Key result
Simulation of a trileaflet mechanical heart valve revealed shear rates up to 20,000 s⁻¹ in pivot regions, with 0.7% of blood volume exposed to shear rates high enough to cause platelet activation.
Computational fluid dynamics can effectively simulate flow through mechanical heart valves to identify high shear rate regions, such as pivots, that may cause platelet activation, thereby aiding in valve design.
High-shear pivot regions may guide mechanical valve redesign; leaves open whether CFD thresholds predict clinical thrombosis.
Thromboembolic complications are one of the major challenges faced by designers and researchers in development of artificial organs with blood-contacting devices such as heart valve prostheses, especially mechanical valves. Besides increasing the thrombogenic potential, these valves change the hydrodynamic performance of the heart. In this study, the flow through a trileaflet, mechanical heart valve prosthesis was modeled with transient computational fluid dynamics to analyze flow patterns causing thrombus formations on valves. The valve was simulated under conditions of a test rig (THIA II), which was specially designed to analyze different valves with respect to thrombosis. The main goal of this study was to mimic the exact conditions of the test rig to be able to compare numerical and experimental results. The boundary conditions were obtained from experimental data as leaflet kinematics and pressure profiles. One complete cycle of the valve was simulated. Numerical flow and pressure results were analyzed and compared with experimental results. Shear stress and shear rates were determined with respect to thrombogenic potential, especially in the pivot regions, which seem to be the main influence for activation and deposition of thrombocytes. Approximately 0.7% of the blood volume moving through the fluid domain of the valve was exposed to shear rates high enough to cause platelet activation. However, shear rates of up to 20,000 s⁻¹ occurred in pivot regions. The pressure differences between the simulation and experimental data were approximately 2.5% during systole and increased up to 25% during diastole. The presented method, however, can be used to gain more information about the flow through different heart valve prostheses and, thus, improve the development process.
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Kaufmann et al. (2011) studied Thromboembolic complications in mechanical heart valve prostheses. Trileaflet mechanical heart valve prosthesis simulation vs. Experimental test rig data was evaluated on Shear stress, shear rates, and pressure differences. Simulation of a trileaflet mechanical heart valve revealed shear rates up to 20,000 s⁻¹ in pivot regions, with 0.7% of blood volume exposed to shear rates high enough to cause platelet activation.
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