The grades of ischemia on the presenting electrocardiogram of patients with ST elevation acute myocardial infarction.

Patients with acute myocardial infarction who have terminal QRS distortion in addition to ST-segment elevation (grade III ischemia) on their presenting electrocardiogram have higher mortality and larger final infarct size than patients with ST-segment elevation without changes in the terminal portion of the QRS complex (grade II ischemia). This article discusses the data concerning the prognostic significance of the grades of ischemia on the presenting electrocardiogram and the possible underlying mechanism of terminal QRS distortion. Patients with grade III ischemia have more severe ischemia and faster progression of necrosis than patients with grade II ischemia. This might be related to less protection by "ischemic preconditioning" or presence of collateral circulation.