The smallest cardiac veins (also known as the Thebesian veins (named for
Adam Christian Thebesius)) are small, valveless
veins in the walls of all four
heart chambers[1] that drain venous blood from the
myocardium[2] directly into any of the heart chambers.[3]
The smallest cardiac veins vary greatly in size and number. Those draining the right atrium have a lumen of up to 2 mm in diameter, whereas those draining the right ventricle have lumens as small as 0.5 mm in diameter.[5]
Course
They run a perpendicular course to the endocardial surface, directly connecting the heart chambers to the medium-sized, and larger coronary veins.[6]
Openings
The openings of the smallest cardiac veins are located in the
endocardium. Here the smallest cardiac veins return
blood into the
heart chambers from the
capillary bed in the muscular cardiac wall, enabling a form of collateral circulation unique to the heart. Not every endocardial opening connects to the smallest cardiac veins, as some connect to the vessels of Wearn, which are arteries. Therefore, the endocardial opening must be traced to a vein before it is definitely called an opening of the smallest cardiac veins.[citation needed]
Function
The small cardiac veins are responsible for venous return of 10% of the coronary blood supply.[7] The small cardiac venous network is considered an alternative venous drainage of the
myocardium. The smallest cardiac veins draining into the left heart, along with deoxygenated blood originating from the
bronchial veins draining into the
pulmonary veins, contribute to normal physiologic
shunting of blood. As a consequence of the input of these vessels, blood in the left heart is less oxygenated than the blood found at the pulmonary capillary beds, usually to a very small degree.
History
Etymology
The smallest cardiac veins are also known as the Thebesian veins.[8][9] They are named after the German
anatomistAdam Christian Thebesius, who described them in a 1708 treatise called Disputatio medica inauguralis de circulo sanguinis in corde.[10][11]
Mislabelling
The smallest cardiac veins are sometimes accurately referred to as vessels, but they are frequently confused with a distinct set of
artery connections,[12][13][14][15] eponymously referred to as the "vessels of Wearn".[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.[18]
^Singhal, S; Khoury, S (2008). "Images in clinical medicine. Imaging of thebesian venous system". The New England Journal of Medicine. 359 (7): e8.
doi:
10.1056/nejmicm072885.
PMID18703466.
^Thebesius, AC (1708). Disputatio medica inauguralis de circulo sanguinis in corde. Doctoral dissertation, Leiden.
^Boeder, NF; Nef, HM; Bauer, T (2016). "Thebesian veins as drainage to the ventricle: A case report". Cardiovascular Revascularization Medicine. 18 (3): 213–214.
doi:
10.1016/j.carrev.2016.09.007.
PMID27743821.
^Grollman, JH Jr (1998). "Re: three major coronary artery-to-left ventricular shunts". CardioVascular and Interventional Radiology. 21 (2): 183.
doi:
10.1007/s002709900240.
PMID9502691.
S2CID40212007.