The electrocardiogram may provide valuable information regarding the identity of the culprit coronary artery and the location of obstructing lesion within the artery, which may be of guidance in selecting the therapeutic modality. Previous studies have concluded that changes in lateral leads (I, aVL, V5, V6) are predictive of left circumflex coronary artery obstruction in inferior wall acute myocardial infarction. Elect-rocardiographic criteria for determining the location of the obstructing lesion, however, have not been well established. The purpose of this study is to investigate the patterns of ST segment depression in lateral leads in inferior wall acute myocardial infarction and the obstruction site of culprit artery according to ST segment depression in lateral leads.

We examined 78 patients with inferior wall acute myocardial infarction analizing their electrocardiogram and coronary angiography which performed during acute hospitalization.

Of the fifty-five patients in which the culprit artery could be determined, 1)in 41 the culprit artery was the right coronary artery (19 proximal to the right ventricular branch and 22 distal), and in 14 the left circumflex coronary artery (7 proximal to the first obtuse marginal branch or involving a high first obtuse marginal branch, and 7 with distal obstruction). 2)Significant ST depression (ST≤1 mm) in leads I and aVL was more common in right coronary artery obstruction (p<0.05 and p=0.01 respectively) than left circumflex artery. 3)It was difficult to define the location of obstruction with ST segment change of lateral precordial leads (V5, V6).

In acute inferior wall myocardial infarction, ST segment depression in lateral limb leads (I, aVL) can be indicative of the right coronary artery obstruction and the ST segment depression pattern in lateral precordial leads was not indicative of the site of obstruction.