Prognostic differences in subgroups of patients with electrographic evidence of subendocardial or transmural myocardial infarction: The favorable outlook for patients with an initially normal QRS complex

To compare the prognostic significance of electrocardiographic descriptors of infarction, the hospital and follow-up course of 635 patients with acute myocardial infarction was evaluated. Patients were divided into two groups based on the initial electrocardiogram following the onset of symptoms: group I, a normal QRS complex; and group II, an abnormal QRS complex secondary to Q waves, bundle branch block or ventricular hypertrophy. Patients were further subdivided on the basis of serial electrocardiograms: A, no new Q waves; and B, the development of new Q waves. Patients in group IA had a lower incidence of atrial and ventricular arrhythmias, atrioventricular block and heart failure than patients in group IIA. There were no hospital deaths in group IA, compared with a 13 percent mortality in group IIA. The hospital mortality was significantly less for patients in group IB than in group IIB (8 percent versus 20 percent, p < 0.001). The mean duration of follow-up was 30 months. There was a significantly lower follow-up mortality in group IA (12 percent) than in group IIA (45 percent), p < 0.001), and in group IB (12 percent) than in group IIB (34 percent, p < 0.001). These data suggest that patients with either “subendocardial” or “transmural” infarctions can be subdivided into low and high risk categories regarding both hospital and long-term prognosis. Patients with a normal QRS complex initially have the greatest likelihood of a benign prognosis following an acute myocardial infarction.