Congenital anomalies involving coronary artery origin are rare, with an incidence of 0.24%–1.3%. We present a case of inferior wall ST-elevation myocardial infarction in which an emergency coronary angiogram showed occlusion of the right coronary artery. However, we were unable to cannulate the left main coronary artery during the event. Interpretation of the infarct-related artery was complicated by the right arm-left arm lead reversal in electrocardiogram, adding to the dilemma in localizing the culprit vessel, namely right versus left circumflex coronary artery-related myocardial infarction. A computed tomography coronary angiogram subsequently showed the left main coronary artery having abnormal origin from the right sinus of Valsalva with inter-arterial course and no lesions in the left circumflex.