Originally described in the late 1960s, the Fontan procedure is used to separate the oxygen-poor (blue) blood from the oxygen-rich (red) blood in patients with single ventricle defect. Many modifications have been performed in the last 10-15 years, including direct connections of the atrium to the pulmonary artery, tunneling of the inferior vena cava inside the heart (lateral tunnel, or total cavopulmonary connection), or conduit insertion from the inferior vena cava to the pulmonary artery ("extracardiac Fontan"). A small hole may be intentionally left in this connection ("fenestrated Fontan").