Design and control of the atrio-aortic left ventricular assist device based on O/sub 2/ consumption

A protocol for optimal timing of the left ventricular assist device (LVAD) is discussed. Timing is studied using a closed-loop analog model of the heart, vascular system, and the LVAD. The model is tested for basic representation of the physiological system. The LVAD is incorporated into the model to discover its interaction with cardiac preload and afterload. Heart workload is computed via the pressure-volume-area method. The normal and impaired heart are modeled; in each case the pump control variables are adjusted. A protocol for adjustment of the LVAD based on reduced heart oxygen consumption is proposed. It was found that the pump should begin ejection immediately after the close of the aortic valve and that the pump filling pressure should be set to a value which produces maximum filling of the pump. Although aortic pressure and flow could be improved at pump rates above the heart rate, oxygen utilization of the heart rates could only be minimized for synchronous pumping.