| An automatic electronic control system is developed for an implantable heart replacement powered by an electric motor. The device includes a reversing brushless DC motor which, through a low-friction mechanism, alternately ejects blood from right and left prosthetic ventricles. The control system is required to assure that the device provides blood flow in accord with demand as reflected in arterial pressure, that safe left atrial pressures are maintained, and that forces applied to tissues during reversals are minimized.;Through a velocity control method which operates in a manner similar to that thought to underlie central nervous system control of rapid, practiced movements, the device is made to follow a trajectory which minimizes the peak absolute value of acceleration for a given ejection time.;From the motor equation, an expression is derived which allows calculation of the instantaneous pressure generated in the left pump from velocity control data. An output balance control, using an estimate of left pump filling derived from the pressure data, varies right diastolic time and thus the filling of the right pump in order to maintain a safe left atrial pressure. It is shown that this control can be set to result in a cardiac output sensitivity to central venous pressure similar to that exhibited by the isolated natural heart.;Through a model of the pressure loss characteristics of the outlet valve and graft, an estimate of the aortic pressure is derived from the ventricular pressure estimate. A control which varies cardiac output in accord with changes in aortic pressure is then implemented.;Results are presented from testing of the device in calves. |
