 | Coronary circulation: Encyclopedia II - Coronary circulation - Coronary anatomy
Coronary circulation - Coronary anatomy
The exact anatomy of the myocardial blood supply varies considerably from person to person. A full evaluation of the coronary arteries requires cardiac catheterization.
In general there are two main coronary arteres, the left and right. Both of these arteries originate from the beginning (root) of the aorta, immediately above the aortic valve. As discussed below, the left coronary artery originates from the left aortic sinus, while the right coronary artery originates from the right aortic sinus.
Coronary circulation - Left coronary artery
The left coronary artery (LCA) arises from the aorta above the left cusp of the aortic valve as the left main (LM) artery. The left main artery typically runs for 1 to 25 mm and then bifurcates into the left anterior descending (LAD) artery and the left circumflex artery (LCX). If an artery arises from the left main between the LAD and LCX, it is known as the ramus intermedius. The ramus intermedius occurs in 37% of the general population, and is considered a normal variant.
The LAD runs down the anterior interventricular groove. In 78% of cases, it reaches the apex of the heart. It supplies the anterolateral myocardium, apex, and interventricular septum. The LAD typically supplies 45-55% of the left ventricle (LV). The LAD gives off two types of branches: septals and diagonals. Septals originate from the LAD at 90 degrees to the surface of the heart, perforating and supplying the intraventricular septum. Diagonals run along the surface of the heart and supply the lateral wall of the LV and the anterolateral papillary muscle.
The LCX runs across the left atrioventricular groove. It gives off obtuse marginal (OM) branches. The LCX supplies the posterolateral LV and the anterolateral papillary muscle. It also supplies the sinoatrial nodal artery in 38% of people. It supplies 15-25% of the left ventricle in right-dominant systems. If the coronary anatomy is left-dominant, the LCX supplies 40-50% of the left ventricle.
Coronary circulation - Right coronary artery
The right coronary artery (RCA) originates above the right cusp of the aortic valve. It travels down the right atrioventricular groove, towards the crux of the heart. At the origin of the RCA is the conus artery. In addition to supplying blood to the right ventricle (RV), the RCA supplies 25% to 35% of the left ventricle (LV). In 85% of patients, the RCA gives off the posterior descending artery (PDA). In the other 15% of cases, the PDA is given off by the left circumflex artery. The PDA supplies the inferior wall, ventricular septum, and the posteromedial papillary muscle. The RCA also supplies the SA nodal artery in 60% of patients. 40% of the time, the SA nodal artery is supplied by the LCX.
Coronary circulation - Coronary artery dominance
The artery that supplies the posterior descending artery and the posterolateral artery (PLA) determines the coronary dominance. If the RCA supplies both these arteries, the circulation can be classified as "right-dominant". If the LCX supplies both these arteries, the circulation can be classified as "left-dominant". If the RCA supplies the PDA and the LCX supplies the PLA, the circulation is known as "co-dominant". Approximately 70% of the general population are right-dominant, 20% are co-dominant, and 10% are left-dominant. [1]
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