Patterns of ST-segment change during acute no-flow myocardial ischemia produced by balloon occlusion during angioplasty of the left anterior descending coronary artery

Abstract

An early manifestation of acute myocardial ischemia is the development of ST-segment and T-wave changes. Clinical decisions for treatment are based on ST-segment shifts on the surface electrocardiogram (ECG). ST-segment depression is believed to represent subendocardial involvement, with less extensive myocardial injury. ST-segment elevation reflects transmural involvement, with greater extent of myocardial injury. 1−3 ST-segment depression is generally induced by factors that increase myocardial demand, such as atrial pacing or exercise stress, whereas ST-segment elevation is induced by near total cessation of coronary blood flow. After acute total occlusion of the vessel, myocardial injury is believed to progress from the endocardium to the epicardial layers. Thus, we would expect to observe ST-segment depression progressing through an isoelectric point to ST-segment elevation. This may explain why some patients have no significant changes on the ECG when presenting with an acute myocardial infarction. To test this hypothesis in humans, we used balloon angioplasty of the coronary arteries as the model for acute noflow ischemia. Intracoronary electrograms were obtained from the center of the ischemic zone by attaching the proximal end of the balloon angioplasty guidewire to the V 1 lead on the surface ECG. Patterns of ST-segment responses on the intracoronary electrogram and surface leads II and V 5 were continuously recorded.