Numerical model of the circulatory system for heart assistance simulation: effect of a LVAD on energetic relationships inside the left ventricle

A modular numerical model is used to study the interaction, in terms of energetic relationships, between the cardiovascular system and a pneumatic left ventricle assist device (LVAD). The experiments are performed in two steps: in the first the left ventricle is characterized, with an open loop model of the circulatory system, computing External Work (EW), Pressure Volume Area (PVA) and Cardiac Mechanical Efficiency (CME) as a function of atrial pressure and peripheral resistance. PVA is compared to EW and CME surfaces respectively. In the second step the same variables are evaluated, with a closed loop model, assisting synchronously the left ventricle with the LVAD and changing two of its control parameters: Driving Pressure (DP) and Systole-Diastole (SD) ratio. The path of the working point is related to the value of the arterial elastance, modified by the LVAD, and only in few points the target to minimize PVA and EW and maximize CME is reached.