---

Abstract Background: Current electrocardiography (ECG) criteria are insensitive for the detection of posterior acute myocardial infarction (AMI) and most of these cases remain undiagnosed. The purpose of this study has been evaluated of prevalence and clinical value of ST-segment in posterior electrocardiography leads during acute myocardial infarction. Materials and Methods: In cross- sectional analytic study, posterior ECG leads (V7, V8 and V9) as well as standard 12 leads in 210 consecutive patients with acute myocardial infarction admitted to CCU wards of Shahid Rijaie hospital. Reinforcing, continuous arrhythmia, hypotension, cardiologic shock, marked heart failure and/or acute pulmonary edema were considered. Related parameters to basic characteristics and next process of patients in two groups with/ without ST- segment elevation in posterior ECG lead were compared. Results: There were 153 patients with ST-segment elevation 1 mm in 2 contiguous leads. 12.4% patients had STE1 mm in 2 posterior leads, either as an isolated finding (4.6%) or in association with STE at inferior or lateral sites (7.8%). The standard 12-lead electrocardiogram was normal in two patients and 5 other patients were admitted with the diagnosis of non-Q infarctions. Tall R waves in V1/V2 developed in 5 cases. In-hospital complications were significantly more frequent among patients with STE in posterior leads (47.4% vs. 20.9% respectively, P=0.01). Conclusion: STE in posterior electrocardiography leads is not uncommon during acute myocardial infarction and may portend a worse in-hospital course.