Prognostic significance of electrocardiographic site of infarction after correction for enzymatic size of infarction.

To assess whether the site of myocardial infarction is an independent prognostic indicator, the outcome of patients with anterior myocardial infarction was compared with that of patients with inferior infarction. A consecutive series of patients who had suffered their first myocardial infarction was analyzed (398 with anterior and 391 with inferior infarction). Patients with anterior myocardial infarction had a higher 1 year mortality than those with inferior infarction (18.3% vs 10.5%, p = .002). When patients were matched for infarct size determined by peak creatine kinase (CK) level expressed as a multiple of the upper limit of normal, those with anterior myocardial infarction tended to have a higher 1 year mortality than those with inferior infarction for all subgroups of peak CK. Early mortality (day 1 to 28 after myocardial infarction) was greater in the anterior than in the inferior myocardial infarction group (10% vs 6.4%, p = .03); this was most significant when peak CK was greater than four times normal (12.4% vs 7.0%, p = .04). Late mortality was also higher in the anterior (8.4% vs 4.1%, p = .04) than the inferior infarction group and this was most significant when peak CK was less than two times normal (15.2% vs 0%, p = .02) or greater than eight times normal (10.6% vs 4.1%, p = .04). Multivariate analysis with proportional-hazards regression confirmed the prognostic significance of location of infarction independent of peak CK level. Thus, infarct location was found to be a predictor of prognosis that is independent of infarct size based on peak CK levels.