Glenn shunt

The Glenn shunt, also known as Glenn procedure,is a palliative procedure for a variety of cyanotic congenital heart disease.

Rationale

In this procedure, the systemic venous return is re-directed to the pulmonary circulation, bypassing the right heart ^1-3.

It can be used in a variety of situations, including:

• cyanotic congenital cardiac anomalies that eventually lead to a single anatomical or functional ventricle (i.e. tricuspid atresia)
• right or left ventricular hypoplasia (i.e. hypoplastic left heart syndrome)
• as an initial step before the Fontan form of a total right heart bypass

Procedure

The classic (unidirectional) Glenn shunt involved:

• ligation of the distal end of the superior vena cava (SVC)
• anastomosis of the side of the SVC above the ligation with the distal end of the divided right pulmonary artery, providing unilateral (right) lung perfusion

In a modified (bidirectional) Glenn or hemi-Fontan shunt, anastomosis is created between the transected end of the SVC and the side of the undivided right pulmonary artery, providing balanced bilateral pulmonary circulation ^1-3. 

The Glenn shunt is now considered the first stage of a complete systemic venous to pulmonary arterial anastomosis, also known as a Fontan procedure. The Fontan procedure is basically a bidirectional Glenn shunt combined with a conduit or tunnel through or around the right atrium, shunting blood from the inferior vena cava to the pulmonary arteries.

Complications

Complications of the Glenn shunt include ^2-4:

• superior vena cava (SVC)SVC syndrome
• shunt and pulmonary artery thrombosis
• stenosis of the cavopulmonary anastomosis
• sinus node injury with subsequent rhythm disturbance
• pulmonary arteriovenous malformation (AVM)
• aortopulmonary collaterals 

History and etymology

The Glenn shunt was introduced in 1958 by Dr. William Glenn and modifications to the procedure were published by Dr. Gaetano Azzolina in 1973 ^5-6.