Smallest Cardiac Veins

The smallest cardiac veins or Thebesian veins or veins of Thebesius are minute valveless veins in the walls of all four heart chambers and they are often confused with the distinct set of arterial connections, the "vessels of Wearn". They are most abundant in the right atrium and least in the left ventricle. They drain the myocardium and pass through the endocardial layer to empty mostly into the right atrium, but a few empty into the ventricles. The openings of the chambers are called the foramina venarum minimarum.

The Thebesian venous network is considered an alternative (secondary) pathway of venous drainage of the myocardium.

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.