Middle cardiac veinThe middle cardiac vein commences at the apex of the heart. It passes posteriorly along the inferior interventricular sulcus to end at the coronary sinus near the sinus' termination.StructureOriginThe middle cardiac vein commences at the cardiac apex.VariationThe middle cardiac vein has a constant location on the surface of the ventricles.Clinical significanceThe middle cardiac vein is useful for epicardial access to the inferior side of the ventricles.