Coronary angiography in a patient scheduled for CABG shows the posterior descending artery arising from the circumflex artery. How is this coronary circulation classified, and approximately how common is it?

• A Right dominant, about 85 percent
• B Balanced or codominant, about 15 percent
• C Left dominant, about 40 percent
• D Left dominant, about 10 percent ✓

Explanation

Dominance is defined by the artery that gives rise to the posterior descending artery and supplies the posterior interventricular septum. When the PDA arises from the circumflex branch of the left coronary 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 options A and B describe the common patterns, not this patient's pattern.

Reference: Gray's Anatomy for Students, 4th ed.

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