Clinical use of posterior electrocardiographic leads: a prospective electrocardiographic analysis during coronary occlusion.

Posterior electrocardiographic leads have been described for quite a while; however, their use in diagnosing acute posterior wall myocardial infarction and identifying infarct-related arteries has not been well used. We prospectively studied electrocardiographic changes during balloon occlusion of single-vessel right coronary artery (RCA) and circumflex coronary arteries (LCX). Thirty four inflations were performed in RCAs and 38 in LCXS. Analysis of the patients with ECG changes revealed that the most common ECG change during RCA occlusion was inferior ST-segment elevation in leads II, III, and aVF (95 percent), and the most common change during LCX occlusion was posterior ST elevation in leads V7, V8, and V9 (68 percent). ST elevation was always seen in inferior leads in the RCA group and in posterior leads in the LCX group. Thus posterior leads helped identify RCA versus LCX as the infarct-related artery. ST elevation was also noted by posterior leads in seven (36.8 percent) additional patients. Thus there was a definite added benefit of posterior leads during LCX occlusion. In the appropriate clinical setting, posterior leads may help in differentiating LCX occlusion from RCA occlusion.