LVAD speed increase during exercise, which patients would benefit the most? A simulation study.

Abstract

Patients supported with an LVAD have impaired cardiovascular adaptations during exercise, resulting in reduced total cardiac output and exercise intolerance. The aim of this study is to report associations among these impaired cardiovascular parameters and exercise hemodynamics, and to identify in which conditions an LVAD speed increase can provide substantial benefits to exercise. A cardiorespiratory simulator was used to reproduce the average hemodynamics of LVAD patients at exercise. Then, a sensitivity study was conducted where cardiovascular parameters were changed individually ±20% of their baseline value at exercise (heartrate, left/right ventricular contractility, total peripheral resistance and valve pathologies). Simulations were performed at a baseline LVAD speed of 2700 rpm and repeated at 3500 rpm to evaluate the benefits of a higher LVAD support on hemodynamics. Total cardiac output (TCO) was mostly impaired by a poor left ventricular contractility or vasodilation at exercise (-0.6 L/min), followed by a poor chronotropic response (-0.3 L/min) and by a poor right ventricular contractility (-0.2 L/min). LVAD speed increase better unloads the left ventricle and improves total cardiac output in all the simulated conditions. The most substantial benefits from LVAD speed increase were observed in case of poor left ventricular contractility (TCO +1.6 l/min) and vascular dysfunction (TCO +1.4 l/min) followed by lower heartrate (TCO +1.3 l/min) and impaired right ventricular contractility (TCO +1.1 l/min). Despite the presence of the LVAD, exercise hemodynamic is strongly depending on the ability of the cardiovascular system to adapt to exercise. A poor left ventricular inotropic response and a poor vascular function can strongly impair cardiac output at exercise. In these conditions LVAD speed increase can be an effective strategy to augment total cardiac output and unload the left ventricle. These results evidence the need to design a physiological LVAD speed controller, tailored on specific patient s needs.