The right coronary artery (RCA) arises from the right coronary sinus of the aortic root and supplies the right ventricle, the inferior (diaphragmatic) wall of the left ventricle, and the cardiac conduction system in most individuals.
Origin and Course
The RCA originates from the right coronary sinus (sinus of Valsalva) of the ascending aorta, typically in the upper third of the sinus. The ostium is usually located slightly below the sinotubular junction.
The RCA exits the aorta and courses anteriorly and rightward, passing between the pulmonary trunk (anteriorly) and the right atrial appendage (posteriorly). It then descends in the right atrioventricular groove.
Course segments:
- Proximal RCA: From origin to the first right ventricular branch
- Mid RCA: From first RV branch to the acute marginal branch
- Distal RCA: From acute marginal branch to the crux (posterior atrioventricular junction)
- Posterior descending (PDA): Continuation beyond the crux in the posterior interventricular groove
Branches
Conus Branch (Arterial Conus Branch)
The first branch of the RCA in approximately 50-60% of hearts. It supplies the right ventricular outflow tract (infundibulum) and the pulmonary conus.
Collateral importance: The conus branch forms an important collateral network (Vieussens ring) with branches of the LAD.
Sinoatrial Nodal Artery
The sinoatrial nodal artery arises from the proximal RCA in approximately 60% of hearts (from the LCx in 40%).
- Courses along the anterior right atrial wall
- Supplies the sinoatrial (SA) node
- May also supply the crista terminalis and Bachmann bundle
Right Ventricular Branches
Acute Marginal Branch:
- The largest and most consistent RV branch
- Courses along the acute margin of the heart (the sharp border between the anterior and diaphragmatic surfaces)
- Supplies the anterior and lateral right ventricular wall
Smaller RV branches: Multiple small branches to the anterior right ventricle
Right Atrial Branches
Small branches to the right atrium, including the SA nodal artery (described above).
Posterior Descending Artery (PDA)
Also called the posterior interventricular artery. Arises from the RCA at the crux in right-dominant hearts (70-80%).
Course: Descends in the posterior interventricular groove toward the apex
Branches:
- Septal perforators to the posterior one-third of the interventricular septum
- Small branches to the adjacent right and left ventricles
Atrioventricular Nodal Artery
Arises from the RCA at the crux in approximately 80-90% of hearts. Supplies the atrioventricular (AV) node. Courses from the crux superiority to the AV node in the triangle of Koch.
Posterolateral Branches
In right-dominant hearts, the RCA gives off posterolateral branches after the PDA origin, supplying the posterior left ventricular wall.
Dimensions
| Segment | Typical Diameter |
|---|---|
| Proximal RCA | 3.0-5.0 mm |
| Mid RCA | 2.5-4.0 mm |
| Distal RCA | 2.0-3.0 mm |
| PDA | 2.0-3.0 mm |
| Acute marginal | 1.5-2.5 mm |
Myocardial Territory Supplied
| Territory | Supply |
|---|---|
| Right ventricle (anterior, lateral) | Acute marginal and RV branches |
| Right ventricle (posterior) | PDA branches |
| Right ventricular outflow tract | Conus branch |
| Inferior left ventricle | PDA (via septal perforators) and posterolateral branches |
| Posterior one-third of septum | PDA septal perforators |
| Inferior/posterior left ventricle | Posterolateral branches |
| Sinoatrial node | SA nodal artery (60%) |
| AV node | AV nodal artery (80-90%) |
| Right atrium | Right atrial branches |
| Bachmann bundle | SA nodal artery (60%) |
Anatomic Variants
RCA Dominance
The RCA is dominant in approximately 70-80% of hearts, meaning it gives off the PDA and posterolateral branches.
Anomalous Origin
Anomalous RCA from the Left Sinus:
- RCA originates from the left coronary sinus
- May course between aorta and pulmonary trunk (interarterial)
- Associated with sudden cardiac death during exercise
- Requires surgical correction if interarterial
Anomalous RCA from the Pulmonary Artery:
- Extremely rare
- Presents with myocardial ischemia
Absent RCA
Rare; the right ventricle is supplied entirely by the LAD or LCx.
Clinical Significance
RCA Myocardial Infarction (Inferior STEMI)
The RCA is the culprit vessel in approximately 40-50% of all myocardial infarctions and is the most common cause of inferior STEMI.
ECG Findings:
- ST elevation in II, III, aVF
- III > II (indicating RCA culprit)
- ST depression in I, aVL
- Right-sided leads (V4R) show ST elevation in RV infarction
Types of RCA Occlusion:
| Occlusion Level | Territory Affected | Complications |
|---|---|---|
| Proximal RCA (before RV branches) | RV, inferior LV, posterior septum, SA node, AV node | RV infarction, bradycardia, heart block |
| Mid RCA (after RV branches, before PDA) | Inferior LV, posterior septum, AV node | AV node block, no RV involvement |
| Distal RCA (PDA alone) | Inferior septum, limited inferior wall | Smaller infarct, lower complication rate |
Right Ventricular Infarction
Occurs when the proximal RCA is occluded before the acute marginal branch.
Features:
- Hypotension, elevated jugular venous pressure, clear lungs (Kussmaul sign)
- ST elevation in V4R (right precordial lead)
- Requires aggressive volume resuscitation
- Avoid nitrates and diuretics (preload-dependent)
Bradyarrhythmias in RCA Infarction
Sinus bradycardia: SA nodal ischemia (proximal RCA occlusion)
AV block:
- First-degree AV block (PR prolongation)
- Wenckebach (Mobitz I): Usually transient
- Complete heart block: Often with a narrow escape rhythm (AV nodal)
- Usually resolves within days
- May require temporary pacing
RCA in Percutaneous Coronary Intervention
Challenges:
- Catheter engagement may be difficult (Shepherd hook vs. Judkins Right)
- Proximal RCA is prone to ostial dissection
- The acute marginal branch origin may be a bifurcation lesion
- RCA tortuosity is common in older patients
- PDA engagement may require microcatheter support
RCA in Cardiac Surgery
The RCA courses in the right atrioventricular groove and is at risk during:
- Tricuspid valve surgery (annular sutures)
- Right ventricular assist device placement
- Right atriotomy (for maze procedure or ASD closure)
- Heart transplantation (anastomotic site)