Wikipedia
Coronary sulcus
The atria of the heart are separated from the ventricles by the coronary sulcus (also called coronary groove, auriculoventricular groove, atrioventricular groove, AV groove); this contains the trunks of the nutrient vessels of the heart, and is deficient in front, where it is crossed by the root of the pulmonary trunk. On the posterior surface of the heart, the coronary sulcus contains the coronary sinus.