The Fontan operation was introduced in 1971 and represented a milestone in the management of congenital heart disease with univentricular heart physiology. Even today it remains the main palliation and a life-saving procedure for children born with a functionally univentricular cardiac anatomy that is not amenable to biventricular repair. The surgical palliation consists of the separation of the systemic and pulmonary venous returns without the use of a subpulmonary ventricle. Since its original description with an atriopulmonary anastomosis, multiple modifications of the procedure have been applied.1

Today, more than 40 years after the initial procedure, we are witnessing a substantial number of adult patients living with Fontan circulation. All Fontan variants share similar physiology in which one effective ventricle delivers oxygenated blood to the systemic circulation and gradient between central venous pressure and left atrial pressure drives passively deoxygenated blood into the pulmonary arteries and the lungs. The Fontan physiology is —in part—paradoxical in that it imposes systemic venous hypertension with concomitant pulmonary …