Primary culprit lesion location

# Primary Culprit Lesion Location
The coronary anatomy is divided into the following defined segments for identification of the culprit artery.
- 0. None: No lesion of >50% present angiographically.
- 1. Proximal right coronary artery (R1): Extends from the ostium of the right coronary artery to the first of the three longest acute marginal branches.
- 2. Mid right coronary artery (R2): Extends from the origin of the first acute marginal branch to the origin of the third acute marginal branch.
- 3. Distal right coronary artery (R3): Extends from the origin of the third acute marginal to the origin of the posterior descending artery.
- 4. Right posterolateral artery (R4): Also called right retroventricular artery, this is the distal continuation of the right coronary artery after the origin of the posterior descending artery. It often has an inverted U shape as described by James and the AV nodal branch originates from this artery. It carries blood to the right posterior and right inferior arteries in large right dominant anatomy, to just the right inferior branch in small right dominant anatomy, and it is not present in left or balanced dominant systems.
- 5, 6, 7. Acute marginal arteries (A1, A2, A3): The longest three arteries arising from the right coronary artery to supply the right ventricular wall, numbered from proximal to distal.
- 8. Right posterior descending artery (RD): Also called right posterior interventricular artery. In all but left dominant systems, this vessel runs in the posterior interventricular groove and supplies septal perforator branches. When present, it is one of the three longest branches on the inferior wall of the heart.
- 9. Right inferior artery (RI): Arises from the fourth segment of the right coronary artery and supplies the inferior wall. In small right dominant anatomy, it is the distal most branch arising from the right coronary artery, while in large right dominant anatomy it arises proximal to the origin of the right posterior artery. When present, it is one of the three longest branches on the inferior wall of the heart.
- 10. Right posterior artery (RP): Distal most branch to arise from the right coronary artery, but present only in large right dominant systems. When present, it is one of the three longest branches on the inferior wall of the heart.
- 11. Left main (LM): Extends from the origin of the left coronary artery to the bifurcation into the left anterior descending and circumflex arteries.
- 12. Proximal left anterior descending artery (L1): Extends from the bifurcation of the left main coronary artery to the origin of the first septal.
- 13. Mid left anterior descending artery (L2): Extends from the origin of the first septal artery to the origin of the third septal artery.
- 14. Distal left anterior descending artery (L3): Extends from the origin of the third septal artery to the apex of the left ventricle. If there is no third septal branch, then the third segment begins halfway between S1 and the apex of the left ventricle.
- 15. The left anterior descending artery terminus on the inferior wall (L4): The continuation of the left anterior descending artery beyond the apex of the left ventricle in the event that the LAD is a wrap around variant.
- 16. First diagonal artery (D1): The first of the three longest branches off of the left anterior descending artery, which supplies the anterolateral wall of the left ventricle.
- 17. Second diagonal artery (D2): The second of the three longest branches off of the left anterior descending artery which supplies the anterolateral wall of the left ventricle.
- 18. Third diagonal artery (D3): The third of the three longest branches off of the left anterior descending artery which supplies the anterolateral wall of the left ventricle. In an RAO projection, this artery often arises where the left anterior descending angles toward the apex.
- 19, 20, 21. Septal arteries (S1, S2, S3): The three largest branches off of the left anterior descending supplying the septum.
- 22. Median Ramus (MR): Also called Intermedius Ramus. An artery whose origin bisects the origins of both the left anterior descending artery and the circumflex artery. When a median ramus branch is present, the left main will be seen to trifurcate in the LAO caudal projection, and the median ramus artery is the middle artery at this point of trifurcation. When grouping with general culprit lesion location it is grouped with the LCx unless trial protocol states otherwise.
- 23. Proximal circumflex artery (C1): Extends from the origin of the circumflex off of the left main to the origin of the first marginal or obtuse marginal branch. When a second obtuse marginal is present and the first marginal is absent, the C1  C2 transition is defined as halfway from the origin of the circumflex to the origin of the second obtuse marginal.
- 24. Mid circumflex artery (C2): Extends from the origin of the first marginal or obtuse marginal branch to the origin of the second marginal or obtuse marginal branch. When a second obtuse marginal is present and the first marginal is absent, the C1  C2 transition is defined as halfway from the origin of the circumflex to the origin of the second obtuse marginal. When a first obtuse marginal is present and the second marginal is absent, the C2  C3 transition is defined to be halfway from the first obtuse marginal to the end of C3.
- 25. Distal circumflex artery (C3): Extends from the origin of the second marginal or obtuse marginal to the termination of the circumflex artery in large right dominant anatomy or to the origin of the circumflex posterior branch (CP) in all other dominance.
- 26. Left posterolateral artery (C4): In left dominant or balanced systems this is the distal continuation of the circumflex artery in the atrio-ventricular groove. It carries blood to the left posterior descending artery and circumflex inferior artery in left dominant systems and to just the circumflex inferior artery in balanced dominant systems.
- 27. Circumflex posterior artery (CP): In all but large right dominant anatomy, this branch originates at the distal end of the third segment of the circumflex at the border of the inferior and lateral left ventricular walls where it traditionally has been called a 4th marginal branch. When present, it is one of the three longest branches supplying the inferior wall of the heart.
- 28. Circumflex inferior artery (CI): Arises from the junction between C3 and C4 and supplies the inferior wall. In balanced dominant anatomy, it is the distal most branch arising from the circumflex, while in left dominant anatomy it arises proximal to the origin of the left posterior descending artery. When present, it is one of the three longest branches on the inferior wall of the heart.
- 29. Left posterior descending artery (CD): In left dominant systems this is the distal continuation of the left circumflex artery which travels in the interventricular groove and supplies septal perforators at the base of the heart. This branch is the distal continuation of the circumflex after it leaves the atrio-ventricular groove in left dominant anatomy. When present, it is one of the three longest branches on the inferior wall of the heart.
- 30, 31, 32. Marginal arteries (M1, M2, M3): The three longest branches off of the circumflex artery supplying the lateral wall of the left ventricle, unless there is a large branching vessel which dominates the lateral left ventricular wall. When a large dominating artery is present, it is called an obtuse marginal. These marginal arteries are numbered from one (proximal) to three (distal).
- 33, 37, 41. Obtuse marginal arteries (OM1-OM3): A large branching artery which dominates the lateral left ventricular wall. An obtuse marginal is composed of anterior and posterior branches which share a common trunk. The anterior and posterior branches may substitute for the first and second marginal branches (or the second and third marginal branches), although a first (or third) marginal is permitted if present. No more than a single obtuse marginal may be present. An obtuse marginal is further specified as OM1, OM2, or OM3 depending on where the trunk arises compared to the usual origins of the first, second, and third marginal arteries.
- 36, 40, 44. Obtuse marginal trunk (OT): The common trunk of an artery connecting the anterior and posterior branches of an obtuse marginal to the circumflex. As no more than a single obtuse marginal may be present, the OT is not numbered.
The 36 corresponds with OM1/OT, the 40 with OM2/OT, the 44 with OM3/OT.
- 34, 38, 42. Anterior branch of the obtuse marginal artery (OA): The anterior branch of an artery when it is a large branching vessel which dominates the lateral left ventricular wall. As no more than a single obtuse marginal may be present, the OA is not numbered.
The 34 corresponds with OM1/OA, the 38 with OM2/OA, the 42 with OM3/OA.
- 35, 39, 43. Posterior branch of the obtuse marginal artery (OP): The posterior branch of an artery when it is a large branching vessel which dominates the lateral left ventricular wall. As no more than a single obtuse marginal may be present, the OP is not numbered.
The 35 corresponds with OM1/OP, the 39 with OM2/OP, the 43 with OM3/OP.
- 45. Saphenous Vein Graft to the LAD: (SVGLAD)
- 46. Saphenous Vein Graft to Circumflex: (SVGCX)
- 47. Saphenous Vein Graft to the Right Coronary Artery: (SVGRCA)
- 48. Saphenous Vein Graft to the PDA: (SVGPDA)
- 49. Saphenous Vein Graft to the Obtuse Marginal: (SVGOM)
- 50. Saphenous Vein Graft to Diagonal: (SVGD)
- 51. Left Internal Mammary Artery to the Left anterior descending artery: (LIMA)
- 52. Right Internal Mammary Artery to the Left anterior descending artery: (RIMA)

# Definitions of Segmental Coronary Anatomy
- 1. If a lesion occurs at a branchpoint, then the lesion is said to be part of the proximal vessel adjacent to the branchpoint.
- 2. If the lesion involves both parent vessel and a sidebranch at a branchpoint (such as occurs with a trifurcation lesion or Mercedes Benz emblem lesion involving the LAD and the origin of a diagonal) then the larger parent vessel is defined as the culprit.