The circumflex artery branches off of the left coronary artery and supplies
most of the left atrium: the posterior and lateral free walls of the left
ventricle, and part of the anterior papillary muscle. The circumflex
artery may give off a variable number of left marginal branches to supply
the left ventricle. The terminal branch is usually the largest of these
branches. More likely, the circumflex artery may continue through the AV
sulcus to supply the posterior wall of the left ventricle and (with the
right coronary artery) the posterior papillary muscle of the bicuspid valve.
The left circumflex branches decrease in diameter along their lengths.
In 40-50% of hearts the circumflex artery supplies the artery to the SA node.