Relation between the electrocardiographic stress test and degree and location of myocardial ischemia

Factors that influence frequency and location of stress-induced electrocard iographic (ECG) ST depression and the development of chest pain are incompl etely understood. We studied 331 patients with ischemic myocardial nuclear defects in response to routine clinical tread-mill testing with simultaneou s ECG recording. Nuclear defects were analyzed for location and extent of m yocardium involved, Exercise-induced ischemic ST changes were demonstrated in 59% of patients (196 of 331), Subjects with stress-induced ECG changes a nd/or chest pain had more extensive nuclear perfusion defects, Diabetic pat ients were significantly less likely to experience chest pain (24%) versus nondiabetics (41%) during (p = 0.04). Larger perfusion defects were associa ted with greater magnitude, lead distribution, and incidence of ECG changes , The number of ECG lead zones (anterior, lateral, and inferior) responding positively were related to both magnitude of ST depression and severity of ischemia, but not to location of ischemic defects. Regardless of location of ischemia, ST depression occurred with similar frequency, Thus, exercise- induced ECG ST depression remains a valuable indicator of the severity of m yocardial ischemia, Greater ST depression involving multiple leads usually signified extensive myocardial ischemia, but provided no information regard ing its location. Anginal-type chest pain induced by exercise testing also denoted more extensive ischemia. (C) 1999 by Excerpta Medico, Inc.