Coronary sinus
Sinus coronarius
The coronary sinus is the main venous channel of the heart. It is a wide vein about 2–5 cm long in the posterior part of the left atrioventricular groove that collects most of the heart's venous blood and empties it into the right atrium.
Overview
The coronary sinus continues on from the great cardiac vein. The point of transition is marked by the oblique vein of the left atrium (vein of Marshall) and a small valve (valve of Vieussens). The sinus runs to the right along the posterior AV groove and opens into the right atrium between the IVC orifice and the tricuspid orifice. Its opening is partly guarded by a semilunar flap, the Thebesian valve.
It receives the great, middle and small cardiac veins, the posterior vein of the left ventricle and the oblique vein of the left atrium. Not all cardiac venous blood passes through it. The anterior cardiac veins drain the front of the right ventricle directly into the right atrium. The venae cordis minimae (Thebesian veins) open directly into all four chambers. Those draining into the left side add a small amount of deoxygenated blood to the arterial circulation, one cause of the normal physiological shunt.
Anatomy
- Tributaries
The great cardiac vein (its continuation), the posterior vein of the left ventricle, the oblique vein of the left atrium, the middle cardiac vein and the small cardiac vein.
- Development
The coronary sinus forms from the left horn of the sinus venosus. A persistent left superior vena cava, found in about 0.3–0.5% of people, drains into it and makes it dilated.
Function
- Returns most cardiac venous blood to the right atrium.
- Provides a route for transvenous access to the left ventricle.
Clinical significance
Cardiac resynchronisation therapy
In biventricular pacing, the left ventricular lead is passed into the coronary sinus and then into a lateral cardiac vein. It paces the left ventricular free wall so that both ventricles contract together again.
Electrophysiology and surgery
The coronary sinus ostium marks the base of the triangle of Koch, which guides ablation of the slow pathway in AV nodal re-entrant tachycardia. Surgeons can also deliver cardioplegia retrogradely through the coronary sinus.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.