On a coronary CT angiogram, the posterior descending artery and the posterolateral ventricular branch both arise from the right coronary artery. How should the coronary circulation be classified?

• A Left dominant
• B Codominant (balanced)
• C Right dominant ✓
• D Superdominant left circumflex

Explanation

Dominance is determined by which artery gives rise to the posterior descending artery and supplies the posterolateral left ventricular wall. When both arise from the right coronary artery, the circulation is right dominant, the pattern in roughly 80 to 85% of people. Left dominance means the PDA arises from the circumflex, and codominance means the PDA territory is shared by both arteries. Dominance matters clinically because infarct territory and collateral potential depend on it.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.