CORONARY CIRCULATION ANATOMY
Drawing of the Heart and its Blood Vessels, from the Anatomical Notebooks, Leonardo da Vinci, Bibliotecha Ambrosiana, Milan, Italy, Late Fifteenth Century.

CORONARY CIRCULATION ANATOMY
Introduction
Most textbook descriptions of the coronary circulation are traditionally based on views and perspectives obtained directly from specimens. As such there has been an emphasis on landmarks that are visible on the gross specimen.
These landmarks however are not easily recognizable on traditional cine radiographic images.
When studying a cine arteriogram, however, a physician uses an entirely different set of reference points and is less inclined to emphasize landmarks that are seen only on the gross specimen.
Because these anatomic landmarks are not easily recognized with traditional arteriography, clinicians have adopted slightly different nomenclature to describe normal coronary anatomy.
1
Cardiac computed tomography (CT) provides detailed anatomic information, but its use requires a firm understanding of gross coronary anatomy. Furthermore, detailed appreciation of the “normal” origin, course, branching, adjacent structures, and myocardial distribution of these vessels is vital so that variations of the “normal” anatomy can be more easily recognized and applied to clinical practice.
The following gives a general description of the coronary circulation.
It should be noted however that the coronary artery anatomy has great individual variability. The arteries vary in size, length, course, and branches. It is therefore important to understand the individual anatomy of a patient in order not to mistakenly report disease or occlusion of an artery.
Dominance of the Left and Right Circulations
There are many variations of “normal” that are not considered “anomalous” in the coronary circulation.
As a result, the concept of dominance has been adopted into the clinical vernacular to describe which artery (the left or the right coronary) gives rise to:
●
The posterior descending artery ( PDA ) and the
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Posterolateral artery ( PLA ) and the

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Atrioventricular ( AV ) nodal artery which, in turn, supply the inferior aspect of the interventricular septum, the inferior aspect of the left ventricle, and the AV node, respectively.
If these arteries originate from the right coronary artery ( RCA ), the circulation can be classified as
“right-dominant”
(Figure 1 below)
Alternatively, if they are supplied by the left circumflex artery ( LCx ), the circulation can be classified as
“left dominant”
(Figure 2 below).
Left: Shows a Right Dominant Coronary Circulation. Right: Shows a Left Dominant
Coronary Circulation.
Coronary Artery Branch Nomenclature
Generally accepted abbreviations for the branch vessels of the coronary circulation are as follows:
The main coronary braches:
LMCA: Left Main Coronary Artery:
●
LCx: Left Circumflex Artery

RCA:
●
LAD: Left Anterior Descending Artery
Right Coronary Artery.
The named lesser branches of the coronary vessels:
Branches of the LAD:
The LAD is, for practical purposes, is really just a continuation of the left main artery, after it has given off the LCx artery.
The Septal branches:
These are branches that travel deep into the interventricular septum and come off in order as:
●
●
Septal 1
Septal 2
(S1)
(S2)
●
Septal 3 (S3)
The Diagonal branches:
These come off in order as:
●
●
●
Diagonal 1
Diagonal 2
Diagonal 3
(D1)
(D2)
(D3)
Clinicians to more accurately describe the location of an LAD artery lesion, divide the
LAD into 3 segments: proximal LAD (from origin to D1), mid LAD (from D1 to D2), and distal LAD (beyond D3)
Branches of the Left Circumflex Artery:
This is a true branch of the LMCA, coming off at virtually right angles to it.
●
●
In front of the heart, The Obtuse Marginal branches:
These come off in order as:
First Obtuse Marginal (OM1)
Second Obtuse Marginal (OM2)

●
Third right Obtuse Marginal (OM3)
Clinicians to more accurately describe the location of a circumflex artery lesion, divide the circumflex artery into 3 branches: proximal circumflex (from ostium OM1), mid circumflex (between OM1 and OM2), and distal circumflex (from the OM2 to the crux).
Behind the heart the Left Circumflex gives off the Left Posterolateral branches:
●
Left Posterolateral branch 1 (LPL1)
●
●
Termination:
●
Left Posterolateral branch 2 (LPL2)
Left Posterolateral branch 3 (LPL3)
In left dominant circulations, terminates at the crux to become the
Descending Artery (LPDA)
Left Posterior
Branches of the Right Coronary Artery:
2 Proximal branches:
●
●
Sinoatrial (SA) Nodal artery
Conus artery
The Right Marginal branches:
In front of the heart, these come off in order as:
●
First right marginal (RM1)
●
●
Termination:
●
Second right marginal (RM2)
Third right marginal (RM3)
In right dominant circulations, gives off the
(RPDA)
Right Posterior Descending Artery
Continues on behind the heart to give off Right Posterolateral branches:
●
●
Right Posterolateral branch 1
Right Posterolateral branch 2
(RPL1)
(RPL2)

●
●
●
●
●
Right Posterolateral branch 3 (RPL3)
Clinicians to more accurately describe the location of an RCA lesion, divide the RCA into proximal RCA (ostium to RM1), mid RCA (RM1 to RM2), and distal RCA (RM2 to the crux) (See Appendix 1 below).
Normal Calibers of the Major Coronary Vessels
LMCA:
LAD:
LCx :
4.5 ± 0.5 mm
3.7 ± 0.4 mm
3.5 ± 0.5 mm (4.2 mm when dominant)
RCA: 3.9 ± 0.6 mm (2.8 mm when non-dominant)

Appendix 1
Diagram illustrating the proximal, mid, and distal segments of the right coronary artery.

References
1. Fiss D.M; Normal coronary anatomy and anatomic variations. Supplement to
Applied Radiology, January 2007. www.appliedradiology.com
Dr J. Hayes
October 2012.