The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. As the left and right coronary arteries run on the surface of the heart, they can be called epicardial coronary arteries. The coronary arteries are classified as "end circulation" since they represent the only source of blood supply to the myocardium; there is very little redundant blood supply, which is why blockage of these vessels can be so critical.
The two coronary arteries originate from the left side of the heart at the beginning (root) of the aorta, just after the aorta exits the left ventricle.
The right coronary artery (RCA) is an artery originating above the right cusp of the aortic valve. It supplies the SA and AV nodes, and infarct of the RCA may lead to bradycardia or heart block. It branches into the posterior descending artery and the right marginal artery. In addition to supplying blood to the right ventricle, the RCA supplies 25% to 35% of the left ventricle. In 85% of patients (right dominant), the RCA gives off the posterior descending artery (PDA).
The right marginal branch of right coronary artery (or right marginal artery) is a large marginal branch which follows the acute margin of the heart and supplies branches to both surfaces of the right ventricle.
The posterior descending artery (PDA) is an artery running in the posterior interventricular sulcus to the apex of the heart where it meets with the anterior interventricular artery. It supplies the posterior 1/3rd of the interventricular septum and the posterior walls of ventricles. It is typically a branch of the right coronary artery (right dominance). Alternately, the PDA can be a branch of the circumflex coronary artery (15%, known as left dominance) which itself is a branch of the left coronary artery.
The left coronary artery (LCA) is an artery that arises from the aorta above the left cusp of the aortic valve and feeds blood to the left side of the heart.
The left anterior descending artery (LAD) is the first branch off of the LCA. Coronary artery occlusion happens more often at this artery, hence the nickname "the widowmaker." It supplies the anterolateral myocardium, apex, anterior 2/3rds of the interventricular septum, and anterior papillary muscle. The LAD typically supplies 45-55% of the left ventricle.
The circumflex artery curves to the left around the heart within the coronary sulcus, giving rise to one or more left marginal arteries as it curves toward the posterior surface of the heart. 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.
The left marginal artery is a branch of the circumflex artery, originating at the anterior interventricular sulcus, traveling along the left margin of heart towards the apex of the heart. The left marginal artery lies in the AV septum.
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