Inferior ST segment depression as a useful marker for identifying proximal left anterior descending artery occlusion during acute anterior myocardial infarction

To determine whether or not ST segment deviation on admissionelectrocardiograms can identify patients with anterior acutgemyocardial infarction due to proximal left anterior descendingartery occlusion, the magnitude and location of ST segment elevationor depression were compared between patients with proximal leftanterior descending artery occlusion (group A, n=47) and thosewith distal left anterior descending artery occlusion (groupB, n =59). ST segment depression in each of the inferior leadswas significantly greater in group A than in group B. The incidenceof ST segment depression 1 mm in each of the inferior leads(II; 81% vs 27%, III; 85% vs 54%, aVF; 87% vs 47%, P<0.01)was significantly higher in group A than in group B. In addition,the incidence of ST segment depression 1 mm in all of the inferiorleads was significantly greater in group A than in group B (77%vs 22%, P<0.01). In group A, maximal ST segment elevationwas more frequent in lead V alone (43% vs 14%, P<0.01). GroupA had greater ST segment elevation in lead a VL than group B,and the incidence of ST segment elevation 1 mm in lead a VLwas significantly higher in group A than in group B (66% vs47%, P<0.05). ST segment depression 1 mm in all of the inferiorleads was most valuable for identifying group A patients (77%sensitivity and 78% specificity). In contrast, the maximal STsegment elevation in lead V₂ alone or ST segment elevation 1 mm in lead a VL had a low diagnostic value (43% sensitivityand 86% specificity, 66% sensitivity and 53% specificity, respectively).In conclusion, this study indicates that analysis of ST segmentdeviation in the inferior leads is useful for identifying patientswith acute anterior myocardial infarction due to proximal leftanterior descending occlusion.