The great cardiac vein is the main tributary of the coronary sinus. Its first part, the anterior interventricular vein, begins near the apex of the heart and ascends with the anterior interventricular branch of the left coronary artery. At the coronary sulcus, it turns left and its second part runs around the left side of the heart with the circumflex branch of the left coronary artery to reach the coronary sinus. The great cardiac vein drains the areas of the heart supplied by the left coronary artery.