PRESERVATION OF HIGH REGIONAL BLOOD-FLOW AT EPICARDIAL RIM AFTER CORONARY-OCCLUSION IN DOGS

A thin myocardial layer adjacent to the epicardium (epicardial rim) often survives after transmural myocardial infarction. Regional myocardial blood flow (Q(m)) at this rim may be high enough to maintain myocardial viability during coronary occlusion. To test this hypothesis, we measured Q(m) in 12 anesthetized dogs during left anterior descending coronary artery occlusion using nonradioactive colored microspheres. Myocardium in the region supplied by the occluded artery was sliced into sections similar to 0.5 mm thick from the epicardial surface to the endocardium, and the Q(m) in each section was determined. During occlusion, the Q(m) of myocardium within 0.5 mm of the epicardial surface remained at 74.8 +/- 8.8% of the preocclusion level. Maintenance of this high Q(m) during occlusion was abolished when an epicardial incision similar to 1 mm deep was made around the occluded area. These findings suggest that Q(m) is maintained at a surprisingly high level at the epicardial rim after coronary occlusion through epicardial arterial communications, which may be sufficient to maintain myocardial viability.