The left coronary artery (LCA) splits into the anterior interventricular artery and the circumflex artery. The anterior interventricular artery is further divided into proximal, middle, and distal segments, while the left circumflex artery is divided into proximal and distal parts.

Anterior interventricular artery

The anterior interventricular artery (also known as the left anterior descending artery) travels inferolaterally within the anterior interventricular sulcus. It gives off the following branches on its way:

Left conus artery - supplies the outflow tract of the left ventricle;
Anterior ventricular branches - divided into right and left branches:
- Right anterior ventricular branches - small vessels, provide blood supply to a small portion of the anterior aspect of the right ventricle;
- Left anterior ventricular branches - supply the left ventricle, may give off up to seven or eight diagonal branches;
Interventricular septal branches - grouped into anterior and inferior branches:
- Anterior interventricular septal branches - supply the anterior 2/3 of the interventricular septum, as well as the atrioventricular bundle;
- Inferior interventricular septal branches - provide blood supply to the distal 1/3 of the inferior interventricular septum.

This anterior interventricular artery may terminate at the apex of the heart, but more often it continues onto the diaphragmatic surface and contacts the terminal branches of the posterior interventricular artery, which arises from the right coronary artery (RCA).

Circumflex artery

The circumflex artery (also known as the left circumflex artery, circumflex branch of the left coronary artery) takes a left course in the atrioventricular groove while being overlapped by the left auricle (left atrial appendage) and then crosses over the left border of the heart.

Branches of the circumflex artery may include the following:

Atrial branches (posterior, lateral, anterior) - arise from the proximal part of the circumflex artery and supply the left atrium;
Kugel's anastomotic artery - provides anastomotic pathways between the RCA and LCA;
Left marginal branch - supplies the lateral part of the left ventricle;
Anterior and posterior ventricular arteries - supply the left ventricle;
Sinuatrial nodal branch (arises from the circumflex artery in around 40% cases) - supplies the left atrium and the sinuatrial node.

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Branches of left coronary artery (LCA)