New electrocardiographic criteria for predicting the site of coronary artery occlusion in inferior wall acute myocardial infarction

In patients with inferior wall acute myocardial infarction (AMI), the site of the culprit lesion is an important determinant of outcome. Patients with right ventricular infarction have a poor prognosis, whereas those with occlusion of the left circumflex coronary artery (LCx) have a good prognosis. Therefore, we assessed whether standard 12-lead electrocardiograms obtained on admission could identify the site of coronary artery occlusion, (i.e., a site proximal to the origin of the right ventricular branch of the right coronary artery [RCA], a site distal to the origin of the right ventricular branch of the RCA, or a site in the LCx). The ratio of ST depression in lead V3 to ST elevation in lead III (V3/III ratio) was evaluated immediately before coronary angiography in 152 patients with a first inferior wall AMI confirmed by coronary angiography within 12 hours after the onset of symptoms. For occlusion of the proximal RCA, distal RCA, and LCx, V3/III ratio was 0.2 ± 0.3, 0.8 ± 0.5, and 2.5 ± 2.5 (p = 0.0001), respectively. The V3/III ratio <0.5 identified proximal RCA occlusion, 0.5 <V3/III ratio ≤1.2 identified distal RCA occlusion, and 1.2 <V3/III ratio identified LCx occlusion with sensitivities of 91%, 84%, and 84%, and specificities of 91%, 93%, and 95%, respectively. We conclude that the V3/III ratio is useful in predicting the site of coronary artery occlusion in patients with inferior wall AMI.