A surgeon ligates the right coronary artery in its proximal third. Which structure is most at risk for ischemia due to this ligation?

• A Left anterior descending artery territory (anterior interventricular septum)
• B Sinoatrial node in most individuals (supplied by the right coronary artery SA nodal branch in ~60% of people) ✓
• C Posterior papillary muscle of the mitral valve in all individuals
• D Atrioventricular node exclusively (supplied only by right coronary)

Explanation

In approximately 60% of individuals (right dominant circulation), the SA nodal artery arises from the proximal right coronary artery (first few centimeters); in the remaining 40%, it comes from the left circumflex artery. Therefore, proximal RCA ligation puts the SA nodal artery at risk in most people, potentially causing SA node ischemia and sinus arrest or bradyarrhythmias. The AV node is supplied by the posterior descending artery (PDA) — from RCA in right dominant (~85%), circumflex in left dominant — but at a more distal level. The posterior papillary muscle of the mitral valve is supplied by the PDA (dominant artery), not the proximal RCA directly.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.