Electrocardiographic identification of the infarct-related artery in acute inferior myocardial infarction

Differentiation between left circumflex occlusion and right coronary occlusion in inferior acute myocardial infarction is a common clinical problem. This study investigated new electrocardiographic markers for differentiation, including T wave inversion, and individual inferior and precordial lead ST level, versus the traditional criterion of lateral ST elevation. In 95 angiographically characterised patients, ST elevation in lateral chest lead V5 or V6 had a sensitivity of 56% and specificity of 92% to predict left circumflex related acute myocardial infarction while the absence of lateral T inversion in I and AVL was even more sensitive (89%) though less specific (74%). A criterion of ST depression in V1 > 0.1 mV has a sensitivity of 61% and specificity of 84% whereas a criterion of ST level in III minus II ≤ 0.1 mV has a sensitivity of 94% and specificity of 37% in predicting left circumflex related acute myocardial infarction. These criteria were then tested in another 49 patients subsequently recruited with inferior acute myocardial infarction. Useful parameters that discriminated left circumflex related acute myocardial infarction from right coronary related acute myocardial infarction include lateral ST elevation (38% vs. 7%, P < 0.05), absence of lateral T inversion (50% vs. 15%, P < 0.05), and ST depression in V1 of more than 0.1 mV (50% vs. 7%, P < 0.05). The present study revealed new electrocardiographic clues to suggest a left circumflex related inferior acute myocardial infarction other than lateral ST elevation. However, it should be noted that no single electrocardiographic variable or their combinations could identify the infarct-related artery with complete certainty.