Diagnostic value of the arithmetic sum of the ST segment of inferior and V2 leads, II + V2, III + V2 and aVF + V2 in identifying the artery responsible for inferior acute myocardial infarction.

In order to evaluate electrocardiographic changes in the diagnosis of the artery responsible for inferior myocardial infarction, a prospective study was performed on inferior and V2 ST segment deviation and its correlation using the arithmetic sum: II + V2, III + V2, and aVF + V2. A group of 66 patients with inferior acute myocardial infarction (AMI) was studied. A standard 12-leads electrocardiogram was performed within six hours of the onset of chest pain. Coronary arteriography was performed on each of the patients between one and twelve weeks after infarction. Right coronary artery (RCA) lesion was found in 46 patients, 27 at a proximal level and 19 at a distal level; in 20 patients the left circumflex coronary artery was affected. The isolated value of the magnitude of the inferior ST segment is not an efficient parameter for identifying the artery responsible for inferior AMI. In lead V2 all the patients with a lesion of the left circumflex artery showed ST segment depression > or = 1 mm (P < 0.001) and all those presenting ST segment elevation had stenosis of the proximal RCA. The most useful parameters for identifying the artery responsible for inferior AMI, with 100% specificity are: (1) for occlusion of the RCA, the arithmetic sum of ST segments: aVF + V2 > 0, with 86.9% sensitivity (P < 0.001); (2) for occlusion of the left circumflex artery III + V2 < 0, with 90% sensitivity (P < 0.001); and (3) for proximal occlusion of the RCA: aVF + V2 > or = 1, with 96.2% sensitivity (P < 0.001). No specific marker was observed for distal occlusion of the RCA. The value of the arithmetic sum of the ST segment: III + V2 between 0 and 0.9 was the most significant, with 94.7% sensitivity and 95.7% specificity (P < 0.001).