The great cardiac vein is the largest of the veins draining into the coronary sinus from the myocardium. It commences near to the apex of the heart in the anterior part of the interventricular groove. It passes superiorly in the company of the anterior interventricular artery. At the junction of the interventricular groove with the atrioventricular groove, it enter the latter and passes to the left in the company of the circumflex artery. It passes over the left border of the heart within the atrioventricular groove to merge with the left end of the coronary sinus.
The great cardiac vein drains the territory supplied by the left coronary artery e.g. the left atrium and ventricle.