Page 15, O2 Uptake, Exercise & Cor. Circ., Dr. D. Penney

Coronary Circulation (continued..)

The coronary circulation arises as two ostia in the sinuses of Valsalva, immediately distal to the aortic valve (Figure 3.07). The left main coronary artery (LCA) arises from the left coronary cusp and supplies more than 70% of the contractile myocardium of the left ventricle. It is considered the "widow maker", because occlusion so severely reduces blood flow to the heart. The LCA immediately bifurcates into the left anterior descending artery (LAD) which supplies the anterior septum via septal perforating arteries and the anterolateral wall via anterolateral or diagonal branches, and the circumflex artery (CIRC), which supplies the lateral and posterolateral walls via lateral and posterolateral branches.

In approximately 10% of cases the CIRC supplies the inferior wall via a posterior descending artery. The right coronary artery (RCA) arises from the right coronary cusp and supplies the right ventricle and most often, the inferior wall of the left ventricle and inferoposterior septum. Branches of the RCA supply the sinoatrial node in 60% and atrioventricular node in 90% of people.

See an angiogram of the heart.