A Computational Study of Aortic Insufficiency in Patients Supported with Left Ventricular Assist Devices

Abstract

Purpose Aortic insufficiency (AI) following left ventricular assist device (LVAD) implantation is common. Speed augmentation to overcome the regurgitant flow (RF) is used but this leads to progressive AI and may have deleterious effects on shear stress (SS) and the right ventricle (RV). Methods We employed a closed-loop mathematical model of the cardiovascular system to generate boundary conditions for blood flow simulations performed in a three-dimensional (3D) model of the aortic arch. AI was introduced and the impact of speed augmentation and blood pressure control on SS and RV oxygen consumption (MVO2) were determined in a model with a coupled and uncoupled RV. Results Addition of severe AI to the coupled RV at 5500 RPM led to a reduction in net flow from 5.4 L/min (no AI) to 2.1 L/min (severe). Increasing speed to 6400 RPM in the severe AI and coupled RV, led to a 42% increase in net flow and a 16% increase in RF with a nominal decrease of 0.9% in RV MVO2. Blood pressure control with the coupled RV with severe AI at 5500 RPM led to an 81% increase in net flow with a 15% reduction RF and an 8% reduction in RV MVO2 (Fig A). With an uncoupled RV, addition of severe AI at 5500 RPM led to a reduction in net flow from 5.0 L/min (no AI) to 1.8 L/min (severe). Increasing speed to 6400 RPM with severe AI and uncoupled RV increased net flow by 45%, RF by 15% and RV MVO2 by 4.2%. For the uncoupled RV with severe AI, blood pressure control alone led to a 22% increase in net flow, 4.2% reduction in RF and 6.1% reduction in RV MVO2; whereas combined BP control and pulmonary vasodilation led to a 113% increase in net flow, 20% reduction in RF and 41% reduction in RV MVO2 (Fig B). Compared to speed augmentation, blood pressure control consistently resulted in a reduction in SS (Fig C). Conclusion Speed augmentation to overcome AI in patients supported by CF-LVAD will augment flow but at the expense of RV MVO2, RF and SS. Aggressive blood pressure control and pulmonary vasodilation can improve net flow with more advantageous effects on the RV and aortic valve integrity.