Introduction: A few electrocardiographic criteria have been described to identify the infarct-related artery in inferior myocardial infarction. The aim of this study was to devise an arithmetic score to further improve the diagnostic accuracy.
Materials and methods: From 2004 to 2006, 78 patients who underwent primary angioplasty for inferior myocardial infarction within 6 hours from symptom onset were recruited for electrocardiographic and angiographic analysis.
Results: The mean age of patients was 65 ± 12 years with male predominance (74%). Less ST depression in lead I and aVL, and more prominent ST depression in lead V1-3 were observed in left circumflex artery (LCX) than right coronary artery (RCA) occlusions. In addition, more prominent ST depression in lead I and ST elevation in V1 were found in proximal RCA than distal RCA occlusions. Based on the findings, the Jeopardised Inferior Myocardium (JIM) score was constructed and defi ned as [II-V3/III+V1- I]. The sensitivity and specificity of JIM score ≤0.5 to predict proximal RCA occlusions; 0.5 <JIM score ≤1.5 to predict distal RCA occlusions; and JIM score >1.5 to predict LCX occlusions were 58% and 85%, 69% and 68%, and 79% and 94%, respectively. The accuracy of prediction is slightly better than the 2 previously reported criteria.
Conclusion: By taking into account more leads, the JIM score is capable of identifying the infarct-related artery with an improved diagnostic accuracy.