Coronary Arteries

These consist of a left main coronary artery which bifurcates to the circumflex coronary artery and left anterior descending coronary artery (Fig. 1.4). The orifice of the left main coronary artery lies in the left coronary sinus. The orifice of the right coronary artery arises from the right coronary sinus. The circumflex coronary artery lies in the groove between the left atrium and left ventricle adjacent to the coronary sinus. The circumflex coronary artery gives off obtuse marginal branches because they lie on the obtuse surface of the heart. The branches of the left anterior descending artery are called diagonal branches. The right coronary artery has a first branch called an acute marginal artery which supplies the free ventricular surface and may also give off a conal branch which supplies the infundibulum of the right ventricle. The right coronary artery continues to bifurcate into a posterior descending artery as well as a continuing posterior ventricular branch, also called a posterolateral branch or LV extension branch. The dominance of the coronary arteries is determined by which side, i.e. right or left, supplies the posterior descending artery. In 90% of people, the posterior descending artery is a continuation of the right coronary artery; in 10% it is a continuation of the circumflex coronary artery or the left anterior descending coronary artery. The collaterals going from the right coronary artery to the left anterior descending artery is called the loop of Vieussens. Septal arteries arise perpendicularly from the left anterior descending artery to supply the interventricular septum. This is often helpful in angiographic identification of the LAD and differentiating the septal branches from diagonal branches. The right coronary artery courses down the right atrialventricular groove. The right coronary artery crosses the crux of

Posterolateral Ventricular Branch

the heart where it gives off a AV node artery at the apex of the bend. It then terminates into the posterior descending artery and posterolateral segment artery (same as posterior ventricular branch or LV extension branch).

The sinus node artery usually originates from the right coronary artery. The sinus node artery arises from the right coronary artery in 55% of hearts and from the left circumflex or left main coronary artery in the rest. As noted above, the AV node artery usually arises from the bend of the right coronary artery as it crosses the crux of the heart. The AV node is usually supplied by the dominant coronary artery.

An important accessory blood supply to the AV node is Kugel's artery which originates from the right coronary artery or circumflex artery, coursing through the interatrial septum. The left ventricular anterolateral papillary muscle is supplied by the left anterior descending artery and obtuse marginal branches, however, the posteromedial papillary muscle is supplied by the terminal right coronary artery or terminal circumflex coronary artery, i.e. whichever is dominant in the particular person. The posteromedial papillary muscle is supplied by only one coronary artery. The posteromedial muscle is thus more often susceptible to ischemia in patients with coronary artery disease than the anterolateral papillary muscle. This is of clinical significance because ischemia of the posteromedial papillary muscle may lead to ischemic mitral regurgitation. In more severe cases the muscle may infarct, leading to rupture of the papillary muscle, severe mitral regurgitation, and pulmonary edema.

Suggested Reading

1. Wilcox BW, Anderson RH. Surgical anatomy of the heart. In: Baue AE, Geha AS, Hammond GL et al. eds. Glenn's Thoracic and Cardiovascular Surgery. 5th edition, East Norwalk: Appleton and Lange, 1991:1333-1344.

2. Wilcox BR, Anderson RH. Surgical Anatomy of the Heart. New York: Raven Press, 1985.

3. McAlpine WA. Heart and Coronary Arteries. New York: Springer-Verlag, 1975.

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