In vitro development of automatic control for the actively filled electrohydraulic heart

The in vitro development of automatic control of the actively filled, alternately pumped, volumetrically coupled, electrohydraulic total artificial heart was the goal of this investigation. Control features under study were (a) cardiac output (CO) response to preload; (b) CO relationship to mean aortic pressure (AoP); and (c) control of balanced ventricular outputs. A modified pulmonic valve to increase backflow was used as a balancing mechanism. Hydraulic fluid pressure transducers monitored diastolic pressures, and microprocessor control of motor speed maintained in a mild suction to yield filling rate dependent on atrial pressure. Results indicated a rise in CO from 5 to 9 L/min, with a change in mean right atrial pressure (RAP) from 0 to 7 mm Hg. No significant difference in CO was found as AoP was varied from 80 to 120 mm Hg with a maximum variation of +/- 0.5 L/min on CO and +/- 1 mm Hg on RAP. Balance was maintained for bronchial flows up to 50% with mean left atrial pressure never exceeding 15 mm Hg. An alternately pumped electrohydraulic heart was automatically controlled to respond sensitively to preload changes. Afterload changes did not alter the CO response curve. Automatically controlled, balanced ventricular outputs were maintained.