USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

In a right dominant heart, which artery typically supplies the SA and AV nodes?

1. Left Circumflex Artery (LCX)

2. Right Coronary Artery (RCA)

3. Left Anterior Descending Artery (LAD)

4. Posterior Descending Artery (PDA)

The correct answer is: Right Coronary Artery (RCA)

The right coronary artery plays a crucial role in supplying blood to the sinoatrial (SA) node and the atrioventricular (AV) node in a right dominant heart. In a majority of individuals, particularly those with a right dominant coronary system, the SA node receives its blood supply from a branch of the RCA, which is crucial for maintaining the heart's rhythm. The RCA also typically supplies the AV node, ensuring it has the necessary blood supply for proper electrical conduction between the atria and ventricles. In contrast, the left circumflex artery primarily supplies the lateral and posterior aspects of the left atrium and left ventricle and does not play a significant role in supplying the nodes responsible for initiating and conducting electrical impulses. The left anterior descending artery is mainly responsible for the blood supply to the anterior wall of the left ventricle and does not typically supply the nodes in question. Lastly, the posterior descending artery, which can arise from the right coronary artery in a right dominant system, does contribute to supplying parts of the heart, but its primary role is not in supplying the SA and AV nodes. Thus, the right coronary artery is indeed the key vessel involved in supplying these essential cardiac structures.