In an inferior ST-elevation myocardial infarction, which artery is most commonly involved?

• A. Left anterior descending artery
• B. Right coronary artery
• C. Left circumflex artery
• D. Posterior descending artery

Answer: (B)

Inferior ST-elevation myocardial infarction happens when the artery that feeds the inferior wall of the left ventricle becomes occluded. In most people, this region is supplied by the right coronary artery (RCA), especially in the common right-dominant pattern where the RCA gives rise to the posterior descending artery that nourishes the inferior wall. When the RCA is blocked, blood flow to the inferior wall drops, producing ST elevations in the inferior leads (II, III, and aVF). Because right-dominant anatomy is much more common, RCA occlusion is the typical cause of inferior STEMI. There are anatomical variants—if the heart is left-dominant, the left circumflex can supply the inferior wall via the PDA—but that’s less common. The left anterior descending artery mainly supplies the anterior wall, so it’s not the usual culprit in inferior MI. Therefore, the artery most commonly involved is the right coronary artery.