Flow induced platelet activation in prosthetic heart valves - In vitro and numerical studies

In vitro study was conducted to estimate the thrombogenic potential of various Prosthtic Heart Valve (PHV) designs. A new polymer (Quatromer) trileaflet design was tested for its thrombogenic potential and compared to that of existing prosthetic heart valves (PHVs) routinely implanted in patients: a St. Jude Medical bileaflet mechanical heart valve (MHV) and a St. Jude porcine bioprosthetic tissue valve. The valves were mounted in a left ventricular assist device (LVAD) and the procoagulant activity of the platelets was measured using a platelet activation state (PAS) assay. The PAS measurements indicated that the platelet activation level induced by the polymeric valve was very similar to that induced by the St. Jude Medical MHV and the St. Jude tissue valve. No significant difference was observed between the three valves, indicating that they have a comparable thrombogenic potential. Numerical simulations of turbulent, transient, non-Newtonian blood flow patterns generated by two types of MHVs (monoleaflet and bileaflet) were conducted using the Wilcox k-ω turbulence model and Large Eddy Simulations (LES). Platelet shear stress histories were calculated and averaged over a large number of platelet trajectories within the flow field, and compared with the in vitro PAS measurements. This confirmed the CFD platelet shear stress histories, which clearly indicated a higher level of stimulation of platelets for the bileaflet MHV