A 60-year-old man presents 3 hours after onset of crushing chest pain. ECG shows ST elevation in leads II, III, and aVF with reciprocal ST depression in I and aVL. He is taken for primary PCI. Which coronary artery is most likely occluded?

• A Left anterior descending artery
• B Left circumflex artery
• C Left main coronary artery
• D Right coronary artery ✓

Explanation

ST elevation in leads II, III, aVF (inferior leads) with reciprocal changes in I and aVL is the classic pattern of an inferior STEMI, caused by occlusion of the right coronary artery (RCA) in 80–85% of cases. The RCA supplies the inferior wall, AV node, and right ventricle. LAD occlusion produces anterior/anteroseptal changes (V1–V4); left circumflex occlusion may cause lateral changes (I, aVL, V5–V6) or a posterior STEMI.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.