Isolated right ventricular infarction (RVI) is an increasingly recognized cause of precordial ST-segment elevation (STE). A patient is described who developed STE in leads V1-V5 secondary to occlusion of the right ventricular branch during stent angioplasty to the right coronary artery. The pattern of precordial STE was thought to be suggestive of anteroseptal myocardial infarction because of progressive STE toward lead V3. Repeat angiography disclosed a patent left anterior descending artery. Subsequent scrutiny of the electrocardiogram (ECG) revealed that leads V2 and V3 were switched and ECG interpretation considering this technical error revealed STE in V2>V3, which favored RVI. Furthermore, the mean spatial ST vector was approximately +120° in the frontal plane producing ST-segment depression in lead I which argued against anteroseptal myocardial infarction and indicated right ventricular epicardial injury. This report highlights that analysis of the ECG using vector concepts is a useful adjunct to pattern recognition for the diagnosis of RVI.