• Vol. 41 No. 7, 300–304
  • 15 July 2012

Jeopardised Inferior Myocardium (JIM) Score: An Arithmetic Electrocardiographic Score to Predict the Infarct-Related Artery in Inferior Myocardial Infarction

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ABSTRACT

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 defined as [II–V3/III+V1– I]. The sensitivity and specificity of JIM score ≤0.5 to predict proximal RCA occlusions; 0.5 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.


Inferior myocardial infarction classically manifests as ST elevations in inferior leads, together with ST changes in other leads that may be the result of concomitant ischaemia of other zones or a reciprocal image. It is exclusively caused either by left circumflex artery (LCX) or right coronary artery (RCA) occlusion, with the latter having worse prognosis owing to its association with right ventricular infarction. There are a few reported electrocardiographic criteria capable of identifying the infarct-related artery with high accuracy. These criteria are simple, focusing on one or two leads, and user-friendly. However, the same prediction accuracy may not be reproducible in other populations because of heterogeneity in patients’ baseline characteristics and variations in the individual’s coronary anatomy. Analysis of multiple electrocardiographic leads may instead plausibly minimise the errors and improve the diagnostic accuracy. The purpose of this study was to devise an arithmetic electrocardiographic score which takes into account multiple leads from a 12-lead electrocardiogram (ECG) to predict the infarct- related artery in inferior myocardial infraction.

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