The relation of ST segment deviations in 12-lead conventional Electrocardiogram, right and posterior leads with the site of occlusion in acute inferior myocardial infarction

Background: In addition to diagnosing the acute myocardial infarction (MI), stratifying high-risk patients and proper treatment strategies are important issues in managing patients complaining of chest pain and suspecting MI. Many studies have been conducted to predict the occlusion site by interpreting the ST segment deviations in Electrocardiogram (ECG).Additional posterior and right precordial leads are suggested in literature to increase the sensitivity of prediction. The goal of this study was to determine the relation of ST segment changes in ECG (conventional 12 leads ECG besides right and posterior leads) with the site of occlusion within the vessel. Methods: Retrospectively, from total 138 patients, 76 of them were analyzed as single vessel acute Inferior ST elevation Myocardial infarction (I-STEMI)-ST which 56 (74%) had Right Coronary Artery (RCA) occlusion [22(29.3%) proximal RCA, 24(32%) middle RCA and 10(13.3%) distal occlusion of RCA], 19(25%) had Left Circumflex artery (LCx) lesion and one had middle Left Anterior Descending (LAD) artery occlusion. On admission ECGs and coronary artery intervention films, were reported within maximum time of 6 days in hospital stay, and re-evaluated by two cardiologists. Results: Fiol’s algorithm was 93% sensitive and 50% specific for predicting RCA occlusion. The ST elevation in lead III was associated with RCA stenosis (Odds Ratio (OR): 12, Confidence Interval (CI): 2.2-68.9), the association between ST elevation in lead II with LCx involvement was not significant. The V4R was a good marker for RV involvement on-admission, (OR=8, CI: 1.6-37.5). Sum of ST deviation in posterior leads (V7 to V9) ≥ 2mm had positive and significant relation to LCx stenosis (OR=4, CI: 1.3-14). Conclusion: Benefit of adding posterior and right leads to 12-lead ECG is shown to be noteworthy in present and prior studies, in identifying LCx stenosis and poor prognosis involvement.