Energy considerations in mechanical in-series cardiac assistance

Cardiac oxygen supply and consumption were used to evaluate the effectiveness of intraaortic balloon pumping. These variables were also used to compare the relative contributions of ventricular unloading and of coronary perfusion augmentation to the total energy balance of the heart. A detailed computer simulation of the cariovascular system and the assist device predicted that, in response to changes in balloon timing, increases in the potential oxygen availability is more significant than the reduction in oxygen consumption. End diastolic pressure, which is presently used as an index of unloading, was minimized by a deflation time which did not correspond to the time for minimal oxygen consumption. Data obtained from dog experiments indicated similar trends. Indirect, clinically available, hemodynamic variables related to oxygen consumption and supply are being used to formulate a performance index reflecting energy balance.<>