The Fontan procedure is used in pediatric patients who possess only a single functional ventricle, either due to lack of a heart valve, an abnormality of the pumping ability of the heart, or a complex congenital heart disease where a bi-ventricular repair is impossible or inadvisable. The single ventricle is doing nearly twice the expected amount of work because it has to pump blood for the body and lungs. Patients typically present as neonates with cyanosis or congestive heart failure. Fontan completion is usually carried out when the patient is 2–5 years of age, but is also performed before 2 years of age.
Contraindications
After Fontan completion, blood must flow through the lungs without being pumped by the heart. Therefore, children with high pulmonary vascular resistance may not tolerate a Fontan procedure. Often, cardiac catheterization is performed to check the resistance before proceeding with the surgery. This is also the reason a Fontan procedure cannot be done immediately after birth; the pulmonary vascular resistance is high in utero and takes months to drop. Fontan procedure is also contraindicated in those with pulmonary artery hypoplasia, patients with left ventricular dysfunction and significant mitral insufficiency.
Types
There are four variations of the Fontan procedure:
Ventricularization of the Right Atrium
Atriopulmonary connection
Intracardiac total cavopulmonary connection
Extracardiac total cavopulmonary connection
Approach
The Fontan is usually done as a two staged repair. The first stage, also called a Bidirectional Glenn procedure or Hemi-Fontan, involves redirecting oxygen-poor blood from the top of the body to the lungs. That is, the pulmonary arteries are disconnected from their existing blood supply. The superior vena cava, which carries blood returning from the upper body, is disconnected from the heart and instead redirected into the pulmonary arteries. The inferior vena cava, which carries blood returning from the lower body, continues to connect to the heart. The second stage, also called Fontan Kreutzer completion, involves redirecting the blood from the IVC to the lungs. At this point, the oxygen-poor blood from upper and lower body flows through the lungs without being pumped. This corrects the hypoxia and leaves the single ventricle responsible only for supplying blood to the body.
Post-operative complications
In the short term, children can have trouble with pleural effusions. This can require a longer stay in the hospital for drainage with chest tubes. To address this risk, some surgeons make a fenestration from the venous circulation into the atrium. When the pressure in the veins is high, some of the oxygen-poor blood can escape through the fenestration to relieve the pressure. However, this results in hypoxia, so the fenestration may eventually need to be closed by an interventional cardiologist. In a 2016 review, Dr. Jack Rychik, head of the Single Ventricle Survivorship Program at Children's Hospital of Philadelphia summarized the long-term consequences of Fontan circulation as an "indolent and progressive state of heart failure" with predictable long term consequences on several organ systems. Chronic venous hypertension and lowered cardiac output are assumed to be at the root of lymphatic complications such as chylothorax, protein losing enteropathy and plastic bronchitis which may occur in the immediate post-operative period as well as in the medium term. New interventional and surgical strategies have been investigated to relief the lymphatic complications associated with the Fontan circulation. Concerns about damage to the liver have emerged more recently, as the Fontan circulation produces congestion and lymphedema in this organ which leads to progressive hepatic fibrosis. Screening protocols and treatment standards are emerging in the light of these discoveries. The Fontan procedure is palliative — not curative — but in nearly 70 % of the cases it can result in normal or near-normal growth, development, exercise tolerance, and good quality of life. However, in 20–30% of cases, patients will eventually require heart transplantation and given the long-term consequences of chronic venous hypertension and insidious organ damage, freedom from morbidity is unlikely in the long term.
History
The Fontan procedure was initially described in 1971 by Dr. Francis Fontan from Bordeaux, France. Prior to this, the surgical treatment for tricuspid atresia consisted of creating a shunt between a systemic artery and the pulmonary artery or the superior vena cava and the pulmonary artery. These procedures were associated with high mortality rates, commonly leading to death before the age of one year. In an attempt to improve this, Fontan was engaged in research between 1964 and 1966 endeavouring to fully redirect flow from the superior and inferior vena cavae to the pulmonary artery. His initial attempts in dogs were unsuccessful and all experimental animals died within a few hours; however, despite these failures, he successfully performed this operation in a young woman with tricuspid atresia in 1968 with Dr Eugene Baudet. The operation was completed on a second patient in 1970, and after a third case the series was published in the international journal Thorax in 1971. Dr. Guillermo Kreutzer from Buenos Aires, Argentina without any knowledge of Fontan's experience performed a similar procedure in july, 1971 without placing a valve in the Inferior Vena Cava inlet and introducing the concept of "fenestration" leaving a small Atrial septal to serve as a pop-off valve for the circulation.
