Electrocardiographic diagnosis of the responsible coronary artery in acute inferior myocardial infarction through right chest leads V3R-V8R. A prospective study.

In order to identify the electrocardiographic changes that occur in right-chest leads V3R-V8R for the most significant diagnosis of the responsible coronary artery of acute myocardial infarction, the authors performed a prospective study on 66 patients in whom coronary arteriography was done between the first and twelfth weeks after suffering the infarction. Electrocardiograms were done within the first six hours after the onset of symptoms. Lesions of the right coronary artery were found in 46 patients--27 at a proximal level and 19 at a distal one--and in 20 patients the circumflex coronary artery was injured. The electrocardiographic findings were studied in 2 groups of leads: V3R-V4R and V5R-V8R. An ST elevation equal to or higher than 0.5 mm and the presence of Q waves in V3R-V4R are specific markers of lesions of the right coronary artery (P < 0.001). Lowering of the ST segment in V3R-V4R is a specific marker of a circumflex artery lesion (P < 0.001). An ST elevation equal to or higher than 1 mm in V3R-V4R is specific for a proximal lesion of the right coronary artery (P < 0.001). No specific marker for a lesion of the distal right coronary artery was identified, its more significant characteristic being an "isoelectrical" ST segment (between 0 and 0.4 mm), an rS morphology and positive T waves in V3R-V4R.