All the veins directly open into right atrium except

THE VEINS OF THE HEA These are the great cardiac vein, the middle cardiac vein, the right marginal vein, the posterior vein of the left ventricle, the oblique vein of the left atrium, the right marginal vein, the anterior cardiac veins, and the venae Cordis minimi . All veins except the last two drain into the coronary sinus which opens into the right atrium. The anterior cardiac veins and the venae cordis minimae open directly into the right atriumReference: Vishram Singh Anatomy; 2nd edition; Page no: 265