Flow induced platelet activation and damage in mechanical heart valves - numerical studies

Computational fluid dynamics (CFD) simulations were used to describe blood flow through mechanical heart valve. Flow calculation results were used to obtain platelet stress and damage accumulation. Numerical simulation of St. Jude medical (SJM) valve implanted in physiologic 3D geometry was conducted. Blood was modeled as non-Newtonian two-phase fluid. Unsteady Reynolds averaged Navier-Stokes (URANS) approach was used with Wilcox komega turbulent model. A new platelet damage model, incorporating damage history, was developed to estimate flow induced platelet activation. Comparison of the thrombogenic potential of two bileaflet MHV geometries was conducted using fluid-structure interaction (FSI) computation. The two geometries, ATS and SJM, are commercially available valves which differ in their hinge design. The thrombogenic potential of the two valves was based on computed wall shear stresses on the leaflets and cumulative shear stress on multiple particles released during forward and backward flow phases. The results of the FSI study indicate the SJM to have higher thrombogenic potential than ATS. Valve generated flow patters are conducive to platelet activation and provide conditions for activated platelets to interact. The new damage model was utilized to estimate the effects of repeated passages and platelet senescence in estimating the thrombogenic potential.