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A significant problem in the operation of mechanical heart valve prostheses is the propensity for thrombus formation near the valve leaflet and housing. This may be caused by the high shear stresses present in the leakage jet flows through small gaps between leaflets and the valve housing during the valve closure phase.
This two-dimensional study was undertaken to demonstrate that design changes in bi-leaflet mechanical valves result in notable changes in the flow-induced stresses and prediction of platelet activation. A Cartesian grid technique is used for the 2D simulation of blood flow through two models of the bi-leaflet mechanical valve and their flow patterns, closure characteristics and platelet activation potential are compared. A local mesh refinement algorithm allows efficient and fast flow computations with mesh adaptation based on the gradients of the flow field in the gap between the leaflet and housing at the instant of valve closure. Leaflet motion is calculated dynamically based on the fluid forces acting on it. Platelets are modeled and tracked as point particles by a Lagrangian particle tracking method which incorporates the hemodynamic forces on the particles.
The comparison of results shows that the velocity, wall shear stress, and simulated platelet activation parameter are lower in the valve model with a smaller angle of leaflet traverse between the fully open to the fully closed position. The parameters are also affected to a lesser extent by the local changes in the leaflet and housing geometry.
Computational simulations can be used to examine local design changes to help minimize the fluid induced stresses that may play a key role in thrombus initiation with the implanted mechanical valves.
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