Fontan procedure is a type of open-heart surgery, used to take blood from the lower part of the body go directly to the lungs. This helps the blood pick up oxygen without having to pass through the heart.
This procedure is mainly performed in babies, to treat hypoplastic left heart syndrome, in which low oxygen blood from the lower part of the body mixes with high oxygen blood. After the Fontan procedure, low oxygen blood and high oxygen blood no longer mix. This lets the blood deliver only high oxygen blood to the body.