Recovery of myocardial function during coronary artery bypass grafting. Intraoperative assessment by pressure-volume loops.

Radionuclide angiocardiography and left ventricular manometry were performed simultaneously in 12 men undergoing elective coronary artery bypass grafting. Pressure-volume loops constructed from these data allow calculation of stroke work and provide a more complete description of global left ventricular function immediately before cardiopulmonary bypass and at a mean of 18 and 34 minutes after termination of ischemic arrest. Early reperfusion was characterized by significant elevation of end-diastolic pressure (p less than 0.01) without a corresponding increase in end-diastolic volume. With continued reperfusion, end-diastolic volume, calculated stroke work, and cardiac output increased significantly with respect to control (p less than 0.05). Heart rate, ejection fraction, mean arterial pressure, stroke work/end-diastolic volume, and maximal dP/dt remained unchanged during the study period. No new focal abnormalities were detected in regional wall motion. These data indicate that minimal residual impairment of diastolic function exists during the acute recovery from cardioplegic arrest and bypass grafting but improves with further reperfusion. Systolic function appears to normalize more rapidly than diastolic function after ischemic arrest.