The right ventricular myocardium receives its blood supply from branches of the right coronary artery, For this reason, infarction of the right ventricle not infrequently accompanies an inferior wall infarction caused by occlusion of the proximal right coronary artery. Indeed, it is estimated that right ventricular infarction accompanies an inferior wall infarction in about 40% of cases However, right ventricular infarction is difficult to diagnose from the routine 12 lead ECG because lead V1 is the only lead recorded over the right ventricle. In order to increase the sensitivity of the ECG to right ventricular events, particularly right ventricular infarction, leads are placed on the right side of the chest. These most typically include leads labeled V3R and V4R. Lead V3R is placed to the right of the sternum in the lead V3 position and lead V4R is to the right of the sternum in the V4 position. ST segment elevation in these leads is quite sensitive and specific for a right ventricular infarction.