Coronary Arteries

The coronary arteries are the primary vessels that supply oxygenated blood to the myocardium. They arise from the ascending aorta just above the aortic valve and encircle the heart in the atrioventricular and interventricular grooves. There are two main coronary arteries: the right coronary artery (RCA) and the left coronary artery (LCA). Each gives off branches that deliver blood to specific regions of the heart.

Origin

Both coronary arteries originate from the aortic sinuses located just above the aortic valve within the ascending aorta:

• Right coronary artery (RCA): Originates from the right aortic sinus
• Left coronary artery (LCA): Originates from the left aortic sinus

Right Coronary Artery (RCA)

The RCA runs in the right atrioventricular (coronary) sulcus and supplies blood to the right atrium, right ventricle, inferior part of the left ventricle, the posterior interventricular septum, and often parts of the cardiac conduction system.

Main Branches

• SA nodal artery: Supplies the sinoatrial node (~60% of cases)
• Right marginal artery: Supplies the right ventricular wall
• AV nodal artery: Supplies the atrioventricular node
• Posterior interventricular artery (PDA): Supplies the posterior interventricular septum and adjacent ventricular walls (in right-dominant hearts)

Left Coronary Artery (LCA)

The LCA is usually short and divides into two main branches shortly after its origin. It supplies the left atrium, most of the left ventricle, part of the right ventricle, and the anterior two-thirds of the interventricular septum.

Main Branches

• Left anterior descending artery (LAD): Also called the anterior interventricular artery; supplies the anterior walls of both ventricles and most of the interventricular septum
• Circumflex artery (LCx): Runs in the left atrioventricular groove and gives off the left marginal artery to supply the lateral and posterior left ventricle
• Left marginal artery: A branch of the circumflex that supplies the lateral wall of the left ventricle

Coronary Artery Dominance

Coronary dominance refers to the artery that gives rise to the posterior interventricular artery (PDA):

• Right-dominant (≈70%): PDA arises from RCA
• Left-dominant (≈10–15%): PDA arises from circumflex branch of LCA
• Co-dominant (≈15–20%): PDA arises from both RCA and LCA branches

Distribution Summary

Topographic Relationships

• RCA: Right atrioventricular groove, near right atrium and right ventricle
• LCA: Between left auricle and pulmonary trunk; bifurcates into LAD and circumflex
• LAD: Anterior interventricular groove
• Circumflex: Left atrioventricular groove, posteriorly

Clinical Significance (Minimal)

Coronary artery disease (CAD) occurs when these arteries become narrowed or blocked due to atherosclerosis. The LAD is particularly vulnerable and its occlusion is often fatal, earning it the nickname “widowmaker.” Understanding the coronary artery distribution is essential in interpreting ECGs, coronary angiography, and planning bypass graft surgeries.

Summary

• Main vessels: Right and Left Coronary Arteries
• Key branches: LAD, Circumflex, Right Marginal, PDA
• Dominance: Determined by origin of the posterior interventricular artery
• Supply: Heart muscle, conduction system, septum