STUDIES ON THE CORONARY CIRCULATION. VI. LOSS OF MYOCARDIAL CONTRACTILITY AFTER CORONARY ARTERY OCCLUSION

Abstract

Myocardial contractility was studied by means of slow motion color pictures in dogs after coronary occlusion. Following coronary artery ligation, the ischemic myocardium may become non-contractile in as little as 5 sec. after the ligation. In some expts., under certain circumstances following coronary occlusion, the ischemic region continues to contract. This conclusively proves that the coronary arteries physiologically are not end-arteries. The ballooning of the ischemic region may spontaneously appear and disappear. This also proves that the coronary arteries are not end-arteries. The ballooning may occur only later in systole, the ischemic region contracting early in the first phase of systole and bulging out in the last phase of systole. Full systolic ballooning and late systolic ballooning may occur simultaneously in different regions of the same heart. The non-contractile portion may be made to contract during and following electrically induced premature systoles. Electrical conductivity to and from the ischemic region does not appear to be impaired. An increase of the work of the heart as a result of a rise of blood pressure caused by constriction of the aorta may cause increased ballooning of ischemic myocardium. The clinical importance of this observation in so-called coronary insufficiency or failure is obvious. Possible clinical application of this study on non-contractility of the myocardium, which may be of diagnostic value, has been made in 2 patients with coronary artery disease.