Abstract
This study aimed to clarify the significance of ST-segment depression in the lateral chest leads in anterior wall acute myocardial infarction (AMI) with ST-segment elevation. A total of 196 patients with their first anterior wall AMI (≤6 h) were divided into 2 groups according to the presence (group A, n=39) or absence (group B, n=157) of ST-segment depression ≥0.1 mV in V5 and/or V6 on the admission electrocardiogram. Patients with electrocardiographic confounding factors were excluded. No patients had persistent ST-segment depression in the lateral chest leads. Emergency coronary angiography revealed that group A had higher incidences of occlusion of the left anterior descending coronary artery (LAD) proximal to its first septal branch (77% vs 51%, p<0.01) and good collateral circulation than group B (46% vs 25%, p<0.05). Peak creatine kinase levels were significantly lower in group A than in group B (2060±1099 vs 2873±2077 IU/L, p<0.01). Left ventricular ejection fraction in the chronic phase was significantly greater in group A than in group B. Regional wall motion in the infarct region in the chronic phase was better in group A than in group B. These results indicate that patients with `transient' ST-segment depression in the lateral chest leads in anterior wall AMI had a relatively smaller infarct size, despite their higher incidence of occlusion of the LAD proximal to its first septal branch, because of their higher incidence of good collateral circulation. (Jpn Circ J 1999; 63: 873 - 876)
