Summary of coronary arteries

1-Left coronary artery:

-Origin: From left aortic sinus.

-It runs between  right pulmonary outflow tract anteriorly and left atrium posteriorly.

-Immediately after its origin, it becomes divided into circumflex and left anterior descending arteries.

-In 15% of cases a third branch arises in between the LAD and the Cx, known as the ramus intermedius or intermediate branch. 

2-Left anterior descending artery (LAD).

-Course: Runs across anterior inter ventricular groove giving septal branches to supply anterior part of the septum and Diagonal branches to supply antero-lateral surface of the left ventricle. It supply by itself most of the left ventricle and A-V Bundle.

-First diagonal branch acts as boundary between proximal and middle parts of LAD.

3-Circumflex artery:

-Course: Lies in the left atrio-ventricular groove and supply vessels of the lateral wall of the left ventricle.

-These vessels are known as obtuse marginals (M1, M2...), because they supply the lateral margin of the left ventricle and branch off with an obtuse angle.

- In most cases the Cx ends as an obtuse marginal branch, but 10% of patients have a left dominant circulation in which the Cx also supplies the posterior descending artery (PDA).

4-Right Coronary Artery:

-The right coronary artery arises from the anterior sinus of Valsalva and courses through the right atrioventricular (AV) groove between the right atrium and right ventricle to the inferior part of the septum.

-In 50-60% the first branch of the RCA is the small conus branch, that supplies the right ventricle outflow tract.
In 20-30% the conus branch arises directly from the aorta.

- In 60% a sinus node artery arises as second branch of the RCA, that runs posteriorly to the SA-node (in 40% it originates from the Cx).
The next branches are some diagonals that run anteriorly to supply the anterior wall of the right ventricle.
The large acute marginal branch (AM) comes off with an acute angle and runs along the margin of the right ventricle above the diaphragm.
The RCA continues in the AV groove posteriorly and gives off a branch to the AV node.
In 65% of cases the posterior descending artery (PDA) is a branch of the RCA (right dominant circulation).
The PDA supplies the inferior wall of the left ventricle and inferior part of the septum.