Relationship between myocardial metabolism and epicardial ST segment alterations during myocardial ischemia

Acute myocardical ischemia was produced by ligating the midlevel left anterior descending coronary artery for 17 min in anesthetized dogs. Epicardial electrocardiograms were recorded from 15 sites surrounding the area of left anterior descending coronary artery ligation with a smooth tip, rounded epicardial electrode. Sites of ST segment elevation and isoelectric sites within the grossly ischemic portion of the left ventricle were needle biopsied to obtain tissue samples of less than 6 mg wet weight to assess myocardial metabolism at these precise sites. Epicardial areas of ST segment elevation had marked lactate accumulation and high energy phosphate depletion. Isoelectric sites were areas of either no lactate accumulation or mild lactate accumulation and high energy phosphate concentrations that were greater than those found at site of ST segment elevation. Thus, the data obtained indicate that epicardial sites of ST segment elevation are locations of profound anaerobic metabolism and of both epicardial and endocardial ischemia.