Aortic Valve Dynamics and Blood Flow Control in Continuous Flow Left Ventricular Assist Devices

摘要

The dynamics of the aortic valve plays a critical role in the understanding of heart failure and its treatment using the continuous flow left ventricular assist device (LVAD). Maintaining proper and active dynamics of the aortic valve is important when the LVAD is used as a bridge-to-recovery treatment. This treatment requires that the LVAD pump control must be adjusted so that a proper balance between the volume of blood contributed through the aortic valve and that contributed though the pump must be maintained. That is, the pump control must be adjusted so that the pump does not take over the entire pumping function in the circulatory system but instead must share with the left ventricle in ejecting the total amount of blood needed by the circulatory system. In this paper, we derive an expression that determines the fraction of total blood volume ejected in a cardiac cycle that goes through the pump in order to have adequate sharing between the pump and left ventricle to yield proper aortic valve dynamics. We show that this fraction depends on several factors which include the degree of heart failure and the level of activity of the patient. The aortic valve dynamics is tested in computer simulation over a wide range of physiological conditions of LVAD patients. Simulation results demonstrate that there exists a small range of pump power that produces adequate sharing of blood volume ejected between pump and aortic valve. This method may provide a reliable platform that can be effectively used in the pump control for bridge to recovery LVAD patients.