Clinical and electrocardiographic characterization of total occlusion of the left main versus proximal or mid-occlusion of the left anterior descending artery

BACKGROUND: Acute occlusion of the left main coronary artery is rare but associated with exceptionally high mortality. Rapid recognition is essential to initiate timely reperfusion therapy. This study aimed to compare the clinical and electrocardiographic characteristics of left main total occlusion with those of proximal and mid-left anterior descending coronary artery occlusions, to identify features enabling early diagnostic suspicion. METHODS: A retrospective observational study was conducted in patients with anterior STsegment elevation myocardial infarction. Clinical, hemodynamic, and ECG parameters were analyzed using logistic regression analysis. A total of 173 patients were included: 23 with left main STEMI identified over 15 years, were compared with 98 consecutive patients with proximal LAD occlusion, and 52 with mid-LAD occlusion. RESULTS: The characteristic ECG pattern of left main STEMI comprised marked ST-segment elevation in leads I, aVL, and V2-V6, with reciprocal depression in inferior leads, isoelectric or depressed ST in V1, and frequent coexistence of right bundle branch block and left anterior fascicular block. The presence of cardiogenic shock emerged as the strongest clinical determinant. Marked ST-segment elevation in aVL and reciprocal ST-segment depression in lead III, particularly in patients with RBBB and cardiogenic shock, constitute a sensitive and specific sign for left main STEMI. CONCLUSIONS: In patients with anterior STEMI, ST-segment elevation in lead aVL and marked STsegment depression in lead III, particularly in association with cardiogenic shock, is sufficient to suspect left main occlusion. Recognition of this pattern, particularly in prehospital settings, should prompt immediate transfer to centers with 24-h catheterization capability for urgent reperfusion therapy.