Sequential changes in left ventricular compliance during acute coronary occlusion in the isovolumic working canine heart.

Abstract

The effect of cardiopulmonary bypass, transient acute coronary occlusion (2-5 min), prolonged coronary occlusion (> 60 min) and coronary reperfusion on the left ventricular diastolic pressure-volume curve was studied using an isovolumic working canine heart preparation in which heart rate, intraventricular volume and aortic pressure were controlled. Cardiopulmonary bypass caused no significant change in left ventricular compliance but was associated with a slight decrease in left ventricular contractility. Acute transient coronary occlusion caused no significant change in left ventricular compliance despite a marked decrease in left ventricular contractility. Prolonged coronary occlusion caused a significant progressive decrease in left ventricular compliance beginning 20-30 min after coronary occlusion which was associated with improved left ventricular contractility. Coronary reperfusion after prolonged coronary occlusion caused a further decrease in left ventricular compliance associated with an increase in left ventricular contractility. Although left ventricular compliance is not affected immediately by coronary occlusion, it can begin to decrease as early as 20-30 min after occlusion. The early decrease found in left ventricular compliance following coronary occlusion in comparison to previous studies suggests that the ratio of ischemic to nonischemic myocardium is a determinant factor of the effect of myocardial ischemia on left ventricular diastolic compliance. The effect of coronary reperfusion on left ventricular compliance is related to the duration of coronary occlusion and myocardial ischemia.