Coronary sinus

The coronary sinus is the major coronary vein. It returns the majority of the left ventricular blood flow to the right atrium.

Gross anatomy

The coronary sinus courses along the posterior wall of the left atrium into the left atrioventricular groove. It normally drains into the right atrium. The ostium of the coronary sinus is partially covered by the thebesian valve.

Veins draining into the coronary sinus are highly variable, but usually include:

• great cardiac vein
• middle cardiac vein
• small cardiac vein
• posterior vein of the left ventricle
• vein of Marshall (oblique vein of the left atrium)

Development

The coronary sinus develops from one of the two sinus horns of the sinus venosum. The other horn becomes part of the right atrium. The right venous valve of the sinus venosum develops into the thebesian valve and the Eustachian valve.

Variant anatomy

• the coronary sinus may act as a conduit between a persistent left superior vena cava and the right atrium
• rarely, the coronary sinus may drain into the left atrium, causing a left-to-right shunt (or right-to-left in cases of right heart failure)

Related pathology

The coronary sinus may be involved in a number of different procedures or pathologic processes:

• the coronary sinus is a good position for lead placement in biventricular pacing
• the coronary sinus may be an ablation target for some arrhythmia/dysrhythmias (e.g. Wolff-Parkinson-White syndrome)
• the coronary sinus rarely may have an abnormal connection to the left atrium on its way to the right atrium (unroofed coronary sinus), a rare kind of atrial septal defect
  • associated with heterotaxy syndromes and persistent left-sided SVC