Prognostic significance of the initial electrocardiographic pattern in patients with inferior wall acute myocardial infarction

Abstract

The purpose of the study was to determine whether the initial electrocardiographic pattern is predictive of in-hospital mortality in inferior wall acute myocardial infarction. It is commonly perceived that patients with acute myocardial infarction presenting with greater ST elevation have a worse prognosis. The initial electrocardiogram of patients (n = 213) with inferior wall myocardial infarction was categorized based on the pattern of ST-segment elevation in inferior leads: (A) ST< 1 mm with tall T waves, (B) ST±1 mm with normal terminal QRS, and (C) ST±1 mm with distortion of terminal QRS. ST deviation from baseline was calculated for all leads. Patients with maximal precordial ST depression in V4-V6 and pattern A had an in hospital mortality rate of 68.8% compared with 16.9% for the entire study group. By univariate analysis, only pattern A was significantly predictive of in-hospital mortality [odds ratio = 2.91,95% confidence interval (CI) 1.226.93], but by multivariate analysis adjusted for (1) age, (2) diabetes mellitus, (3) previous myocardial infarction, (4) thrombolytic therapy, (5) precordial ST-depression pattern, and (6) patterns of ST elevation, maximal ST depression in V4-V6 was significantly predictive (odds ratio = 4.93, 95% CI 1.79-13.56), whereas pattern A was not (odds ratio = 1.12, 95% CI 0.36-3.52). Contrary to popular perception, patients with inferior wall myocardial infarction presenting with minimal ST-segment elevation are at highest risk for in-hospital mortality, especially if accompanied by maximal precordial ST depression in V4-V6.