Background: Comprehensive information about the independent value of different electrocardiographic (ECG) variables in predicting major adverse cardiac events (MACE) after acute myocardial infarction (AMI) in the era of modern therapy is limited. The purpose of this study was to examine the prognostic significance of different ECG parameters in predicting MACE after AMI. Methods: Between January 2006 and January 2008, 529 patients (355 males; mean age = 67.5 짹 11.5 year-old) with AMI underwent standard electrocardiogram from 5 to 7 days after AMI. Several time intervals and PQRST abnormalities were analyzed from the electrocardiogram. The 1-year MACEs were defined as death, non-fatal MI, revascularization including repeat percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). Mean follow-up duration was 360.0짹119.3 days. Results: Of these patients, 497 (94.0%) patients provided complete follow-up data. The rate of 1-year MACEs was 16.3% (n=86) including 39 (7.4%) cardiac deaths, 7 (1.3%) noncardiac deaths, 18 (3.4%) non-fatal MIs, 16 (3.0%) repeat PCIs, and 6 (1.1%) CABGs. In univariate analysis, heart rate, corrected QT interval, left ventricular hypertrophy (S in lead V2 + R in lead V5 = 35mm or more), pathologic Q waves in lead V1-4 or lead V5-6, ST-segment elevation in lead V1-4 or lead V 5-6, I, and aVL, ST-segment depression in lead V5-6 or I, aVL, T wave inversion in V1-4, V5-6, and I, aVL had a significant association with MACEs. In the Cox regression hazard model, lateral ST-segment depression (hazard ratio [HR] 2.260, 95% confidence interval [CI] 1.204 to 4.241, p=0.011) and corrected QT interval (HR 1.007, 95% CI 1.002 to 1.011, p=0.004) were independent predictors of 1-year MACEs among ECG variables. After adjustment for all risk variables, lateral ST-segment depression (HR 3.024, 95% CI 1.037 to 8.817, p=0.043) in addition to PCI and serum creatinine levels were the only ECG variable that independently predicted 1-year MACEs. In multivariate logistic regression analysis, non-ST segment elevation MI, higher Killip class, and prior coronary heart disease had a significant independent association with lateral ST-segment depression. Conclusions: Lateral ST depression on the electrocardiogram is an independent predictor of 1-year MACEs after AMI. It may be that the ST segment in lateral leads is more sensitive than the ST segment in other leads, not only to ischemia and myocardial changes, but also to the other above-mentioned risk factors.