Implications of ST-Segment Elevation in Leads V5 and V6 in Patients With Reperfused Inferior Wall Acute Myocardial Infarction

During inferior acute myocardial infarction, ST-segment elevation (ST↑) often occurs in leads V5 to V6, but its clinical implications remain unclear. We examined the admission electrocardiograms from 357 patients with a first inferior acute myocardial infarction who had Thrombolysis In Myocardial Infarction 3 flow of the right coronary artery or left circumflex artery within 6 hours after symptom onset. The patients were divided according to the presence (n = 76) or absence (n = 281) of ST↑ >2 mm in leads V5 and V6. Patients with ST↑ in leads V5 and V6 were subdivided into 2 groups according to the degree of ST↑ in leads III and V6: ST↑ in lead III greater than in V6 (n = 53) and ST↑ in lead III equal to or less than in V6 (n = 23). The perfusion territory of the culprit artery was assessed using the angiographic distribution score, and a mega-artery was defined as a score of ≥0.7. ST↑ in leads V5 and V6 with ST↑ in lead III greater than in V6 and ST↑ in leads V5 and V6 with ST↑ in lead III equal to or less than in V6 were associated with mega-artery occlusion and impaired myocardial reperfusion, as defined by myocardial blush grade 0 to 1. Right coronary artery occlusion was most common (96%) in the former, and left circumflex artery occlusion was most common (96%) in the latter, especially proximal left circumflex occlusion (74%). Multivariate analysis showed that ST↑ in leads V5 and V6 with ST↑ in lead III greater than that in V6 (odds ratio 4.81, p <0.001) and ST↑ in leads V5 and V6 with ST↑ in lead III equal or less than that in V6 (odds ratio 5.96, p <0.001) were independent predictors of impaired myocardial reperfusion. In conclusion, ST↑ in leads V5 and V6 suggests a greater risk area and impaired myocardial reperfusion in patients with inferior acute myocardial infarction. Furthermore, comparing the degree of ST↑ in lead V6 with that in lead III is useful for predicting the culprit artery.