ST-segment elevation (ST ↑) ≥1.0 mm in lead V4R is considered a reliable marker of right ventricular involvement (RVI) in inferior acute myocardial infarction (IMI). However, the impact of posterior involvement (PI) on the relation between RVI and ST ↑ in lead V4R is unknown. We studied 267 patients with a first IMI who had total occlusion and TIMI 3 flow of the right coronary artery within 6 h after the onset. A 12-lead ECG, lead V4R, and leads V7–9 were recorded on admission. RVI was defined as occlusion proximal to the first right ventricular branch. The perfusion territory was assessed by angiographic distribution score, and PI was defined as a score of ≥0.7. Myocardial blush grade was assessed immediately after reperfusion. Patients were stratified according to the presense or absense of PI and RVI. Times to admission and reperfusion were similar in the 4 groups. RVI was associated with higher peak creatine kinase and higher rates of impaired myocardial reperfusion (blush grade 0/1) and congestive heart failure during hospitalization in the presense or absense of PI, especially the former. RVI was associated with a higher rate of ST ↑ in lead V4R in the absence, but not in the presence, of PI. ST ↑ in lead V4R identified RVI with sensitivities of 34% and 96% (p<0.001) and specificities of 83% and 82% (NS) in the presence and absence of PI, respectively. In patients with reperfused IMI, RVI is associated with a larger infarct size and impaired myocardial reperfusion. However, the incidence of RVI diagnosed by ST ↑ in lead V4R was underestimated in the presence of posterior involvement. ST ↑ in lead V4R caused by RVI might be attenuated due to a reciprocal change in posterior ST ↑.
LATERAL ST-SEGMENT ELEVATION IS A STRONG PREDICTOR OF IMPAIRED MYOCARDIAL REPERFUSION IN PATIENTS WITH INFERIOR ACUTE MYOCARDIAL INFARCTION