Professional and Linguistic Assessments Board (PLAB) Practice Exam

In a left dominant heart, what artery arises from the left circumflex artery?

1. Anterior interventricular artery

2. Posterior descending artery

3. Left marginal artery

4. Right coronary artery

The correct answer is: Posterior descending artery

In a left dominant heart configuration, the posterior descending artery is typically supplied by the left circumflex artery rather than the right coronary artery. This configuration means that the left circumflex artery extends further back, providing blood supply to the posterior part of the heart, which is crucial for maintaining adequate blood flow to the inferior wall of the left ventricle and the interventricular septum. In this anatomical arrangement, the posterior descending artery branches from the left circumflex artery, ensuring that the entire heart is effectively perfused. Understanding the implications of a left dominant system is essential, as it alters the typical coronary artery dominance most medical practitioners are taught, where the right coronary artery is usually responsible for supplying the posterior descending artery in a right dominant system. The other choices represent different arteries that do not arise from the left circumflex artery. The anterior interventricular artery is a branch of the left anterior descending artery, and the left marginal artery is a branch of the left circumflex artery itself, specifically supplying the lateral wall of the left ventricle. The right coronary artery arises from the right side and does not connect to the left circumflex artery under normal anatomical variations.