Click image to view full screen

On the posterior surface of the heart the right coronary artery usually gives a branch, the posterior interventricular artery, that descends in the posterior interventricular groove toward the apex of the heart. In some individuals, the posterior interventricular artery is a branch of the
circumflex artery.

Links and References:
Grant's: 1.50, 1.51, 1.53
Netter: 204, 205, 206, 207
Rohen/Yokochi: 237, 239, 244