Background Patients with on anterolateral acute myocardial infarction (AMI) have a worse prognosis, and those with additional inferolateral wall involvement might be higher risk because of more extensive area at risk, Lead -aVR obtained by inversion of images in lead aVR has been reported to provide useful information For inferolateral lesion. Methods we examined the relation between ST-segment deviation in lead aVR on admission electrocardiogram (ECG) and left ventricular function in 105 patients with an anterolateral AMI undergoing successful reperfusion less than or equal to6 hours after onset. Patients were classified according to ST-segment deviation in lead aVR on admission EGG: group A, 23 patients with ST elevation of greater than or equal to0.5 mm; group B, 47 patients without ST deviation; and group C, 35 patients with ST depression of greater than or equal to0.5 mm. Results. There were no differences among the 3 groups in age, sex, or site of the culprit lesion. In groups A, B, and C, the peak creatine kinase level was 3661 +/- 1428, 4440 +/- 1889, and 6959 +/- 2712 mU/mL, and the left ventricular election fraction (LVEF) measured by predischarge left ventriculography was 54% +/- 9%, 48% +/- 7%, and 37% +/- 9%, respectively (P < .01). During hospitalization, congestive heart failure occurred more frequently in group C than in groups A or B (P < .05). ST-segment depression in lead aVR had a higher predictive accuracy than other ECG findings in identifying patients with predischarge LVEF less than or equal to 35%. Conclusions we conclude that in patients with an anterolateral AMI, ST-segment depression in lead aVR on admission ECG is useful for predicting larger infarct and left ventricular dysfunction despite successful reperfusion.