[4][better source needed] The smallest cardiac veins vary greatly in size and number.

[5] They run a perpendicular course to the endocardial surface, directly connecting the heart chambers to the medium-sized, and larger coronary veins.

[citation needed] The small cardiac veins are responsible for venous return of 10% of the coronary blood supply.

[8][9] They are named after the German anatomist Adam Christian Thebesius, who described them in a 1708 treatise called Disputatio medica inauguralis de circulo sanguinis in corde.

[16] In his 1928 publication, Wearn himself referred to the arterio-cameral connections (vessels of Wearn) as Thebesian,[17] but later, after additional research, provided disambiguation and strictly used the term Thebesian for coronary vein-heart chamber connections.