The localization of coronary artery stenoses by 12 lead ECG response to graded exercise test: support for intercoronary steal.

In 39 consecutive patients with unequivocally positive postexercise ECG we have correlated the location and severity of the coronary artery stenoses with the ECG leads in which ischemic ST changes occured. Patients with major stenoses of the right coronary artery, with or without disease of the left coronary system, showed ischemic ST changes in Leads II, III, and aVF. Patients with major stenoses of the left coronary system, many of whom had suffered old inferior wall infarction, showed ST changes in Leads I, aVL, and the chest leads. A group of 11 patients showed ischemic ST changes in leads other than those expected on the basis of the location and severity of coronary artery stenoses. In each of these 11 patients large collateral channels were donated by the vessel in whose territory the ischemic changes occurred. This finding lends support to the concept of intercoronary "steal" during exercise in coronary artery disease, at the same time reducing the value of the postexercise 12 lead ECG in predicting the location and severity of coronary artery stenoses.