Cardiac Medicine Certification (CMC) Practice Exam

In inferior wall MIs, which artery is typically associated with perfusing the sinoatrial node?

1. Left anterior descending artery

2. Circumflex artery

3. Right coronary artery

4. Posterior descending artery

The correct answer is: Right coronary artery

The sinoatrial (SA) node, known as the heart's natural pacemaker, is typically perfused by the right coronary artery in most individuals, especially in those with a right-dominant coronary system, which is the case for approximately 70% of the population. In inferior wall myocardial infarctions (MIs), the right coronary artery is often affected, leading to impaired blood flow to the areas it supplies, including the SA node. When inferior wall MIs occur, they can disrupt the normal electrical conduction due to ischemia affecting the structures involved in pacemaking. The right coronary artery's dominance in supplying the SA node emphasizes its critical role in maintaining normal heart rhythm, particularly in instances of inferior wall MIs. While the circumflex artery does supply portions of the heart, it generally does not perfuse the SA node in the majority of anatomical variants. Both the left anterior descending artery and posterior descending artery have limited direct relevance to the SA node's perfusion. Therefore, the right coronary artery is indeed the artery most commonly associated with supplying the sinoatrial node in the context of inferior wall myocardial infarctions.