Experimental studies on the effect of temporary occlusion of coronary arteries: II. The production of myocardial infarction

Abstract

1. 1. Experiments were performed on thirty-nine dogs to learn whether temporary occlusion of a coronary artery would produce myocardial infarction and persistent electrocardiographic changes characteristic of myocardial ischemia. 2. 2. In twelve of eighteen animals which were allowed to survive four or more days, electrocardiographic changes typical of myocardial ischemia, and of a character not observed in control experiments, were found during the first few days to weeks after occlusion of a coronary artery for five to forty-five minutes. The type, anterior or posterior, of these electrocardiographic changes varied according to whether the anterior descending or left circumflex artery was temporarily occluded. 3. 3. Eight animals died of ventricular fibrillation during the first five minutes of occlusion of the artery, or on re-establishment of the circulation after occlusions lasting fifteen to thirty minutes. 4. 4. No gross evidences of myocardial infarction were found in the seven animals which lived for four to forty days after occlusion of a coronary artery had been maintained for five to twenty minutes. 5. 5. There were gross evidences, proved subsequently by microscopic examination, of infarction in eight of eleven experiments in which occlusion of a coronary artery was maintained for twenty-five to forty-five minutes. 6. 6. In the hearts which showed infarction, the extent of the infarct was roughly in direct proportion to the duration of the arterial occlusion; the infarcted area in several of the hearts in which an artery had been occluded for forty to forty-five minutes was as large as that which occurs after permanent and complete occlusion of the artery. 7. 7. These observations afford evidence that temporary ischemia may cause irreversible myocardial changes, and, if the ischemia be of sufficient duration, may cause myocardial infarction of the same character and degree as that which occurs after permanent and complete occlusion of an artery. 8. 8. The electrocardiographic and myocardial observations on certain patients with coronary artery disease are discussed with reference to the information gained in this study.