A 62-year-old man presents with 45 minutes of severe substernal chest pain radiating to the left arm, diaphoresis, and nausea. ECG shows ST elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Which artery is most likely occluded?

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

Explanation

ST elevation in inferior leads (II, III, aVF) with reciprocal changes in I and aVL indicates an inferior STEMI, which is caused by occlusion of the right coronary artery (RCA) in approximately 80% of cases. The RCA supplies the inferior wall of the left ventricle, the SA node, and the AV node. The left circumflex artery supplies the inferoposterior wall and is responsible in 20% of inferior MIs.

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

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Written and medically reviewed by the StethoPrep medical team.