Smallest right atrial veins

The smallest right atrial veins are the veins belonging to the group of smallest cardiac veins (Thebesian veins) that are minute cardiac veins that drain directly into the one of the four cardiac chambers, and in this case directly into the the right atrium. These vessels represent part of the smaller cardiac vascular system and are distinct from the larger coronary venous drainage pathways.

In the right atrium specifically, these smallest veins are particularly numerous and constitute one of three groups of right atrial venous drainage. They typically drain through short or large intramural tunnels or sinuses in the walls of the right atrial appendage and atrioventricular node area, with their generally valveless openings arranged in a circle-like pattern just above the tricuspid valve and between the openings of both venae cavae. The right atrium and right ventricle contain a greater number of Thebesian veins compared to left-sided cardiac chambers.