DETECTION OF TOTAL ASSIST AND SUCKING POINTS BASED ON THE PULSATILITYOF A CONTINUOUS-FLOW ARTIFICIAL-HEART - IN-VIVO EVALUATION

Our novel control strategy for a continuous flow artificial heart by d etecting the total assist and sucking points based on pump pulsatility was evaluated in acute animal experiments using beagle dogs and our m ixed flow pump. The pump was installed as a left ventricular (LV) bypa ss through a left thoracotomy. To change LV contractility, the left co ronary arteries were occluded for 30 min, followed by a 120 min reperf usion. To change LV end diastolic pressure (LVEDP), dextran solution w as rapidly infused. To estimate the pump pulsatility without any speci fic sensor, we calculated the index of current amplitude (ICA), which was obtained from the amplitude of the motor current waveform divided by the simultaneous mean value. To investigate the basic characteristi cs of the ICA, the pump speed was changed temporarily from 2,300 rpm t o 5,000 rpm. In 92% of all measurements, the ICA plotted against the p ump speed had a peak point (t-point) that corresponded highly with the turning point from partial to total assistance. The ICA also had a tr ough (s-point) that corresponded with the beginning of severe sucking in most cases. Only preload significantly influenced pump flow rate at the t-point from among preload (LVEDP), afterload (SAoP), and contrac tility (max LV dP/dt), by which we can simulate Starling's law of the natural heart. We concluded that a continuous flow artificial heart co uld be well controlled by detecting the t-point and s-point.