sentences:  The thebesian veins are most abundant in the right atrium and least in the left ventricle.They drain the myocardium and run a perpendicular course to the endocardial surface, directly connecting the heart chambers to the medium-sized, and larger coronary veins.Thebesian veins have been successfully identified by following the route of contrast flow - during catheterization procedures - from the subendocardium, through the thebesian veins, into larger veins, and into the coronary sinus.