Implications of the absence of st‐segment elevation in lead V 4R in patients who have inferior wall acute myocardial infarction with right ventricular involvement

Background : ST‐segment elevation of ± 1.0 mm in lead V 4R has been shown to be a reliable marker of right ventricular involvement (RVI), a strong predictor of a poor outcome in patients with inferior acute myocardial infarction (IMI). However, patients with no ST‐segment elevation in lead V 4R despite the presence of RVI have received little attention. Hypothesis : The study was undertaken to study the clinical features of patients with no ST‐segment elevation in lead V 4R despite the presence of RVI, which means false negative, as such patients have received little attention in the past. Methods : We studied 62 patients with a first IMI. who had total occlusion of the right coronary artery (RCA) proximal to the first right ventricular branch and successful reperfusion within 6 h from symptom onset, to examine the implications of the absence of ST‐segment elevation in lead V 4R despite the presence of RVI. Results : A standard 12‐lead electrocardiogram (ECG) and right precordial ECG (lead V 4R ) were recorded on admission, and three posterior chest ECGs (leads V 7 to V 9 ) were additionally recorded in 34 patients. Patients were classified according to the absence (Group 1, n = 18) or presence (Group 2, n = 44) of ST‐segment elevation of ± 1.0 mm in lead V 4R on admission. Patients in Group 1 had a greater ST‐segment elevation in leads V 7 to V 9 (2.9 ± 2.4 vs. 1.4 ± 3.0 mm, p < 0.05), a higher frequency of a dominant RCA (defined as the distribution score ≥ 0.7) (72 vs. 11%, p < 0.001), and a higher peak creatine kinase level (3760 ±; 1548 vs. 2809 ± 1824 mU/ml, p < 0.05) than those in Group 2. Conclusions : In patients with IMI caused by the occlusion of the RCA proximal to the first right ventricular branch, no ST‐segment elevation in lead V 4R can occur because of concomitant posterior involvement. In such patients, the incidence of RVI may be underestimated on the basis of ST‐segment elevation in lead V 4R .