A simplified state-space model of biventricular assist device-cardiovascular system interaction

A simplified state-space model of biventricular assist device (BiVAD)-cardiovascular system (CVS) interaction is presented. The state-space equations includes a six-compartments CVS model incorporating the ventricles, the pulmonary and systemic circulations as well as the non-linear behavior of the valve flow, together with a left ventricular assist device (LVAD) and a right ventricular assist device (RVAD) component. The left and right pump speeds serve as the input variables for the state-space model. The model is simulated with three operational modes, i.e. (i) RVAD speed < LVAD speed, (ii) same LVAD and RVAD speeds and (iii) inclusion of a 6 mm restriction at the right outflow cannula. The effect of RVAD speed variation on the steady state hemodynamics is also studied with and without an outflow banding restriction. Our simulated results are validated with experimental data obtained from clinical, in vivo and in vitro studies provided in the literatures. We observed that despite its simplicity, the model is able to reproduce the observed trends in the reported studies, thus making it feasible for the development of robust yet practical control algorithms.