Fontan circulation

Fontan circulation


Classic Fontan repair was an atriopulmonary connection with anastomosis of right atrial appendage to the pulmonary artery which is no longer used. Currently the term Fontan repair is used to univentricular repairs diverting systemic venous blood flow to the pulmonary artery. This unloads the single ventricle from a volume overload at the expense of an increase in the systemic venous pressure which drives the blood flow into the pulmonary circulation for oxygenation. Fontan repair is considered in all those with a functionally single ventricle and combines a bidirectional Glenn procedure with a connection of the inferior vena cava to the pulmonary artery. This connection can be either using a lateral tunnel within the atrium or with an extra cardiac conduit. A fenestration may be created between the tunnel and the pulmonary atrium if undue elevation of systemic venous pressure is considered likely. This trades off systemic desaturation with systemic venous congestion. The repair is also known as TCPC or total cavopulmonary connection.

Clinical findings post Fontan repair

Clinical finding in a post Fontan person may be an elevated jugular venous pressure which is non pulsatile, though a prominent a wave has also been described. Second sound is single and often accentuated and murmurs are usually absent.

Stages of Fontan repair

Fontan repair is usually done in a staged manner. A palliative procedure is done in the neonatal period to prepare the pulmonary arteries. If there is severe pulmonary stenosis, a systemic to pulmonary artery anastomosis like a Blalock-Taussig shunt is done to favour the growth of the pulmonary arteries. Pulmonary artery banding is done in case of unrestricted pulmonary flow. Balloon atrial septostomy may also be done if indicated.
Second stage of palliation is usually between four to twelve months of age and consists of a bidirectional Glenn procedure with end-to-side anastomosis of the superior vena cava to the right pulmonary artery. The final Fontan procedure or TCPC is planned between the ages of one to five years.

Fontan failure

If the Fontan fails leading to decreased exercise tolerance or recurrent atrial tachycardia in case of lateral tunnel due to atrial scarring, a revision of the circuit to an extracardiac conduit with a maze procedure may be the option. Final option is of course, cardiac transplantation. Though the extracardiac conduit avoids atrial scarring and long term arrhythmias, in a child it has the disadvantage of lack of growth. Extracardiac conduits are also more prone for thrombosis.

Late complications of Fontan

Ideal candidates taken for Fontan procedure has a reported survival of over eighty percent at ten years. Late complications other than atrial reentrant tachycardia are thrombotic events, right atrial dilatation with hepatic dysfunction, protein losing enteropathy and pulmonary arteriovenous malformations. Pulmonary arteriovenous malformations occur mainly when the hepatic outflow does not reach the lungs as in Glen procedure without a TCPC so that the hepatic angiogenesis inhibiting factor does not reach the lung. Other reported complications include obstructions or leaks in the Fontan circuits, myocardial dysfunction, systemic venous collateralization, sinus node dysfunction following extensive atrial dissection during repair and plastic bronchitis. Plastic bronchitis is characterised by marked obstruction of the large airways due to the formation of bronchial casts with rubber like consistency. Elevated central venous pressure leading to endobronchial lymph leakage is thought to be the mechanism of plastic bronchitis in post Fontan state.

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