Abstract
In isolated, Langendorff perfused hearts, 60 direct-current extracellular electrograms were simultaneously recorded from the left ventricular epicardium. In each experiment, the left circumflex branch and the left anterior descending coronary artery were successively occluded for 15 minutes, each occlusion separated by a long reperfusion period. During the occlusion, perfusion pressure to the nonoccluded arteries was changed from a high to a low value and vice versa, and the position of the electrophysiologic border (the zone where T-Q segment potentials became negative) was determined. In some experiments tissue biopsy samples were taken from recording sites and analyzed for lactate and creatine phosphate. In all experiments the metabolic border correlated well with the electrophysiologic border. In other experiments, the coronary arteries were injected with barium sulfate; epicardial collateral channels were found in dog hearts, but not in pig hearts. In seven of eight dog hearts, the border could be shifted by changing perfusion pressure; in seven of eight pig hearts, it remained constant. Thus, depending on the presence of collateral channels, changes in perfusion pressure could enlarge or reduce the area showing ischemic changes. Despite species differences, not all hearts within one species behaved the same: One pig heart behaved as a dog heart, one dog heart as a pig heart.
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