Depression of the S-T segment in epicardial electrocardiogram associated with experimental major coronary artery constriction

Abstract

Electrocardiograms in more than 15 leads were recorded from the left ventricular surface during graded constriction of the major coronary arteries or their branches in anesthetized dogs. With mild to moderate constriction of the left circumflex, the anterior descending artery or their distal branches, a horizontal or flat depression of the S-T segment was recorded from leads over the distribution area of each constricted artery. The depth of S-T depression was of greatest magnitude at the border and decreased as the center was approached. S-T elevation or decreasing magnitude of S-T depression began to develop following severe constriction. These results will provide an experimental basis for interpretation of electrocardiographic changes during angina pectoris. In contrast to the border of the ischemic area, where S-T depression was recorded with any degree of constriction, elevation after severe constriction was not infrequently the only S-T displacement at the center. It is suggested that the direction of S-T displacement following coronary artery constriction depends on the position of the electrode with respect to the ischemic area. The epicardial S-T depression observed in this study is thought to be a reciprocal effect of subendocardial injury, as has been generally accepted.