An Unusual ECG Pattern in Mid-Left Anterior Descending Artery Occlusion

A 52-year-old dyslipidemic gentleman with no previous cardiovascular symptoms presented with acute typical angina for 4 h. The electrocardiogram (ECG) demonstrated ST-elevation in leads III, aVR, and V1, ST-segment depression in I, aVL, and V6, and hyperacute T-waves in leads V2-V6. Emergent angiography revealed critical single-vessel disease of the mid-left anterior descending artery (LAD) involving the first septal artery (S1) and proximal to the first diagonal artery (D1). This case illustrates how a significant ST-elevation myocardial infarction involving the mid-left anterior descending artery can potentially be underestimated in the electrocardiogram due to vector shifts related to the ramus intermedius artery. ST-elevation in leads III and aVF with upsloping ST-segment depression in V2-V6 may suggest a mid-left anterior descending artery acute anterior wall myocardial infarction in patients with a large ramus intermedius artery or an early obtuse marginal artery.