Electrocardiogram, Myocardial Oxygen and Contraction in Scar and Collaterally Supplied Muscle After Experimental Coronary Ligation

Abstract

Studies of myocardial electrocardiograms, oxygen, and cinematographic muscle contraction were carried out in dogs during coronary branch ligation and after 2 to 12 weeks' recovery. Scars were found in 12 of 13 animals. Five were transmural at some point and seven entirely subendocardial. Myocardial electrocardiographic abnormalities were found in every animal with a scar. Epicardial electrocardiographic abnormalities (localized Q waves or low R waves) were roughly conterminous with the surface projection of the entire extent of all transmural scars and of six out of seven subendocardial scars. Precordial leads were abnormal in only three animals, all with transmural scars. Responses to oxygen inhalation, hypoxia, and levarterenol for these animals were within the range of normal variation, but there was a tendency to develop ventricular fibrillation, unrelated to the amount of scar. Study of the acute ischemic dysfunction consequent to coronary ligation is not of great value for the interpretation of the situation at re-exploration two or more weeks later. The behavior of recovered collaterally supplied muscle, assessable by the techniques employed in these studies (provided that epicardial thickening has been avoided by minimizing exposure and trauma at the time of ligation), has relevance to many human coronary disease situations in which regional circulation is carried on by intramyocardial or small caliber vessels.