The Fontan procedure was first successfully performed in 1971 in a patient with tricuspid atresia,1 and has become the preferred approach for surgical palliation in patients in whom a biventricular circulation is not possible. The underlying principle is to divert the systemic venous return directly to the pulmonary arteries, thereby reducing volume overload of the single ventricle and increasing systemic oxygenation. The initial operation utilised a Glenn anastomosis with placement of valved conduits between the right atrium and ventricle and the right ventricle and pulmonary artery. The technique has undergone many modifications attempting to reduce early mortality and morbidity.
A modification that is still encountered frequently in adult patients is the connection of the right atrium to the pulmonary artery either directly or via a conduit. It had been assumed that incorporation of the pulsatile atrial chamber into the circuit would assist flow into the pulmonary circulation. In reality, atrial contraction is not essential to the maintenance of pulmonary blood flow and this approach has been shown to result in progressive atrial dilatation with increased turbulence and even flow reversal. The resultant energy loss may actually hinder flow through the Fontan pathway.2 Further, right atrial dilatation leads to additional problems such as increased thrombus formation, arrhythmias, and pulmonary vein compression.
More recent modifications have attempted to preserve laminar flow within the Fontan circuit by routing systemic venous blood either through a lateral intra-atrial tunnel to the pulmonary artery, or by direct anastomosis of the venae cava to the pulmonary artery utilising a conduit placed externally to the heart to achieve continuity with the inferior vena cava.3 These later approaches are also referred to as a total cavopulmonary circulation.