PHYSIOLOGICAL CONTROL OF A TOTAL ARTIFICIAL-HEART - CONDUCTANCE-BASEDAND ARTERIAL PRESSURE-BASED CONTROL

To obtain a physiological response by a total artificial heart (TAH), while eliminating the hemodynamic abnormalities commonly observed with its use, we proposed the use of a conductance-and arterial pressure-b ased method (1/R control) to determine TAH cardiac output. In this stu dy, we endeavored to make use of a variable more closely tied to centr al nervous system (CNS) efferents, systemic conductance, to provide th e CNS with more direct control over the output of the TAH. The control equation that calculates the target cardiac output of the TAH was con structed on the basis of measurement of blood pressures and TAH flow T he YR control method was tested in TAH-recipient goats with an automat ic method by using a microcomputer. In 1/R control animals. the typica l TAH pathologies, such as mild arterial hypertension and substantial systemic venous hypertension, did not occur. Cardiac output varied acc ording to daily activity level and exercise in a manner similar to tha t observed in natural heart goats. These results indicate that we have determined a control method for the TAH that avoids hemodynamic abnor malities exhibited by other TAH control systems and that exhibits phys iological responses to exercise and daily activities under the conditi ons tested. The stability of the control and the complete lack of inap propriate excursions in cardiac output is suggestive of CNS involvemen t in stabilizing the system.