Left coronary artery

The left coronary artery (LCA) LCA originates from the left aortic sinus of the ascending aorta, just distal to the aortic valve. It emerges between the left auricle and the pulmonary trunk.

Branches The LCA usually divides into two main branches:

1- Paraconal interventricular branch (ramus interventricularis paraconalis, anterior interventricular artery in humans)

• Courses along the paraconal interventricular groove toward the apex of the heart

• Supplies:

  • Left ventricular free wall (cranial portion)

  • Part of the right ventricular wall

  • Interventricular septum (via septal branches)

• Gives of septal branches and ventricular (diagonal) branches to the left ventricle

2 - Circumflex branch (ramus circumflexus, circumflex artery in humans)

• Runs in the coronary groove toward the caudal aspect of the heart

• Gives some branches:

  • Atrial branches: supply the left atrium

  • Ventricular branches with the left marginal branches: supply the lateral wall of the left ventricle

  • May give rise to the subsinosal interventricular branch in left-dominant hearts.

• Supplies:

  • Left atrium

  • Caudal part of the left ventricle

In dogs, the left coronary artery typically has a short main trunk before dividing into its principal branches (or these two branches, the paraconal and circumflex, may arise directly from the left coronary ostium).

The LCA supplies (varying with the coronary dominance*):

• Most of the left ventricle

• Part of the right ventricle

• Interventricular septum (major portion)

• Left atrium

*The coronary dominance of a heart refers to the coronary artery (LCA or RCA) that perfuses the majority of the myocardial tissue and variable methods to determine this have been reported including which coronary artery supplies the subsinuosal interventricular branch, which coronary artery extends beyond the crux of the heart, the relative lengths and number of branches of the LCA or RCA, and the origination and layout of the arteries at the apex of the heart. The dog normally displays a left dominant coronary circulation , the cat is less studied but appears variable with a majority of cases indicating right coronary dominance, the rabbit is variable with predominately left coronary dominance, and the goat, swine, horse and donkey, cow, camelids, and 90% of humans are right dominant. In the mouse and rabbit, the subsinuosal interventricular branch is reported to be absent [1].