valve re-replacement, sub-annular pannus removing and aortic annulus enlargement procedures through combined cardiac incision passing through aortic root, right atrium (RA), and upper atrial septum. This incision provides optimal visual operative field and simplifies dissection. PMID:29850170

Transcatheter aortic valve implantation in failed bioprosthetic surgical valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John G; Bleiziffer, Sabine

2014-01-01

for patients with structural valve deterioration; however, a comprehensive evaluation of survival after the procedure has not yet been performed. OBJECTIVE: To determine the survival of patients after transcatheter valve-in-valve implantation inside failed surgical bioprosthetic valves. DESIGN, SETTING......, stroke, and New York Heart Association functional class. RESULTS: Modes of bioprosthesis failure were stenosis (n = 181 [39.4%]), regurgitation (n = 139 [30.3%]), and combined (n = 139 [30.3%]). The stenosis group had a higher percentage of small valves (37% vs 20.9% and 26.6% in the regurgitation...... and combined groups, respectively; P = .005). Within 1 month following valve-in-valve implantation, 35 (7.6%) patients died, 8 (1.7%) had major stroke, and 313 (92.6%) of surviving patients had good functional status (New York Heart Association class I/II). The overall 1-year Kaplan-Meier survival rate was 83...

The development of fusion sensor techniques for condition monitoring of a check valve

International Nuclear Information System (INIS)

Seong, S.H.; Kim, J.S.; Hur, S.; Kim, J.T.; Park, W.M.; Cha, D.B.

2004-01-01

The failures of check valves are one of the most important problems in nuclear power plants because the reverse flows through the failed check valve impact on the healthy hydraulic loop. The present test method of finding out the mechanical failure of a check valve is very risky in the radiated environments during normal operation. In addition, the detection of failures in the overhaul period is very costly and tedious because many check valves are used in the plants and manual disassembly work is required. We have suggested the fusion sensor technology for detecting the failures of check valves through measuring and analyzing the backward leakage flow and mechanical vibration without disassembling the check valve. The fusion sensor means that more than two sensors are used in order to identify and analyze the changes of the frequency response between the failed check valve and healthy check valve. We use the accelerometer and acoustic emission sensor as an alternative to the fusion sensor methodology. We have found that the acoustic emission sensor would be capable of directly detecting a high frequency acoustic wave generated from backward leakage flow itself at a low pressure and temperature. The accelerometer for detecting the mechanical vibration induced from leakage flows would, also, be useful at a high pressure and temperature from the previous studies. The effectiveness of this system is that it is possible for predictive maintenance and information of the problem valve will be captured and it reduces the radiation exposure for the maintenance personnel during power operation as well as the maintenance period. (orig.)

Heart valve replacement with the Sorin tilting-disc prosthesis. A 10-year experience.

Science.gov (United States)

Milano, A; Bortolotti, U; Mazzucco, A; Mossuto, E; Testolin, L; Thiene, G; Gallucci, V

1992-02-01

aortic valve replacement, 92% +/- 4% after mitral valve replacement, and 89% +/- 3% after aortic valve replacement, with no cases of mechanical fracture. The Sorin valve has shown a satisfactory long-term overall performance, comparable with other mechanical prostheses, and an excellent durability that renders it a reliable heart valve substitute for the mitral and aortic positions.

Multidetector computed tomography sizing of bioprosthetic valves: guidelines for measurement and implications for valve-in-valve therapies

International Nuclear Information System (INIS)

Rajani, R.; Attia, R.; Condemi, F.; Webb, J.; Woodburn, P.; Hodson, D.; Nair, A.; Preston, R.; Razavi, R.; Bapat, V.N.

2016-01-01

Aim: To describe a technique for bioprosthetic multidetector computed tomography (MDCT) sizing and to compare MDCT-derived values against manufacturer-provided sizing. Materials and methods: Fourteen bioprosthetic stented valves commonly used in the aortic valve position were evaluated using a Philips 256 MDCT system. All valves were scanned using a dedicated cardiac CT protocol with a four-channel electrocardiography (ECG) simulator. Measurements were made of major and minor axes and the area and perimeter of the internal stent using varying reconstruction kernels and window settings. Measurements derived from MDCT (MDCT ID) were compared against the stent internal diameter (Stent ID) as provided by the valve manufacturer and the True ID (Stent ID + insertion of leaflets). All data were collected and analysed using SPSS for Mac (version 21). Results: The mean difference between the MDCT ID and Stent ID was 0.6±1.9 mm (r=0.649, p=0.012) and between MDCT ID and True ID 2.1±2 mm (r=0.71, p=0.005). There was no difference in the major (p=0.90), minor (p=0.87), area (p=0.92), or perimeter (p=0.92) measurements when sharp, standard, and detailed stent kernels were used. Similarly, the measurements remained consistent across differing windowing levels. Conclusion: Bioprosthetic stented valves may be reliably sized using MDCT in patients requiring valve-in-valve (VIV) interventions where the valve type and size are unknown. In these cases, clinicians should be aware that MDCT has a tendency to overestimate the True ID size. - Highlights: • Cardiac CT is likely to be ideally suited for bioprosthetic aortic valve sizing for valve in valve procedures. • We compared MDCT sizing for 14 varying bioprosthetic aortic valves across varying window settings and reconstruction kernels. • We provide “normal” MDCT sizing for varying valves and show their relationship to surgical sizing. • Bioprosthetic valves may be reliably sized by MDCT but require adjustment owing to

Internal combustion engine with rotary valve assembly having variable intake valve timing

Science.gov (United States)

Hansen, Craig N.; Cross, Paul C.

1995-01-01

An internal combustion engine has rotary valves associated with movable shutters operable to vary the closing of intake air/fuel port sections to obtain peak volumetric efficiency over the entire range of speed of the engine. The shutters are moved automatically by a control mechanism that is responsive to the RPM of the engine. A foot-operated lever associated with the control mechanism is also used to move the shutters between their open and closed positions.

Swing check valve

International Nuclear Information System (INIS)

Eminger, H.E.

1977-01-01

A swing check valve which includes a valve body having an inlet and outlet is described. A recess in the valve body designed to hold a seal ring and a check valve disc swingable between open and closed positions. The disc is supported by a high strength wire secured at one end in a support spacer pinned through bearing blocks fixed to the valve body and at its other end in a groove formed on the outer peripheral surface of the disc. The parts are designed and chosen such to provide a lightweight valve disc which is held open by minimum velocity of fluid flowing through the valve which thus reduces oscillations and accompanying wear of bearings supporting the valve operating parts. (Auth.)

A novel polymeric prosthetic heart valve: design, manufacture, and testing

OpenAIRE

Brubert, Jacob

2016-01-01

In this thesis a flexible leaflet polymeric prosthetic aortic heart valve was designed, manufactured, and tested. The prosthesis was designed with the aim of overcoming the need for anticoagulant therapy, which is required for current mechanical prostheses; while also having lifelong durability, which current bioprosthetic heart valves are not able to achieve. Inspired by the anisotropic architecture of collagen in the natural valve, a shortlist of polystyrene based block copolymers (BCPs), w...

The JUPITER registry: 1-year results of transapical aortic valve implantation using a second-generation transcatheter heart valve in patients with aortic stenosis.

Science.gov (United States)

Silaschi, Miriam; Treede, Hendrik; Rastan, Ardawan J; Baumbach, Hardy; Beyersdorf, Friedhelm; Kappert, Utz; Eichinger, Walter; Rüter, Florian; de Kroon, Thomas L; Lange, Rüdiger; Ensminger, Stephan; Wendler, Olaf

2016-11-01

Transcatheter aortic valve replacement (TAVR) is an established therapy for patients with aortic stenosis (AS) at high surgical risk. The JenaValve™ is a second-generation, self-expanding transcatheter heart valve (THV), implanted through transapical access (TA). During stent deployment, a specific 'clipping-mechanism' engages native aortic valve cusps for fixation. We present 1-year outcomes of the JUPITER registry, a post-market registry of the JenaValve for TA-TAVR. The JUPITER registry is a prospective, multicentre, uncontrolled and observational European study to evaluate the long-term safety and effectiveness of the Conformité Européenne-marked JenaValve THV. A total of 180 patients with AS were enrolled between 2012 and 2014. End-points were adjudicated in accordance with the valve academic research consortium document no. 1 definitions. The mean age was 80.4 ± 5.9 years and the mean logistic European system for cardiac operative risk evaluation I 21.2 ± 14.7%. The procedure was successful in 95.0% (171/180), implantation of a second THV (valve-in-valve) was performed in 2.2% (4/180) and conversion to surgical aortic valve replacement (SAVR) was necessary in 2.8% (5/180). No annular rupture or coronary ostia obstruction occurred. Two patients required SAVR after the day of index procedure (1.1%). All-cause mortality at 30 days was 11.1% (20/180), being cardiovascular in 7.2% (13/180). A major stroke occurred in 1.1% (2/180) at 30 days, no additional major strokes were observed during 1 year. All-cause mortality after 30 days was 13.1% (21/160) and combined efficacy at 1 year was 80.8% (122/151). At 1-year follow-up, no patient presented with more than moderate paravalvular leakage, while 2 patients (3.2%) showed moderate, 12 (19.0%) mild and 49 (82.4%) trace/none paravalvular regurgitation. In a high-risk cohort of patients undergoing TA-TAVR for AS, the use of the JenaValve THV is safe and effective. In patients at higher risk for coronary ostia

Practical use of valve seating machine with remote control system for main steam isolation valve at N.P.S

International Nuclear Information System (INIS)

Ito, Sadao; Noda, Hiroshi; Sadamura, Morito; Utsunomiya, Yasushi.

1975-01-01

The main steam isolation valves in BWR power stations are installed at the boundary of reactor containment vessels, and 2 valves in each main steam system total 8 valves in a plant. They are pneumatically operated Y type globe valves for preventing the release of radioactive substances in the atmosphere in case of the breaking of main steam pipes and also preventing the loss of coolant in case of the breaking of recirculating equipments. Therefore careful leak test, inspection, and seat-fitting are carried out to the valves at each regular maintenance. The manual maintenance work is difficult because of narrow space and the reduction of exposure, and the seat-fitting work requires the skill of high degree, therefore Okano Valve Manufacturing Co. and Tokyo Electric Power Co. jointly started the research and development of an automatic valve seating machine, and successfully put it to practical use in Fukushima No.1 Nuclear Power Station in Nov. 1974. First, the problems in the manual seat-fitting work were investigated, and the means to mechanically solve them were materialized with a prototype machine. After its mock-up test, an actual machine was designed and manufactured. The test result showed remarkable reduction of exposure and labor-saving, and the leak evaluation was sufficiently below the allowable value. (Kako, I.)

Experimental apparatus to test air trap valves

Science.gov (United States)

Lemos De Lucca, Y. de F.; de Aquino, G. A.; Filho, J. G. D.

2010-08-01

It is known that the presence of trapped air within water distribution pipes can lead to irregular operation or even damage to the distribution systems and their components. The presence of trapped air may occur while the pipes are being filled with water, or while the pumping systems are in operation. The formation of large air pockets can produce the water hammer phenomenon, the instability and the loss of pressure in the water distribution networks. As a result, it can overload the pumps, increase the consumption of electricity, and damage the pumping system. In order to avoid its formation, all of the trapped air should be removed through "air trap valves". In Brazil, manufacturers frequently have unreliable sizing charts, which cause malfunctioning of the "air trap valves". The result of these malfunctions causes accidents of substantial damage. The construction of a test facility will provide a foundation of technical information that will be used to help make decisions when designing a system of pipelines where "air trap valves" are used. To achieve this, all of the valve characteristics (geometric, mechanic, hydraulic and dynamic) should be determined. This paper aims to describe and analyze the experimental apparatus and test procedure to be used to test "air trap valves". The experimental apparatus and test facility will be located at the University of Campinas, Brazil at the College of Civil Engineering, Architecture, and Urbanism in the Hydraulics and Fluid Mechanics laboratory. The experimental apparatus will be comprised of various components (pumps, steel pipes, butterfly valves to control the discharge, flow meter and reservoirs) and instrumentation (pressure transducers, anemometer and proximity sensor). It should be emphasized that all theoretical and experimental procedures should be defined while taking into consideration flow parameters and fluid properties that influence the tests.

Experimental apparatus to test air trap valves

Energy Technology Data Exchange (ETDEWEB)

Lemos De Lucca, Y de F [CTH-DAEE-USP/FAAP/UNICAMP (Brazil); Aquino, G A de [SABESP/UNICAMP (Brazil); Filho, J G D, E-mail: yvone.lucca@gmail.co [Water Resources Department, University of Campinas-UNICAMP, Av. Albert Einstein, 951, Cidade Universitaria-Barao Geraldo-Campinas, S.P., 13083-852 (Brazil)

2010-08-15

It is known that the presence of trapped air within water distribution pipes can lead to irregular operation or even damage to the distribution systems and their components. The presence of trapped air may occur while the pipes are being filled with water, or while the pumping systems are in operation. The formation of large air pockets can produce the water hammer phenomenon, the instability and the loss of pressure in the water distribution networks. As a result, it can overload the pumps, increase the consumption of electricity, and damage the pumping system. In order to avoid its formation, all of the trapped air should be removed through 'air trap valves'. In Brazil, manufacturers frequently have unreliable sizing charts, which cause malfunctioning of the 'air trap valves'. The result of these malfunctions causes accidents of substantial damage. The construction of a test facility will provide a foundation of technical information that will be used to help make decisions when designing a system of pipelines where 'air trap valves' are used. To achieve this, all of the valve characteristics (geometric, mechanic, hydraulic and dynamic) should be determined. This paper aims to describe and analyze the experimental apparatus and test procedure to be used to test 'air trap valves'. The experimental apparatus and test facility will be located at the University of Campinas, Brazil at the College of Civil Engineering, Architecture, and Urbanism in the Hydraulics and Fluid Mechanics laboratory. The experimental apparatus will be comprised of various components (pumps, steel pipes, butterfly valves to control the discharge, flow meter and reservoirs) and instrumentation (pressure transducers, anemometer and proximity sensor). It should be emphasized that all theoretical and experimental procedures should be defined while taking into consideration flow parameters and fluid properties that influence the tests.

In-operation inspection technology development-4 ''development of degradation prediction technology for motor-operated valves''

International Nuclear Information System (INIS)

Kikuo, Takeshima; Yuichi, Higashikawa; Masahiro, Koike; Kenji, Matsumoto; Eiji, O'shima

2001-01-01

A method for degradation predicting technology has been proposed for motor operated valves in nuclear power plants which is based on the concept of condition monitoring for maintenance. This method (degradation prediction technology) eliminates the unnecessary overhaul of valves and realizes high reliability and economy. The degradation mechanism was clarified by long time heating experiments of gasket and gland packing and the wear test for them and stem nut to research valve parts degradation by stress (pressure, temperature, etc) during plant operation. Effective electric power measurements for motor operated valves were confirmed to be useful discovering valve part failures. The motor operated valve degradation prediction system was developed on the basis of the experiment results and mechanism. The system is able to predict the degradation of valve parts (gasket/gland packing, stem, stem nut, etc) utilizing plant data (pressure, temperature, etc) and effective power of the motor. The life of valve parts can be estimated from the experimental results. (authors)

Valve Disease

Science.gov (United States)

... blood. There are 4 valves in the heart: tricuspid, pulmonary, mitral, and aortic. Two types of problems can disrupt blood flow through the valves: regurgitation or stenosis. Regurgitation is also called insufficiency or incompetence. Regurgitation happens when a valve doesn’ ...

On-line two-dimensional capillary electrophoresis with mass spectrometric detection using a fully electric isolated mechanical valve.

Science.gov (United States)

Kohl, Felix J; Montealegre, Cristina; Neusüß, Christian

2016-04-01

CE is becoming more and more important in many fields of bioanalytical chemistry. Besides optical detection, hyphenation to ESI-MS detection is increasingly applied for sensitive identification purposes. Unfortunately, many CE techniques and methods established in research and industry are not compatible to ESI-MS since essential components of the background electrolyte interfere in ES ionization. In order to identify unknown peaks in established CE methods, here, a heart-cut 2D-CE separation system is introduced using a fully isolated mechanical valve with an internal loop of only 20 nL. In this system, the sample is separated using potentially any non-ESI compatible method in the first separation dimension. Subsequently, the portion of interest is cut by the internal sample loop of the valve and reintroduced to the second dimension where the interfering compounds are removed, followed by ESI-MS detection. When comparing the separation efficiency of the system with the valve to a system using a continuous capillary only a slight increase in peak width is observed. Ultraviolet/visible detection is integrated in the first dimension for switching time determination, enabling reproducible cutting of peaks of interest. The feasibility of the system is successfully demonstrated by a 2D analysis of a BSA tryptic digest sample using a nonvolatile (phosphate based) background electrolyte in the first dimension. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estimation of viscous dissipative stresses induced by a mechanical heart valve using PIV data.

Science.gov (United States)

Li, Chi-Pei; Lo, Chi-Wen; Lu, Po-Chien

2010-03-01

Among the clinical complications of mechanical heart valves (MHVs), hemolysis was previously thought to result from Reynolds stresses in turbulent flows. A more recent hypothesis suggests viscous dissipative stresses at spatial scales similar in size to red blood cells may be related to hemolysis in MHVs, but the resolution of current instrumentation is insufficient to measure the smallest eddy sizes. We studied the St. Jude Medical (SJM) 27 mm valve in the aortic position of a pulsatile circulatory mock loop under physiologic conditions with particle image velocimetry (PIV). Assuming a dynamic equilibrium assumption between the resolved and sub-grid-scale (SGS) energy flux, the SGS energy flux was calculated from the strain rate tensor computed from the resolved velocity fields and the SGS stress was determined by the Smagorinsky model, from which the turbulence dissipation rate and then the viscous dissipative stresses were estimated. Our results showed Reynolds stresses up to 80 N/m2 throughout the cardiac cycle, and viscous dissipative stresses below 12 N/m2. The viscous dissipative stresses remain far below the threshold of red blood cell hemolysis, but could potentially damage platelets, implying the need for further study in the phenomenon of MHV hemolytic complications.

Valve for the mechanical isolation of a pipe to take up a test probe

International Nuclear Information System (INIS)

Uecker, D.F.

1976-01-01

A valve is introduced for application in a pipe in which a test probe is arranged. The valve serves to isolate the pipe in a gas-tight way, thus preventing the escape of radioactive gas or dust during operation in a nuclear reactor. (TK) [de

Variable valve trains for internal combustion engines to control the valve height and the opening time; Variable Ventiltriebe fuer Verbrennungsmotoren zur Veraenderung von Ventilhub und Oeffnungsdauer

Energy Technology Data Exchange (ETDEWEB)

Martin, Gunther [ThyssenKrupp Presta TecCenter AG, Eschen (Liechtenstein). R and D Projects

2009-11-15

The PDVC (Presta Delta Valve Control) continuously variable valve lift system is a mechanical system of valve control for achieving optimum performance and resulting in improved fuel consumption and reduced emissions across the entire operating range of the combustion engine. The continuous variability allows for engine load control by adjusting the valve height and therefore can also be used to replace the traditional throttle. The advantages are lower fuel consumption, reduction in emissions, quicker engine response, higher torque during the low speed range as well as more stable idling. The PSVC (Presta Shiftable Valve Control) is a 3 step shiftable valve lift system that offers the possibility to achieve a major part of these performance and associated consumption benefits with a simpler and therefore more cost-effective system. (orig.)

241-AN-A valve pit manifold valves and position indication acceptance test procedure

Energy Technology Data Exchange (ETDEWEB)

VANDYKE, D.W.

1999-08-25

This document describes the method used to test design criteria for gear actuated ball valves installed in 241-AN-A Valve Pit located at 200E Tank Farms. The purpose of this procedure is to demonstrate the following: Equipment is properly installed, labeled, and documented on As-Built drawings; New Manifold Valves in the 241-AN-A Valve Pit are fully operable using the handwheel of the valve operators; New valve position indicators on the valve operators will show correct valve positions; New valve position switches will function properly; and New valve locking devices function properly.

Flow induced vibration of the large-sized sodium valve for MONJU

Energy Technology Data Exchange (ETDEWEB)

Sato, K [Sodium Engineering Division, O-arai Engineering Centre, Power Reactor and Nuclear Fuel Development Corporation, Nariata-cho, O-arai Machi, Ibaraki-ken (Japan)

1977-12-01

Measurements have been made on the hydraulic characteristics of the large-sized sodium valves in the hydraulic simulation test loop with water as fluid. The following three prototype sodium valves were tested; (1) 22-inch wedge gate type isolation valve, (2) 22-inch butterfly type isolation valve, and (3) 16-inch butterfly type control valve. In the test, accelerations of flow induced vibrations were measured as a function of flow velocity and disk position. The excitation mechanism of the vibrations is not fully interpreted in these tests due to the complexity of the phenomena, but the experimental results suggest that it closely depends on random pressure fluctuations near the valve disk and flow separation at the contracted cross section between the valve seat and the disk. The intensity of flow induced vibrations suddenly increases at a certain critical condition, which depends on the type of valve and is proportional to fluid velocity. (author)

Flow induced vibration of the large-sized sodium valve for MONJU

International Nuclear Information System (INIS)

Sato, K.

1977-01-01

Measurements have been made on the hydraulic characteristics of the large-sized sodium valves in the hydraulic simulation test loop with water as fluid. The following three prototype sodium valves were tested; (1) 22-inch wedge gate type isolation valve, (2) 22-inch butterfly type isolation valve, and (3) 16-inch butterfly type control valve. In the test, accelerations of flow induced vibrations were measured as a function of flow velocity and disk position. The excitation mechanism of the vibrations is not fully interpreted in these tests due to the complexity of the phenomena, but the experimental results suggest that it closely depends on random pressure fluctuations near the valve disk and flow separation at the contracted cross section between the valve seat and the disk. The intensity of flow induced vibrations suddenly increases at a certain critical condition, which depends on the type of valve and is proportional to fluid velocity. (author)

[Pannus Formation Two Years after Bioprosthetic Aortic Valve Implantation;Report of a Case].

Science.gov (United States)

Ono, Kimiyo; Kuroda, Hiroaki

2015-08-01

We report a case of early deterioration of the bioprosthetic aortic valve 23 months postoperatively. A 77-year-old man who had undergone aortic valve replacement with a 23-mm Epic valve( St. Jude Medical [SJM])presented to us after a syncopal episode. Echocardiography revealed severe aortic stenosis, and redo aortic valve replacement with a 21-mm SJM mechanical valve was performed. All 3 cusps of the tissue valve were thickened by fibrous pannus overgrowth. Neither calcification nor invasion of inflammatory cells was observed. The cause of pannus formation at such an early stage after implantation remains unknown.

Aortic Valve Stenosis

Science.gov (United States)

... most cases, doctors don't know why a heart valve fails to develop properly, so it isn't something you could have prevented. Calcium buildup on the valve. With age, heart valves may accumulate deposits of calcium (aortic valve ...

Added value of cardiac computed tomography for evaluation of mechanical aortic valve: Emphasis on evaluation of pannus with surgical findings as standard reference.

Science.gov (United States)

Suh, Young Joo; Lee, Sak; Im, Dong Jin; Chang, Suyon; Hong, Yoo Jin; Lee, Hye-Jeong; Hur, Jin; Choi, Byoung Wook; Chang, Byung-Chul; Shim, Chi Young; Hong, Geu-Ru; Kim, Young Jin

2016-07-01

The added value of cardiac computed tomography (CT) with transesophageal echocardiography (TEE) for evaluating mechanical aortic valve (AV) dysfunction has not yet been investigated. The purposes of this study were to investigate the added value of cardiac CT for evaluation of mechanical AVs and diagnoses of pannus compared to TEE, with surgical findings of redo-aortic valve replacement (AVR) used as a standard reference. 25 patients who underwent redo-AVR due to mechanical AV dysfunction and cardiac CT before redo-AVR were included. The presence of pannus, encroachment ratio by pannus, and limitation of motion (LOM) were evaluated on CT. The diagnostic performance of pannus detection was compared using TEE, CT, and CT+TEE, with surgical findings as a standard reference. The added value of CT for diagnosing the cause of mechanical AV dysfunction was assessed compared to TTE+TEE. In two patients, CT analysis was not feasible due to severe metallic artifacts. On CT, pannus and LOM were found in 100% (23/23) and 60.9% (14/23). TEE identified pannus in 48.0% of patients (12/25). CT, TEE, and CT+TEE correctly identified pannus with sensitivity of 92.0%, 48.0%, and 92.0%, respectively (P=0.002 for CT vs. TEE). In 11 of 13 cases (84.6%) with inconclusive or negative TEE results for pannus, CT detected the pannus. Among 13 inconclusive cases of TTE+TEE for the cause of mechanical AV dysfunction, CT suggested 6 prosthetic valve obstruction (PVO) by pannus, 4 low-flow low-gradient PVO, and one LOM without significant PVO. Cardiac CT showed added diagnostic value with TEE in the detection of pannus as the cause of mechanical AV dysfunction. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Ultrasound-targeted transfection of tissue-type plasminogen activator gene carried by albumin nanoparticles to dog myocardium to prevent thrombosis after heart mechanical valve replacement

Directory of Open Access Journals (Sweden)

Ji J

2012-06-01

Full Text Available Ji Jun, Ji Shang-Yi, Yang Jian-An, He Xia, Yang Xiao-Han, Ling Wen-Ping, Chen Xiao-LingDepartment of Pathology and Cardiovascular Surgery, Shenzhen Sun Yat-Sen Cardiovascular Hospital, Shenzhen, Guangdong, People's Republic of ChinaBackground: There are more than 300,000 prosthetic heart valve replacements each year worldwide. These patients are faced with a higher risk of thromboembolic events after heart valve surgery and long-term or even life-long anticoagulative and antiplatelet therapies are necessary. Some severe complications such as hemorrhaging or rebound thrombosis can occur when the therapy ceases. Tissue-type plasminogen activator (t-PA is a thrombolytic agent. One of the best strategies is gene therapy, which offers a local high expression of t-PA over a prolonged time period to avoid both systemic hemorrhaging and local rebound thrombosis. There are some issues with t-PA that need to be addressed: currently, there is no up-to-date report on how the t-PA gene targets the heart in vivo and the gene vector for t-PA needs to be determined.Aims: To fabricate an albumin nano-t-PA gene ultrasound-targeted agent and investigate its targeting effect on prevention of thrombosis after heart mechanic valve replacement under therapeutic ultrasound.Methods: A dog model of mechanical tricuspid valve replacement was constructed. A highly expressive t-PA gene plasmid was constructed and packaged by nanoparticles prepared with bovine serum albumin. This nanopackaged t-PA gene plasmid was further cross-linked to ultrasonic microbubbles prepared with sucrose and bovine serum albumin to form the ultrasonic-targeted agent for t-PA gene transfection. The agent was given intravenously followed by a therapeutic ultrasound treatment (1 MHz, 1.5 w/cm2, 10 minutes of the heart soon after valve replacement had been performed. The expression of t-PA in myocardium was detected with multiclonal antibodies to t-PA by the indirect immunohistochemical method

The modification of main steam safety valves in Qinshan phase Ⅱ expansion project

International Nuclear Information System (INIS)

Chen Haiqiao

2012-01-01

The main steam safety valves of NPP steam system are second- class nuclear safety component. It used to limit the pressure of SG secondary side and main steam system via emitting steam into the environment. At present, the main steam safety valves have mechanical valves and assisted power valves. According to the experience of power plants at home and abroad, including Qinshan Phase Ⅱ unit 1/2 experience feedback, Qinshan Phase Ⅱ expansion project made modification on valve type, setting value and valve body. This paper introduce the characteristics of different safety valve types, the modification of main steam safety valves and the modification analysis on safety issues.security and impact on the other systems in Qinshan Phase Ⅱ expansion project. (author)

Operating experience feedback report -- Pressure locking and thermal binding of gate valves

International Nuclear Information System (INIS)

Hsu, C.

1993-03-01

The potential for valve inoperability caused by pressure locking and thermal binding has been known for many years in the nuclear industry. Pressure locking or thermal binding is a common-mode failure mechanism that can prevent a gate valve from opening, and could render redundant trains of safety systems or multiple safety systems inoperable. In spite of numerous generic communications issued in the past by the Nuclear Regulatory Commission (NRC) and industry, pressure locking and thermal binding continues to occur to gate valves installed in safety-related systems of both boding water reactors (BWRs) and pressurized water reactors (PWRs). The generic communications to date have not led to effective industry action to fully identify, evaluate, and correct the problem. This report provides a review of operating events involving these failure mechanisms. As a result of this review this report: (1) identifies conditions when the failure mechanisms have occurred, (2) identifies the spectrum of safety systems that have been subjected to the failure mechanisms, and (3) identifies conditions that may introduce the failure mechanisms under both normal and accident conditions. On the basis of the evaluation of the operating events, the Office for Analysis and Evaluation of Operational Data (AEOD) of the NRC concludes that the binding problems with gate valves are an important safety issue that needs priority NRC and industry attention. This report also provides AEOD's recommendation for actions to effectively prevent the occurrence of valve binding failures

Acute failure of a St. Jude's prosthetic aortic valve: large pannus formation masked by a small thrombus.

Science.gov (United States)

Hurwitz, Seth Eric; Waxman, Daniel; Hecht, Susan

2009-09-01

Pannus formation and valve thrombus can cause prosthetic valve failure. The authors report the case of a 50-year-old woman who presented to the emergency room with decompensated heart failure secondary to mechanical valve dysfunction. On two-dimensional and transesophageal echocardiography, the patient had severe aortic stenosis and regurgitation. A thrombus seen on the valve was felt to be the etiology of her prosthetic valve failure. She underwent emergent cardiac surgery for aortic valve replacement. Pathology revealed that although a small thrombus was present, extensive pannus was the underlying mechanism of valve dysfunction. Differentiation between pannus and thrombus may have important clinical implications, but this case illustrates that distinguishing between these entities by echocardiographic and clinical criteria may not be possible.

Materials and methods for hard-facing of power engineering valves

International Nuclear Information System (INIS)

Frumin, I.I.; Gladkii, P.V.; Eremeev, V.B.; Perepliotchikov, E.F.

1980-01-01

In the Soviet Union a large experience in hard-facing for the water and steam valves has been accumulated. A workability of valves largely depends upon materials used and a technology of their deposition. Mechanized methods have been recently successfully developed, new hard-facing materials created are considered

Valve assembly

International Nuclear Information System (INIS)

Sandling, M.

1981-01-01

An improved valve assembly, used for controlling the flow of radioactive slurry, is described. Radioactive contamination of the air during removal or replacement of the valve is prevented by sucking air from the atmosphere through a portion of the structure above the valve housing. (U.K.)

Direct right ventricular puncture for hemodynamic evaluation of a mechanical tricuspid valve prosthesis: a new indication for an old procedure.

Science.gov (United States)

Gibson, M A; Carell, E S

1997-11-01

The advent of transvenous right heart catheterization has relegated direct transthoracic right ventricular puncture largely to the role of "interesting historical footnote." However, in the case of a right ventricle that is "protected" by a mechanical tricuspid valve prosthesis, direct right ventricular puncture represents a reasonable alternative for obtaining accurate hemodynamic information.

Mitral Valve Stenosis

Science.gov (United States)

... the left ventricle from flowing backward. A defective heart valve fails to either open or close fully. Risk factors Mitral valve stenosis is less common today than it once was because the most common cause, ... other heart valve problems, mitral valve stenosis can strain your ...

Structural valve deterioration in a starr-edwards mitral caged-disk valve prosthesis.

Science.gov (United States)

Aoyagi, Shigeaki; Tayama, Kei-Ichiro; Okazaki, Teiji; Shintani, Yusuke; Kono, Michitaka; Wada, Kumiko; Kosuga, Ken-Ichi; Mori, Ryusuke; Tanaka, Hiroyuki

2013-01-01

The durability of the Starr-Edwards (SE) mitral caged-disk valve, model 6520, is not clearly known, and structural valve deterioration in the SE disk valve is very rare. Replacement of the SE mitral disk valve was performed in 7 patients 23-40 years after implantation. Macroscopic examination of the removed disk valves showed no structural abnormalities in 3 patients, in whom the disk valves were removed at valves excised >36 years after implantation in 4 patients. Disk fracture, a longitudinal split in the disk along its circumference at the site of incorporation of the titanium ring, was detected in the valves removed 36 and 40 years after implantation, respectively, and many cracks were also observed on the outflow aspect of the disk removed 40 years after implantation. Disk fracture and localized disk wear were found in the SE mitral disk valves implanted >36 years previously. The present results suggest that SE mitral caged-disk valves implanted >20 years previously should be carefully followed up, and that those implanted >30 years previously should be electively replaced with modern prosthetic valves

The contribution of matrix and cells to leaflet retraction in heart valve tissue engineering

NARCIS (Netherlands)

Vlimmeren, van M.A.A.

2011-01-01

Heart valve tissue engineering is a promising technique to overcome the drawbacks of currently used mechanical and prosthetic heart valve replacements. Tissue engineered (TE) heart valves are viable and autologous implants that have the capacity to grow, remodel and repair throughout a patient’s

Spontaneous Thrombosis of a Bicuspid Aortic valve due to Primary Antiphospholipid Syndrome

Directory of Open Access Journals (Sweden)

Sarah Farrell

2010-08-01

Full Text Available We present the case of a 51-year-old man who was admitted as an emergency with spontaneous thrombosis of the aortic valve and ascending aorta. At operation he was found to have a congenitally bicuspid aortic valve and subsequent investigation revealed primary antiphospholipid syndrome. He underwent successful removal of the thrombus combined with mechanical replacement of the aortic valve.

A method for evaluating pressure locking and thermal binding of gate valves

Energy Technology Data Exchange (ETDEWEB)

Dogan, T.

1996-12-01

A method is described to evaluate the susceptibility of gate valves to pressure locking and thermal binding. Binding of the valve disc in the closed position due to high pressure water trapped in the bonnet cavity (pressure locking) or differential thermal expansion of the disk in the seat (thermal binding) represents a potential mechanism that can prevent safety-related systems from functioning when called upon. The method described here provides a general equation that can be applied to a given gate valve design and set of operating conditions to determine the susceptibility of the valve to fail due to disc binding. The paper is organized into three parts. The first part discusses the physical mechanisms that cause disc binding. The second part describes the mathematical equations. The third part discusses the conclusions.

Fluid mechanics of needle valves with rounded components Part III: Pressure distributions on walls

Czech Academy of Sciences Publication Activity Database

Tesař, Václav

2016-01-01

Roč. 248, September (2016), s. 138-147 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * pressure measurements * valves Subject RIV: BK - Fluid Dynamics Impact factor: 2.499, year: 2016 http://www.sciencedirect.com/science/article/pii/S0924424716303417

Impact of pannus formation on hemodynamic dysfunction of prosthetic aortic valve: pannus extent and its relationship to prosthetic valve motion and degree of stenosis.

Science.gov (United States)

Koo, Hyun Jung; Ha, Hojin; Kang, Joon-Won; Kim, Jeong A; Song, Jae-Kwan; Kim, Hwa Jung; Lim, Tae-Hwan; Yang, Dong Hyun

2018-02-19

Although pannus is an important cause of prosthetic valve dysfunction, the minimum pannus size that can induce hemodynamic dysfunction has not yet been determined. This study investigated the correlation between the limitation of motion (LOM) of the prosthetic valve and pannus extent and determined the pannus extent that could induce severe aortic stenosis. This study included 49 patients who underwent mechanical aortic valve replacement (AVR) and showed pannus on cardiac computed tomography (CT). Pannus width, ratio of pannus width to valve diameter, pannus area, effective orifice area, encroachment ratio by pannus, pannus involvement angle and percent LOM of mechanical valves were evaluated on CT. Transvalvular peak velocity (TPV) and transvalvular pressure gradient (TPG) were measured by transesophageal echocardiography to determine the degree of aortic stenosis. The relationship between percent LOM of the prosthetic valve and pannus extent and the cut-off of pannus extent required to induce severe aortic stenosis were evaluated. The mean interval between AVR and pannus formation was 11 years and was longer in patients with than without severe aortic stenosis (14.0 vs. 7.3 years). On CT, the percent LOM of the prosthetic valve was significantly associated with the extent of pannus only in patients with pannus involvement angle > 180° (r = 0.55-0.68, P Pannus width, effective orifice area, and encroachment ratio were significantly associated with increased TPV and TPG (r = 0.51-0.62, P Pannus width > 3.5 mm, pannus width/valve inner diameter > 0.15, and encroachment ratio > 0.14 were significantly associated with severe aortic stenosis (TPV > 4 m/s; mean TPG ≥ 35 mmHg), with c-indices of 0.74-079 (P pannus extent parameters are good indicators of significant hemodynamic changes with increased TPV and mean TPG.

BWR control rod drive scram pilot valve monitoring system

International Nuclear Information System (INIS)

Soden, R.A.; Kelly, V.

1984-01-01

The control rod drive system in a Boiling Water Reactor is the most important safety system in the power plant. All components of the system can be verified except the solenoid operated, scram pilot valves without scramming a rod. The pilot valve mechancial works is the weak link to the control rod drive system. These pilot valves control the hydraulic system which applies pressure to the ''insert'' side of the control rod piston and vents the ''withdraw'' side of the piston causing the rods to insert during a scam. The only verification that the valve is operating properly is to scram the rod. The concern for this portion of the system is demonstrated by the high number of redundant components and complete periodic testing of the electrical circuits. The pilot valve can become hung-up through wear, fracture of internal components, mechanical binding, foreign material or chemicals left in the valve during maintenance, etc. If the valve becomes hung-up the electrical tests performed will not indicate this condition and scramming the rod is in jeopardy. Only an attempt to scram a rod will indicate the hung-up valve. While this condition exists the rod is considered inoperative. This paper describes a system developed at a nuclear power plant that monitors the pilot valves on the control rod drive system. This system utilizes pattern recognition to assure proper internal workings of the scram pilot valves to plant operators. The system is totally automatic such that each time the valve is operated on a ''half scram'', a printout is available to the operator along with light indication that each of the 370 valves (on one unit of a BWR) is operating properly. With this monitoring system installed, all components of the control rod drive system including the solenoid pilot valves can be verified as operational without scramming any rods

Microfluidic sieve valves

Science.gov (United States)

Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

2015-01-13

Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

Quantitative assessment of an aortic and pulmonary valve function according to valve fenestration

International Nuclear Information System (INIS)

Mirkhani, S.H.; Golestani, M.G.; Hosini, M.; Kazemian, A.

1999-01-01

There are some reasons for malfunction of aortic and pulmonary valve like fibrosis, calcification, and atheroma. Although, in some papers fenestration were known as a pathologic sign, but it is not generally accepted, while this matter is important in choosing suitable Homograft Heart Valve. In this paper fenestrations and its size, numbers and situation effect was studied. We collected 98 hearts, the donors died because of accident, we excluded valves with atheroma, calcification, fibrosis and unequal cusps, 91 aortic and 93 pulmonary valves were given further consideration. We classified valves according to situation, number and size of fenestration. Each valve was tested with 104 cm of non-nal saline column pressure which is equal to 76 mm Hg. Valve efficacy was detected by fluid flow assay. With study of 184 valves, 95 had no fenestration, 64 had less than 2 fenestration and 25 had more than 2 fenestration. Valve efficacy in condition of less than 2 fenestration was more than others (p <0.01). Malfunction effects of fenestration increased in larger valve and it will be decreased if their situation would be marginal (free margin of cusp). In the comparison of aortic and pulmonary valve we saw that malfunction effect of fenestration in pulmonary valve was more than aortic valve. Our experience in Immam Khomeini Homograft Valve Bank has shown that a great deal of valves is fenestrated. It seems that fenestration must be considered as a quality criterion in homograft valve preparation, especially in pulmonary and large aortic valves; but complementary studies is necessary

Sequential transcatheter aortic valve implantation due to valve dislodgement - a Portico valve implanted over a CoreValve bioprosthesis.

Science.gov (United States)

Campante Teles, Rui; Costa, Cátia; Almeida, Manuel; Brito, João; Sondergaard, Lars; Neves, José P; Abecasis, João; M Gabriel, Henrique

2017-03-01

Transcatheter aortic valve implantation (TAVI) has become an important treatment in high surgical risk patients with severe aortic stenosis (AS), whose complications need to be managed promptly. The authors report the case of an 86-year-old woman presenting with severe symptomatic AS, rejected for surgery due to advanced age and comorbidities. The patient underwent a first TAVI, with implantation of a Medtronic CoreValve ® , which became dislodged and migrated to the ascending aorta. Due to the previous balloon valvuloplasty, the patient's AS became moderate, and her symptoms improved. After several months, she required another intervention, performed with a St. Jude Portico ® repositionable self-expanding transcatheter aortic valve. There was a good clinical response that was maintained at one-year follow-up. The use of a self-expanding transcatheter bioprosthesis with repositioning features is a solution in cases of valve dislocation to avoid suboptimal positioning of a second implant, especially when the two valves have to be positioned overlapping or partially overlapping each other. Copyright © 2017 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.

EFFECT OF OXYGEN INHALATION ON MICROEMBOLIC SIGNALS IN PATIENTS WITH MECHANICAL AORTIC VALVE

Directory of Open Access Journals (Sweden)

K. Ghandehari Z. Izadimoud

2005-06-01

Full Text Available Microembolic signals (MES are frequently observed in transcranial ‎Doppler (TCD recordings of patients with mechanical heart valve (MHV. If gaseous bubbles are the underlying cause, number of MES produced by MHV could be reduced with oxygen ‎inhalation. From September 2003 to September ‎2004, a consecutive series of 14 patients ‎with St Jude aortic valve visited in the cardiology clinic were referred to ‎neurosonology unit, Valie Asr Hospital, Khorasan. TCD monitoring of MES was performed with an ultrasound device and a 2 MHz probe. The MES counts were recorded during 30 ‎minutes breathing room air and thereafter 30 minutes breathing through a facial mask ‎with reservoir bag (6 liter O2 per minute. The criteria of MES detection were ‎characteristic chirping sound, unidirectional signal, random appearance within cardiac ‎cycle and intensity increase ≥ 3dB above background. The MES counts in two periods ‎of monitoring were compared with paired t test and significance was declared at P ‎< 0.05. Twelve patients (8 females and 4 males were investigated. Oxygen ventilation ‎caused a significant decrease of MES counts in the patients in comparison to breathing ‎room air (P = 0.001. It seems that MES in patients with MHV are mainly gaseous bubbles ‎caused by blood agitation with MHV. The quantity of MES in patients with MHV is ‎not related to the risk of thromboembolic complications in these patients.

Supercritical Carbon Dioxide–Based Sterilization of Decellularized Heart Valves

Directory of Open Access Journals (Sweden)

Ryan S. Hennessy, MD

2017-02-01

Full Text Available Summary: Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid– and supercritical carbon dioxide–treated valves were found to be sterile using histology, microbe culture, and electron microscopy assays. The cusp tensile properties of supercritical carbon dioxide–treated valves were higher compared with valves treated with other techniques. Superior sterility and integrity was found in the decellularized valves treated with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues. Key Words: decellularized, decontamination, heart valve, tensile properties, tissue engineering

Ahmed glaucoma valve implant: surgical technique and complications.

Science.gov (United States)

Riva, Ivano; Roberti, Gloria; Oddone, Francesco; Konstas, Anastasios Gp; Quaranta, Luciano

2017-01-01

Implantation of Ahmed glaucoma valve is an effective surgical technique to reduce intraocular pressure in patients affected with glaucoma. While in the past, the use of this device was reserved to glaucoma refractory to multiple filtration surgical procedures, up-to-date mounting experience has encouraged its use also as a primary surgery for selected cases. Implantation of Ahmed glaucoma valve can be challenging for the surgeon, especially in patients who already underwent previous multiple surgeries. Several tips have to be acquired by the surgeon, and a long learning curve is always needed. Although the valve mechanism embedded in the Ahmed glaucoma valve decreases the risk of postoperative hypotony-related complications, it does not avoid the need of a careful follow-up. Complications related to this type of surgery include early and late postoperative hypotony, excessive capsule fibrosis around the plate, erosion of the tube or plate edge, and very rarely infection. The aim of this review is to describe surgical technique for Ahmed glaucoma valve implantation and to report related complications.

Rotary pneumatic valve

Science.gov (United States)

Hardee, Harry C.

1991-01-01

A rotary pneumatic valve which is thrust balanced and the pneumatic pressure developed produces only radial loads on the valve cylinder producing negligible resistance and thus minimal torque on the bearings of the valve. The valve is multiplexed such that at least two complete switching cycles occur for each revolution of the cylinder spindle.

Scissor thrust valve actuator

Science.gov (United States)

DeWall, Kevin G.; Watkins, John C; Nitzel, Michael E.

2006-08-29

Apparatus for actuating a valve includes a support frame and at least one valve driving linkage arm, one end of which is rotatably connected to a valve stem of the valve and the other end of which is rotatably connected to a screw block. A motor connected to the frame is operatively connected to a motor driven shaft which is in threaded screw driving relationship with the screw block. The motor rotates the motor driven shaft which drives translational movement of the screw block which drives rotatable movement of the valve driving linkage arm which drives translational movement of the valve stem. The valve actuator may further include a sensory control element disposed in operative relationship with the valve stem, the sensory control element being adapted to provide control over the position of the valve stem by at least sensing the travel and/or position of the valve stem.

Heavy gas valves

Energy Technology Data Exchange (ETDEWEB)

Steier, L [Vereinigte Armaturen Gesellschaft m.b.H., Mannheim (Germany, F.R.)

1979-01-01

Heavy gas valves must comply with special requirements. Apart from absolute safety in operation there are stringent requirements for material, sealing and ease of operation even in the most difficult conditions. Ball valves and single plate pipe gate valves lateral sealing rings have a dual, double sided sealing effect according to the GROVE sealing system. Single plate gate valves with lateral protective plates are suitable preferably for highly contaminated media. Soft sealing gate valves made of cast iron are used for low pressure applications.

Differentiation of thrombus from pannus as the cause of acquired mechanical prosthetic heart valve obstruction by non-invasive imaging: a review of the literature

NARCIS (Netherlands)

Tanis, Wilco; Habets, Jesse; van den Brink, Renee B. A.; Symersky, Petr; Budde, Ricardo P. J.; Chamuleau, Steven A. J.

2014-01-01

For acquired mechanical prosthetic heart valve (PHV) obstruction and suspicion on thrombosis, recently updated European Society of Cardiology guidelines advocate the confirmation of thrombus by transthoracic echocardiography, transesophageal echocardiography (TEE), and fluoroscopy. However, no

Fluid mechanics of needle valves with rounded components. Part II: Preliminary measurements

Czech Academy of Sciences Publication Activity Database

Tesař, Václav

2016-01-01

Roč. 251, November (2016), s. 52-58 ISSN 0924-4247 R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : needle valves * pressure measurements * valves Subject RIV: BK - Fluid Dynamics Impact factor: 2.499, year: 2016 http://ac.els-cdn.com/S092442471630440X/1-s2.0-S092442471630440X-main.pdf?_tid=45acccf4-951f-11e6-a831-00000aab0f02&acdnat=1476787402_bf349ff3cfc7a824c1a01397a9a5b8b3

Imaging of aortic valve dynamics in 4D OCT

Directory of Open Access Journals (Sweden)

Schnabel Christian

2015-09-01

Full Text Available The mechanical components of the heart, especially the valves and leaflets, are enormous stressed during lifetime. Therefore, those structures undergo different pathophysiological tissue transformations which affect cardiac output and in consequence living comfort of affected patients. These changes may lead to calcific aortic valve stenosis (AVS, the major heart valve disease in humans. The knowledge about changes of the dynamic behaviour during the course of this disease and the possibility of early stage diagnosis is of particular interest and could lead to the development of new treatment strategies and drug based options of prevention or therapy. 4D optical coherence tomography (OCT in combination with high-speed video microscopy were applied to characterize dynamic behaviour of the murine aortic valve and to characterize dynamic properties during artificial stimulation. We present a promising tool to investigate the aortic valve dynamics in an ex vivo disease model with a high spatial and temporal resolution using a multimodal imaging setup.

Hemodynamics in the Valsalva sinuses after transcatheter aortic valve implantation (TAVI).

Science.gov (United States)

Ducci, Andrea; Tzamtzis, Spyridon; Mullen, Michael J; Burriesci, Gaetano

2013-09-01

The study aim was to assess, in vitro, the hemodynamic modifications produced by transcatheter valves in the Valsalva sinuses, by mean of phase-resolved particle image velocimetry (PIV) measurements. Flow measurements were performed on a glass mock aortic root that included three polymeric valve leaflets, before and after the implantation of a Medtronic CoreValve device and of an Edwards SAPIEN valve. All experiments were carried out in a hydro-mechanical cardiovascular pulse duplicator system (Vivitro Superpump System SP3891) that reproduced physiologically equivalent pressures and flow rates conforming to the requirements of the standard ISO 5840:2005. The flow dynamics, before and after implantation of the two prosthetic devices, was characterized on the basis of phase-resolved velocity field and viscous shear rate measurements. Direct comparison indicated that both transcatheter valves determined a significant variation of flow during the early stages of valve opening and during valve closure. In general, the presence of the two valve implants significantly reduced the flow activity in the Valsalva sinuses, promoting regions of stagnation at their base. The reduction in flow in the Valsalva sinuses could be associated with the higher incidence of ischemic events reported after transcatheter heart valve implantation.

THE RESULTS OF SURGICAL TREATMENT OF TRICUSPID VALVE INFECTIVE ENDOCARDITIS USING VALVE REPAIR AND VALVE REPLACEMENT OPERATIONS

Directory of Open Access Journals (Sweden)

S. A. Kovalev

2015-01-01

Full Text Available Aim. To evaluate in-hospital and long-term results of surgical treatment of patients with infective endocarditis of the tricuspid valve, to compare the effectiveness of valve repair and valve replacement techniques, and to identify risk factors of mortality and reoperations. Materials and methods. 31 surgical patients with tricuspid valve infective endocarditis were evaluated. Patients were divided into 2 groups. In Group 1 (n = 14 repairs of the tricuspid valve were performed, in Group 2 (n = 17 patients had undergone tricuspid valve replacements. Epidemiological, clinical, microbiological and echocardiographic data were studied. Methods of comparative analysis, the Kaplan–Meier method, and Cox risk models were applied. Results. The most common complication of in-hospital stay was atrioventricular block (17.7% of cases in Group 2. In Group 1, this type of complication was not found. Hospital mortality was 7.14% in Group 1, and 0% in Group 2. Long-term results have shown the significant reduction of heart failure in general cohort and in both groups. In Group 1 the severity of heart failure in the long term was less than in Group 2. No significant differences in the severity of tricuspid regurgitation were found between the groups. In 7-year follow up no cases of death were registered in Group 1. Cumulative survival rate in Group 2 within 60 months was 67.3 ± 16.2%. No reoperations were performed in patients from Group 1. In Group 2, the freedom from reoperation within 60 months was 70.9 ± 15.3%. Combined intervention was found as predictor of postoperative mortality. Prosthetic valve endocarditis was identified as risk factor for reoperation. Conclusion. Valve repair and valve replacement techniques of surgical treatment of tricuspid valve endocarditis can provide satisfactory hospital and long-term results. Tricuspid valve repair techniques allowed reducing the incidence of postoperative atrioventricular block. In the long-term, patients

Midterm Results of Aortic Valve Replacement with Cryopreserved Homografts

Directory of Open Access Journals (Sweden)

Emre Özker

2012-06-01

Full Text Available Objective: The aim of this study was to analyze the midterm clinical results of aortic valve replacement with cryopreserved homografts.Materials and Methods: Aortic valve replacement was performed in 40 patients with cryopreserved homograft. The indications were aortic valve endocarditis in 20 patients (50%, truncus arteriosus in 6 patients (15%, and re-stenosis or regurtitation after aortic valve reconstruction in 14 (35% patients. The valve sizes ranged from 10 to 27mm. A full root replacement technique was used for homograft replacement in all patients.Results: The 30-day postoperative mortality rate was 12.5% (5 patients. There were four late deaths. Only one of them was related to cardiac events. Overall mortality was 22.5%. Thirty-three patients were followed up for 67±26 months. Two patients needed reoperation due to aortic aneurysm caused by endocarditis. The mean transvalvular gradient significantly decreased after valve replacement (p<0.003. The last follow up showed that the 27 (82% patients had a normal left ventricular function.Conclusion: Cryopreserved homografts are safe alternatives to mechanical valves that can be used when there are proper indications. Although it has a high perioperative mortality rate, cryopreserved homograft implantation is an alternative for valve replacement, particularly in younger patients and for complex surgical problems such as endocarditis that must be minimalized.

Near net shape, low cost ceramic valves for advanced engine applications

Energy Technology Data Exchange (ETDEWEB)

Pidria, M.; Merlone, E.; Parussa, F. [Fiat Research Centre, Orbassano (Italy); Handelsman, J.; Gorodnev, A. [Ceracom Materials Ltd., Yavneh (Israel)

2003-07-01

Future gasoline and diesel engines with electro-hydraulic or electro-mechanical valve control systems require the development of lighter valves to achieve the best results in terms of increased performances, lower fuel consumption and overall efficiency. Ceramic materials can adequately satisfy the required mechanical and thermal properties, nevertheless they still lack as far as manufacturing costs are concerned. Objective of the work was the development of a low-cost forming and sintering process, to produce near-net shape ceramic valves thus requiring very low finishing operations and significantly minimizing material waste. Between available technical ceramic materials, silicon nitride has been chosen to replace conventional steels and Ni-based alloys for the exhaust valves application. The work was then devoted to (i) the selection of the best starting materials composition, taking into account the requirements of a cost effective and high volume production, (ii) the development of an innovative pressure-injection molding process to produce near-net shape parts via a thermosetting feedstock and (iii) the optimization of a proper pressure-less sintering route to obtain cost-competitive, real scale components with adequate final density and mechanical properties. (orig.)

Cobalt reduction of NSSS valve hardfacings for ALARA

Energy Technology Data Exchange (ETDEWEB)

Kim, Joo Hak; Lee, Sang Sub [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author).

Cobalt reduction of NSSS valve hardfacings for ALARA

International Nuclear Information System (INIS)

Kim, Joo Hak; Lee, Sang Sub

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author)

Radiographic investigation of the function of the Bjoerk-Shiley artificial valve

Energy Technology Data Exchange (ETDEWEB)

Erdelyi, M Jr [Orszagos Roentgen es Sugarfizikai Intezet, Budapest (Hungary)

1980-01-01

The normal opening and closing mechanism of the tip-up valve, containing a metal ring, was investigated by kino and spot-film techniques in 58 patients. A new and simple method was elaborated for the calculation of the opening angle of the tip-up valve, rendering superfluous the complicated calculations published by Bjoerk. In accordance with literature data the regular opening angle of the examined 71 valve prostheses was found to be 60 deg (+-2 deg).

Developmental basis for filamin-A-associated myxomatous mitral valve disease

Science.gov (United States)

Sauls, Kimberly; de Vlaming, Annemarieke; Harris, Brett S.; Williams, Katherine; Wessels, Andy; Levine, Robert A.; Slaugenhaupt, Susan A.; Goodwin, Richard L.; Pavone, Luigi Michele; Merot, Jean; Schott, Jean-Jacques; Le Tourneau, Thierry; Dix, Thomas; Jesinkey, Sean; Feng, Yuanyi; Walsh, Christopher; Zhou, Bin; Baldwin, Scott; Markwald, Roger R.; Norris, Russell A.

2012-01-01

Aims We hypothesized that the structure and function of the mature valves is largely dependent upon how these tissues are built during development, and defects in how the valves are built can lead to the pathological progression of a disease phenotype. Thus, we sought to uncover potential developmental origins and mechanistic underpinnings causal to myxomatous mitral valve disease. We focus on how filamin-A, a cytoskeletal binding protein with strong links to human myxomatous valve disease, can function as a regulatory interface to control proper mitral valve development. Methods and results Filamin-A-deficient mice exhibit abnormally enlarged mitral valves during foetal life, which progresses to a myxomatous phenotype by 2 months of age. Through expression studies, in silico modelling, 3D morphometry, biochemical studies, and 3D matrix assays, we demonstrate that the inception of the valve disease occurs during foetal life and can be attributed, in part, to a deficiency of interstitial cells to efficiently organize the extracellular matrix (ECM). This ECM organization during foetal valve gestation is due, in part, to molecular interactions between filamin-A, serotonin, and the cross-linking enzyme, transglutaminase-2 (TG2). Pharmacological and genetic perturbations that inhibit serotonin-TG2-filamin-A interactions lead to impaired ECM remodelling and engender progression to a myxomatous valve phenotype. Conclusions These findings illustrate a molecular mechanism by which valve interstitial cells, through a serotonin, TG, and filamin-A pathway, regulate matrix organization during foetal valve development. Additionally, these data indicate that disrupting key regulatory interactions during valve development can set the stage for the generation of postnatal myxomatous valve disease. PMID:22843703

Tomographic and echocardiographic diagnosis of mitral prosthetic valve thrombosis

International Nuclear Information System (INIS)

Sainz Gonzalez de la Penna, Benito; Ramos Gutierrez, Luis Benito; Gonzalez Artiles, Iovank

2010-01-01

Despite the progress achieved in the design of mechanical prosthetic valves, prosthetic valve thrombosis remains a frequent cause of morbidity, usually due to incorrect anticoagulation. A patient was presented with mitral prosthetic thrombosis one year after implantation, who had been diagnosed by transthoracic transesophageal echocardiography imaging and 64-slice computed tomography. Thrombolytic therapy was successful and led to the satisfactory evolution of the patient

Non-cardiac surgery in patients with prosthetic heart valves: a 12 years experience.

Science.gov (United States)

Akhtar, Raja Parvez; Abid, Abdul Rehman; Zafar, Hasnain; Gardezi, Syed Javed Raza; Waheed, Abdul; Khan, Jawad Sajid

2007-10-01

To study patients with mechanical heart valves undergoing non-cardiac surgery and their anticoagulation management during these procedures. It was a cohort study. The study was conducted at the Department of Cardiac Surgery, Punjab Institute of Cardiology, Lahore and Department of Surgery, Services Institute of Medical Sciences, Lahore, from September 1994 to June 2006. Patients with mechanical heart valves undergoing non-cardiac surgical operation during this period, were included. Their anticoagulation was monitored and anticoagulation related complications were recorded. In this study, 507 consecutive patients with a mechanical heart valve replacement were followed-up. Forty two (8.28%) patients underwent non-cardiac surgical operations of which 24 (57.1%) were for abdominal and non-abdominal surgeries, 5 (20.8%) were emergency and 19 (79.2%) were planned. There were 18 (42.9%) caesarean sections for pregnancies. Among the 24 procedures, there were 7(29.1%) laparotomies, 7(29.1%) hernia repairs, 2 (8.3%) cholecystectomies, 2 (8.3%) hysterectomies, 1(4.1%) craniotomy, 1(4.1%) spinal surgery for neuroblastoma, 1(4.1%) ankle fracture and 1(4.1%) carbuncle. No untoward valve or anticoagulation related complication was seen during this period. Patients with mechanical valve prosthesis on life-long anticoagulation, if managed properly, can undergo any type of non-cardiac surgical operation with minimal risk.

Acute obstruction by Pannus in patients with aortic medtronic-hall valves: 30 years of experience.

Science.gov (United States)

Ellensen, Vegard Skalstad; Andersen, Knut Sverre; Vitale, Nicola; Davidsen, Einar Skulstad; Segadal, Leidulf; Haaverstad, Rune

2013-12-01

Acute dysfunction of mechanical aortic valve prostheses is a life-threatening adverse event. Pannus overgrowth, which is fibroelastic hyperplasia originating from the periannular area, is one cause of dysfunction. The aim of this study was to determine the annual incidence of readmittance resulting from acute obstruction caused by pannus during 30 years of observation in patients with Medtronic-Hall aortic valve prostheses and to analyze the risk factors associated with pannus development. From 1982 to 2004, 1,187 patients in our department underwent aortic valve replacement with Medtronic-Hall mechanical monoleaflet valve prostheses. As of December 31, 2012, 27 of these patients (2.3%) had presented with acute valve dysfunction caused by pannus obstruction. The annual incidence of pannus was 0.7 per 1,000. The median time from the primary operation to prosthetic dysfunction was 11.1 years (range, 1.2 to 26.8 years). Of the 20 patients who underwent reoperation, 2 died. Seven patients died before reoperation. Women had a higher risk for the development of obstructing pannus, and patients with pannus obstruction were younger. Valve size was not an independent risk factor. Women and younger patients are at higher risk for pannus development. When acute dysfunction by pannus is suspected in a mechanical aortic valve, an immediate echocardiogram and an emergency aortic valve replacement should be carried out because of the potential of a fatal outcome. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Force measuring valve assemblies, systems including such valve assemblies and related methods

Science.gov (United States)

DeWall, Kevin George [Pocatello, ID; Garcia, Humberto Enrique [Idaho Falls, ID; McKellar, Michael George [Idaho Falls, ID

2012-04-17

Methods of evaluating a fluid condition may include stroking a valve member and measuring a force acting on the valve member during the stroke. Methods of evaluating a fluid condition may include measuring a force acting on a valve member in the presence of fluid flow over a period of time and evaluating at least one of the frequency of changes in the measured force over the period of time and the magnitude of the changes in the measured force over the period of time to identify the presence of an anomaly in a fluid flow and, optionally, its estimated location. Methods of evaluating a valve condition may include directing a fluid flow through a valve while stroking a valve member, measuring a force acting on the valve member during the stroke, and comparing the measured force to a reference force. Valve assemblies and related systems are also disclosed.

Magnetically operated check valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-06-01

A magnetically operated check valve is disclosed. The valve is comprised of a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

A high performance magnetorheological valve with a meandering flow path

International Nuclear Information System (INIS)

Imaduddin, Fitrian; Amri Mazlan, Saiful; Azizi Abdul Rahman, Mohd; Zamzuri, Hairi; Ubaidillah; Ichwan, Burhanuddin

2014-01-01

The huge developments in the field of magnetorheological (MR) fluid-based devices will have a great influence on the future of mechatronic applications due to the ease of interfacing between electronic controls and the mechanical components that they provide. Among various MR fluid-based devices, an MR valve would be particularly significant for the development of other devices, if it could be successfully achieved. One of the most challenging obstacles to MR valve development is the difficulty of achieving device miniaturization while, at the same time, improving the achievable performance. This study demonstrates a novel design for an MR valve, using the meandering flow path approach in order to increase the effective area so that the MR fluid can be regulated within a small-sized valve. The meandering flow path is formed by combining multiple annular, radial and orifice flow channels. In order to analyze the valve performance, a mathematical model of the proposed MR valve is derived and combined with numerical simulation using the finite element method, with the intention of predicting the achievable pressure drop that can be generated by the valve. The predicted MR valve performances are then experimentally evaluated using an oscillation-disturbed bypass hydraulic cylinder. The simulation results show that the proposed MR valve design could yield substantial pressure drop improvement, which is confirmed by the experiment

Calcific aortic valve damage as a risk factor for cardiovascular events

International Nuclear Information System (INIS)

Wasilewski, Jarosław; Mirota, Kryspin; Wilczek, Krzysztof; Głowacki, Jan; Poloński, Lech

2012-01-01

Aortic valve calcification (AVC) is a common disease of the elderly. It is a progressive disease ranging from mild valve thickening to severe calcification with aortic valve stenosis. Risk factors for AVC are similar to those for atherosclerosis: age, gender, hypercholesterolemia, diabetes, hypertension, smoking and renal failure. AVC shares many similarities to atherosclerosis, including inflammatory cells and calcium deposits, and correlates with coronary plaque burden. Presence of AVC is associated with increased risk of adverse cardiovascular events. The objective for this review is to discuss the clinical features, natural history and prognostic significance of aortic valve calcifications, including mechanical and hemodynamic factors of flow distribution

A remote control valve

International Nuclear Information System (INIS)

Cachard, Maurice de; Dumont, Maurice.

1976-01-01

This invention concerns a remote control valve for shutting off or distributing a fluid flowing at a high rate and low pressure. Among the different valves at present in use, electric valves are the most recommended for remote control but their reliability is uncertain and they soon become costly when large diameter valves are used. The valve described in this invention does away with this drawback owing to its simplicity and the small number of moving parts, this makes it particularly reliable. It mainly includes: a tubular body fitted with at least one side opening; at least one valve wedge for this opening, coaxial with the body, and mobile; a mobile piston integral with this wedge. Several valves to the specifications of this invention can be fitted in series (a shut-off valve can be used in conjunction with one or more distribution valves). The fitting and maintenance of the valve is very simple owing to its design. It can be fabricated in any material such as metals, alloys, plastics and concrete. The structure of the valve prevents the flowing fluid from coming into contact with the outside environment, thereby making it particularly suitable in the handling of dangerous or corrosive fluids. Finally, the opening and shutting of the valve occurs slowly, thereby doing away with the water hammer effect so frequent in large bore pipes [fr

Pannus-related prosthetic valve dysfunction. Case report.

Science.gov (United States)

Moldovan, Maria-Sînziana; Bedeleanu, Daniela; Kovacs, Emese; Ciumărnean, Lorena; Molnar, Adrian

2016-01-01

Pannus-related prosthetic valve dysfunction, a complication of mechanical prosthetic valve replacement, is rare, with a slowly progressive evolution, but it can be acute, severe, requiring surgical reintervention. We present the case of a patient with a mechanical single disc aortic prosthesis, with moderate prosthesis-patient mismatch, minor pannus found on previous ultrasound examinations, who presented to our service with angina pain with a duration of 1 hour, subsequently interpreted as non-ST segment elevation myocardial infarction (NSTEMI) syndrome. Coronarography showed normal epicardial coronary arteries, an ample movement of the prosthetic disc, without evidence of coronary thromboembolism, and Gated Single-Photon Emission Computerized Tomography (SPECT) with Technetium (Tc)-99m detected no perfusion defects. Transthoracic echocardiography (TTE) evidenced a dysfunctional prosthesis due to a subvalvular mass; transesophageal echocardiography (TOE) showed the interference of this mass, with a pannus appearance, with the closure of the prosthetic disc. Under conditions of repeated angina episodes, under anticoagulant treatment, surgery was performed, with the intraoperative confirmation of pannus and its removal. Postoperative evolution was favorable. This case reflects the diagnostic and therapeutic management problems of pannus-related prosthetic valve dysfunction.

Infective Endocarditis of the Aortic Valve with Anterior Mitral Valve Leaflet Aneurysm

NARCIS (Netherlands)

Tomsic, Anton; Li, Wilson W. L.; van Paridon, Marieke; Bindraban, Navin R.; de Mol, Bas A. J. M.

2016-01-01

Mitral valve leaflet aneurysm is a rare and potentially devastating complication of aortic valve endocarditis. We report the case of a 48-year-old man who had endocarditis of the native aortic valve and a concomitant aneurysm of the anterior mitral valve leaflet. Severe mitral regurgitation occurred

Endoscopic Appearance of the Gastroesophageal Valve and Competence of the Cardia

Directory of Open Access Journals (Sweden)

T. Ismail

1996-01-01

Full Text Available The endoscopic appearance of the gastroesophageal valve, viewed by the retroflexed gastroscope, has been studied in 51 patients with and without reflux esophagitis. Esophagitis was graded according to its severity, and the yield pressure (YP was measured in all patients to assess the competence of the cardia. There was a close relationship between the YP and the grades of the gastroesophageal valve. YP was significantly lower in patients with endoscopic oesophagitis than in patients with no evidence of reflux esophagitis (p <0.0001. An increased abnormality of the gastroesophageal valve was associated with all grades of esophagitis and with a low YP. The valve mechanism at the cardia has an important role in determining its competence. YP is possibly a measure of the flap valve component of the gastroesophageal junction.

Integrating valve-inspired design features into poly(ethylene glycol) hydrogel scaffolds for heart valve tissue engineering.

Science.gov (United States)

Zhang, Xing; Xu, Bin; Puperi, Daniel S; Yonezawa, Aline L; Wu, Yan; Tseng, Hubert; Cuchiara, Maude L; West, Jennifer L; Grande-Allen, K Jane

2015-03-01

The development of advanced scaffolds that recapitulate the anisotropic mechanical behavior and biological functions of the extracellular matrix in leaflets would be transformative for heart valve tissue engineering. In this study, anisotropic mechanical properties were established in poly(ethylene glycol) (PEG) hydrogels by crosslinking stripes of 3.4 kDa PEG diacrylate (PEGDA) within 20 kDa PEGDA base hydrogels using a photolithographic patterning method. Varying the stripe width and spacing resulted in a tensile elastic modulus parallel to the stripes that was 4.1-6.8 times greater than that in the perpendicular direction, comparable to the degree of anisotropy between the circumferential and radial orientations in native valve leaflets. Biomimetic PEG-peptide hydrogels were prepared by tethering the cell-adhesive peptide RGDS and incorporating the collagenase-degradable peptide PQ (GGGPQG↓IWGQGK) into the polymer network. The specific amounts of RGDS and PEG-PQ within the resulting hydrogels influenced the elongation, de novo extracellular matrix deposition and hydrogel degradation behavior of encapsulated valvular interstitial cells (VICs). In addition, the morphology and activation of VICs grown atop PEG hydrogels could be modulated by controlling the concentration or micro-patterning profile of PEG-RGDS. These results are promising for the fabrication of PEG-based hydrogels using anatomically and biologically inspired scaffold design features for heart valve tissue engineering. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Mechanical damage due to corrosion of parts of pump technology and valves of LWR power installations

International Nuclear Information System (INIS)

Hron, J.; Krumpl, M.

1986-01-01

Two types are described of uneven corrosion of austenitic chromium-nickel steel: pitting and slit corrosion. The occurrence of slit corrosion is typical of parts of pumping technology and valves. The corrosion damage of austenitic chromium-nickel steels spreads as intergranular, transgranular or mixed corrosion. In nuclear power facilities with LWR's, intergranular corrosion is due to chlorides and sulphur compounds while transgranular corrosion is due to the presence of dissolved oxygen and chlorides. In mechanically stressed parts, stress corrosion takes place. The recommended procedures are discussed of reducing the corrosion-mechanical damage of pumping equipment of light water reactors during design, production and assembly. During the service of the equipment, corrosion cracks are detected using nondestructive methods and surface cracks are repaired by grinding and welding. (E.S.)

Transcatheter aortic valve-in-valve treatment of degenerative stentless supra-annular Freedom Solo valves: A single centre experience.

Science.gov (United States)

Cockburn, James; Dooley, Maureen; Parker, Jessica; Hill, Andrew; Hutchinson, Nevil; de Belder, Adam; Trivedi, Uday; Hildick-Smith, David

2017-02-15

Redo surgery for degenerative bioprosthetic aortic valves is associated with significant morbidity and mortality. Report results of valve-in-valve therapy (ViV-TAVI) in failed supra-annular stentless Freedom Solo (FS) bioprostheses, which are the highest risk for coronary occlusion. Six patients with FS valves (mean age 78.5 years, 50% males). Five had valvular restenosis (peak gradient 87.2 mm Hg, valve area 0.63 cm 2 ), one had severe regurgitation (AR). Median time to failure was 7 years. Patients were high risk (mean STS/Logistic EuroScore 10.6 15.8, respectively). FS valves ranged from 21 to 25 mm. Successful ViV-TAVI was achieved in 4/6 patients (67%). Of the unsuccessful cases, (patient 1 and 2 of series) patient 1 underwent BAV with simultaneous aortography which revealed left main stem occlusion. The procedure was stopped and the patient went forward for repeat surgery. Patient 2 underwent successful ViV-TAVI with a 26-mm CoreValve with a guide catheter in the left main, but on removal coronary obstruction occurred, necessitating valve snaring into the aorta. Among the successful cases, (patients 3, 4, 5, 6) the TAVIs used were CoreValve Evolut R 23 mm (n = 3), and Lotus 23 mm (n = 1). In the successful cases the peak gradient fell from 83.0 to 38.3 mm Hg. No patient was left with >1+ AR. One patient had a stroke on Day 2, with full neurological recovery. Two patients underwent semi-elective pacing for LBBB and PR >280 ms. ViV-TAVI in stentless Freedom Solo valves is high risk. The risk of coronary occlusion is high. The smallest possible prosthesis (1:1 sizing) should be used, and strategies to protect the coronary vessels must be considered. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Significant intra-valvular pressure loss across EPIC SUPRA and perimount magna supra-annular designed aortic bioprostheses in patients with normal aortic size

Directory of Open Access Journals (Sweden)

Jagdish C. Mohan

2017-01-01

Full Text Available Doppler-derived trans-prosthetic gradients are higher and the estimated effective valve area is smaller than the catheter-derived and directly measured hemodynamic values, mostly due to pressure recovery phenomenon. Pressure recovery to a varying extent is common to all prosthetic heart valves including bioprostheses. Pressure recovery-related differences are usually small except in patients with bileaflet metallic prosthesis, wherein high-pressure local jets across central orifice have been documented since long back and also in patients with narrow aortic root. We describe two patients with normally functioning stented aortic bioprostheses with supra-annular design (EPIC SUPRA and PERIMOUNT MAGNA, wherein very high trans-prosthetic gradients and critically reduced estimated effective valve orifice areas in presence of normal aortic size were consistently recorded over long periods of follow-up. The valve leaflets, however had normal excursion, were thin, opened with a triangular or oblong shape and had expected geometric valve area (1.7 and 1.6 cm2 respectively measured by 3D trans-oesophageal echocardiographic planimetry. Pressure recovery upstream the valves accounted for 20% and 12% of total pressure gradients respectively. Dominant site for pressure drop was intra-valvular (75–85%. Such a phenomenon has not been reported in vivo for these two valve designs.

Significant intra-valvular pressure loss across EPIC SUPRA and perimount magna supra-annular designed aortic bioprostheses in patients with normal aortic size.

Science.gov (United States)

Mohan, Jagdish C; Mohan, Vishwas; Shukla, Madhu; Sethi, Arvind

Doppler-derived trans-prosthetic gradients are higher and the estimated effective valve area is smaller than the catheter-derived and directly measured hemodynamic values, mostly due to pressure recovery phenomenon. Pressure recovery to a varying extent is common to all prosthetic heart valves including bioprostheses. Pressure recovery-related differences are usually small except in patients with bileaflet metallic prosthesis, wherein high-pressure local jets across central orifice have been documented since long back and also in patients with narrow aortic root. We describe two patients with normally functioning stented aortic bioprostheses with supra-annular design (EPIC SUPRA and PERIMOUNT MAGNA), wherein very high trans-prosthetic gradients and critically reduced estimated effective valve orifice areas in presence of normal aortic size were consistently recorded over long periods of follow-up. The valve leaflets, however had normal excursion, were thin, opened with a triangular or oblong shape and had expected geometric valve area (1.7 and 1.6cm 2 respectively) measured by 3D trans-oesophageal echocardiographic planimetry. Pressure recovery upstream the valves accounted for 20% and 12% of total pressure gradients respectively. Dominant site for pressure drop was intra-valvular (75-85%). Such a phenomenon has not been reported in vivo for these two valve designs. Copyright © 2016. Published by Elsevier B.V.

Atrioventricular valve repair in patients with functional single-ventricle physiology: impact of ventricular and valve function and morphology on survival and reintervention.

Science.gov (United States)

Honjo, Osami; Atlin, Cori R; Mertens, Luc; Al-Radi, Osman O; Redington, Andrew N; Caldarone, Christopher A; Van Arsdell, Glen S

2011-08-01

This study was to determine whether atrioventricular valve repair modifies natural history of single-ventricle patients with atrioventricular valve insufficiency and to identify factors predicting survival and reintervention. Fifty-seven (13.5%) of 422 single-ventricle patients underwent atrioventricular valve repair. Valve morphology, regurgitation mechanism, and ventricular morphology and function were analyzed for effect on survival, transplant, and reintervention with multivariate logistic and Cox regression models. Comparative analysis used case-matched controls. Atrioventricular valve was tricuspid in 67% and common in 28%. Ventricular morphology was right in 83%. Regurgitation mechanisms were prolapse (n = 24, 46%), dysplasia (n = 18, 35%), annular dilatation (n = 8, 15%), and restriction or cleft (n = 2, 4%). Postrepair insufficiency was none or trivial in 14 (26%), mild in 33 (61%), and moderate in 7 (13%). Survival in repair group was lower than in matched controls (78.9% vs 92.7% at 1 year, 68.7% vs 90.6% at 3 years, P = .015). Patients with successful repair and normal ventricular function had equivalent survival to matched controls (P = .36). Independent predictors for death or transplant included increased indexed annular size (P = .05), increased cardiopulmonary bypass time (P = .04), and decreased postrepair ventricular function (P = .01). Ventricular dilation was a time-related factor for all events, including failed repair. Survival was lower in single-ventricle patients operated on for atrioventricular valve insufficiency than in case-matched controls. Patients with little postoperative residual regurgitation and preserved ventricular function had equivalent survival to controls. Lower grade ventricular function and ventricular dilation correlated with death and repair failure, suggesting that timing of intervention may affect outcome. Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All

Design and performance characteristic analysis of servo valve-type water hydraulic poppet valve

International Nuclear Information System (INIS)

Park, Sung Hwan

2009-01-01

For water hydraulic system control, the flow or pressure control using high-speed solenoid valve controlled by PWM control method could be a good solution for prevention of internal leakage. However, since the PWM control of on-off valves cause extensive flow and pressure fluctuation, it is difficult to control the water hydraulic actuators precisely. In this study, the servo valve-type water hydraulic valve using proportional poppet as the main valve is designed and the performance characteristics of the servo valve-type water hydraulic valve are analyzed. Furthermore, it is demonstrated through experiments that a decline in control chamber pressure that follows the change of pilot flow is caused by the occurrence of cavitation around the proportional poppet, and that fundamental characteristics of the developed valve remain unaffected by the occurrence of cavitation

Which valve is which?

Directory of Open Access Journals (Sweden)

Pravin Saxena

2015-01-01

Full Text Available A 25-year-old man presented with a history of breathlessness for the past 2 years. He had a history of operation for Tetralogy of Fallot at the age of 5 years and history suggestive of Rheumatic fever at the age of 7 years. On echocardiographic examination, all his heart valves were severely regurgitating. Morphologically, all the valves were irreparable. The ejection fraction was 35%. He underwent quadruple valve replacement. The aortic and mitral valves were replaced by metallic valve and the tricuspid and pulmonary by tissue valve.

A 3D velocimetry study of the flow through prosthetic heart valves

Science.gov (United States)

Ledesma, R.; Zenit, R.; Pulos, G.; Sanchez, E.; Juarez, A.

2006-11-01

Blood damage commonly appears in medical valve prothesis. It is a mayor concern for the designers and surgeons. It is well known that this damage and other complications result from the modified fluid dynamics through the replacement valve. To evaluate the performance of prosthetic heart valves, it is necessary to study the flow through them. To conduct this study , we have built a flow channel that emulates cardiac conditions and allows optical access such that a 3D-PIV velocimetry system could be used. The experiments are aimed to reconstruct the downstream structure of the flow through a mechanical and a bio-material tricuspid heart valve prothesis. Preliminary results show that the observed coherent structures can be related with haemolysis and trombosis, illnesses commonly found in valve prothesis recipients. The mean flow, the levels of strain rate and the turbulence intensity generated by the valves can also be directly related to blood damage. In general, bio-material made valves tend to reduce these complications.

Mitral Valve Prolapse

Science.gov (United States)

Mitral valve prolapse (MVP) occurs when one of your heart's valves doesn't work properly. The flaps of the valve are "floppy" and ... to run in families. Most of the time, MVP doesn't cause any problems. Rarely, blood can ...

Imaging of Mitral Valve Prolapse: What Can We Learn from Imaging about the Mechanism of the Disease?

Directory of Open Access Journals (Sweden)

Ronen Durst

2015-07-01

Full Text Available Mitral valve prolapse (MVP is the most common mitral valve disorder affecting 2%–3% of the general population. Two histological forms for the disease exist: Myxomatous degeneration and fibroelastic disease. Pathological evidence suggests the disease is not confined solely to the valve tissue, and accumulation of proteoglycans and fibrotic tissue can be seen in the adjacent myocardium of MVP patients. MVP is diagnosed by demonstrating valve tissue passing the annular line into the left atrium during systole. In this review we will discuss the advantages and limitations of various imaging modalities in their MVP diagnosis ability as well as the potential for demonstrating extra associated valvular pathologies.

Compact UHV valve with field replaceable windows

International Nuclear Information System (INIS)

Johnson, E.D.; Freeman, J.; Powell, F.

1991-01-01

There are many applications in synchrotron radiation research where window valves can be usefully employed. Examples include gas cells for monochromator calibration, filters for high order light rejection, and as vacuum isolation elements between machine and experimental vacua. Often these devices are fairly expensive, and have only fixed (ie non-removable) windows. The development of a new type of seal technology by VAT for their series 01 valves provides a gate surface which is free from obstructions due to internal mechanical elements. This feature allows a threaded recess to be machined into the gate to receive a removable window frame which can carry standard size Luxel thin film windows. The combination of these features results in a DN 40 (2.75in. conflat flange) valve which provides a clear aperture of 21mm diameter for the window material. 8 refs., 2 figs

Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve

DEFF Research Database (Denmark)

Aagaard, Jan; Geha, Alexander S.

2007-01-01

BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area....... This study evaluates the authors' clinical experience with Top Hat supra-annular aortic valve size selection, and the technical aspects of implantation. METHODS: Between January 1999 and October 2005, a total of 251 consecutive patients underwent 252 aortic valve replacements with Top Hat supra...... required unplanned coronary bypass, and 30-day mortality was 2.0% (5/251), indicating a good safety profile for the valves implanted in this series. CONCLUSION: The general distribution of implant sizes in the US indicates that cardiac surgeons may be under-sizing the Top Hat supra-annular aortic valve...

AREVA's innovative solutions for valve diagnostics and in-situ valve repair

International Nuclear Information System (INIS)

Damies, H.; Breitenberger, U.; Munoz, L.; Kostroun, F.

2012-01-01

Optimized maintenance strategies are a key aspect for safe and undisturbed plant operation. Innovative valve service solutions can support that in an efficient way. The ADAM®/SIPLUG® valve monitoring system allows full online monitoring of valves and actuators with automatic evaluation and assessment. Especially for safety-related and operation-related valves this provides valuable information on components condition to ensure proper function and contribute to optimization of maintenance strategies as well as effective maintenance performance. More than 25 years of experience in various plants worldwide show that application of ADAM®/SIPLUG® valve diagnostics solution leads to increased plant safety and availability. With the innovative AVARIS technology an in-situ valve repair is possible. It has the unique ability to conduct several steps in-situ, to maintain the sealing seat of gate or check valves. By applying AVARIS, the valve is restored in its original state, the system remains unchanged. Thus, all original documents remain valid and applicable. In comparison to previous procedures like cutting valves out of the pipeline and repairing hard facings or damaged seal seats in a separate workshop or alternatively replacement by a new valve body the new AVARIS technology avoids costs, risk and effort. (author)

Pressure locking and thermal binding of gate valves

Energy Technology Data Exchange (ETDEWEB)

Kelly, E.M.

1996-12-01

Pressure locking and thermal binding represent potential common mode failure mechanisms that can cause safety-related power-operated gate valves to fail in the closed position, thus rendering redundant safety-related systems incapable of performing their safety functions. Supplement 6 to Generic Letter 89-10, {open_quotes}Safety-Related Motor-Operated Gate Valve Testing and Surveillance,{close_quotes} provided an acceptable approach to addressing pressure locking and thermal binding of gate valves. More recently, the NRC has issued Generic Letter 95-07, {open_quotes}Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,{close_quotes} to request that licensees take certain actions to ensure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions within the current licensing bases. Over the past two years, several plants in Region I determined that valves in certain systems were potentially susceptible to pressure locking and thermal binding, and have taken various corrective actions. The NRC Region I Systems Engineering Branch has been actively involved in the inspection of licensee actions in response to the pressure locking and thermal binding issue. Region I continues to maintain an active involvement in this area, including participation with the Office of Nuclear Reactor Regulation in reviewing licensee responses to Generic Letter 95-07.

Reliability analysis of a hydraulic on/off fast switching valve

DEFF Research Database (Denmark)

Bender, Niels Christian; Pedersen, Henrik Clemmensen; Plöckinger, Andreas

2017-01-01

allowed internal leakage across the valve seat (0.0005 and 0.5 L/min). The study shows that the probability of a low leakage failure is close to 100% before 5 years of operation and 10% risk of high leakage failure after 25 years of operation. Valve seat failure is therefore a potential threat to limit....... Specifically, the mechanical topology of Fast Switching hydraulic Valves (FSVs) are of interest since these undergo operating cycles in the gigacycle regime in theirs functional lifetime. Application of these FSVs is relevant in e.g. digital displacement units, which for the specific design considered...

Delayed onset of tricuspid valve flow in repaired tetralogy of Fallot: an additional mechanism of diastolic dysfunction and interventricular dyssynchrony

Directory of Open Access Journals (Sweden)

Benson Lee N

2011-08-01

Full Text Available Abstract Background Diastolic dysfunction of the right ventricle (RV is common after repair of tetralogy of Fallot. While restrictive physiology in late diastole has been well known, dysfunction in early diastole has not been described. The present study sought to assess the prevalence and mechanism of early diastolic dysfunction of the RV defined as delayed onset of the tricuspid valve (TV flow after TOF repair. Methods The study population consisted of 31 children with repaired TOF (mean age ± SD, 12.3 ± 4.1 years who underwent postoperative cardiovascular magnetic resonance (CMR. The CMR protocol included simultaneous phase-contrast velocity mapping of the atrioventricular valves, which enabled direct comparison of the timing and patterns of tricuspid (TV and mitral (MV valve flow. The TV flow was defined to have delayed onset when its onset was > 20 ms later than the onset of the MV flow. The TV and MV flow from 14 normal children was used for comparison. The CMR results were correlated with the findings on echocardiography and electrocardiography. Result Delayed onset of the TV flow was observed in 16/31 patients and in none of the controls. The mean delay time was 64.81 ± 27.07 ms (8.7 ± 3.2% of R-R interval. The delay time correlated with the differences in duration of the TV and MV flow (55.94 ± 32.88 ms (r = 0.90, p Conclusions Early diastolic dysfunction with delayed onset of TV flow is common after TOF repair, and is associated with reduced RV ejection fraction. It is a further manifestation of interventricular dyssynchrony and represent an additional mechanism of ventricular diastolic dysfunction.

Differential MicroRNA Expression Profile in Myxomatous Mitral Valve Prolapse and Fibroelastic Deficiency Valves

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Yei-Tsung Chen

2016-05-01

Full Text Available Myxomatous mitral valve prolapse (MMVP and fibroelastic deficiency (FED are two common variants of degenerative mitral valve disease (DMVD, which is a leading cause of mitral regurgitation worldwide. While pathohistological studies have revealed differences in extracellular matrix content in MMVP and FED, the molecular mechanisms underlying these two disease entities remain to be elucidated. By using surgically removed valvular specimens from MMVP and FED patients that were categorized on the basis of echocardiographic, clinical and operative findings, a cluster of microRNAs that expressed differentially were identified. The expressions of has-miR-500, -3174, -17, -1193, -646, -1273e, -4298, -203, -505, and -939 showed significant differences between MMVP and FED after applying Bonferroni correction (p < 0.002174. The possible involvement of microRNAs in the pathogenesis of DMVD were further suggested by the presences of in silico predicted target sites on a number of genes reported to be involved in extracellular matrix homeostasis and marker genes for cellular composition of mitral valves, including decorin (DCN, aggrecan (ACAN, fibromodulin (FMOD, α actin 2 (ACTA2, extracellular matrix protein 2 (ECM2, desmin (DES, endothelial cell specific molecule 1 (ESM1, and platelet/ endothelial cell adhesion molecule 1 (PECAM1, as well as inverse correlations of selected microRNA and mRNA expression in MMVP and FED groups. Our results provide evidence that distinct molecular mechanisms underlie MMVP and FED. Moreover, the microRNAs identified may be targets for the future development of diagnostic biomarkers and therapeutics.

A Typical Immune T/B Subset Profile Characterizes Bicuspid Aortic Valve: In an Old Status?

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Carmela R. Balistreri

2018-01-01

Full Text Available Bicuspid valve disease is associated with the development of thoracic aortic aneurysm. The molecular mechanisms underlying this association still need to be clarified. Here, we evaluated the circulating levels of T and B lymphocyte subsets associated with the development of vascular diseases in patients with bicuspid aortic valve or tricuspid aortic valve with and without thoracic aortic aneurysm. We unveiled that the circulating levels of the MAIT, CD4+IL−17A+, and NKT T cell subsets were significantly reduced in bicuspid valve disease cases, when compared to tricuspid aortic valve cases in either the presence or the absence of thoracic aortic aneurysm. Among patients with tricuspid aortic valve, these cells were higher in those also affected by thoracic aortic aneurysm. Similar data were obtained by examining CD19+ B cells, naïve B cells (IgD+CD27−, memory unswitched B cells (IgD+CD27+, memory switched B cells (IgD−CD27+, and double-negative B cells (DN (IgD−CD27−. These cells resulted to be lower in subjects with bicuspid valve disease with respect to patients with tricuspid aortic valve. In whole, our data indicate that patients with bicuspid valve disease show a quantitative reduction of T and B lymphocyte cell subsets. Future studies are encouraged to understand the molecular mechanisms underlying this observation and its pathophysiological significance.

Analysis of vibration of exhaust valve pipeline in nuclear power plant

International Nuclear Information System (INIS)

Tan Ping

2005-01-01

Pipeline system for conveying pressurized steam often operates under time-varying conditions due to the valve operations. This may cause vibration problems as a result the pipeline system suffered vibration damage. In this paper, a finite element formulation for the exhaust dynamic equations that include the effect of all pipe supports, and hangers is introduced and applied to the dynamic analysis of the pipeline system used in a nuclear power plant. the vibration response of steam-conveying pipeline induced by valve exhaust has been studied. The model is validated with a fieldwork experimental pipeline system. the mechanical vibrations from steam exhaust valves can be eliminated by careful design of the valve plug and seat. (authors)

Catheter Ablation of Atrial Fibrillation in Patients with Hardware in the Heart - Septal Closure Devices, Mechanical Valves and More.

Science.gov (United States)

Bartoletti, Stefano; Santangeli, Pasquale; DI Biase, Luigi; Natale, Andrea

2013-01-01

Patients with mechanical "hardware" in the heart, such as those with mechanical cardiac valves or atrial septal closure devices, represent a population at high risk of developing AF. Catheter ablation of AF in these subjects might represent a challenge, due to the perceived higher risk of complications associated with the presence of intracardiac mechanical devices. Accordingly, such patients were excluded or poorly represented in major trials proving the benefit of catheter ablation for the rhythm-control of AF. However, recent evidence supports the concept that catheter ablation procedures might be equally effective in these patients, without a significant increase in the risk of procedural complications. This review will summarize the current state-of-the-art on catheter ablation of AF in patients with mechanical "hardware" in the heart.

Heart Valve Diseases

Science.gov (United States)

Your heart has four valves. Normally, these valves open to let blood flow through or out of your heart, and then shut to keep it from flowing ... close tightly. It's one of the most common heart valve conditions. Sometimes it causes regurgitation. Stenosis - when ...

Valve repair for traumatic tricuspid regurgitation.

Science.gov (United States)

Maisano, F; Lorusso, R; Sandrelli, L; Torracca, L; Coletti, G; La Canna, G; Alfieri, O

1996-01-01

The review of six cases of valve repair for traumatic tricuspid regurgitation in our institution and 74 in the literature in order to assess effective methods of treating this lesion. Tricuspid valve regurgitation is a rare complication of blunt chest trauma. Optimal treatment for this condition is still controversial ranging from long-term medical therapy to early surgical correction. We followed the cases of six consecutive patients with post-traumatic tricuspid incompetence who were successfully treated with reparative techniques. All patients were male and their ages ranged from 18 years to 42 years. Valve regurgitation was always secondary to blunt chest trauma due to motor vehicle accident. The mechanism of valve insufficiency was invariably anterior leaflet prolapse due to chordal or papillary muscle rupture associated with annular dilatation. Surgical procedures included Carpentier ring implant (5 patients), Bex posterior annuloplasty (1 patient), implant of artificial chordae (4 patients), papillary muscle reinsertion (2 patients), commissuroplasty (1 patient) and "artificial double orifice" technique (1 patient). Tricuspid insufficiency improved in all patients after the correction. No complications were recorded and all patients were asymptomatic at the follow-up. Since post-traumatic tricuspid regurgitation is effectively correctable with reparative techniques, early operation is recommended to relieve symptoms and to prevent right ventricular dysfunction.

Prosthetic valve endocarditis after transcatheter aortic valve implantation

DEFF Research Database (Denmark)

Olsen, Niels Thue; De Backer, Ole; Thyregod, Hans G H

2015-01-01

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is an advancing mode of treatment for inoperable or high-risk patients with aortic stenosis. Prosthetic valve endocarditis (PVE) after TAVI is a serious complication, but only limited data exist on its incidence, outcome, and procedural......%) were treated conservatively and 1 with surgery. Four patients (22%) died from endocarditis or complications to treatment, 2 of those (11%) during initial hospitalization for PVE. An increased risk of TAVI-PVE was seen in patients with low implanted valve position (hazard ratio, 2.8 [1.1-7.2]), moderate...

Identification of critical zones in the flow through prosthetic heart valves

Science.gov (United States)

Lopez, A.; Ledesma, R.; Zenit, R.; Pulos, G.

2008-11-01

The hemodynamic properties of prosthetic heart valves can cause blood damage and platelet activation due to the non- physiological flow patterns. Blood recirculation and elevated shear stresses are believed to be responsible for these complications. The objective of this study is to identify and quantify the conditions for which recirculation and high stress zones appear. We have performed a comparative study between a mechanical monoleaflet and biological valve. In order to generate the flow conditions to test the prosthesis, we have built a hydraulic circuit which reproduces the human systemic circulation, on the basis of the Windkessel model. This model is based on an electrical analogy which consists of an arterial resistance and compliance. Using PIV 3D- Stereo measurements, taken downstream from the prosthetic heart valves, we have reconstructed the full phase-averaged tridimensional velocity field. Preliminary results show that critical zones are more prominent in mechanical prosthesis, indicating that valves made with bio-materials are less likely to produce blood trauma. This is in accordance with what is generally found in the literature.

Spontaneous Tricuspid Valve Chordal Rupture in Idiopathic Pulmonary Hypertension.

Science.gov (United States)

Rodrigues, Ana Clara Tude; Afonso, José E; Cordovil, Adriana; Monaco, Claudia; Piveta, Rafael; Cordovil, Rodrigo; Fischer, Claudio H; Vieira, Marcelo; Lira-Filho, Edgar; Morhy, Samira S

2016-03-01

Rupture of tricuspid valve is unusual, occurring mainly in the setting of blunt trauma or endomyocardial biopsy. Spontaneous tricuspid valve chordal rupture is particularly rare. We report herein a case of a patient with severe pulmonary hypertension, on the lung transplantation waiting list, who presented with spontaneous chordal rupture, exacerbation of tricuspid insufficiency and worsening of clinical status. Diagnosis and treatment, along with possible mechanisms for this complication, are discussed. © 2015, Wiley Periodicals, Inc.

Valve monitoring ITI-MOVATS

International Nuclear Information System (INIS)

Moureau, S.

1993-01-01

ITI-MOVATS provides a wide range of test devices to monitor the performance of valves: motor operated gate or globe valve, butterfly valve, air operated valve, and check valve. The ITI-MOVATS testing equipment is used in the following three areas: actuator setup/baseline testing, periodic/post-maintenance testing, and differential pressure testing. The parameters typically measured with the MOVATS diagnostic system as well as the devices used to measure them are described. (Z.S.)

The nordic aortic valve intervention (NOTION) trial comparing transcatheter versus surgical valve implantation

DEFF Research Database (Denmark)

Thyregod, Hans Gustav; Søndergaard, Lars; Ihlemann, Nikolaj

2013-01-01

Degenerative aortic valve (AV) stenosis is the most prevalent heart valve disease in the western world. Surgical aortic valve replacement (SAVR) has until recently been the standard of treatment for patients with severe AV stenosis. Whether transcatheter aortic valve implantation (TAVI) can...

Fluid control valves

International Nuclear Information System (INIS)

Rankin, J.

1980-01-01

A fluid control valve is described in which it is not necessary to insert a hand or a tool into the housing to remove the valve seat. Such a valve is particularly suitable for the control of radioactive fluids since maintenance by remote control is possible. (UK)

What Is Heart Valve Surgery?

Science.gov (United States)

... working correctly. Most valve replacements involve the aortic Tricuspid valve and mitral valves. The aortic valve separates ... where it shouldn’t. This is called incompetence, insufficiency or regurgitation. • Prolapse — mitral valve flaps don’t ...

What Is Heart Valve Disease?

Science.gov (United States)

... and replacing it with a man-made or biological valve. Biological valves are made from pig, cow, or human ... the valve. Man-made valves last longer than biological valves and usually don’t have to be ...

Análise do tratamento cirúrgico da raiz da aorta com o tubo valvulado e com a preservação da valva aórtica Analysis of aortic root surgery with composite mechanical aortic valve conduit and valve-sparing reconstruction

Directory of Open Access Journals (Sweden)

Ricardo Ribeiro Dias

2010-12-01

Full Text Available OBJETIVO: Análise comparativa dos resultados imediatos e tardios da reconstrução da raiz da aorta com o tubo valvulado e com a preservação da valva aórtica. MÉTODOS: No período de novembro de 2002 a setembro de 2009, 164 pacientes com idade média de 54 ± 15 anos, sendo 115 do sexo masculino, foram submetidos ao tratamento cirúrgico da raiz da aorta. Foram 125 tubos valvulados e 39 reconstruções da raiz da aorta com preservação da valva aórtica. Dezesseis por cento dos pacientes eram portadores de síndrome de Marfan e 4,3% apresentavam valva aórtica bivalvulada. Cento e quarenta e quatro (88% pacientes foram acompanhados durante tempo médio de seguimento de 41,1 ± 20,8 meses. RESULTADOS: A mortalidade hospitalar total foi de 4,9%; sendo 5,6% nas operações com tubo valvulado e 2,6% nas preservações da valva aórtica (POBJECTIVE: Comparative analysis of early and late results of aortic root reconstruction with aortic valve sparing operations and the composite mechanical valve conduit replacement. METHODS: From November 2002 to September 2009, 164 consecutive patients with mean age 54 ± 15 years, 115 male, underwent the aortic root reconstruction (125 mechanical valve conduit replacements and 39 valve sparing operations. Sixteen percent of patients had Marfan syndrome and 4.3% had bicuspid aortic valve. One hundred and forty-four patients (88% were followed for a mean period of 41.1 ± 20.8 months. RESULTS: The hospital mortality was 4.9%, 5.6% in operations with valved conduits and 2.6% in the valve sparing procedures (P <0.05. There was no difference neither in survival (95% CI = 86% - 96%, P= 0.1 nor in reoperation-free survival (95% CI = 85% - 90%, P = 0.29. The survival free of complications such as bleeding, thromboembolism and endocarditis were favorable to the valve sparing operations, respectively (95% CI = 70% - 95%, P = 0.001, (95% CI = 82% - 95% P = 0.03 and (95% CI = 81% - 95%, P = 0.03. Multivariate analysis

Relief valve testing study

International Nuclear Information System (INIS)

BROMM, R.D.

2001-01-01

Reclosing pressure-actuated valves, commonly called relief valves, are designed to relieve system pressure once it reaches the set point of the valve. They generally operate either proportional to the differential between their set pressure and the system pressure (gradual lift) or by rapidly opening fully when the set pressure is reached (pop action). A pop action valve allows the maximum fluid flow through the valve when the set pressure is reached. A gradual lift valve allows fluid flow in proportion to how much the system pressure has exceeded the set pressure of the valve (in the case of pressure relief) or has decreased below the set pressure (vacuum relief). These valves are used to protect systems from over and under pressurization. They are used on boilers, pressure vessels, piping systems and vacuum systems to prevent catastrophic failures of these systems, which can happen if they are under or over pressurized beyond the material tolerances. The construction of these valves ranges from extreme precision of less than a psi tolerance and a very short lifetime to extremely robust construction such as those used on historic railroad steam engines that are designed operate many times a day without changing their set pressure when the engines are operating. Relief valves can be designed to be immune to the effects of back pressure or to be vulnerable to it. Which type of valve to use depends upon the design requirements of the system

Comparative study between CardiaMed valves (freely floating valve leaflets versus St. Jude Medical (fixed valve leaflets in mitral valve replacement surgery

Directory of Open Access Journals (Sweden)

Mostafa Ahmed

2017-09-01

Conclusions: CardiaMed freely floating leaflet prostheses showed good hemodynamic characteristics. The prosthesis adequately corrects hemodynamics and is safe and no worse than the St. Jude Medical valve in the mitral valve position.

Face-Sealing Butterfly Valve

Science.gov (United States)

Tervo, John N.

1992-01-01

Valve plate made to translate as well as rotate. Valve opened and closed by turning shaft and lever. Interactions among lever, spring, valve plate, and face seal cause plate to undergo combination of translation and rotation so valve plate clears seal during parts of opening and closing motions.

Butterfly valves for seawater

International Nuclear Information System (INIS)

Yamanaka, Katsuto

1991-01-01

Recently in thermal and nuclear power stations and chemical plants which have become large capacity, large quantity of cooling water is required, and mostly seawater is utilized. In these cooling water systems, considering thermal efficiency and economy, the pipings become complex, and various control functions are demanded. For the purpose, the installation of shut-off valves and control valves for pipings is necessary. The various types of valves have been employed, and in particular, butterfly valves have many merits in their function, size, structure, operation, maintenance, usable period, price and so on. The corrosion behavior of seawater is complicated due to the pollution of seawater, therefore, the environment of the valves used for seawater became severe. The structure and the features of the butterfly valves for seawater, the change of the structure of the butterfly valves for seawater and the checkup of the butterfly valves for seawater are reported. The corrosion of metallic materials is complicatedly different due to the locating condition of plants, the state of pipings and the condition of use. The corrosion countermeasures for butterfly valves must be examined from the synthetic viewpoints. (K.I.)

Analysis of electromagnetic field of direct action solenoid valve with current changing

International Nuclear Information System (INIS)

Liu Qianfeng; Bo Hanliang; Qin Benke

2009-01-01

Control rod hydraulic drive mechanism(CRHDM) is a newly invented patent of Institute of Nuclear and New Energy Technology of Tsinghua University. The direct action solenoid valve is the key part of this technology, so the performance of the solenoid valve directly affects the function of the CRHDM. With the current and the air gap changing,the electromagnetic field of the direct action solenoid valve was analyzed using the ANSYS software,which was validated by the experiment. The result shows that the electromagnetic force of the solenoid valve increases with the current increasing or the gap between the two armatures decreasing. Further more, the working current was confirmed. (authors)

Delayed Presentation of a Giant Ascending Aortic Aneurysm following Aortic Valve Replacement

Directory of Open Access Journals (Sweden)

Tugrul Göncü

2009-01-01

Full Text Available Giant ascending aortic aneurysm formation following aortic valve replacement is rare. A 28-year-old man who underwent aortic valve replacement with a prosthetic valve for aortic regurgitation secondary to congenital bicuspid aortic valve about 10 years ago was diagnosed with a giant ascending aortic aneurysm about 16 cm in diameter in follow-up. The aneurysm was resected leaving the functional old mechanical prosthesis in place and implanted a 34-mm Hemashield woven graft, associated with the left and right coronary artery button implantation. Histological findings of the aortic aneurysm wall showed cystic medial necrosis. The postoperative course was uneventful and postoperative examination demonstrated good surgical results.

Supra-annular valve strategy for an early degenerated transcatheter balloon-expandable heart valve.

Science.gov (United States)

Kamioka, Norihiko; Caughron, Hope; Corrigan, Frank; Block, Peter; Babaliaros, Vasilis

2018-01-23

Currently, there are no recommendations regarding the selection of valve type for a transcatheter heart valve (THV)-in-THV procedure. A supra-annular valve design may be superior in that it results in a larger effective orifice area and may have a lower chance of valve thrombosis after THV-in-THV. In this report, we describe the use of a supra-annular valve strategy for an early degenerated THV. © 2018 Wiley Periodicals, Inc.

Sixty-Four-Section Cardiac Computed Tomography in Mechanical Prosthetic Heart Valve Dysfunction: Thrombus or Pannus.

Science.gov (United States)

Gündüz, Sabahattin; Özkan, Mehmet; Kalçik, Macit; Gürsoy, Ozan Mustafa; Astarcioğlu, Mehmet Ali; Karakoyun, Süleyman; Aykan, Ahmet Çağri; Biteker, Murat; Gökdeniz, Tayyar; Kaya, Hasan; Yesin, Mahmut; Duran, Nilüfer Ekşi; Sevinç, Deniz; Güneysu, Tahsin

2015-12-01

Distinguishing pannus and thrombus in patients with prosthetic valve dysfunction is essential for the selection of proper treatment. We have investigated the utility of 64-slice multidetector computed tomography (MDCT) in distinguishing between pannus and thrombus, the latter amenable to thrombolysis. Sixty-two (23 men, mean age 44±14 years) patients with suspected mechanical prosthetic valve dysfunction assessed by transesophageal echocardiography were included in this prospective observational trial. Subsequently, MDCT was performed before any treatment was started. Periprosthetic masses were detected by MDCT in 46 patients, and their attenuation values were measured as Hounsfield Units (HU). Patients underwent thrombolysis unless contraindicated, and those with a contraindication or failed thrombolysis underwent surgery. A mass which was completely lysed or surgically detected as a clot was classified as thrombus, whereas a mass which was surgically detected as tissue overgrowth was classified as pannus. A definitive diagnosis could be achieved in 37 patients with 39 MDCT masses (22 thrombus and 17 pannus). The mean attenuation value of 22 thrombotic masses was significantly lower than that in 17 pannus (87±59 versus 322±122; Ppannus from thrombus. Complete lysis was more common for masses with HUpannus overgrowth, whereas a lower value is associated with thrombus formation. A higher attenuation (HU>90) is associated with reduced lysis rates. © 2015 American Heart Association, Inc.

The use of check valve performance data to support new concepts (probabilistic risk assessment, condition monitoring) for check valve program

Energy Technology Data Exchange (ETDEWEB)

Hart, K.A.; Gower, D.

1996-12-01

The concept of developing an integrated check valve database based on the Nuclear Power Reliability Data System (NPRDS) data was presented at the last Symposium. The Nuclear Industry Check Valve Group (NIC), working in cooperation with the Oak Ridge National Laboratory (ORNL), has completed an operational database of check valve performance from 1984 to the present. NIC has committed to the nuclear industry to periodically update the data and maintain this information accessible. As the new concepts of probabilistic risk analysis and condition monitoring are integrated into the American Society of Mechanical Engineers (ASME) Code, a critical element will be performance data. From check valve performance data, feasible failure modes and rates can be established. When a failure rate or frequency of failures can be established based on a significant enough population (sampling), a more solid foundation for focusing resources and determining appropriate frequencies and testing can be determined. The presentation will give the updated status of the NIC Check Valve Performance Database covering (1) methodology used to combine the original ORNL data; (2) process/controls established for continuing update and refinement of the data; (3) discussion of how this data is being utilized by (a) OM-22 for condition monitoring, and (b) risk-based inservice testing work of Westinghouse Owners` Group; and (4) results/trends of data evaluations. At the 1994 Symposium, ORNL provided an update as of 1991 to their original work of 1984 -1990 which they had performed to characterize check valve degradations and failures in the nuclear industry. These characterizations will be updated to 1995 and additional reviews provided to give insight into the current condition and trends of check valve performance.

The use of check valve performance data to support new concepts (probabilistic risk assessment, condition monitoring) for check valve program

International Nuclear Information System (INIS)

Hart, K.A.; Gower, D.

1996-01-01

The concept of developing an integrated check valve database based on the Nuclear Power Reliability Data System (NPRDS) data was presented at the last Symposium. The Nuclear Industry Check Valve Group (NIC), working in cooperation with the Oak Ridge National Laboratory (ORNL), has completed an operational database of check valve performance from 1984 to the present. NIC has committed to the nuclear industry to periodically update the data and maintain this information accessible. As the new concepts of probabilistic risk analysis and condition monitoring are integrated into the American Society of Mechanical Engineers (ASME) Code, a critical element will be performance data. From check valve performance data, feasible failure modes and rates can be established. When a failure rate or frequency of failures can be established based on a significant enough population (sampling), a more solid foundation for focusing resources and determining appropriate frequencies and testing can be determined. The presentation will give the updated status of the NIC Check Valve Performance Database covering (1) methodology used to combine the original ORNL data; (2) process/controls established for continuing update and refinement of the data; (3) discussion of how this data is being utilized by (a) OM-22 for condition monitoring, and (b) risk-based inservice testing work of Westinghouse Owners' Group; and (4) results/trends of data evaluations. At the 1994 Symposium, ORNL provided an update as of 1991 to their original work of 1984 -1990 which they had performed to characterize check valve degradations and failures in the nuclear industry. These characterizations will be updated to 1995 and additional reviews provided to give insight into the current condition and trends of check valve performance

Real-time three-dimensional transesophageal echocardiography in valve disease: comparison with surgical findings and evaluation of prosthetic valves.

Science.gov (United States)

Sugeng, Lissa; Shernan, Stanton K; Weinert, Lynn; Shook, Doug; Raman, Jai; Jeevanandam, Valluvan; DuPont, Frank; Fox, John; Mor-Avi, Victor; Lang, Roberto M

2008-12-01

Recently, a novel real-time 3-dimensional (3D) matrix-array transesophageal echocardiographic (3D-MTEE) probe was found to be highly effective in the evaluation of native mitral valves (MVs) and other intracardiac structures, including the interatrial septum and left atrial appendage. However, the ability to visualize prosthetic valves using this transducer has not been evaluated. Moreover, the diagnostic accuracy of this new technology has never been validated against surgical findings. This study was designed to (1) assess the quality of 3D-MTEE images of prosthetic valves and (2) determine the potential value of 3D-MTEE imaging in the preoperative assessment of valvular pathology by comparing images with surgical findings. Eighty-seven patients undergoing clinically indicated transesophageal echocardiography were studied. In 40 patients, 3D-MTEE images of prosthetic MVs, aortic valves (AVs), and tricuspid valves (TVs) were scored for the quality of visualization. For both MVs and AVs, mechanical and bioprosthetic valves, the rings and leaflets were scored individually. In 47 additional patients, intraoperative 3D-MTEE diagnoses of MV pathology obtained before initiating cardiopulmonary bypass were compared with surgical findings. For the visualization of prosthetic MVs and annuloplasty rings, quality was superior compared with AV and TV prostheses. In addition, 3D-MTEE imaging had 96% agreement with surgical findings. Three-dimensional matrix-array transesophageal echocardiographic imaging provides superb imaging and accurate presurgical evaluation of native MV pathology and prostheses. However, the current technology is less accurate for the clinical assessment of AVs and TVs. Fast acquisition and immediate online display will make this the modality of choice for MV surgical planning and postsurgical follow-up.

Remote actuated valve implant

Science.gov (United States)

McKnight, Timothy E; Johnson, Anthony; Moise, Jr., Kenneth J; Ericson, Milton Nance; Baba, Justin S; Wilgen, John B; Evans, III, Boyd McCutchen

2014-02-25

Valve implant systems positionable within a flow passage, the systems having an inlet, an outlet, and a remotely activatable valve between the inlet and outlet, with the valves being operable to provide intermittent occlusion of the flow path. A remote field is applied to provide thermal or magnetic activation of the valves.

Numerical investigation on cavitation in pressure relief valve for coal liquefaction

International Nuclear Information System (INIS)

Ou, G F; Li, W Z; Xiao, D H; Zheng, Z J; Dou, H S; Wang, C

2015-01-01

The pressure relief valve for regulating the level of the high-pressure separator works under a pressure difference up to 15 MPa in the temperature of 415 °C. Severe cavitation erosion and particle impact lead to the valve disc's mass loss. In this paper, three-dimensional turbulent cavitating flows in the pressure relief valve are numerically simulated to reveal the mechanism of mass loss at valve disc. The RNG k-ε turbulence model and the mixture model with a mass transfer for cavitation are employed to simulate the cavitating flow in the pressure relief valve. The result shows that there is phase change in the pressure relief process and cavitation bubbles would be transported by high-velocity backflow to the head of valve disc. For the local pressure higher than the saturated vapor pressure, the bubbles collapse at the head of disc and cavitation erosion is formed at the head of the disc. By comparing the cases of opening of 40%, 50%, and 60%, backflow velocity and cavitation region in front of the disc decrease with the opening increase. Therefore, during the actual operation, the pressure relief valve should be kept to a relatively large opening

In-operation inspection technology development-4 ''development of degradation prediction technology for motor-operated valves''

Energy Technology Data Exchange (ETDEWEB)

Kikuo, Takeshima; Yuichi, Higashikawa [Hitachi Engineering and Production Div., Nuclear Systems Div., Hitachi, Ltd., Ibaraki (Japan); Masahiro, Koike [Power and Industrial Systems R and D Lab., Hitachi, Ltd., (Japan); Kenji, Matsumoto [Tokyo Research and Development Center, Japan Power Engineering and Inspection Corp. (Japan); Eiji, O' shima [Tokyo Institute of Technology (Japan)

2001-07-01

A method for degradation predicting technology has been proposed for motor operated valves in nuclear power plants which is based on the concept of condition monitoring for maintenance. This method (degradation prediction technology) eliminates the unnecessary overhaul of valves and realizes high reliability and economy. The degradation mechanism was clarified by long time heating experiments of gasket and gland packing and the wear test for them and stem nut to research valve parts degradation by stress (pressure, temperature, etc) during plant operation. Effective electric power measurements for motor operated valves were confirmed to be useful discovering valve part failures. The motor operated valve degradation prediction system was developed on the basis of the experiment results and mechanism. The system is able to predict the degradation of valve parts (gasket/gland packing, stem, stem nut, etc) utilizing plant data (pressure, temperature, etc) and effective power of the motor. The life of valve parts can be estimated from the experimental results. (authors)

Energy-saving compression valve of the rock drill

Science.gov (United States)

Glazov, A. N.; Efanov, A. A.; Aikina, T. Yu

2015-11-01

The relevance of the research is due to the necessity to create pneumatic rock drills with low air consumption. The article analyzes the reasons for low efficiency of percussive machines. The authors state that applying a single distribution body in the percussive mechanism does not allow carrying out a low-energy operating cycle of the mechanism. Using the studied device as an example, it is substantiated that applying a compression valve with two distribution bodies separately operating the working chambers makes it possible to significantly reduce the airflow. The authors describe the construction of a core drill percussive mechanism and the operation of a compression valve. It is shown that in the new percussive mechanism working chambers are cut off the circuit by the time when exhaust windows are opened by the piston and air is not supplied into the cylinder up to 20% of the cycle time. The air flow rate of the new mechanism was 3.8 m3/min. In comparison with the drill PK-75, the overall noise level of the new machine is lower by 8-10 dB, while the percussive mechanism efficiency is 2.3 times higher.

Multiple-port valve

International Nuclear Information System (INIS)

Doody, T.J.

1978-01-01

A multiple-port valve assembly is designed to direct flow from a primary conduit into any one of a plurality of secondary conduits as well as to direct a reverse flow. The valve includes two mating hemispherical sockets that rotatably receive a spherical valve plug. The valve plug is attached to the primary conduit and includes diverging passageways from that conduit to a plurality of ports. Each of the ports is alignable with one or more of a plurality of secondary conduits fitting into one of the hemispherical sockets. The other hemispherical socket includes a slot for the primary conduit such that the conduit's motion along that slot with rotation of the spherical plug about various axes will position the valve-plug ports in respect to the secondary conduits

Nuclear reactor steam depressurization valve

International Nuclear Information System (INIS)

Moore, G.L.

1991-01-01

This patent describes improvement in a nuclear reactor plant, an improved steam depressurization valve positioned intermediate along a steam discharge pipe for controlling the venting of steam pressure from the reactor through the pipe. The improvement comprises: a housing including a domed cover forming a chamber and having a partition plate dividing the chamber into a fluid pressure activation compartment and a steam flow control compartment, the valve housing being provided with an inlet connection and an outlet connection in the steam flow control compartment, and a fluid duct in communication with a source of fluid pressure for operating the valve; a valve set mounted within the fluid flow control compartment comprising a cylindrical section surrounding the inlet connection with one end adjoining the connection and having a radially projecting flange at the other end with a contoured extended valve sealing flange provided with an annular valve sealing member, and a valve cylinder traversing the partition plate and reciprocally movable within an opening in the partition plate with one terminal and extending into the fluid pressure activation compartment and the other terminal end extending into the steam flow control compartment coaxially aligned with the valve seat surrounding the inlet connection, the valve cylinder being surrounded by two bellow fluid seals and provided with guides to inhibit lateral movement, an end of the valve cylinder extending into the fluid flow control compartment having a radially projecting flange substantially conterminous with the valve seat flange and having a contoured surface facing and complimentary to the contoured valve seating surface whereby the two contoured valve surfaces can meet in matching relationship, thus providing a pressure actuated reciprocatable valve member for making closing contact with the valve seat and withdrawing therefrom for opening fluid flow through the valve

Double-disc gate valve

International Nuclear Information System (INIS)

Wheatley, S.J.

1979-01-01

The invention relates to an improvement in a conventional double-disc gate valve having a vertically movable gate assembly including a wedge, spreaders slidably engaged therewith, a valve disc carried by the spreaders. When the gate assembly is lowered to a selected point in the valve casing, the valve discs are moved transversely outward to close inlet and outlet ports in the casing. The valve includes hold-down means for guiding the disc-and-spreader assemblies as they are moved transversely outward and inward. If such valves are operated at relatively high differential pressures, they sometimes jam during opening. Such jamming has been a problem for many years in gate valves used in gaseous diffusion plants for the separation of uranium isotopes. The invention is based on the finding that the above-mentioned jamming results when the outlet disc tilts about its horizontal axis in a certain way during opening of the valve. In accordance with the invention, tilting of the outlet disc is maintained at a tolerable value by providing the disc with a rigid downwardly extending member and by providing the casing with a stop for limiting inward arcuate movement of the member to a preselected value during opening of the valve

Piezoelectric valve for massive gas injection in ASDEX upgrade

Energy Technology Data Exchange (ETDEWEB)

Dibon, Mathias; Neu, Rudolf [Max-Planck-Institute for Plasmaphysics, Boltzmannstr. 2, 85748 Garching (Germany); Technical University Munich, Boltzmannstr. 15, 85748 Garching (Germany); Herrmann, Albrecht; Mank, Klaus; Mertens, Vitus; Pautasso, Gabriella; Ploeckl, Bernhard [Max-Planck-Institute for Plasmaphysics, Boltzmannstr. 2, 85748 Garching (Germany)

2016-07-01

A sudden loss of plasma temperature can cause a disruption, which poses a significant problem for current Tokamaks and future fusion devices. Hence, mitigating forces and thermal loads during disruptions is important for the integrity of the vessel and first wall components. Therefore, high speed gas valves are used to deliver a pulse of noble gas onto the plasma, which irradiates the thermal energy quickly, avoiding localized heat loads and mechanical stress due to induced currents. A new design for such a valve is currently under development. The valve plate is driven by two piezoelectric stack actuators. The stroke of the actuators (0.07 mm) is amplified by a monolithic titanium frame and reaches 2 mm. The frame also serves as spring to pre-load the actuators. In the idle state, it also presses the conical valve plate into the seal, closing the gas chamber (42 cm{sup 3}). The actuators accelerate the stem and the valve plate until it is fully opened after 2 ms. The orifice of the valve has a diameter of 14 mm. This allows a peak mass flow rate of the gas up to 8 . 10{sup 4} (Pa.m)/(s) after 1.8 ms and an average mass flow rate of 2 . 10{sup 4} (Pa.m)/(s) over the evacuation time of 10 ms. Therefore, one valve would be sufficient to deliver the required amount of gas to mitigate disruptions at ASDEX Upgrade.

Intracardiac echocardiography to diagnose pannus formation after aortic valve replacement.

Science.gov (United States)

Yamamoto, Yoshiya; Ohara, Takahiro; Funada, Akira; Takahama, Hiroyuki; Amaki, Makoto; Hasegawa, Takuya; Sugano, Yasuo; Kanzaki, Hideaki; Anzai, Toshihisa

2016-03-01

A 66-year-old female, under regular follow-up for 20 years after aortic valve replacement (19-mm Carbomedics), presented dyspnea on effort and hypotension during hemodialysis. A transthoracic echocardiogram showed elevation of transvalvular velocity up to 4 m/s, but the structure around the aortic prosthesis was difficult to observe due to artifacts. Fluoroscopy revealed normal motion of the leaflets of the mechanical valve. Intracardiac echocardiography (ICE) revealed a pannus-like structure in the left ventricular outflow tract. Transesophageal echocardiogram also revealed this structure. ICE can visualize structural abnormalities around a prosthetic valve after cardiac surgery even in patients in whom conventional imaging modalities failed.

MEPR versus EEPR valves in open supermarket refrigerated display cabinets

International Nuclear Information System (INIS)

Tahir, A.; Bansal, P.K.

2005-01-01

This paper presents the comparative experimental field performance of mechanical evaporator pressure regulating valves (MEPR) and electronic evaporator pressure regulating valves (EEPR) under the identical operating conditions of supermarket open multi-deck refrigerated display cabinets. The main goal of the supermarket refrigeration system design is to keep the displayed product at the required constant temperature, while minimising the cooling load to increase the overall energy efficiency of the system. Field tests have shown that the electronic evaporator pressure valve has a significant effect on improving the cabinet temperature and reducing the rate of frost formation on the evaporator coils with subsequent improvements in the air curtain strength

Validation of a numerical FSI simulation of an aortic BMHV by in vitro PIV experiments.

Science.gov (United States)

Annerel, S; Claessens, T; Degroote, J; Segers, P; Vierendeels, J

2014-08-01

In this paper, a validation of a recently developed fluid-structure interaction (FSI) coupling algorithm to simulate numerically the dynamics of an aortic bileaflet mechanical heart valve (BMHV) is performed. This validation is done by comparing the numerical simulation results with in vitro experiments. For the in vitro experiments, the leaflet kinematics and flow fields are obtained via the particle image velocimetry (PIV) technique. Subsequently, the same case is numerically simulated by the coupling algorithm and the resulting leaflet kinematics and flow fields are obtained. Finally, the results are compared, revealing great similarity in leaflet motion and flow fields between the numerical simulation and the experimental test. Therefore, it is concluded that the developed algorithm is able to capture very accurately all the major leaflet kinematics and dynamics and can be used to study and optimize the design of BMHVs. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

A review of historical check valve failure data

International Nuclear Information System (INIS)

Casada, D.A.; Todd, M.D.

1992-01-01

Check valve operating problems in recent years have resulted in significant operating transients, increased cost, and decreased system availability. In response, additional attention has been given to check valves by utilities, as well as the US Nuclear Regulatory Commission (NRC) and the American Society of Mechanical Engineers Operation and Maintenance Committee. All these organizations have the fundamental goal of ensuring reliable operation of check valves. A key ingredient of an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. Oak Ridge National Laboratory is currently conducting a detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System. The focus of the review is on check valve failures that have involved significant degradation of the valve internal parts. A variety of parameters are being considered during the review, including size, age, system of service, method of failure discovery, the affected valve parts, attributed causes, and corrective actions. This work is being carried out under the auspices of the NRC's Nuclear Plant Aging Research program. At this time, the study is approximately 50% complete. All failure records have been reviewed and categorized, and preliminary tabulation and correlation of data is underway. The bulk of the tabulation and correlation portion of the work is expected to be completed by the end of June 1992. A report draft is expected in the fall of 1992

Ahmed glaucoma valve implant: surgical technique and complications

Directory of Open Access Journals (Sweden)

Riva I

2017-02-01

Full Text Available Ivano Riva,1 Gloria Roberti,1 Francesco Oddone,1 Anastasios GP Konstas,2 Luciano Quaranta3 1IRCCS “Fondazione GB Bietti per l’Oftalmologia”, Rome, Italy; 21st University Department of Ophthalmology, Glaucoma Unit, AHEPA Hospital, Thessaloniki, Greece; 3Department of Medical and Surgical Specialties, Section of Ophthalmology, University of Brescia, Brescia, Italy Abstract: Implantation of Ahmed glaucoma valve is an effective surgical technique to reduce intraocular pressure in patients affected with glaucoma. While in the past, the use of this device was reserved to glaucoma refractory to multiple filtration surgical procedures, up-to-date mounting experience has encouraged its use also as a primary surgery for selected cases. Implantation of Ahmed glaucoma valve can be challenging for the surgeon, especially in patients who already underwent previous multiple surgeries. Several tips have to be acquired by the surgeon, and a long learning curve is always needed. Although the valve mechanism embedded in the Ahmed glaucoma valve decreases the risk of postoperative hypotony-related complications, it does not avoid the need of a careful follow-up. Complications related to this type of surgery include early and late postoperative hypotony, excessive capsule fibrosis around the plate, erosion of the tube or plate edge, and very rarely infection. The aim of this review is to describe surgical technique for Ahmed glaucoma valve implantation and to report related complications. Keywords: glaucoma, surgical technique, glaucoma drainage devices, Ahmed glaucoma valve, complications

Studies of valve lifter for automotive heavy duty diesel engine by ceramic materials. II. Development of SiC valve lifter by injection molding method

Energy Technology Data Exchange (ETDEWEB)

Yun, H W [Technical Centre of KIA-ASIA MOTORS (Korea, Republic of); Han, I S [Korea Institute of Energy Research, Tajeon (Korea, Republic of); Lim, Y S; Chung, Y J [Myong Ji University (Korea, Republic of)

1998-02-01

Valve lifter, namely tappet, is supported by lifter hole which is located upper side of camshaft in cylinder block, transforms rotatic movement of camshaft into linear movement and helps to open and shut the engine valve as an engine parts. The face of valve lifter, which is continuously contacting with camshaft, brings about abnormal wears, such as unfair wear and early wear, because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently, this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears, therefore, the valve lifter cast in metal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance. As a result, the optimum process conditions like injection condition, mixture ratio and debonding process could be established. After sintering, fine-sinered dual microstructure in which prior {alpha}-SiC, carbon and silicon was obtained. Based on the new SiC({beta}-SiC) produced by reaction among the {alpha}-SiC, carbon and silicon was obtained. Based on the study, it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100{approx}1200 bending strength (300{approx}350 Pa), fracture toughness (1.5{approx}1.7 MPacentre dotm{sup 1/2}). Through engine dynamo testing, SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such early fracture, unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resistance, reliability, and lightability.

Trans-apical aortic valve implantation in a patient with stentless valve degeneration.

Science.gov (United States)

Kapetanakis, Emmanouil I; MacCarthy, Philip; Monaghan, Mark; Wendler, Olaf

2011-06-01

Trans-apical valve-in-valve trans-catheter aortic valve implantation (TAVI) has successfully been performed in selected, high-risk patients, who suffered prosthetic degeneration after aortic valve replacement using stented xenografts. We report the case of a 79-year-old male patient who underwent one of the first successful TAVIs in a failing stentless bioprosthesis. Copyright © 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Prosthetic tricuspid valve dysfunction assessed by three-dimensional transthoracic and transesophageal echocardiography.

Science.gov (United States)

Yuasa, Toshinori; Takasaki, Kunitsugu; Mizukami, Naoko; Ueya, Nami; Kubota, Kayoko; Horizoe, Yoshihisa; Chaen, Hideto; Kuwahara, Eiji; Kisanuki, Akira; Hamasaki, Shuichi

2013-09-01

A 39-year-old male who had undergone tricuspid valve replacement for severe tricuspid regurgitation was admitted with palpitation and general edema. Two-dimensional (2D) echocardiography showed tricuspid prosthetic valve dysfunction. Additional three-dimensional (3D) transthoracic and transesophageal echocardiography (TEE) could clearly demonstrate the disabilities of the mechanical tricuspid valve. Particularly, 3D TEE demonstrated a mass located on the right ventricular side of the tricuspid prosthesis, which may have caused the stuck disk. This observation was confirmed by intra-operative findings.

Early clinical outcome of aortic transcatheter valve-in-valve implantation in the Nordic countries

DEFF Research Database (Denmark)

Ihlberg, Leo; Nissen, Henrik Hoffmann; Nielsen, Niels Erik

2013-01-01

Transcatheter valve-in-valve implantation has emerged as an option, in addition to reoperative surgical aortic valve replacement, to treat failed biologic heart valve substitutes. However, the clinical experience with this approach is still limited. We report the comprehensive experience...

Prosthetic mitral valve obstruction: role of real-time three-dimensional transesophageal echocardiography in diagnosis.

Science.gov (United States)

Kannan, Arun; Jahan, Kahroba; Lotun, Kapildeo; Janardhanan, Rajesh

2015-09-21

Acute prosthetic valve thrombosis is a potentially serious complication with an incidence as high as 6% per patient-year for prostheses in the mitral position. Accurate diagnosis of the degree of obstruction and differentiation of pannus versus thrombus is critical in determination of the best mode of therapy. We discuss a case of a patient with multiple comorbidities who presented with mechanical mitral valve obstruction where both transthoracic and two-dimensional transesophageal echocardiography (TEE) were limited in making an accurate diagnosis regarding the mechanism of obstruction. Real-time 3D-TEE (RT-3DTEE) was critical in identifying a partial thrombus on the mechanical valve and guided the choice of thrombolysis as the most appropriate intervention, thus avoiding high-risk surgery in this patient with significant multiple comorbidities. 2015 BMJ Publishing Group Ltd.

Nuclear valves latest development

International Nuclear Information System (INIS)

Isaac, F.; Monier, M.

1993-01-01

In the frame of Nuclear Power Plant upgrade (Emergency Power Supply and Emergency Core Cooling), Westinghouse had to face a new valve design philosophy specially for motor operated valves. The valves have to been designed to resist any operating conditions, postulated accident or loss of control. The requirements for motor operated valves are listed and the selected model and related upgrading explained. As part of plant upgrade and valves replacement, Westinghouse has sponsored alternative hardfacing research programme. Two types of materials have been investigated: nickel base alloys and iron base alloys. Programme requirements and test results are given. A new globe valve model (On-Off or regulating) is described developed by Alsthom Velan permitting the seat replacement in less than 10 min. (Z.S.) 2 figs

Magnetic Check Valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-01-01

Poppet in proposed check valve restored to closed condition by magnetic attraction instead of spring force. Oscillations suppressed, with consequent reduction of wear. Stationary magnetic disk mounted just upstream of poppet, also containing magnet. Valve body nonmagnetic. Forward pressure or flow would push poppet away from stationary magnetic disk so fluid flows easily around poppet. Stop in valve body prevents poppet from being swept away. When flow stopped or started to reverse, magnetic attraction draws poppet back to disk. Poppet then engages floating O-ring, thereby closing valve and preventing reverse flow. Floating O-ring facilitates sealing at low loads.

Effects of valve timing, valve lift and exhaust backpressure on performance and gas exchanging of a two-stroke GDI engine with overhead valves

International Nuclear Information System (INIS)

Dalla Nora, Macklini; Lanzanova, Thompson Diórdinis Metzka; Zhao, Hua

2016-01-01

Highlights: • Two-stroke operation was achieved in a four-valve direct injection gasoline engine. • Shorter valve opening durations improved torque at lower engine speeds. • The longer the valve opening duration, the lower was the air trapping efficiency. • Higher exhaust backpressure and lower valve lift reduced the compressor work. - Abstract: The current demand for fuel efficient and lightweight powertrains, particularly for application in downsized and hybrid electric vehicles, has renewed the interest in two-stroke engines. In this framework, an overhead four-valve spark-ignition gasoline engine was modified to run in the two-stroke cycle. The scavenging process took place during a long valve overlap period around bottom dead centre at each crankshaft revolution. Boosted intake air was externally supplied at a constant pressure and gasoline was directly injected into the cylinder after valve closure. Intake and exhaust valve timings and lifts were independently varied through an electrohydraulic valve train, so their effects on engine performance and gas exchanging were investigated at 800 rpm and 2000 rpm. Different exhaust backpressures were also evaluated by means of exhaust throttling. Air trapping efficiency, charging efficiency and scavenge ratio were calculated based on air and fuel flow rates, and exhaust oxygen concentration at fuel rich conditions. The results indicated that longer intake and exhaust valve opening durations increased the charge purity and hence torque at higher engine speeds. At lower speeds, although, shorter valve opening durations increased air trapping efficiency and reduced the estimated supercharger power consumption due to lower air short-circuiting. A strong correlation was found between torque and charging efficiency, while air trapping efficiency was more associated to exhaust valve opening duration. The application of exhaust backpressure, as well as lower intake/exhaust valve lifts, made it possible to increase

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis

Directory of Open Access Journals (Sweden)

Rajesh Janardhanan

2016-05-01

Full Text Available In intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Learning objectives: • Early recognition of a mitral valve aneurysm (MVA is important because it may rupture and produce catastrophic mitral regurgitation (MR in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR. • Real-time 3D-transesophageal echocardiography (RT-3DTEE is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA.

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis.

Science.gov (United States)

Janardhanan, Rajesh; Kamal, Muhammad Umar; Riaz, Irbaz Bin; Smith, M Cristy

2016-03-01

SummaryIn intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve) endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Early recognition of a mitral valve aneurysm (MVA) is important because it may rupture and produce catastrophic mitral regurgitation (MR) in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR).Real-time 3D-transesophageal echocardiography (RT-3DTEE) is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA. © 2016 The authors.

Fixation and mounting of porcine aortic valves for use in mock circuits.

Science.gov (United States)

Schlöglhofer, Thomas; Aigner, Philipp; Stoiber, Martin; Schima, Heinrich

2013-10-01

Investigations of the circulatory system in vitro use mock circuits that require valves to mimic the cardiac situation. Whereas mechanical valves increase water hammer effects due to inherent stiffness and do not allow the use of pressure lines or catheters, bioprosthetic valves are expensive and of limited durability in test fluids. Therefore, we developed a cheap, fast, alternative method to mount valves obtained from the slaughterhouse in mock circuits. Porcine aortic roots were obtained from the abattoir and used either in native condition or after fixation. Fixation was performed at a constant retrograde pressure to ensure closed valve position. Fixation time was 4 h in a 0.5%-glutaraldehyde phosphate buffer. The fixed valves were molded into a modular mock circulation connector using a fast curing silicone. Valve functionality was evaluated in a pulsatile setting (cardiac output = 4.7 l/min, heart rate = 80 beats/min) and compared before and after fixation. Leaflet motion was recorded with a high-speed camera and valve insufficiency was quantified by leakage flow under steady pressure application (80 mmHg). Under physiological conditions the aortic valves showed almost equal leaflet motion in native and fixed conditions. However, the leaflets of the native valves showed lower stiffness and more fluttering during systole than the fixed specimens. Under retrograde pressure, fresh and fixed valves showed small leakage flows of <30 ml/min. The new mounting and fixation procedure is a fast method to fabricate low cost biologic valves for the use in mock circuits.

Transcatheter Aortic Valve Replacement for Degenerative Bioprosthetic Surgical Valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John; Brecker, Stephen

2012-01-01

Transcatheter aortic valve-in-valve implantation is an emerging therapeutic alternative for patients with a failed surgical bioprosthesis and may obviate the need for reoperation. We evaluated the clinical results of this technique using a large, worldwide registry....

Transcatheter aortic valve replacement

Science.gov (United States)

... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

Overflow control valve

International Nuclear Information System (INIS)

Kessinger, B.A.; Hundal, R.; Parlak, E.A.

1982-01-01

An overflow control valve for use in a liquid sodium coolant pump tank which can be remotely engaged with and disengaged from the pump tank wall to thereby permit valve removal. An actuating shaft for controlling the valve also has means for operating a sliding cylinder against a spring to retract the cylinder from sealing contact with the pump tank nozzle. (author)

Bridge Therapy Outcomes in Patients With Mechanical Heart Valves.

Science.gov (United States)

Delate, Thomas; Meisinger, Stephanie M; Witt, Daniel M; Jenkins, Daniel; Douketis, James D; Clark, Nathan P

2017-11-01

Bridge therapy is associated with an increased risk of major bleeding in patients with atrial fibrillation and venous thromboembolism (TE) without a corresponding reduction in TE. The benefits of bridge therapy in patients with mechanical heart valve (MHV) prostheses interrupting warfarin for invasive procedures are not well described. A retrospective cohort study was conducted at an integrated health-care delivery system. Anticoagulated patients with MHV interrupting warfarin for invasive diagnostic or surgical procedures between January 1, 2006, and March 31, 2012, were identified. Patients were categorized according to exposure to bridge therapy during the periprocedural period and TE risk (low, medium, and high). Outcomes validated via manual chart review included clinically relevant bleeding, TE, and all-cause mortality in the 30 days following the procedure. There were 547 procedures in 355 patients meeting inclusion criteria. Mean cohort age was 65.2 years, and 38% were female. Bridge therapy was utilized in 466 (85.2%) procedures (95.2%, 77.3%, and 65.8% of high, medium, and low TE risk category procedures, respectively). The 30-day rate of clinically relevant bleeding was numerically higher in bridged (5.8%; 95% confidence interval [CI], 3.9%-8.3%) versus not bridged procedures (1.2%; 95% CI, bridge therapy is common among patients with MHV and may be associated with increased bleeding risk. Further research is needed to determine whether bridge therapy reduces TE in patients with MHV interrupting warfarin for invasive procedures.

Improved Survival After the Ross Procedure Compared With Mechanical Aortic Valve Replacement.

Science.gov (United States)

Buratto, Edward; Shi, William Y; Wynne, Rochelle; Poh, Chin L; Larobina, Marco; O'Keefe, Michael; Goldblatt, John; Tatoulis, James; Skillington, Peter D

2018-03-27

It is unclear whether the Ross procedure offers superior survival compared with mechanical aortic valve replacement (AVR). This study evaluated experience and compared long-term survival between the Ross procedure and mechanical AVR. Between 1992 and 2016, a total of 392 Ross procedures were performed. These were compared with 1,928 isolated mechanical AVRs performed during the same time period as identified using the University of Melbourne and Australia and New Zealand Society of Cardiac and Thoracic Surgeons' Cardiac Surgery Databases. Only patients between 18 and 65 years of age were included. Propensity-score matching was performed for risk adjustment. Ross procedure patients were younger, and had fewer cardiovascular risk factors. The Ross procedure was associated with longer cardiopulmonary bypass and aortic cross-clamp times. Thirty-day mortality was similar (Ross, 0.3%; mechanical, 0.8%; p = 0.5). Ross procedure patients experienced superior unadjusted long-term survival at 20 years (Ross, 95%; mechanical, 68%; p mechanical, 84%; p = 0.018). In this Australian, propensity-score matched study, the Ross procedure was associated with better long-term survival compared with mechanical AVR. In younger patients, with a long life expectancy, the Ross procedure should be considered in centers with sufficient expertise. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

[Minor strut fracture of the Björk-Shiley mitral valve].

Science.gov (United States)

Sugita, T; Yasuda, R; Watarida, S; Onoe, M; Tabata, R; Mori, A

1990-06-01

In May, 1982, a 49-year-old man underwent mitral valve replacement (MVR) in our hospital with a 31 mm Björk-Shiley prosthesis for mitral regurgitation. He had been doing well until his episode of palpitation and dyspnea of sudden onset, and was transferred to our ICU with severe cardiogenic shock in Aug, 1986. Chest X-ray film revealed pulmonary edema and breakage of the valve with migration of the disc and the minor strut of the prosthesis. He was operated upon 5 hours after the onset of his complaints. The minor strut was removed from the left upper pulmonary vein and mitral valve re-replacement was done with a 29 mm Björk-Shiley Monostrut valve. The disc which had dislocated into the abdominal aorta was also recovered on the twenty-third post operative day. His postoperative course was uneventful. Immediate diagnosis and subsequent re-operation is absolute indication for rescue from acute cardiac failure due to mechanical failure of any prosthetic valve.

Comparative study of Butterfly valves

International Nuclear Information System (INIS)

Galmes Belmonte, F.B.

1998-01-01

This work tries to justify the hydrodynamic butterfly valves performance, using the EPRI tests, results carried out in laboratory and in situ. This justification will be possible if: - The valves to study are similar - Their performance is calculated using EPRI's methodology Looking for this objective, the elements of the present work are: 1. Brief EPRI butterfly valve description it wild provide the factors which are necessary to define the butterfly valves similarity. 2. EPRI tests description and range of validation against test data definition. 3. Description of the spanish butterfly analyzed valves, and comparison with the EPRI performance results, to prove that this valves are similar to the EPRI test valves. In this way, it will not be necessary to carry out particular dynamic tests on the spanish valves to describe their hydrodynamic performance. (Author)

Intelligent Flow Control Valve

Science.gov (United States)

Kelley, Anthony R (Inventor)

2015-01-01

The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.

MANAGEMENT OF FAILED MITRAL VALVE REPLACEMENT. THE DURBAN EXPERIENCE.

Science.gov (United States)

Kistan, D; Booysen, M; Alexander, G; Madiba, T E

2017-06-01

Mitral valve replacement is the procedure of choice in patients with severe mitral valve disease. However, these patients are surviving longer and are thus at an increased risk of prosthesis failure or valve-related complications. Study setting: Inkosi Albert Luthuli Central Hospital, a tertiary referral Hospital in Durban. Study population: All patients undergoing redo mechanical mitral valve replacement surgery between January 2005 and December 2014. Study design: Retrospective analysis of patients undergoing redo mitral valve replacement. Patients were identified from theatre record books, their files were electronically accessed and pertinent information extracted onto a data capture sheet. Information documented included demographics, duration to failure, INR, Albumin, HIV status, clinical findings and outcome. The data was stored on an Excel datasheet. Fifty-eight patients were documented (mean age 32 ± 15.81 years; M:F 1:3). Ten patients (17%) were HIV positive (median CD4 count 478). Mean duration between first surgery and redo was 8.8 years. Thirty-five patients (60%) had no co-morbidities. Presenting features at redo surgery were congestive cardiac failure (27), chest pain (11) and palpitations (17). Mean preoperative Ejection Fraction was 51.65 %. Twenty-nine patients (55%) had emergency redo surgery. Twenty-two patients (75%) had acute prosthetic valve thrombosis. Thirty-two patients had tricuspid regurgitation. Original pathology was documented in 23 patients (40%) as Rheumatic valve disease. Prosthetic valve thrombosis was documented in 31 patients (54%). The most commonly used valve was the On-X. Mean presenting INR was 1.96 + 1.2 and mean presenting serum albumin was 36.7 + 7.8 g/l. Forty-one patients (71%) were found to be compliant to Warfarin therapy prior to redo surgery. Mean ICU stay was 6 +9 days. Two patients died postoperatively. Mean followup was 32 + 26.6 months. Twelve patients (20.7%) developed postoperative complications. Patients

Experience with valves for PHWR reactors

International Nuclear Information System (INIS)

Narayan, K.; Mhetre, S.G.

1977-01-01

Material specifications and inspection and testing requirements of the valves meant for use in nuclear reactors are mentioned. In the heavy water systems (both primary and moderator) of a PHWR type reactor, the valves used are gate valves, globe valves, diaphragm valves, butterfly valves, check valves and relief valves. Their locations and functions they perform in the Rajasthan Atomic Power Station Unit-1 are described. Experience with them is given. The major problems encountered with them have been : (1) leakage from the stem seals and body bonnet joint, (2) leakage due to failure of diaphragm and/or washout of the packing and (3) malfunctioning. Measures taken to solve these are discussed. Finally a mention has been made of improved versions of valves, namely, metal diaphragm valve and inverted relief valve. (M.G.B.)

Leaving Moderate Tricuspid Valve Regurgitation Alone at the Time of Pulmonary Valve Replacement: A Worthwhile Approach.

Science.gov (United States)

Kogon, Brian; Mori, Makoto; Alsoufi, Bahaaldin; Kanter, Kirk; Oster, Matt

2015-06-01

Pulmonary valve disruption in patients with tetralogy of Fallot and congenital pulmonary stenosis often results in pulmonary insufficiency, right ventricular dilation, and tricuspid valve regurgitation. Management of functional tricuspid regurgitation at the time of subsequent pulmonary valve replacement remains controversial. Our aims were to (1) analyze tricuspid valve function after pulmonary valve replacement through midterm follow-up and (2) determine the benefits, if any, of concomitant tricuspid annuloplasty. Thirty-five patients with tetralogy of Fallot or congenital pulmonary stenosis were analyzed. All patients had been palliated in childhood by disrupting the pulmonary valve, and all patients had at least moderate tricuspid valve regurgitation at the time of subsequent pulmonary valve replacement. Preoperative and serial postoperative echocardiograms were analyzed. Pulmonary and tricuspid regurgitation, along with right ventricular dilation and dysfunction were scored as 0 (none), 1 (mild), 2 (moderate), and 3 (severe). Right ventricular volume and area were also calculated. Comparisons were made between patients who underwent pulmonary valve replacement alone and those who underwent concomitant tricuspid valve annuloplasty. At 1 month after pulmonary valve replacement, there were significant reductions in pulmonary valve regurgitation (mean 3 vs 0.39, p tricuspid valve regurgitation (mean 2.33 vs 1.3, p tricuspid regurgitation 1 month postoperatively between patients who underwent concomitant tricuspid annuloplasty and those who underwent pulmonary valve replacement alone (mean 1.31 vs 1.29, p = 0.81). However, at latest follow-up (mean 7.0 ± 2.8 years), the degree of tricuspid regurgitation was significantly higher in the concomitant annuloplasty group (mean 1.87 vs 1.12, p = 0.005). In patients with at least moderate tricuspid valve regurgitation, significant improvement in tricuspid valve function and right ventricular size occurs in the first

Evaluation Of Factors Influencing On Causes Of Prosthetic Valve Re-operation And Early Postoperative Survival Tehran Emam hospital (1991-2001

Directory of Open Access Journals (Sweden)

Rahmani Reaza

2003-06-01

Full Text Available Prosthetic valve re-operation has greater mortality and morbidity than primary valve replacement. By recognition of factors influencing on causes of redo operation and preoperative survival, one can select appropriate prosthesis at primary valve replacement and when operation performed at appropriate time, surgical risk can be reduced."nMethods and Materials: Two hundred patients that underwent prosthetic valve re-operation from October 1991 through November 2001 were included in this study. There were 68 men and 132 women with the mean age of 42:tl 1.8 years. Structural failure was the commonest cause of bio-prosthesis replacement (93%. Valve thrombosis was the common cause of mechanical valve replacement (32%. Age younger Than 50 (P= 0.01 and interval after the first implantation more than 10 years (P= 0.01 affected bio-prosthesis degeneration."nResults: Atrial fibrillation (P<0.01, Older age especially more than 40 (P<0.05 and mitral position (P<0.01 affected mechanical valve thrombosis. Cross clamp time (P= 0.005, Tricuspid insufficiency (P = 0.001, NYHA IV (P = 0.005 and emergent operation (P= 0.001 were independent determinants of hospital mortality."nConclusion: In conclusion, in patients with more than 10-years life expectancy and age younger than 50, mechanical valve can be selected for primary valve replacement. If operation performed before patients reach deteriorated condition, preoperative survival would be excellent.

Valve-aided twisted Savonius rotor

Energy Technology Data Exchange (ETDEWEB)

Jaya Rajkumar, M.; Saha, U.K.

2006-05-15

Accessories, such as end plates, deflecting plates, shielding and guide vanes, may increase the power of a Savonius rotor, but make the system structurally complex. In such cases, the rotor can develop a relatively large torque at small rotational speeds and is cheap to build, however it harnesses only a small fraction of the incident wind energy. Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades. Such methods have been studied experimentally with a twisted-blade Thus improving a Savonius rotor's energy capture. This new concept has been named as the 'Valve-Aided Twisted Savonius'rotor. Tests were conducted in a low-speed wind tunnel to evaluate performance. This mechanism is found to be independent of flow direction, and shows potential for large machines. [Author].

The Double-Orifice Valve Technique to Treat Tricuspid Valve Incompetence.

Science.gov (United States)

Hetzer, Roland; Javier, Mariano; Delmo Walter, Eva Maria

2016-01-01

A straightforward tricuspid valve (TV) repair technique was used to treat either moderate or severe functional (normal valve with dilated annulus) or for primary/organic (Ebstein's anomaly, leaflet retraction/tethering and chordal malposition/tethering, with annular dilatation) TV incompetence, and its long-term outcome assessed. A double-orifice valve technique was employed in 91 patients (mean age 52.6 ± 23.2 years; median age 56 years; range: 0.6-82 years) with severe tricuspid regurgitation. Among the patients, three had post-transplant iatrogenic chordal rupture, five had infective endocarditis, 11 had mitral valve insufficiency, 23 had Ebstein's anomaly, and 47 had isolated severe TV incompetence. The basic principle was to reduce the distance between the coapting leaflets, wherein the most mobile leaflet could coapt to the opposite leaflet, by creating two orifices, ensuring valve competence. The TV repair was performed through a median sternotomy or right anterior thoracotomy in the fifth intercostal space under cardiopulmonary bypass. The degree and extent of creating a double-valve orifice was determined by considering the minimal body surface area (BSA)-related acceptable TV diameter. Repair was accomplished by passing pledgeted mattress sutures from the middle of the true anterior annulus to a spot on the opposite septal annulus, located approximately two-thirds of the length of the septal annulus to avoid injury to the bundle of His. The annular apposition divides the TV into a larger anterior and a smaller posterior orifices, enabling valve closure, on both sides. In adults, the diameter of the anterior valve orifice should be 23-25 mm, and the posterior orifice 15-18 mm; thus, the total valve orifice area is 5-6 cm2. In children, the total valve orifice should be a standard deviation of 1.7 mm for a BSA of 1.0m2. During a mean follow up of 8.7 ± 1.34 years (median 10 years; range: 1.5-25.9 years) there have been no reoperations for TV insufficiency