Development of a Passive Control System for Ventricular Assist Devices

Abstract

Cardiovascular diseases are a leading cause of death throughout the developed world. With the demand for donor hearts far exceeding the supply, a bridge-to-transplant or permanent solution is required. This can be achieved with rotary ventricular assist devices (VADs). Rotary VADs show a weaker response to preload than the native heart. This may lead to ventricular suction or pulmonary congestion, which can be deleterious to the patient’s recovery. A physiological control system which optimizes responsiveness of VADs may reduce adverse events. Active physiological control systems rely either on pressure and flow measurements or on estimated data. However these controllers may be limited by the low reliability of long term blood pressure and flow sensors or potential of inaccurate estimators due to changes in the VAD circuit (e.g. thrombus formation resulting in false estimation). A passive physiological control system might be able to overcome the limitation of active physiological control systems. This research project had three key aims: • Investigation of the steady state and time response of the healthy heart and circulatory system to changes in patient state (e.g. active postural changes and exercise). • In-vitro development and in-vivo validation of novel compliant inflow cannulae for rotary LVADs and RVADs to improve preload sensitivity of RBPs and provide a passive physiological control system for ventricular suction prevention. • Rigorous in-vitro evaluation of the compliant inflow cannulae together with various active physiological control systems previously presented in the literature under identical conditions.