patients with congenitally malformed hearts characterised by a functionally single ventricle are currently treated using several procedures that bypass the right heart, such as the fontan and hemi-fontan operations, the bidirectional cavopulmonary anastomosis, and the total cavopulmonary connection. all these options are based on the procedures introduced for palliative correction of tricuspid atresia by fontan and baudet in 1971. introduced with the purpose of reducing the pre-operative volume overload, the surgical task mainly consists of separating the pulmonary from the systemic circulation. irrespective of the specific operation performed, we can call the resulting circulation the fontan circulation.