Coronary circulation

The right and left main coronary arteries arise from ostia (small openings) located behind the right and left aortic valve cusps toward the more cephalad portion of the sinus of Valsalva (Figure 52-1). The third aortic cusp is named the posterior or noncoronary cusp. The left main coronary artery travels anteriorly and leftward from the left coronary sinus and, after a 2-mm to 10-mm course between the pulmonary trunk and the left atrium, divides into the left anterior descending (LAD) and left circumflex arteries. Occasionally, a diagonal branch is also present.

The LAD or left interventricular coronary artery is a direct continuation of the left main coronary artery, traveling anterior and caudad, descending in the anterior interventricular groove. This artery terminates in the inferior aspect of the cardiac apex. Branches of this artery include (1) the first diagonal, (2) the first septal perforator, (3) right ventricular branches (inconstant), (4) three to five additional septal perforators, and (5) two to six additional diagonal branches. The LAD provides blood to most of the ventricular septum (anterior two thirds); the anterior, lateral, and apical walls of the left ventricle; most of the right and left bundle branches; and the anterolateral papillary muscle (double blood supply—see later in the chapter) of the left ventricle. It can provide collateral vessels to the anterior right ventricle via the circle of Vieussens, to the ventricular septum via septal perforators, and to the posterior descending artery via the distal LAD artery or a diagonal branch.