Which artery branches into the LAD and circumflex and primarily supplies the left atrium and left ventricle?

• A. Marginal artery
• B. Posterior interventricular artery
• C. Right coronary artery
• D. Left coronary artery

Answer: (D)

The left coronary artery (the left main coronary artery) is the source that splits into the two major branches, the left anterior descending and the left circumflex. The left anterior descending runs down the front of the heart to supply the anterior wall of the left ventricle and the interventricular septum, while the left circumflex travels in the coronary groove to supply the left atrium and the lateral/posterior part of the left ventricle. So, this artery branches into the LAD and circumflex and predominantly supplies the left atrium and left ventricle. The other options don’t fit this pattern: the marginal and posterior interventricular arteries are branches of other arteries and don’t represent the vessel that gives rise to both the LAD and the circumflex.