What are the main coronary arteries supplying the heart and their distribution, including dominance patterns?

Coronary Blood Supply to the Heart

Main Coronary Arteries and Their Distribution

The heart is supplied by two main coronary arteries—the right coronary artery (RCA) and left coronary artery (LCA)—which arise from the right and left aortic sinuses of the ascending aorta, respectively. 1

Left Coronary Artery System

• The left main coronary artery typically bifurcates into two major branches: the left anterior descending (LAD) artery and the left circumflex (LCX) artery 1
• Bifurcation pattern occurs in approximately 65.8% of cases, while trifurcation (adding a ramus intermedius branch) occurs in 20.4% of cases 2
• The LAD supplies the anterior wall of the left ventricle, anterior two-thirds of the interventricular septum, and gives off diagonal branches 1
• The LCX courses in the left atrioventricular groove and gives off obtuse marginal branches that supply the lateral wall of the left ventricle 1

Right Coronary Artery System

• The RCA supplies the right atrium, right ventricle, sinoatrial node (in 60-74% of cases), posterior interventricular septum, and inferior wall of the left ventricle in right-dominant systems 3, 4
• The RCA gives rise to right ventricular branches along its course to supply the right ventricular free wall 3
• The posterior descending artery (PDA) arises from the RCA in right-dominant circulation, running in the posterior interventricular groove and providing septal perforator branches 1, 3
• Posterolateral branches continue from the RCA after the PDA origin to supply the posterior and inferior left ventricular walls 3

Coronary Dominance Patterns

Coronary dominance is determined by which artery gives rise to the posterior descending artery and left posterior ventricular branch. 1

Right Dominance (Most Common)

• Right dominance occurs in approximately 77% of cases, where the RCA supplies both the PDA and posterolateral branches 2
• In this pattern, the RCA provides blood supply to the inferior wall of the left ventricle and the posterior interventricular septum 1, 3

Left Dominance

• Left dominance occurs in approximately 10% of cases, where the LCX (rather than RCA) gives rise to the PDA and posterior left ventricular branches 2
• The LCX courses beyond the obtuse marginal branches to reach the posterior atrioventricular groove 1

Co-Dominance (Balanced)

• Co-dominance occurs in approximately 13% of cases, where both the RCA and LCX contribute to the blood supply of the posterior descending artery and posterior left ventricular branches 2

Clinically Relevant Branches

Assessable Vessels on Imaging

• Coronary CTA can assess vessels of 1.5 to 2 mm in diameter, including all epicardial vessels (left main, LAD, LCX, RCA) and their branches (diagonals, obtuse marginals, left posterior ventricular branch, posterior descending artery) 1

Sinoatrial Node Blood Supply

• The sinoatrial node artery most commonly arises from the RCA (60-74% of cases), though it can originate from the LCX in a significant minority 4
• Obstruction of the SA nodal artery can cause severe rhythm disturbances, sinus node dysfunction, or sudden cardiac death 4

Common Anatomical Variations

Anomalous Origins

• The LCA can be absent in 11.8% of cases, with its branches arising separately from the aorta 2
• Split or double RCA occurs in 4.2% of cases 2
• Anomalous circumflex artery originating from the RCA can occur, typically following a retroaortic course, and is associated with atherosclerotic disease in approximately 35% of cases 5

Supernumerary Arteries

• A third coronary artery (conal artery) arising directly from the aorta occurs in approximately 32% of hearts, typically from the right aortic sinus, and represents an important collateral pathway 6

Clinical Pitfalls and Caveats

• When reporting coronary anatomy, always comment on dominance pattern by identifying which system supplies the PDA and posterior left ventricular branches 1
• Anomalous coronary origins must be specifically identified, particularly those with interarterial courses between the aorta and pulmonary artery, as these carry risk of sudden cardiac death 7
• The most common sites for coronary aneurysms include the proximal RCA and proximal LAD, requiring careful assessment 3
• Atherosclerotic disease may develop earlier and more aggressively in anomalous coronary arteries compared to normal anatomy 5