Coronary angiography in a patient reveals that the posterior descending artery arises from the left circumflex artery. How should this coronary circulation be classified, and approximately how common is it?
- A Right dominant, about 85 percent
- B Balanced (codominant), about 20 percent
- C Left dominant, about 10 percent ✓
- D Right dominant, about 50 percent
Correct answer: C. Left dominant, about 10 percent
Explanation
Dominance is defined by which artery gives rise to the posterior descending artery and supplies the posterior interventricular septum. When the circumflex artery gives off the posterior descending artery, the circulation is left dominant, occurring in roughly 10 percent of individuals. Right dominance accounts for about 85 percent and codominance for the remainder, so classifying this angiogram as right dominant would be incorrect.
Reference: Gray's Anatomy for Students, 4th ed.
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