Finite Element Analysis of a Mechanical Heart Valve in Assembly

2012 ◽  
Vol 569 ◽  
pp. 487-490
Author(s):  
Liang Liang Wu ◽  
Guo Jiang Wan ◽  
Feng Zhou ◽  
Jie Yang ◽  
Nan Huang
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Mechanical Valve ◽  
Mechanical Method ◽  
Assembly Quality ◽  
Element Analysis ◽  
Bileaflet Mechanical Heart Valve ◽  
Valve Assembly ◽  
Ansys Workbench

The Bileaflet Mechanical Heart Valve (BMHV) has been the most successful replacement mechanical heart valve, and is currently the most commonly implanted mechanical valve. Although the BMHV is an improvement over previous mechanical heart valves, there are still serious associated complications with its use that must be eliminated. After the completion of the processing and surface modification, heart valve ring and heart valve leaflets constitute a single whole with mechanical method to achieve its function process. In order to ensure that the heart valve is stable and reliable in service, it is particularly important to improve the assembly quality. The theoretical analysis and simulation used of ANSYS Workbench software for the behavior of the heart valve assembly have been done, the experimental results were verified by testing apparatus, which is a helpful tool used to simulate the new structure of the heart valve assembly, and play a certain significance to improve the accuracy of the assembly.

Static and Dynamic Stresses during Valve Closure of a Bileaflet Mechanical Heart Valve Prosthesis

1991 ◽  
Vol 14 (12) ◽  
pp. 781-788 ◽  
Author(s):  
T.H. Chiang ◽  
H. Lam ◽  
R. Quijano ◽  
R. Donham ◽  
P. Gilliam ◽  
...  
Keyword(s):  
Heart Valve ◽  
Mechanical Heart Valve ◽  
Heart Valve Prosthesis ◽  
Valve Prosthesis ◽  
Valve Closure ◽  
Element Analysis ◽  
Dynamic Stresses ◽  
Magnitude Distribution ◽  
Bileaflet Mechanical Heart Valve ◽  
The Impact

The effect of contact geometry and component compliance on the magnitude, distribution, and state of various types of stresses on a bileaflet mechanical heart valve prosthesis during valve closure was analyzed using an Edwards-Duromedics™ mitral valve as example. Static and dynamic stresses developing on both the leaflet and pivot ball during valve closure were modeled using finite element analysis (FEA). Uniform contact between the leaflet and housing as well as between the pivot ball and pivot slot can significantly reduce both static and dynamic stresses around the contact area. The level of the dynamic flexural stresses can be an order of magnitude higher than that of the static stresses. When both the radial and axial compliance of the housing are taken into consideration, peak dynamic stress was more than 40% less than that generated through the impact between a moving leaflet and a non-compliant rigid housing.

scholarly journals Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

2008 ◽  
Author(s):  
C. Hutchison ◽  
P. E. Sullivan ◽  
C. R. Ethier
Keyword(s):  
Steady Flow ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Stereoscopic Piv ◽  
Bileaflet Mechanical Heart Valve ◽  
Component Particle

Each year over 180,000 mechanical heart valves are implanted worldwide, with the bileaflet mechanical heart valve (BiMHV) accounting for approximately 85% of all valve replacements [1,2]. Although much improved from previous valve designs, aortic BiMHV design is far from ideal, and serious complications such as thromboembolism and hemolysis often result. Hemolysis and platelet activation are thought to be caused by turbulent Reynolds shear stresses in the flow [1]. Numerous previous studies have examined aortic BiMHV flow using LDA and two component Particle Image Velocimetry (PIV), and have shown the flow to be complex and three-dimensional [3,4]. Stereoscopic PIV (SPIV) can obtain all three velocity components on a flow plane, and hence has the potential to provide better understanding of three dimensional flow characteristics. The objective of the current study was to use SPIV to measure steady flow, including turbulence properties, downstream of a BiMHV in a modeled aorta. The resulting dataset will be useful for CFD model validation, and the intent is to make it publicly available.

An Initial Parametric Study on Fluid Flow Through Bileaflet Mechanical Heart Valves Using Computational Fluid Dynamics

1994 ◽  
Vol 208 (2) ◽  
pp. 63-72 ◽  
Author(s):  
M J King ◽  
T David ◽  
J Fisher
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Volumetric Flow Rate ◽  
Flow Fields ◽  
Opening Angle ◽  
Bileaflet Mechanical Heart Valve ◽  
Flow Through

The effect of leaflet opening angle on flow through a bileaflet mechanical heart valve has been investigated using computational fluid dynamics (CFD). Steady state, laminar flow for a Newtonian fluid at a Reynolds number of 1500 was used in the two-dimensional model of the valve, ventricle, sinus and aorta. This computational model was verified using one-dimensional laser Doppler velocimetry (LDV). Although marked differences in the flow fields and energy dissipation of the jets downstream of the valve were found between the CFD predictions and the three-dimensional experimental model, both methods showed similar trends in the changes of the flow fields as the leaflet opening angle was altered. As the opening angle increased the area of recirculating fluid downstream of the leaflets, the pressure drop across the valve and the volumetric flow rate through the outer orifice decreased. For opening angles greater than 80° the jet through the outer orifice recombined with the central jet downstream of the leaflet; for an opening angle of 78° the jet through the outer orifice impinged on the aortic wall before recombining with the central jet. This study suggests that the opening angle has a marked effect on the flow downstream of the bileaflet mechanical heart valve and that valves with opening angles greater than 80° are preferable.

scholarly journals Statistical Characteristics of Flow Field through Open and Semi-Closed Bileaflet Mechanical Heart Valve

2020 ◽  
Vol 2 (4) ◽  
pp. 184-196
Author(s):  
Oleksandr Voskoboinyk ◽  
Lidiia Tereshchenko ◽  
Vladimir Voskoboinick ◽  
Gabriela Fernandez ◽  
Andrey Voskoboinick ◽  
...  
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Pressure Sensors ◽  
Jet Flow ◽  
Operating Conditions ◽  
Mechanical Heart Valves ◽  
Statistical Characteristics ◽  
Diagnostic Tools ◽  
Bileaflet Mechanical Heart Valve

The formation of thrombi on the streamlined surface of the bileaflet mechanical heart valves is one of the main disadvantages of such valves. Thrombi block the valve leaflets and disrupt the cardiovascular system. Diagnosis of thrombosis of the bileaflet mechanical heart valves is relevant and requires the creation of effective diagnostic tools. Hydroacoustic registration of the heart noise is one of the methods for diagnosing the operation of a mechanical heart valve. The purpose of the research is to determine the statistical characteristics of the vortex and jet flow through the open and semi-closed bileaflet mechanical heart valve, to identify hydroacoustic differences and diagnostic signs to determine the operating conditions of the valve. Experimental studies were conducted in laboratory conditions on a model of the left atrium and left ventricle of the heart between which there was the bileaflet mechanical heart valve. Hydrodynamic noise was recorded by miniature pressure sensors, which were located downstream of the valve. The vortex and jet flow behind the prosthetic heart valve were non-linear, random processes and were analyzed using the methods of mathematical statistics and probability theory. The integral and spectral characteristics of the pressure field were obtained and the differences in the noise levels and their spectral components near the central and side jets for the open and semi-closed mitral valve were established. It was shown that hydroacoustic measurements could be an effective basis for developing diagnostic equipment for monitoring the bileaflet mechanical heart valve operation. Doi: 10.28991/SciMedJ-2020-0204-1 Full Text: PDF

Effect of Blood Pressure on Closing Dynamics of Bileaflet Mechanical Heart Valves

2012 ◽  
Author(s):  
Marcio H. Forleo ◽  
Brennan M. Johnson ◽  
Lakshmi P. Dasi
Keyword(s):  
Blood Pressure ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Thromboembolic Complications ◽  
Stress Gradients ◽  
Bileaflet Mechanical Heart Valve ◽  
Sharp Stress ◽  
Rigid Design

Implantation of a bileaflet mechanical heart valve (BMHV) continues to be associated with a risk of thromboembolic complications despite anti-coagulation therapy1. This has been attributed to the structurally rigid design of the leaflets and valve mechanics combined with an intricate hinge mechanism for the rigid leaflets. The lack of a built in compliance within the valve mechanics presumably leads to sharp stress gradients within the flow as well as a violent closure of the valve often associated with the audible impact of the leaflets to the housing, and a potential for momentary cavitation of blood in the wake of leaflet impact.

scholarly journals Near Valve Flows and Potential Blood Damage During Closure of a Bileaflet Mechanical Heart Valve

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
L. H. Herbertson ◽  
S. Deutsch ◽  
K. B. Manning
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
In Vitro Study ◽  
Blood Damage ◽  
Bileaflet Mechanical Heart Valve ◽  
Fluid Velocities ◽  
Design Characteristics ◽  
Valve Housing

Blood damage and thrombosis are major complications that are commonly seen in patients with implanted mechanical heart valves. For this in vitro study, we isolated the closing phase of a bileaflet mechanical heart valve to study near valve fluid velocities and stresses. By manipulating the valve housing, we gained optical access to a previously inaccessible region of the flow. Laser Doppler velocimetry and particle image velocimetry were used to characterize the flow regime and help to identify the key design characteristics responsible for high shear and rotational flow. Impact of the closing mechanical leaflet with its rigid housing produced the highest fluid stresses observed during the cardiac cycle. Mean velocities as high as 2.4 m/s were observed at the initial valve impact. The velocities measured at the leaflet tip resulted in sustained shear rates in the range of 1500–3500 s−1, with peak values on the order of 11,000–23,000 s−1. Using velocity maps, we identified regurgitation zones near the valve tip and through the central orifice of the valve. Entrained flow from the transvalvular jets and flow shed off the leaflet tip during closure combined to generate a dominant vortex posterior to both leaflets after each valve closing cycle. The strength of the peripheral vortex peaked within 2 ms of the initial impact of the leaflet with the housing and rapidly dissipated thereafter, whereas the vortex near the central orifice continued to grow during the rebound phase of the valve. Rebound of the leaflets played a secondary role in sustaining closure-induced vortices.

Simulations of the Hinge Flow Fields of a Bileaflet Mechanical Heart Valve Under Physiologic Pulsatile Aortic Conditions

2008 ◽  
Author(s):  
Hélène A. Simon ◽  
Liang Ge ◽  
Iman Borazjani ◽  
Fotis Sotiropoulos ◽  
Ajit P. Yoganathan
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Prosthetic Heart Valve ◽  
Prosthetic Heart Valves ◽  
Valve Design ◽  
Bileaflet Mechanical Heart Valve ◽  
Hinge Flow ◽  
Blood Elements

Native heart valves with limited functionality are commonly replaced by prosthetic heart valves. Since the first heart valve replacement in 1960, more than three million valves have been implanted worldwide. The most widely implanted prosthetic heart valve design is currently the bileaflet mechanical heart valve (BMHV), with more than 130,000 implants every year worldwide. However, studies have shown that this valve design can still cause major complications, including hemolysis, platelet activation, and thromboembolic events. Clinical reports and recent in vitro experiments suggest that these thrombogenic complications are associated with the hemodynamic stresses imposed on blood elements by the complex non-physiologic flow induced by the valve, in particular in the hinge region.

Alternative mechanical heart valves for the developing world

2019 ◽  
Vol 28 (7) ◽  
pp. 431-443
Author(s):  
Elsmari Wium ◽  
Christiaan Johannes Jordaan ◽  
Lezelle Botes ◽  
Francis Edwin Smit
Keyword(s):  
Heart Valve ◽  
Computer Aided Design ◽  
Heart Valves ◽  
Developing World ◽  
Mechanical Heart Valve ◽  
Mechanical Heart Valves ◽  
Design Approach ◽  
Element Analysis ◽  
Mechanical Valves

Due to the prevalence of rheumatic heart disease in the developing world, mechanical heart valves in the younger patient population remain the prostheses of choice if repair is not feasible. Despite their durability, mechanical valves are burdened by coagulation and thromboembolism. Modern design tools can be utilized during the design process of mechanical valves, which allow a more systematic design approach and more detailed analysis of the blood flow through and around valves. These tools include computer-aided design, manufacturing, and engineering, such as computational fluid dynamics and finite element analysis, modern manufacturing techniques such as additive manufacturing, and sophisticated in-vitro and in-vivo tests. Following this systematic approach, a poppet valve was redesigned and the results demonstrate the benefits of the method. More organized flow patterns and fewer complex fluid structures were observed. The alternative trileaflet valve design has also been identified as a potential solution and, if a similar design approach is adopted, it could lead to the development of an improved mechanical heart valve in the future. It is imperative that researchers in developing countries continue their search for a mechanical heart valve with a reduced thromboembolic risk, requiring less or no anticoagulation.

Mechanical Heart Valve Replacement in a Low-Middle Income Region in the Modern Era: Midterm Results from a Sub-Saharan Center

2018 ◽  
Vol 68 (02) ◽  
pp. 099-106 ◽  
Author(s):  
Charles Mve Mvondo ◽  
Marta Pugliese ◽  
Jean Claude Ambassa ◽  
Alessandro Giamberti ◽  
Emanuele Bovio ◽  
...  
Keyword(s):  
Valve Replacement ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Mechanical Valve ◽  
Midterm Results ◽  
Middle Income ◽  
Sub Saharan ◽  
Valve Implantation

Abstract Background The management of patients with mechanical heart valves remains a major concern in populations with limited resources and medical facilities. This study reports the clinical outcomes of patients who underwent mechanical valve implantation in a sub-Saharan center over an 8-year period. Methods A total of 291 mechanical valves were implanted in 233 patients in our institution between February 2008 and June 2016. A total of 117 patients underwent mitral valve replacement (MVR, 50.2%), 57 had aortic valve replacement (AVR, 24.4%), and 59 underwent both AVR and MVR (double valve replacement [DVR], 25.7%). The mean age at surgery was 27.6 ± 13.4 years (range, 7–62 years). Rheumatic etiology was found in 80.6% of the patients. Hospital mortality, late deaths, and valve-related events were reviewed at follow-up (839 patient-years, range: 1–9.4 years, complete in 93%). Results The 30-day mortality was 4.7% (11/233). The overall survival at 1 and 6 years for the whole cohort was 88.8 ± 2.1% and 78.7 ± 3.3%, respectively. The 6-year survival for AVR, MVR, and DVR was 89.3 ± 4.8%, 73.2 ± 5.4%, and 79.3 ± 5.8%, respectively (p = 0.15). The freedom from neurologic events and anticoagulation-related bleeding at 6 years was 93.1 ± 2.1% and 78.9 ± 3.7%, respectively. No patient had reoperation at follow-up. No case of prosthetic valve thrombosis was identified. Eight full-term pregnancies were reported. Conclusion This preliminary experience reports acceptable midterm results after mechanical heart valve implantation in our region. Both accurate surgical evaluation and strategies, either financial or social, facilitating patient's education and medical assistance are crucial to ensure good results. Long-term follow-up and further studies comparing current nonthrombogenic options are warranted to draw reliable conclusions.

scholarly journals Pyrolytic Carbons and the Design of Mechanical Heart Valve Prostheses

2000 ◽  
Author(s):  
R. B. More
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Heart Valve ◽  
Heart Valves ◽  
Blood Compatibility ◽  
Mechanical Heart Valve ◽  
Mechanical Valve ◽  
Pyrolytic Carbon ◽  
Mechanical Heart Valves ◽  
Pure Carbon

Abstract Pyrolytic carbons have a long successful history in mechanical heart valve prosthesis applications. Originally pyrolytic carbons had been developed for use in nuclear reactors. But in a chance interaction between a scientist studying nuclear energy and another searching for blood compatible materials, the blood compatibility of pyrolytic carbon was discovered. This discovery of blood compatibility prompted an effort that resulted in the development of a form of pyrolytic carbon specifically tailored for use in mechanical heart valves. This form developed by General Atomic Co. was an alloy of approximately 5 to 12 weight percent silicon codeposited with pyrolytic carbon. Fine silicon carbide particles dispersed in the carbon matrix increased the hardness and wear resistance of the pyrolytic carbon, which compensated for difficulties in manufacturing using the process control capabilities available at the time. Use of pyrolytic carbon instead of polymers in the early valve designs allowed the durability, stability and compatibility needed for true long-term implants. Since the first pyrolytic carbon heart valve component implant in 1968, more than 4 million pyrolytic carbon components in more than 25 different valve designs have been implanted to accumulate a clinical experience on the order of 18 million patient years. The physiochemical and mechanical properties of silicon-alloyed pyrolytic carbon, while enabling the practical utilization of mechanical heart valves, placed some severe restrictions upon design. Silicon-alloyed pyrolytic carbon is an extremely hard and nearly ideal linear elastic material with a strain to failure of approximately 1.2 percent. Traditional machining and joining techniques are not feasible, rather the carbon is prepared as a coating upon a pre-form and the coated components are then finished to size using diamond impregnated tools, grinding forms and abrasive polishing techniques. While the silicon-alloyed material was very successful, design features of known hydrodynamic advantage, such as a flared inlet, were not possible and in some valve designs annular area was sacrificed by the addition of metallic rings used to increase stiffness. As a result, mechanical valve designs in the small aortic sizes tended to be stenotic. In the early 1990’s, pyrolytic carbon coating technology was re-examined and methods of process control were redesigned in order to produce pure carbon. The resulting pure pyrolytic carbon had sufficient hardness and wear resistance, but, in addition, had higher strength and toughness with higher deformability than the silicon-alloyed material. The new material eliminated the need for the silicon and improved the carbon mechanical properties. With the improved mechanical properties, it is now possible to manufacture valve designs with greater hydrodynamic efficiency, and eliminate the need for stiffening rings, thus improving the flow behavior in the small aortic valve sizes. A mechanical valve design utilizing the pure carbon with improved hydrodynamic design features has achieved hemodynamic properties comparable to those of homografts and stentless bioprostheses.

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