A 58-year-old man presents 2 hours after onset of chest pain. ECG shows ST elevation in leads II, III, aVF with reciprocal depression in I and aVL. He is taken for primary PCI. Which vessel is MOST likely culprit?

• A Left anterior descending artery (LAD)
• B Left circumflex artery (LCx)
• C Left main coronary artery
• D Right coronary artery (RCA) ✓

Explanation

Inferior STEMI (ST elevation in II, III, aVF) is most commonly caused by RCA occlusion in right-dominant hearts (~85% of population). The reciprocal changes in I and aVL are characteristic of inferior STEMI. LAD occlusion causes anterior STEMI (V1-V4); LCx typically causes lateral or posterior STEMI. Left main occlusion would cause massive anterior-lateral involvement with haemodynamic collapse.

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

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Written and medically reviewed by the StethoPrep medical team.