Anteroseptal ST elevation myocardial infarction (AS-STEMI), in which ST elevation is limited to leads V(1) to V(3), is considered confined to the basal and mid anterior and septal segments, sparing the apex. In contrast, extensive anterior STEMI (EA-STEMI), in which ST elevation extends to leads V(4) to V(6), is considered to involve more apical segments. However, it has been reported that AS-STEMI affects mainly the apex. Others have suggested that AS-STEMI may occur in patients with extensive anterior involvement if proximal occlusion of a wrapping left anterior descending coronary artery (LAD) results in cancelation of the basal-anterior and apical injury vectors. Therefore, the aim of this study was to identify, in 97 consecutive patients with STEMI, distinct coronary angiographic characteristics that could differentiate between cases of AS-STEMI (n = 39) and EA-STEMI (n = 58). Angiography was used to determine the length of the LAD, its site of occlusion, and whether there was an alternative blood supply to the apex. Patients with AS-STEMI were more likely than those with EA-STEMI to have ≥1 branches that reached the apex (p = 0.0015) and to have proximal LAD occlusion combined with either a short LAD or >1 large side branch (35.9% vs 12.1%, p = 0.011). However, patients with AS-STEMI were also more likely to have proximal occlusion before the first septal branch of a long LAD (35.9% vs 10.3%, p = 0.005). In conclusion, AS-STEMI can occur when only the basal and mid portions of the anterior wall are infarcted, but it can also arise when the infarction extensively involves the basal anterior and the distal inferior and apical segments.
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