Cardiac anatomy from right to left

Coronary sinus

The coronary sinus is the main draining vein of the myocardium.
It runs in the atrioventricular groove on the posterior surface of the heart and enters the right atrium in the vicinity of the tricuspid valve.

Axial (left) and coronal oblique (right) reconstructions showing the coronary sinus as it enters the right atrium (blue arrows). A=anterior, P=posterior