A computational fluid dynamics study of the impact of temporal synchronization of the pulsatility mode on platelet activation in left ventricular assist device patients

Left ventricular assist devices are centrifugal pumps implanted in patients with advanced heart failure. Despite design improvements that reduced in-pump thrombosis, the risk of stroke remains high. A speed-modulation was introduced to promote in-pump washout that ramps the pump up and down in rpm for a fraction of a second, every two seconds. However, this LVAD modulation is not synchronized with the cardiac cycle. We investigate the effect of LVAD pulsatility temporal synchronization with the ventricle contraction in promoting intraventricular washout. Four timings of the LVAD pulsatility are investigated, via computational fluid mechanics. Lagrangian particle tracking captures the effect of pulsatility on platelet shear stress history and residence time, which are hemodynamics quantities associated with platelet activation. A virtual angiogram is performed by injecting a passive scalar to understand washout from an Eulerian perspective. Both Lagrangian and Eulerian metrics indicate that synchronizing the speed ramp up with peak systole promotes optimum intraventricular washout. The comparison of the simulated flow fields to those in an in-silico particle image velocimetry experiment in a patient left ventricle phantom implanted with a HeartMate3 commercial LVAD, show very good agreement, validating the simulations and confirming this preliminary finding.