Vein opening directly into right atrium:
Anterior cardiac veinThe anterior cardiac veins (or anterior veins of right ventricle), comprising three or four small vessels which collect blood from the front of the right ventricle and open into the right atrium.Unlike most cardiac veins, it does not end in the coronary sinus.Instead, these veins drain directly into the anterior wall of the right atrium.
Anterior cardiac vein
Middle cardiac vein
Great cardiac vein
Small cardiac vein