Prognostic significance of the admission electrocardiogram in acute myocardial infarction

Objectives. We sought to assess the ST segment and the terminal portion of the QRS complex in the initial electrocardiogram (ECG) as tools to predict outcome in patients with acute myocardial infarction given thrombolytic therapy. Background. Previous studies assessing early risk stratification of patients with acute myocardial infarction by ECG criteria have focused on the number of leads with ST segment elevation or the absolute magnitude of ST deviation. A new classification independent of the absolute values of ST deviation was pursued. Methods. Patients with ST elevation and positive T waves in at least two adjacent leads who received thrombolytic therapy were classified into two groups based on the absence (1,232 patients) or presence (1,371 patients) of distortion of the terminal portion of the QRS complex on the admission ECG. Results. There were no differences between groups in the prevalence of previous angina, hypertension, current smoking, anterior infarction, time from onset of symptoms to therapy or type of thrombolytic regimen. Patients with QRS distortion were less likely to have had a previous infarction (15.0% vs. 18.4%, p = 0.02) or diabetes mellitus (16.9% vs. 21.4%, p = 0.003). They had higher peak creatine kinase levels (1,617 ± 1,670 vs. 1,080 ± 1,343 IU, p = 0.00001). Hospital mortality for those with and without QRS distortion was 6.8% and 3.8%, respectively (p = 0.0008). Multivariable logistic regression analysis confirmed that hospital mortality was independently associated with distortion of the terminal portion of the QRS complex (odds ratio 1.78, 95% confidence interval 1.19 to 2.68, p = 0.004). Conclusions. Distortion of the terminal portion of the QRS complex on the admission ECG is independently associated with a higher hospital mortality rate in patients with acute myocardial infarction given thrombolytic therapy.