A 58-year-old man with a 20-year history of smoking and hypertension presents with acute anterior wall ST-elevation myocardial infarction. Which is the most common coronary artery involved in anterior wall STEMI?

Explanation

## Coronary Artery Distribution in STEMI **Key Point:** The left anterior descending (LAD) artery is the most common vessel involved in acute myocardial infarction overall, and specifically causes anterior wall STEMI in the majority of cases. ### Anatomical Basis The LAD supplies: - Anterior wall of the left ventricle - Anterior two-thirds of the interventricular septum - Diagonal branches to the lateral wall ### STEMI Location and Culprit Vessel Correlation | STEMI Location | Most Common Culprit Artery | Frequency | |---|---|---| | **Anterior wall** | **LAD** | **40–50%** | | Inferior wall | RCA (80%) or LCx (20%) | 30–40% | | Posterior wall | RCA or LCx | 5–10% | | Right ventricular | RCA (proximal) | 3–5% | **High-Yield:** LAD occlusion is the most common cause of acute MI death because it supplies the largest territory of myocardium and the conduction system. ### Clinical Pearl Anterior STEMI (ST elevation in V1–V4) indicates LAD occlusion proximal to the first diagonal branch. Proximal LAD occlusion carries the worst prognosis due to extensive myocardial necrosis and high risk of cardiogenic shock and conduction abnormalities. **Mnemonic:** **LAD = Largest territory, Lethal if occluded** — Remember that LAD is responsible for ~50% of all acute MIs. ### Why LAD is Most Common 1. Largest coronary vessel by diameter and territory supplied 2. Atherosclerosis burden is highest in LAD 3. Most frequent site of plaque rupture and thrombosis