Computational Evaluation of Platelet Activation Induced by a Bioprosthetic Heart Valve

Abstract

It is known that bioprosthetic heart valves (BHVs) have better hemodynamics and lower thromboembolic events compared with their mechanical counterparts; however, patients implanted with BHVs still face the potential of such complications. The risk of a clinical thromboembolism is on average 0.7% per year in patients with tissue valves in sinus rhythm. In this study, we developed a computational fluid dynamic (CFD) model of a BHV implanted in an aortic root and investigated the BHV-induced platelet activation using a damage accumulation model previously applied to mechanical valves. The CFD model was validated against published experimental data, including the flow velocity profile across the valve and the transvalvular pressure drop, and close matches were obtained. Hemodynamic performance measures such as flow velocity, turbulent kinetic energy, and wall shear stress were explored. Lagrangian particle tracking was used to calculate the extent of platelet activation for central bulk flow and flow in the vicinity of the leaflets. A peak flow of 2.22 m/s was observed at 40 msec after peak systole in the vicinity of a fold at the base of the leaflets. With the platelet activation expressed as 0-100% of activation threshold levels, mean damage on one pass was 2.489 × 10(-7)% and maximum damage on one pass was 8.778 × 10(-4)%. Our results suggested that the potential for BHV-induced platelet activation was low and that the leaflet's fully open geometry might play a role in the extent of blood element damage.

Fluid Simulation of a Transcatheter Aortic Valve Deployment into a Patient-Specific Aortic Root

“…In a previous study, we observed a similar fold and high-velocity jet near the base of a bovine-pericardial bioprosthetic valve. 29 Our findings from Scenario 2 were consistent with those of Dwyer et al, who reported a 1.65 m/s peak flow through a normal TAV at systole, and reported a wide central flow region. 11 The change in jet velocity following TAV intervention resulted in peak wall shear stress on the ascending aorta being reduced from 105 Pa down to 38 Pa for Scenario 1 and to less than 1 Pa for Scenario 2.…”

Lagrangian Postprocessing of Computational Hemodynamics

“…(10) alternatively. This has been used in several computational studies to calculate AP [9, 1, 133]. It should be noted however that for incompressible flow, ${\sigma }_{\nu }=\sqrt{2}\mu {\mathbf{e}}_F$, and the two measures provide equivalent results.…”

“…It should be noted however that for incompressible flow, ${\sigma }_{\nu }=\sqrt{2}\mu {\mathbf{e}}_F$, and the two measures provide equivalent results. Some experimental studies have suggested that stress and exposure time should not be “weighted equally,” but AP is better expressed as a power law of stress and exposure time [53, 2, 55, 106], which has been applied in several computational studies [9, 1, 102, 153, 132, 133, 12, 93]. …”

“…Morbiducci et al [102] have shown that spanwise vorticity has a greater effect on platelet activation in MHVs than the streamwise vorticity. The levels of AP in bioprosthetic heart valves (BHV) have also been studied [133]. …”

Model Systems for Cardiovascular Regenerative Biology

“…For example, computational models have predicted the effect of bone marrow stem cell transplantation on fibrosis in the cardiomyopathy associated with Chagas disease (Galvao et al 2008) or platelet activation after implantation of a bioprosthetic heart valve (Sirois and Sun 2010). The McCulloch group has published diverse computational models to study cardiac behavior, ranging from a model of focal myofibril disarray to represent regional septal dysfunction as seen in hypertrophic cardiomyopathy (Usyk et al 2001), to the effect of biventricular pacing on left ventricular function (Kerckhoffs et al 2009) and the influence of myosin regulatory proteins on myosin kinetics (Sheikh et al 2012).…”