The right and left coronary arteries originate from the right and left sinuses of the aortic root. The right coronary artery supplies the right ventricle while the left coronary artery supplies the anterior portion of the ventricular septum and left ventricle. The left main coronary artery bifurcates into the left anterior descending artery and left circumflex artery. The left anterior descending artery supplies the majority of the left ventricle while the left circumflex artery supplies the left ventricle free wall. In approximately 70% of cases, the right coronary artery is the dominant artery supplying the posterior portions of the heart.
2. The right and left coronary arteries originate from the right and left
sinuses of Valsalva of the aortic root, respectively.
The locations of the sinuses are anatomic misnomers:
The right sinus is actually anterior in location and the left sinus is
posterior.
The myocardial distribution of the coronary arteries is somewhat
variable, but the right coronary artery (RCA) almost always supplies
the right ventricle (RV), and the left coronary artery (LCA) supplies the
anterior portion of the ventricular septum and anterior wall of the left
ventricle (LV).
3. Left Coronary Artery
Dominant left
coronary artery anatomy.
Left anterior oblique
schematic diagram of
dominant left coronary
artery anatomy, including
left anterior descending
artery and left circumflex
artery tributaries,
is shown.
AVGA = atrioventricular
groove artery,
PDA = posterior descending
artery.
4. The LCA normally emerges from the left coronary sinus as the left
main (LM) coronary artery.
The LM coronary artery is short (5–10 mm), passes to the left of and
posterior to the pulmonary trunk, and bifurcates into the left anterior
descending (LAD) and LCx arteries.
Occasionally, the LM coronary artery trifurcates into the LAD artery,
the LCx artery, and the ramus intermedius artery.
5. Left main coronary artery bifurcation.
Anterior caudal 10-mm maximum-
intensity-projection image displays
typical bifurcation of left main coronary
artery into left anterior descending and
left circumflex arteries.
Axial 10-mm MIP image shows left
main coronary artery dividing into left
anterior descending artery, left
circumflex artery, and ramus
intermedius branches.
6. The LAD artery courses anterolaterally in the epicardial fat of the
anterior interventricular groove and supplies the majority of the LV.
The major branches of the LAD artery are the diagonal and septal
perforating arteries.
The diagonal branches course laterally and predominantly supply the LV
free wall.
The septal branches course medially and supply the majority of the
interventricular septum, as well as the atrioventricular (AV) bundle and
proximal bundle branch.
7. Oblique axial (a) and vertical long-axis (b) MPR images show the normal
LAD artery (arrows) coursing in the epicardial fat of the interventricular
groove toward the LV apex.
8. Oblique axial MPR (a) and VR (b) images show the septal branches
(black arrowheads) and diagonal branches (white arrowheads) of the
LAD artery. The septal branches quickly reach and penetrate the myocardium,
whereas the diagonal branches course laterally to the LV free wall.
9. Cranial left anterior oblique 10-mm
MIP image shows left anterior
descending artery and two diagonal
branches.
Right anterior oblique 10-mm maximum-
intensity projection (MIP) image displays
left anterior descending artery and septal
perforator branches. Myocardial bridge
overlies left anterior descending artery just
beyond second septal perforator (arrows).
10. The LCx artery is the other major branch of the LCA. It courses in the
left AV groove, giving rise to obtuse marginal branches, sometimes
referred to as lateral branches.
The LCx artery and its branches supply the LV free wall and a variable
portion of the anterolateral papillary muscle.
It variably gives rise to posterolateral and posterior descending artery
(PDA) branches supplying the diaphragmatic portion of the LV.
11. Oblique axial MPR (a) and VR (b) images show the LCx artery (black
arrow) and obtuse marginal branches (white arrows).
12. In approximately 15% of patients, a third branch, the ramus
intermedius (RI) branch, arises at the division of the LCA, resulting in
a trifurcation.
When present, the RI branch courses laterally toward the LV free wall.
Its course is similar to that of a diagonal branch of the LAD artery.
13. (a) Oblique axial MPR image shows the RI branch (arrow) arising between
the LAD artery (black arrowhead) and the LCx artery (white
arrowhead), resulting in a trifurcation of the LCA.
(b) VR image shows the RI branch (arrow) arising from the trifurcation.
Black arrowhead indicates the LAD artery, white arrowhead indicates the
LCx artery.
14. The LCA and its branches can have an anomalous origin. It is
important to be aware of this possibility to avoid misinterpreting
coronary CTA.
15. Axial 10-mm MIP image reveals anomalous origin of left main
coronary artery from right cusp near origin of right coronary artery. It
then takes intraseptal course posterior to right ventricular outflow
tract near cephalad aspect of interventricular septum.
16. Right Coronary Artery
Anterior schematic
diagram of heart shows
course of dominant right
coronary artery and its
tributaries.
AV = atrioventricular,
PDA = posterior
descending artery,
RCA = right coronary
artery,
RV = right ventricular,
SA = sinoatrial.
17. The RCA normally arises from the right coronary sinus (CS) and
courses in the right AV groove toward the crux of the heart (the point
on the posterior surface of the heart where the AV groove transects the
line of the interventricular septum and interatrial septum, forming a
cross).
In approximately 50%–60% of patients, the first branch of the RCA is a
conus artery. The conus artery can also arise directly from the aorta
(30%–35% of patients).
Occasionally, the conus branch can be a branch of the LCA , have a
common origin with the RCA, or have dual or multiple branches.
The conus artery supplies the RV outflow tract (conus arteriosis) and
forms the circle of Vieussens, an anastomosis with the LAD arterial
circulation.
18. Axial 5-mm MIP image shows right
coronary artery as it arises from right
coronary cusp inferior to level of
beginning of left main coronary artery.
Axial 5-mm MIP image shows course
of right coronary artery within anterior
atrioventricular groove.
19. Left anterior oblique 5-mm maximum-
intensity projection (MIP) image shows
conus branch (arrow) as it arises separate
from right coronary artery off of right
coronary cusp.
Left anterior oblique 15-mm MIP
image shows common origin of
conus branch (arrow) and right
coronary.
20. Axial 10-mm MIP image shows
conus branch (arrow) arising from
proximal RCA. It then courses
anteriorly toward right ventricular
outflow tract.
Axial 10-mm MIP image shows
conus branch (arrow) arising from left
anterior descending artery.
21. MPR images (a, c) and VR image (b) show the RCA (black arrow in a) and its
branches.
In this case, the conus artery (arrowhead in a) arises from the aorta.
White arrow indicate the acute marginal branch,
Arrowhead in c indicates the sinoatrial nodal branch.
22. In approximately 58% of patients, the sinoatrial nodal artery arises
from the RCA within few mm of its origin ; in the remaining patients
(42%), it arises from the LCx artery.
In either case, the sinoatrial nodal artery always courses toward the
superior vena cava inflow near the cephalad aspect of the interatrial
septum.
23. Axial 10-mm maximum-intensity-projection (MIP) image shows large
sinoatrial node branch (arrow) as it arises from proximal right coronary
artery. It then courses posteriorly toward cephalad aspect of interatrial
septum (arrowheads) posterior to inflow of superior vena cava.
24. Axial 10-mm MIP image shows sinoatrial node branch
(arrow) as it arises from proximal left circumflex
artery: Sinoatrial branch still courses toward cephalad
aspect of interatrial septum.
25. As the RCA travels within the anterior AV groove, it courses
downward toward the posterior (inferior) interventricular septum.
As it does this, the RCA gives off branches that supply the RV
myocardium; these branches are called “RV marginals” or “acute
marginals”. They supply the RV anterior wall.
After it gives off the RV marginals, the RCA continues around the
perimeter of the right heart in the anterior AV groove and courses
toward the diaphragmatic aspect of the heart.
26. Right anterior oblique 10-mm maximum-
intensity-projection (MIP) image shows
large marginal branch (arrow) arising
from right coronary artery (RCA).
Right anterior oblique volume-rendered
image shows marginal branch (arrow) of
RCA as it courses over right ventricle.
27. The RCA can have an anomalous origin (i.e. Not from right
coronary sinus). It is important to be aware of this possibility to
avoid misinterpreting coronary CTA.
28. Axial 5-mm maximum-intensity-
projection (MIP) image shows anomalous
origin of right coronary artery from
anterior proximal ascending aorta with
subsequent acute rightward course before
reaching anterior atrioventricular groove.
Three-dimensional volume-rendered
projection image shows anomalous right
coronary artery in same patient as A above
level of right coronary cusp (arrow).
29. Dominance
The coronary artery that gives rise to the PDA and posterolateral
branch is referred to as the “dominant” artery, with the RCA being
dominant in approximately 70% of cases.
The LCA is dominant in approximately 10% of cases, supplying the
entire LV, accompanied by the PDA and posterolateral branches from
the LCx artery.
In the remaining cases, the RCA and LCA are codominant; that is,
portions of the LV diaphragmatic wall are supplied by both the RCA
and the LCx artery.
The length of the distal RCA is inversely proportional to the length of
the LCA along the inferior aspect of the heart. The RCA is typically
diminutive compared with the LCx artery in patients with left-dominant
systems.
30. Right dominance.
Left anterior oblique 20-mm maximum intensity- projection image
shows course of entire right coronary artery. Distally, posterior
descending artery and posterior lateral branch are shown, as is
atrioventricular node branch.
31. Left Dominance.
Axial 10-mm MIP image shows dual posterior descending
arteries and posterior lateral branches arising from LCA.
32. Codominance.
Axial 10-mm maximum intensity- projection image reveals
codominant anatomy in which posterior descending artery
arises from right coronary artery and posterior lateral branch
arises from distal left circumflex artery
33. Segmental Coronary Arterial Anatomy
A classification scheme that divides the coronary arteries into segments
based on specific anatomic structures and arterial branches.
Left Coronary Artery.—The LCA extends from the ostium to its bi- or
trifurcation.
LAD Artery.—The LAD artery is divided into proximal, middle, and
distal portions.
Proximal LAD artery extends from the left main bifurcation to the
origin of the first septal branch.
Mid portion of the LAD artery extends to coincide with the origin of
the second septal perforator.
The apical segment represents the termination of the artery.
34. LCx Artery.—The LCx artery is divided into proximal and distal
segments, based on the origin of the (usually large) obtuse marginal
branches.
Right Coronary Artery.—The proximal RCA extends from the ostium
to a point halfway to the acute margin of the heart.
The mid-RCA represents the other half of that distance.
The distal RCA courses along the posterior AV groove, from the acute
angle of the heart to the origin of the PDA.
35. Normal Coronary Artery Diameter
The average size varies with gender (approximately 3 mm in females
and 4 mm in males)
The average diameters of each coronary artery also vary, ranging from
5 mm (LCA in males) to 2 mm (PDA in females)
Focal abnormal dilatation to more than 1.5 times the diameter of an
adjacent normal coronary artery is defined as an aneurysm. If the
process is diffuse, it is known as ectasia.
