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

A thin myocardial layer adjacent to the epicardium (epicardial rim) of ten survives after transmural myocardial infarction. Regional myocardi al blood flow (Q(m)) at this rim may be high enough to maintain myocar dial 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. M yocardium in the region supplied by the occluded artery was sliced int o sections similar to 0.5 mm thick from the epicardial surface to the endocardium, and the Q(m) in each section was determined. During occlu sion, the Q(m) of myocardium within 0.5 mm of the epicardial surface r emained at 74.8 +/- 8.8% of the preocclusion level. Maintenance of thi s high Q(m) during occlusion was abolished when an epicardial incision similar to 1 mm deep was made around the occluded area. These finding s suggest that Q(m) is maintained at a surprisingly high level at the epicardial rim after coronary occlusion through epicardial arterial co mmunications, which may be sufficient to maintain myocardial viability .