A Fontan procedure is a palliative medical operation in which the right atrium of the heart is attached directly to the pulmonary artery, bypassing the right ventricle. This operation is normally performed on children with birth defects of the heart, including tricuspid atresia, pulmonary atresia, hypoplastic heart syndrome, single left ventricle, double outlet right ventricle, and any other single ventricle defects or congenital heart defects that leave the heart with only one functioning ventricle. The Fontan procedure allows blood to travel passively from the atrium into the pulmonary artery, which takes blood to the lungs to get re-oxygenated, instead of passing into the right ventricle, where it is pumped into the pulmonary artery. As a palliative treatment, it helps patients live with their defect, but it does not cure the condition.
A normal heart has four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. The right atrium receives de-oxygenated, “used up” blood from the body through the inferior and superior vena cava, and passes blood into the right ventricle, where it is pumped out into the pulmonary artery. The pulmonary artery takes the blood to the lungs to get re-oxygenated, and then the blood is returned to the left atrium of the heart via the pulmonary vein. The blood then passes into the left ventricle, where it is pumped out into the aorta, which delivers the oxygenated blood to the rest of the body. A Fontan procedure is performed on someone who has a defect that impairs the right ventricle, which is responsible for the vital purpose of getting blood to the lungs, where it gets re-oxygenated.
Several defects, usually caused by a developmental issue in the first eight weeks of gestation, can cause such a condition. In tricuspid atresia, the tricuspid valve that lets blood travel from the atrium to the ventricle does not form, and solid tissue is in its place. In hypoplastic left heart syndrome (HLHS), the left side of the heart fails to properly develop, so the left chambers are often small or nonexistent. Hypoplastic right heart syndrome (HRHS) is a less common condition similar to HLHS, but with right chambers defective and the left chambers functional. A child may also have single left ventricle, in which the right ventricle does not form properly and both atria connect, either through one shared valve or two separate valves, to the left ventricle.
The Fontan procedure strives to get blood to the lungs without overworking the single functioning ventricle by bypassing the right ventricle and taking blood directly from the right atrium to the right ventricle. The operation is typically done in two stages, the Hemi-Fontan, also called the bi-directional Glenn procedure, and the Fontan completion. During the Hemi-Fontan, the pulmonary arteries, which carry oxygen depleted blood from the heart to the lungs, and the superior vena cava (SVC), which takes oxygen depleted blood from the upper body to the heart, are disconnected from the heart. The SVC is the connected to the pulmonary artery, so the oxygen-poor blood flows directly to the lungs. The inferior vena cava (IVC), which carries oxygen depleted blood from the lower body to the heart, remains connected to the heart, so this blood does not get re-oxygenated.
The patient can live with just the first half of the Fontan procedure, but they often suffer from hypoxia, or insufficient oxygen in the blood supply, because the blood from the inferior vena cava isn’t being re-oxygenated. The Fontan completion redirects IVC blood flow from going to the heart, to going directly to the lungs. This allows the child to grow normally and avoid increased susceptibility to illness.
The Fontan procedure is usually performed on babies after two years of age, as infants often cannot tolerate the surgery because of high vascular resistance, or the high amount of work it takes to get blood through the circulatory system. Complications may include infection, pleural effusion, or fluid build-up in the lungs, and atrial fibrillation. These complications may require short or long-term use of medications, chest tubes, and surgery. In some cases, the Fontan procedure may not adequately improve the patient’s health and quality of life, and the patient may need a heart transplant. For many patients, however, the operation allows the child to develop properly and lead a normal, healthy life.