Development of a Test Bank for Fluid Dynamic Analysis of Two Prosthetic Heart Valves Using Air as Working Fluid

2014 ◽  
Author(s):  
Luz M. Rivera ◽  
Ana I. Crispín ◽  
Nelson Escobar ◽  
Lina M. Hoyos ◽  
John Bustamante
Keyword(s):  
Dynamic Analysis ◽  
Heart Valves ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Working Fluid ◽  
Prosthetic Heart Valves ◽  
Pressure Gradients ◽  
Prosthetic Valves ◽  
Hemodynamic Performance ◽  
Clinical Conditions

This work presents the fluid dynamic analysis of the mechanical prosthetic heart valves: Björk Shiley and Sorin Bicarbon™. Analysis of prosthetic valves is currently done with viscous fluids that emulate the behavior of blood; however the developed test bank, wind tunnel, uses air as the working fluid. This working fluid differs from those currently being used due to its low density and viscosity properties, which provides greater sensitivity to small changes in geometry and valve design variations. These features permit to identify relevant changes to the patient’s hemodynamic system based on the effect of the implanted valve. Tests were performed by measuring the fluid-dynamics of both valves; the obtained results show accuracy with the valves’ performance under clinical conditions. The offset design of the Björk Shiley tilting disk gives the valve the ability to generate less blood trauma and increase laminar flow and the Sorin Bicarbon™ bileaflet has a larger orifice for better hemodynamic performance. Furthermore, the transversal pressure gradients and local effects such as turbulence and vortexes were also analyzed; and the obtained results are accurate according to the functionality, geometrical and structural characteristics of both valves at their real environment.

Stereoscopic PIV Measurements of Flow in a Model Left Ventricle with Prosthetic Valves

2004 ◽  
Author(s):  
Donal J. Taylor ◽  
Nathan J. Quinlan ◽  
John A. Eaton
Keyword(s):  
Left Ventricle ◽  
Heart Valves ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stereoscopic Particle Image Velocimetry ◽  
Laboratory Model ◽  
Prosthetic Heart Valves ◽  
Mitral Valves ◽  
Prosthetic Valves ◽  
Component Velocity

Fluid dynamic phenomena are fundamentally important in the function of the heart, and consequently in the design of prosthetic heart valves. Experimental study is complicated by the strongly unsteady and three-dimensional character of flow in the chambers and valves of the heart, and the difficulty of access for instrumentation, even in a laboratory model. This paper describes the novel application of Stereoscopic Particle Image Velocimetry (SPIV) to measure the three-component velocity vector field in a model of the left ventricle with mechanical prosthetic valves. The results illustrate key functional differences between the two prosthetic mitral valves tested. These experiments demonstrate the powerful capability of SPIV as a tool for investigation of the complex flows which occur in biology and medicine.

scholarly journals Imaging of Cardiac Valves by Computed Tomography

Scientifica ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Gudrun Feuchtner
Keyword(s):  
Computed Tomography ◽  
Heart Valves ◽  
Severe Aortic Stenosis ◽  
Multislice Ct ◽  
Valvular Disease ◽  
Special Focus ◽  
Prosthetic Heart Valves ◽  
Cardiac Valves ◽  
Effective Treatment Option ◽  
Prosthetic Valves

This paper describes “how to” examine cardiac valves with computed tomography, the normal, diseased valves, and prosthetic valves. A review of current scientific literature is provided. Firstly, technical basics, “how to” perform and optimize a multislice CT scan and “how to” interpret valves on CT images are outlined. Then, diagnostic imaging of the entire spectrum of specific valvular disease by CT, including prosthetic heart valves, is highlighted. The last part gives a guide “how to” use CT for planning of transcatheter aortic valve implantation (TAVI), an emerging effective treatment option for patients with severe aortic stenosis. A special focus is placed on clinical applications of cardiac CT in the context of valvular disease.

scholarly journals Platelet Suppression Therapy in Arterial Disease: Present Status

1977 ◽  
Author(s):  
J. A. Blakely
Keyword(s):  
Secondary Prevention ◽  
Heart Valves ◽  
Case Reports ◽  
Myocardial Infarct ◽  
Arterial Disease ◽  
Preliminary Evidence ◽  
Prosthetic Heart Valves ◽  
Prosthetic Valves ◽  
Survival Studies ◽  
Cerebral Ischemic

Arterial disease is a severe test of clinical trials methodology. Results to date have defined areas for further study, but clinical indications are not established. Dipyridamole reduces emboli from prosthetic heart valves but applicability to less thrombogenic valves is uncertain. Transient cerebral ischemic attacks are physiologically appropriate and there is preliminary evidence of reduced attacks with Sulfinpyrazone, none with Dipyridamole, and favorable case reports with Aspirin. Effects on stroke and death in patients presenting with TIA or stroke are under study. Sulfinpyrazone has failed to prolong patency time after peripheral vascular surgery. Administration of aspirin and of Sulfinpyrazone to elderly populations has shown no detectable benefit from Aspirin, and has suggested that Sulfinpyrazone should be further studied in patients recovered from thrombotic stroke. The greatest potential benefit may be secondary prevention of myocardial infarct, but to date efficacy has neither been demonstrated nor excluded. Studies in progress include: ASA and/or Sulfinpyrazone and TIA, stroke and death in patients with TIA; ASA with and without Dipyridamole in patients with TIA: Sulfinpyrazone and survival after recovery from thrombotic stroke; Secondary prevention of myocardial infarct with ASA, ASA or ASA + Dipyridamole, Sulfinpyrazone, and Clofibrate; Sulfinpyrazone, ASA, and ASA with anticoagulants and emboli from prosthetic valves. Platelet survival studies may permit selection of populations likely to benefit and assessment of adequacy of therapy.Hypotheses tested by clinical trial must be distinguished from hypotheses formulated from retrospective analysis, and methods must permit effects of treatment to be distinguished from differences in risk.

scholarly journals Analysis of leaflet flutter in biological prosthetic heart valves using PIV measurements

2019 ◽  
Vol 42 ◽  
pp. e41746
Author(s):  
Artur Henrique de Freitas Avelar ◽  
Mairon Assis Guimaris Eller Stófel ◽  
Glenda Dias Vieira ◽  
Jean Andrade Canestri ◽  
Rudolf Huebner
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Particle Image ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Lower Velocity ◽  
Piv Measurements ◽  
Prosthetic Valves ◽  
Image Velocimetry ◽  
Experimental Bench

The use of biological prosthetic valves has increased considerably in recent decades since they have several advantages over mechanical ones, but they still possess the great disadvantage of having a relatively short lifetime. An understudied phenomenon is the flutter effect that causes oscillations in the cusps, which is associated with regurgitation, calcification and fatigue, which can reduce even more the lifetime of bioproteses. In an experimental bench that simulates the cardiac flow, the behavior of a porcine and a bovine pericardium valves was recorded by a high-speed camera to quantify the oscillations of the cusps and an experiment using particle image velocimetry was conducted to study the velocity profiles and shear stresses and their relations with flutter. Results showed that the pericardial valve has lower values of frequencies and amplitudes compared to the porcine valve. Lower velocity values were found in the cusps that did not have flutter, but no relationship was observed between shear stress values and leaflet vibrations. These results may assist in future projects of biological prosthetic valves that have less flutter and longer lifespan.

scholarly journals Fluid–Structure Interaction and In Vitro Analysis of a Real Bileaflet Mitral Prosthetic Valve to Gain Insight Into Doppler-Silent Thrombosis

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Annalisa Dimasi ◽  
Daniela Piloni ◽  
Laura Spreafico ◽  
Emiliano Votta ◽  
Riccardo Vismara ◽  
...  
Keyword(s):  
Prosthetic Valve ◽  
Heart Valves ◽  
Fluid Dynamic ◽  
Fluid Structure Interaction ◽  
Prosthetic Heart Valves ◽  
False Negatives ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Vitro Analysis

Prosthetic valve thrombosis (PVT) is a serious complication affecting prosthetic heart valves. The transvalvular mean pressure gradient (MPG) derived by Doppler echocardiography is a crucial index to diagnose PVT but may result in false negatives mainly in case of bileaflet mechanical valves (BMVs) in mitral position. This may happen because MPG estimation relies on simplifying assumptions on the transvalvular fluid dynamics or because Doppler examination is manual and operator dependent. A deeper understanding of these issues may allow for improving PVT diagnosis and management. To this aim, we used in vitro and fluid–structure interaction (FSI) modeling to simulate the function of a real mitral BMV in different configurations: normally functioning and stenotic with symmetric and completely asymmetric leaflet opening, respectively. In each condition, the MPG was measured in vitro, computed directly from FSI simulations and derived from the corresponding velocity field through a Doppler-like postprocessing approach. Following verification versus in vitro data, MPG computational data were analyzed to test their dependency on the severity of fluid-dynamic derangements and on the measurement site. Computed MPG clearly discriminated between normally functioning and stenotic configurations. They did not depend markedly on the site of measurement, yet differences below 3 mmHg were found between MPG values at the central and lateral orifices of the BMV. This evidence suggests a mild uncertainty of the Doppler-based evaluation of the MPG due to probe positioning, which yet may lead to false negatives when analyzing subjects with almost normal MPG.

Platelet Malondialdehyde in Cardiovascular Disease: Effect of Prosthetic Heart Valves and Cardioactive Drugs on Production

1980 ◽  
Vol 44 (02) ◽  
pp. 076-080 ◽  
Author(s):  
Jay M Sullivan ◽  
J Charles Taylor ◽  
Joseph K Samaha ◽  
Patti Lamar ◽  
Darrell R Patrick ◽  
...  
Keyword(s):  
Heart Valves ◽  
Platelet Rich Plasma ◽  
Blood Platelets ◽  
Normal Subjects ◽  
Serum Levels ◽  
Multiple Drug ◽  
Prosthetic Heart Valves ◽  
Prosthetic Valves ◽  
Enhanced Production ◽  
Platelet Survival

SummaryMalondialdehyde (MDA), a product of platelet lipid peroxidation, was measured in human platelet-rich plasma. Levels of 3.19 n moles/109 platelets ± 0.40 S.E. in 11 patients with prosthetic heart valves were elevated (p<0.25) compared to 17 normal subjects (2.09 ± 0.13 n moles/109 platelets). Reduced production (1.44 ± 0.28 n moles/109 platelets, p<0.5) was found in 10 patients with unstable angina. Normal levels were found in patients with mitral stenosis, cardiomyopathy or hypertension. Usual serum levels of drugs used in cardiac treatment reduced MDA levels as follows: acetaminophen, 47% (p<.01); aspirin, 58% (p<.05); furosemide, 32.6% (p<.005), and sulfinpyrazone, 41% (p<.05). Digoxin, dipyridamole, heparin, hydrochlorothiazide, lidocaine, nitroglycerin, procainamide, propranolol, quinidine, or warfarin had no significant effect at therapeutic concentrations. None of the drugs explained the enhanced production in patients with prosthetic valves while analgesic therapy could explain the decreased levels in other cardiacs. The half-time of platelet survival, measured by suppression of malondialdehyde production, was 3.2 ± 0.24 days in 9 normal subjects but could not be measured reliably in most patients because of multiple drug therapies. We conclude that the blood platelets of patients with prosthetic heart valves differ from those of normal subjects in their capacity to release malondialdehyde after stimulation with n-ethylmaleimide. Additionally, we find that inhibition of malondialdehyde production by several pharmacologic agents limits the usefulness of this method for the measurement of platelet survival in cardiac patients.

scholarly journals Prosthetic Heart Valves and Pregnancy: Challenges and Solutions

2018 ◽  
Vol 03 (02/03) ◽  
pp. 115-125
Author(s):  
Akshyaya Pradhan ◽  
Vikas Gupta ◽  
Pravesh Vishwakarma
Keyword(s):  
Heart Valves ◽  
Heart Diseases ◽  
Care Center ◽  
Tertiary Care ◽  
Normal Pregnancy ◽  
High Rate ◽  
Prosthetic Heart Valves ◽  
Prosthetic Valves ◽  
Dose Warfarin ◽  
Valvular Heart Diseases

AbstractWith improved outcomes of valvular heart diseases and prosthetic valves, many women now survive into child-bearing age and pregnancy. However, the presence of prosthetic valves in pregnancy has an adverse impact on both maternal and fetal outcomes. The bioprosthetic or tissue valves are less thrombogenic. They do not need any anticoagulation and lead to normal pregnancy with normal baseline valve function. However, they have high rate of structural degeneration, especially in the young with an attendant need of reoperation leading to morbidity. Mechanical valves have excellent hemodynamics during pregnancy but are inherently thrombogenic leading to thromboembolic complications, necessitating uninterrupted anticoagulation. Anticoagulation itself leads to a host of maternal and fetal bleeding complication as well as adverse fetal anomalies. The use of low-dose warfarin throughout pregnancy has the best maternal safety profile. Added to this regimen, targeted replacement with parenteral heparin during the first (6–12 weeks) and late third trimesters (beyond 36 weeks) leads to virtual elimination of embryopathy as well as appreciable reductions of maternal mortality. Proper preconception counseling and antenatal care coupled with planned labor or delivery is essential to ensure best outcomes. These patients are best managed in a tertiary care center with proper expertise in managing adverse cardiovascular, obstetric, and neonatal outcomes.

Doppler Hemodynamics of CarboMedics Prosthetic Valves in Aortic Position at Rest and Exercise

1996 ◽  
Vol 4 (3) ◽  
pp. 146-151
Author(s):  
Ichiro Shimada ◽  
Hitoshi Okabayashi ◽  
Takeshi Nishina ◽  
Kenji Minatoya ◽  
Yoshiharu Soga ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Aortic Valve Replacement ◽  
Pressure Gradient ◽  
Valve Replacement ◽  
Performance Index ◽  
Heart Valves ◽  
Peak Pressure ◽  
Prosthetic Heart Valves ◽  
Pressure Gradients ◽  
Theoretical Performance

To evaluate the size adequacy of CarboMedics prosthetic heart valves, Doppler pressure gradients after aortic valve replacement were determined at rest and immediately after exercise in 83 patients, at a mean time of 18.8 days after aortic valve replacement with CarboMedics prosthetic heart valves (31 standard and 52 R-series). There were 54 males and 29 females, average age 55 years; 12 had pure aortic stenosis, 47 had aortic regurgitation, and 24 had combined lesions. Exercise significantly increased (p < 0.01) the peak velocity (from 2.50 to 2.88 m/sec), the peak pressure gradient (from 25.9 to 34.6 mm Hg), and the mean pressure gradient (from 13.9 to 18.4 mm Hg). Significant differences were observed even in patients with seemingly large valve sizes. Significant correlation (p < 0.0001) was observed between pressure gradients at rest and immediately after exercise, as well as between pressure gradients and theoretical performance index. A theoretical performance index larger than 1.0 cm2/m2 was needed to obtain a postexercise Doppler peak pressure gradient of less than 60 mm Hg early after aortic valve replacement using either the Carbomedics standard or R-series prosthetic heart valves.

A Biocompatible Flow Chamber to Study the Hemodynamic Performance of Prosthetic Heart Valves

ASAIO Journal ◽  
2012 ◽  
Vol 58 (5) ◽  
pp. 470-480 ◽  
Author(s):  
Wei Yin ◽  
Ek Ching Ngwe ◽  
David A. Rubenstein
Keyword(s):  
Heart Valves ◽  
Flow Chamber ◽  
Prosthetic Heart Valves ◽  
Hemodynamic Performance
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