Effects of Acute Regional Myocardial Ischemia on Left Ventricular Function in Dogs

Abstract

The immediate functional deficit resulting from acute regional myocardial ischemia was evaluated in 40 anesthetized dogs. Ventricular function curves, maximum dp/dt, isovolumetric force-velocity curves, and peak systolic and resting diastolic length-tension curves were assessed at fixed heart rate and constant aortic pressure before and during occlusion of the anterior descending coronary artery 2 to 3 cm distal to its origin. Mild, moderate, or marked depression of the ventricular function resulted from occlusion of the anterior descending artery, depending upon the anatomy of the intercoronary collateral vessels. Maximum loss of function was apparent 2 minutes after occlusion, and was quantitatively reproducible by reocclusion after an intervening period of unobstructed flow. Resting diastolic length-tension relations were not significantly altered by occlusion of the anterior descending artery. In 12 dogs, force-velocity relations were determined during the inscription of ventricular function curves and in every instance when depressed function was evident from the ventricular function curve, the simultaneously determined force-velocity curve also demonstrated impaired performance. At low preload levels, however, the force-velocity curves inscribed before and during occlusion of the anterior descending artery were not very dissimilar; with increasing ventricular volumes, the force-velocity curve inscribed during coronary artery occlusion progressively shifted downward and to the left of the control curve. Maximum velocity, however, appeared to be unchanged suggesting that this index of contractility is not a satisfactory method for assessing cardiac performance during acute regional myocardial ischemia.