Coronary artery anatomy

Coronary Anatomy

1. Coronary Arteries- Normal Anatomy OSR Dr. Yash Kumar Achantani

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 .

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