Right coronary artery

The right coronary artery (RCA) is one of the two main coronary arteries that supply the heart with oxygenated blood.

Gross anatomy

Origin

The right coronary artery (RCA) ostium arises from the right sinus of Valsalva, found between the aortic valve annulus and the sinotubular junction. 

Course

After a sharply horizontal egress from the aorta, the proximal segment of the RCA courses superiorly and rightward, posterior to the pulmonary trunk and underneath the right atrial appendage. The mid-right coronary artery curves in an inferior direction in the plane of the atrioventricular groove. The distal segment curves toward the cardiac crux as it travels along the posterior interventricular groove, with a subsequent bifurcation forming the posterior left ventricular branch and the posterior descending artery; the formation of the latter defines coronary arterial dominance ⁵.

• when the right coronary artery gives rise to the PDA, this defines a right dominant circulation (70% population)
• contribution from both the RCA and left circumflex artery defines a co-dominant circulation (20%)
• the least common (10%) variant is a left dominant circulation in which the left circumflex artery continues as the PDA

The three segments of the RCA are:

• proximal segment: from the RCA origin to halfway along the acute margin of the heart
• mid segment: from halfway along the acute margin to the acute angle of the heart, where it courses along the posterior AV groove
• distal segment: from the acute angle to the apex

Branches

• proximal RCA
  • conus artery (in 60%)
  • atrial branches
    • sinoatrial nodal artery 
• mid RCA
  • right ventricular branches
  • acute marginal arteries (designated AM1, 2, etc)
• distal RCA
  • posterior descending artery (PDA)
    • defines a right dominant circulation
  • atrioventricular nodal artery
  • ​posterior left ventricular branches (PLV, PLB or PLA)

Supply

• conus branch: right ventricular outflow tract
  • descending septal artery: infundibular septum ⁵
• atrial branches: right and left atria, interatrial septum
  • sinoatrial nodal artery: sinoatrial (SA) node
• right ventricular branches
  • acute and RV marginal branches: right ventricular free wall
• atrioventricular nodal branch: atrioventricular (AV) node
• posterior descending artery: right ventricular inferior wall
  • posterior septal perforators: posterior one-third of the interventricular septum
• posterior left ventricular branches: the inferior wall of the left ventricle

Coronary dominance

Most hearts are right dominant where the PDA is supplied by the RCA. However up to 20% of hearts may be left dominant, where the PDA is supplied by the LAD or LCx or codominant, where a single or duplicated PDA is supplied by branches of both the RCA and LAD/LCx.

For a more in-depth discussion of coronary dominance, see the article coronary arterial dominance.

Variant anatomy

Variations in origin

• from the aorta at or above the sinotubular junction
• from the left coronary sinus or left coronary artery where the proximal RCA takes a 'malignant' inter-arterial course in which the vessel is prone to extrinsic compression
• in up to 50% of cases, there are separate ostia for the RCA and conus artery ² from the sinus or aorta

Variations in branching

• PDA and PLV as terminal branches
• PDA as the only terminal branch (in which the PLV is supplied by the LCx)
• terminates as an acute marginal branch (in left dominant circulations)
• Kugel's artery
  • uncommon proximal branch which communicates with either the left circumflex artery or the distal right coronary artery near the crux
• circle of Vieussens ⁸
  • anastomotic conduit between the conus artery and the left coronary circulation

Variations in course

• intra-atrial course
• inter-arterial course due to an aberrant origin 
• shepherd’s crook right coronary artery

Radiographic features

Coronary angiography

• left anterior oblique (40 degrees) views
  • the right coronary ostium, proximal, and mid-right coronary artery are well delineated
    • the long axis of the posterior descending artery is roughly parallel to the x-ray beam and will be foreshortened
    • favorable anatomy for cannulation of the RCA ostium
  • cranial angulation (25 degrees) permits superior visualization of the distal RCA
    • facilitates evaluation of the bifurcation into the posterior LV branch and PDA
• right anterior oblique (30 degrees) views
  • full length of the PDA becomes visible
    • septal perforators also conspicuous projecting vertically
  • favorable to evaluate mid-RCA and branches to the RV 

See also

• congenital coronary artery anomalies