Different clinical implications for ST depression and T wave inversion in non-Q wave myocardial infarction.

The differences between ST depression and T wave inversion in non-Q wave myocardial infarction were investigated in 42 patients with initial non-Q wave infarction, 22 patients with ST depression (ST group), and 20 patients with T wave inversion (T group). The extent of ischemic area estimated by electrocardiography and two-dimensional echocardiography, characteristic features of electrocardiographic changes, and clinical findings on admission and outcome were estimated. ST elevation preceded T wave inversion in the same leads in 80% (16/20) of the T group, and transient Q waves developed in 55% (11/20). However, neither ST elevation nor transient Q waves were observed in the ST group. Two or three ischemic segments were present in 86% (19/22) of the ST group patients, but only one ischemic segment was present in 60% (12/20) of T group patients, predominantly the anterior segment. The short-axis view of the two-dimensional echocardiogram on the level of papillary muscle showed decreased contraction in two or three of the anterior, lateral, and inferior segments of the left ventricle in 78% (14/18) of ST group patients. Only one segment with decreased contraction was present in 100% (17/17) of T group patients. Cardiac status on admission was lower in the ST than the T group: Killip class II-IV, 59% (13/22) vs 20% (4/20), p < 0.05; mortality rate after 1 month, 41% (9/22) vs 0% (0/20), p < 0.05. Coronary angiograms, left ventriculograms, and autopsy findings also showed extensive myocardial lesions in accordance with multivessel disease in the ST group, but localized myocardial lesion suggesting one-vessel territory in the T group. T wave inversion in non-Q wave myocardial infarction indicates a recovery phase in transient transmural ischemia and localized subendocardial infarction within the presumed one-vessel territory, while ST depression suggests the presence of extensive ischemia in the subendocardium of multivessel territory, and infarction within that region.