A Method to Increase the Pulsatility in Hemodynamic Variables in an LVAD Supported Human Circulation System

Left Ventricular Assist Devices (LVADs) generally operate at a constant speed in the human body. This causes a decrease in the pulsatility of hemodynamic variables. To increase the pulsatility a stepwise change was applied to the LVAD operating speed over a cardiac cycle. To do this, a numerical cardiovascular system model and a pump model were used. The model was developed by considering the static characteristics of the MicroMed DeBakey LVAD. First, the simulations were performed at constant operating speeds, 8500 rpm, 9500 rpm and 10500 rpm. Pulsatility indexes were calculated for left ventricular (LV) pressure, aortic pressure, LV volume and LVAD flow. Cardiac output (CO) was calculated at constant operating speed and these values used for comparing the pulsatility indexes with stepwise and constant operating speeds. The LVAD was operated at two different constant speeds in the stepwise operating speed simulations. Low and high operating speeds were adjusted so as to obtain the same cardiac output values with the constant operating speed simulations. The operating speeds in the simulations were 7800-11250 rpm, 9300-11250 rpm and 10300-11250 rpm. The same cardiac output values were obtained with an increase in the pulsatility of the hemodynamic variables without significant changes in their shapes except the LVAD flow. The obtained results show that it is possible to obtain more physiological results by applying a stepwise change to LVAD operating speed over a cardiac cycle.