Value of ST-segment depression in lead V4R in predicting proximal against distal left circumflex artery occlusion in acute inferoposterior myocardial infarction

Background: Lead V-4R faces the right ventricular free wall; it also reflects ischemia in the posterolateral wall lying opposite and manifests as ST-segment depression. Hypothesis: The aim of this study was to evaluate the usefulness of V4R ST-segment depression in distinguishing proximal from distal left circumflex artery occlusion in acute inferoposterior wall myocardial infarction. Methods: We retrospectively analyzed 239 patients who had first acute inferoposterior myocardial infarction, were admitted within 6 h from onset of symptom, and had coronary angiography performed within 4 weeks. Patients who had bundle-branch block or concomitant significant stenoses in the proximal and distal segments of the same vessel or of both vessels were excluded. The electrocardiographic and angiographic findings were reviewed by two independent groups of investigators. Results: V4R ST-segment depression >= 1.0 mm was found in 8 of 46 patients (17.4%) with left circumflex artery occlusion but none (0%) with right coronary artery occlusion. Among the group with left circumflex artery occlusion, the mean magnitude of V4R ST-segment depression was greater in proximal than distal occlusion (0.82 +/- 0.65 vs. 0.03 +/- 0.12 mm, p < 0.0001). V-4R ST-segment depression >= 1.0 mm was found in 8 of 14 patients (57.1%) with proximal occlusion but none (0%) in 32 patients with distal occlusion. The sensitivity and specificity to predict proximal occlusion were 57.1 and 100%a, respectively. Conclusions: V4R ST-segment depression >= 1.0 mm was not useful for differentiating left circumflex and right coronary artery occlusion because of its low sensitivity. It is a fairly sensitive and very specific sign of proximal left circumflex artery occlusion.