Background: Defining the infarct related artery in acute myocardial infarction helps in better and faster management of patients. Therapeutic choices may differ according to the culprit lesion.
Objectives: This study aimed to evaluate multiple electrocardiography (ECG) criteria and one algorithm in defining the culprit artery in single vessel inferior ST elevation myocardial infarction (I-STEMI). A new criterion based on posterior leads was also proposed.
Materials and Methods: In this retrospective study from June 2007 to July 2012, ECG and angiography films of patients with acute inferior STEMI were reviewed. From a total of 138 studied patients, 25 had 3-vessel disease and 37 had two occluded arteries. Remaining 76 patients were diagnosed with single vessel acute I-STEMI, 56 had right coronary artery (RCA) occlusion [22 (29.3%) proximal RCA, 24 (32%) middle RCA, and 10 (13.3%) distal occlusion of RCA], 19 had left circumflex artery (LCx) lesion and one had middle left anterior descending (LAD) artery occlusion.
Results: Prediction of the RCA as culprit lesion using Tierala's algorithm was 86% sensitive and 50% specific. Prediction of LCx occlusion based on ST-elevation ≥ 1 mm in V6 was 87% specific (P = 0.005). Sum of ST elevation in leads V5 and V6 more than 2.5 mm, was a good marker of LCx prediction (P = 0.044). ST-elevation in V4R was 48% sensitive and 89% specific for RCA prediction (P = 0.004). Wellens' criterion was 82% sensitive and 47% specific for proximal RCA prediction (P = 0.002). Our new criterion ''Sum of ST elevation in posterior leads (V7 - V8 - V9) < 3 mm'' was 82% sensitive and 50% specific for RCA prediction (P = 0.017). We also revised Tierala’s algorithm by adding the presence of ST-elevation in V3 and V4 to the first step (when STe II ≥ III), which increased the specificity and PPV of LCx prediction (86% vs. 84% and 53% vs. 50%).
Conclusions: Although several criteria and algorithms were previously suggested, they could not reliably determine the site of occlusion. Right and posterior leads may be needed in order to increase the accuracy of prediction.