Anterior STEMI ECG recognition: V1–V4 ST elevation
Anterior STEMI presents with ST elevation in the precordial leads V1–V4, reflecting occlusion of the left anterior descending (LAD) artery or one of its major branches. The LAD supplies the anterior wall, most of the interventricular septum, and the anterolateral wall — making anterior STEMI the highest-mortality STEMI territory.
ST elevation criteria: ≥2mm in two contiguous precordial leads. V1–V4 = LAD territory (anterior wall). V1–V2 only = septal involvement. V3–V5 = mid-LAD. V4–V6 = anterior-lateral (diagonal branch involvement). Extensive anterior STEMI shows ST elevation from V1 through V6 — indicating proximal LAD occlusion.
Reciprocal changes: inferior reciprocal ST depression (in II, III, aVF) may be seen with large anterior STEMIs. New deep Q waves in V1–V4 may appear within 30–60 minutes — pathologic Q waves confirm irreversible myocardial injury.
High-risk anterior STEMI patterns: left main and proximal LAD equivalents
ST elevation in aVR with diffuse ST depression: ST elevation in lead aVR ≥ 1mm with diffuse ST depression in multiple leads (I, II, V4–V6) is the 'left main equivalent' pattern — suggests left main or very proximal LAD occlusion with global subendocardial ischemia. This carries the highest mortality of all STEMI presentations. Immediate cath lab activation.
De Winter T-waves: J-point depression (not elevation) with tall, symmetric, upright T waves in V1–V6. This represents LAD occlusion without the classic ST elevation — it is a STEMI equivalent requiring immediate cath lab activation. Often missed on initial triage review because it lacks ST elevation.
New LBBB with chest pain: new left bundle branch block in the context of typical ischemic symptoms carries the same urgency as overt STEMI. Apply modified Sgarbossa criteria to identify superimposed ischemia. Concordant ST elevation (ST in same direction as QRS) of any magnitude in LBBB = acute occlusion.