ST elevations in leads V1 to V5 may be caused by right coronary artery occlusion and acute right ventricular infarction.

In 5 of 69 patients (7%) undergoing intracoronary or intravenous streptokinase treatment, the ST-segment elevations in leads V1 to V5 were caused by occlusion of the right rather than the left anterior descending coronary artery and by myocardial infarction (MI) of the right ventricular (RV) wall rather than the anterior left ventricular (LV) wall or the ventricular septum. RV involvement was documented by technetium pyrophosphate uptake, hypokinesia, dilatation and depressed RV ejection fraction. The left anterior descending artery was patent and the anterior LV wall had normal thallium-201 uptake, no technetium uptake and normal wall motion. ST-segment elevation was highest in lead V1 or V2 and decreased toward lead V5; in patients with anterior LV MI, the ST-segment elevations are usually lowest in lead V1 and increase toward the V5 lead. In contrast to anterior LV infarcts, the R waves in leads V1 to V5 did not decrease and Q waves did not evolve with progression of the MI. The ST-segment elevations in leads V1 to V5 in our patients were associated with small or absent ST-segment elevations in leads, II, III and aVF, suggesting that in other cases of RV infarction, the appearance of ST-segment elevations in leads V1 to V5 is blocked by the dominant electrical forces of the LV inferior MI. This suggestion was confirmed in a canine model. Recognition of the presence of RV infarction may be therapeutically important.