In Vitro Investigation of the Effect of the Timing of Left Ventricular Assist Device Speed Modulation on Intraventricular Flow Patterns

Thromboembolic events remain a common complication for left ventricular assist device (LVAD) patients. To prevent in-pump thrombosis, third-generation LVADs use speed modulation, which is not synchronized with the native left ventricle (LV) contractility. This study aims to investigate the effect of speed modulation on intraventricular flow patterns, and specifically, the impact of timing relative to pressure variations in the LV. Stereo-particle image velocimetry measurements were performed in a patient-derived LV implanted with an LVAD, for different timings of the speed modulation and speed. Speed modulation has a strong effect on instantaneous afterload and flowrate (-16% and +20%). The different timings of the speed modulation resulted in different flowrate waveforms, exhibiting different maxima (5.3-5.9 L/min, at constant average flowrate). Moreover, the timing of the speed modulation was found to strongly influence intraventricular flow patterns, specifically, stagnation areas within the LV. These experiments highlight, once more, the complex relationship between LVAD speed, hemodynamic resistance, and intraventricular pressure. Overall, this study demonstrates the importance of considering native LV contractility in future LVAD controls, to improve hemocompatibility and reduce the risk of thromboembolic complications.