Dynamic simulation of a left ventricular assist device under coupled working state with the natural heart.

The left ventricular assist device (LVAD) goes through a counterclockwise dynamic characteristic loop under heart-pump coupled working state. However, few studies have investigated the underlying physical mechanisms from the flow field perspective. Computational fluid dynamic (CFD) methods are used for unsteady flow field simulations and hemolytic possibility predictions in one cardiac cycle. The pressure boundary conditions are set based on the prior in vitro experiment. Flow blockage started at the inlet guide vanes (IGVs) and affected the downstream flow field at early systole, and occurred mainly at the outlet guide vanes (OGVs) during diastole. At a typical flow-rate, the residence time in IGVs accounted for 42.55% of all parts during systole whereas only 18.75% during diastole. The dynamic characteristic loop is closely related to the movement of vortices within the pump, as the low-speed vortices failing to respond in time to the changes in boundary conditions. An increased likelihood of adverse events is anticipated at early systole. This study reveals the physical mechanisms underlying the flow field changes within the pump during coupled working. The detailed hemolytic analysis at different cardiac events helps the subsequent real-time intelligent pump adjust strategies.