If the circumflex branch supplies the back side of the heart, including the septum, the circulation is considered what?

• A. Dominant left
• B. Dominant right
• C. Balanced
• D. Mixed

Answer: (A)

Coronary artery dominance is determined by which artery gives rise to the posterior descending artery and thus supplies the posterior wall and the posterior part of the interventricular septum. If the circumflex branch of the left coronary artery supplies the back side of the heart, including the septum, this means the left coronary system is providing the PDA—so the circulation is left-dominant. This contrasts with right-dominant circulation, where the right coronary artery supplies the PDA, and co-dominant circulation, where both arteries contribute. The scenario described fits left-dominant anatomy, making that the correct idea.