The middle cardiac vein commences at the apex of the heart.

It passes posteriorly along the inferior interventricular sulcus to end at the coronary sinus near the sinus' termination.

[1] The middle cardiac vein commences at the cardiac apex (here, it is contiguous with the great cardiac vein, thus forming - along with the coronary sinus - a complete venous circle).

[1] The middle cardiac vein has a constant location on the surface of the ventricles.

[2] The middle cardiac vein is useful for epicardial access to the inferior side of the ventricles.