Clinical Values of the Posterior Chest Leads for Patients with Myocardial Infarction

Abstract

Background and Objectives:The standard 12 lead electrocardiography (ECG) is very valuable in the evaluation of myocardial infarction (MI), but it has many limitations for the diagnosis of posterior wall MI. We investigated the ECG patterns of the posterior chest leads in the normal population and we also investigated the values of the posterior chest leads when evaluating the involvement of the posterior wall in patients with MI. Subjects and Methods:To determine the normal ECG patterns of the posterior chest leads (V7-9), 52 healthy young men undergoing military service and 60 patients with MI (acute MI: 50 patients, old MI: 10 patients) were enrolled. We compared the sensitivity and specificity between the leads V1-2 and V7-9 for diagnosing posterior wall MI. Results:In the normal population, the prevalence of the pathologic Q wave was 0% in leads V7 and V8, and 7.5% in lead V9. None of the controls had an ST elevation more than 0.5 mm. For diagnosing posterior wall MI, the sensitivity was 36.4% for leads V1-2 and 72.7% for leads V7-9 and the specificity was 84.2% for leads V1-2 and 86.8% for leads V7-9. The left circumflex coronary artery lesions were more common in patients with concomittent inferior and posterior MI than in patients with isolated inferior wall MI (20.0% vs 6.6%, respectively, p=ns). All the patients with lateral wall MI or pure posterior wall MI had a lesion only in the left circumflex coronary artery. However, posterior wall involvement in patients with inferior wall MI did not exert any significant influence on the in-hospital course. Conclusion:Our results suggest that the recording of posterior chest leads (V7-9) is a simple and valuable method for evaluating posterior wall involvement in patients with MI. (Korean Circulation J 2005; 35:258-263)