Right Coronary Artery (RCA)

Introduction

The right coronary artery (RCA) is one of the two main coronary arteries supplying the myocardium. Arising from the right aortic sinus, the RCA runs along the right atrioventricular (AV) groove, giving off multiple branches that supply the right atrium, right ventricle, sinoatrial (SA) and atrioventricular (AV) nodes, and parts of the interventricular septum. Its anatomy, variations, and clinical significance are critical for understanding coronary artery disease, arrhythmias, and interventional cardiology procedures.

1. Origin and Course of RCA

1.1 Origin

The RCA originates from the right aortic sinus (right sinus of Valsalva), just above the aortic valve.
Typically arises as a single trunk but can occasionally have dual ostia.

1.2 Course

Travels along the right atrioventricular groove between the right atrium and right ventricle.
Initially runs posteriorly around the heart’s right margin before reaching the posterior interventricular groove.
Terminates near the crux of the heart, giving off the posterior descending artery (PDA) in right-dominant circulation (~85% of people).

2. Segments of the RCA

The RCA is generally divided into proximal, mid, and distal segments for descriptive and clinical purposes.

2.1 Proximal RCA

Extends from the ostium to the first major branch (conus artery).
Gives rise to the conus branch and sometimes the SA nodal artery.

2.2 Mid RCA

Runs along the AV groove, giving off right marginal branches that supply the right ventricle.
Typically the site of atherosclerotic plaque formation.

2.3 Distal RCA

Approaches the crux of the heart, gives rise to posterior descending artery (PDA) and posterolateral branches.
Terminates near the origin of the AV nodal artery.

3. Branches of the RCA

3.1 Conus Artery (Infundibular Branch)

First branch from the RCA or sometimes arises directly from the aorta (third coronary artery).
Supplies the right ventricular outflow tract (RVOT) and conus arteriosus.
Clinically relevant in RVOT arrhythmias and angioplasty planning.

3.2 Sinoatrial (SA) Nodal Artery

Supplies the SA node, the natural pacemaker of the heart.
Origin: RCA in ~60% of cases; LCx in ~40%.
Courses posteriorly toward the SA node at the junction of SVC and RA.
Occlusion may cause sinus node dysfunction or bradyarrhythmias.

3.3 Right Atrial Branches

Multiple small branches to the right atrial myocardium.
Also contribute to atrial septal blood supply.

3.4 Right Ventricular Branches (Acute Marginal Arteries)

Arise along the right margin of the heart.
Supply free wall of right ventricle.
Largest branch often called the acute marginal artery, critical in RV perfusion.
Important in right ventricular infarction.

3.5 Posterior Descending Artery (PDA) / Posterior Interventricular Artery

Terminal branch in right-dominant circulation (~85%).
Runs in the posterior interventricular groove toward the apex.
Supplies:
- Posterior third of interventricular septum
- Posterior walls of LV and RV
- Inferior part of AV node
In left-dominant circulation, PDA arises from LCx; RCA may end earlier.

3.6 Posterolateral Branches

Supply the posterolateral left ventricle.
Contribute to collateral circulation in coronary artery disease.

3.7 Atrioventricular (AV) Nodal Artery

Usually arises near the crux of the heart from RCA in right-dominant hearts.
Supplies AV node and proximal His bundle.
Clinical importance: AV block can occur if artery is compromised during inferior MI or PCI.

4. Areas Supplied by RCA

4.1 Right Atrium

Entire myocardium of RA via small atrial branches.
Includes SA node in majority of cases.

4.2 Right Ventricle

Free wall predominantly supplied by acute marginal branches.
RVOT supplied by conus artery.

4.3 Interventricular Septum

Posterior third supplied by posterior descending artery (PDA).
Anterior two-thirds supplied by LAD (left coronary artery).

4.4 Atrioventricular Node

Supplied by AV nodal artery (RCA in right-dominant hearts).

4.5 Inferior Wall of Left Ventricle

Supplied via PDA and posterolateral branches.
Clinically relevant in inferior wall MI.

5. Coronary Dominance

Right-dominant (~85%): PDA arises from RCA.
Left-dominant (~8–10%): PDA arises from LCx; RCA supplies only RV and RA.
Co-dominant (~7%): PDA supplied by both RCA and LCx.
Dominance affects infarct patterns and interventional strategies.

6. Variations of RCA

Dual SA nodal arteries
Absent PDA (rare)
Early termination before crux (in left-dominant hearts)
Anomalous RCA origin from left aortic sinus or pulmonary artery (rare but clinically significant).

7. Clinical Correlations

7.1 RCA Infarction

Usually involves inferior wall MI.
ECG: ST-elevation in II, III, aVF.
May cause right ventricular infarction, AV block, bradyarrhythmias.
RCA lesion often accompanied by hypotension due to RV dysfunction.

7.2 Arrhythmias

SA nodal artery occlusion → sinus bradycardia or arrest
AV nodal artery occlusion → varying degrees of AV block

7.3 Angiography & PCI

RCA visibility on coronary angiography crucial for planning interventions.
Acute marginal and PDA anatomy affects stent placement.

7.4 Collateral Circulation

RCA may provide collaterals to LAD or LCx in chronic occlusion.
Important in coronary artery disease management.

8. Imaging of RCA

Coronary Angiography: Gold standard for branch identification and stenosis evaluation.
CT Coronary Angiography: Non-invasive depiction of origin, course, and anomalies.
Cardiac MRI: Functional assessment of RCA territory perfusion and infarction.
Echocardiography: Indirect assessment of RV perfusion and inferior wall motion abnormalities.

9. Histology

RCA wall structure similar to other epicardial arteries:
- Tunica intima: Endothelial lining
- Tunica media: Smooth muscle for vessel tone
- Tunica adventitia: Connective tissue with vasa vasorum
Branches penetrate myocardium to supply capillary beds.

10. Surgical and Interventional Considerations

RCA is critical in CABG (coronary artery bypass grafting):
- Right internal mammary artery (RIMA) or saphenous vein graft commonly used.
Interventions must preserve SA and AV nodal arteries to avoid arrhythmias.
RCA anomalies are surgically relevant in congenital heart disease correction.