CARD26: Effects of the Artificial Pulse of the HeartMate 3 on Left Ventricular Flow Patterns

Abstract

Purpose of study: In order to reduce the risk of thrombotic events in left ventricular assist device patients, the HeartMate 3 is equipped with an artificial pulse (AP) setting. However, experimental results concerning the AP’s impact on left ventricular (LV) flow patterns and timing within the cardiac contraction are limited. This study aims to analyze LV flow patterns occurring during and after the AP, which is synchronized to the simulated cardiac function inside the mock loop setup. Methods: The in vitro measurements were triggered using a system capable of detecting AP timing and were performed for selected timings within the cardiac cycle. A pulsatile cardiovascular mock loop was developed with a simplified LV model and the flow patterns were imaged via Particle Image Velocimetry. The measurements were performed with stroke volumes of 0ml, 38ml, 49ml, and 57ml, with pump speeds configured to achieve 80mmHg mean aortic pressure and a total cardiac output of 5l/min for all settings. Parameters such as kinetic energy (KE) were computed in specific regions of interest, especially in the LV apex, as they indicate LV washout. Results: The overall influence of the AP on the intraventricular flow appears small (2.5% increase in KEmean for entire flow field), however short durations of large KE increases were observed in the LV apex with the AP turned on (KE mean: +4%; KEpeak: +24%), showing a dependence on the timing of the AP (KEpeak increased by up to 39% for specific timings). This increase can be observed when a counter-clockwise vortex ring of the mitral jet travelled further towards the apex, which was seen for specific timings of the AP. Vortices arising next to the valves could also improve washout there. Conclusion: While the AP produced only minor effects in the overall flow fields, synchronization of the AP with the cardiac cycle could potentially lead to increased LV washout, thus leading to better clinical outcomes.