[Electrocardiographic differentiation between lesions of the right coronary artery and circumflex artery in acute inferior myocardial infarction].

INTRODUCTION AND OBJECTIVES: The objective of this prospective study is to analyze the value of the standard electrocardiogram in the identification of the lesioned coronary artery in the inferior acute myocardial infarction.

METHODS: One-hundred consecutive patients with inferior acute myocardial infarction were studied, 67 with lesion in the right coronary artery and 33 in the circumflex artery. The ST segment changes in inferior, lateral and precordial leads were analized, as was the ST segment relation between the DII and DIII. The arithmetic sum of the ST segment in the inferior and V2 leads (II+V2, III+V2 and aVF+V2).

RESULTS: This study shows that the most useful parameters to predict the lesioned coronary artery in the inferior acute myocardial infarction, with specificity and positive predictive value of 100% are: a) the arithmetic sum of the ST segment: aVF+V2 > 0, with a sensibility of 86.5%, for the right coronary artery; b) the arithmetic sum of the ST segment: III+V2 < 0, with a sensibility of 90.9%, for the circumflex artery, and c) the arithmetic sum of the ST segment: aVF+V2 > 1, with a sensibility of 97.6%, for the proximal right coronary artery. Other useful predicting parameters, with specificity of 100%, although with a lower sensibility, are: a) ST segment elevation in I and ST segment in II > III, for the circumflex artery, and b) ST segment elevation in V1-V3 for the lesion in the proximal right coronary artery.

CONCLUSIONS: These findings demonstrate that the standard electrocardiogram represents an important tool in predicting the lesioned coronary artery, right coronary and circumflex artery, in the acute myocardial infarction, with a sensibility and specificity between 86.5% and 100%, respectively, which are within the published range of the traditionally used right thoracic leads.