Fontan procedure

The Fontan procedure or Fontan–Kreutzer procedure is a palliative surgical procedure used in children with univentricular hearts. It involves diverting the venous blood from the inferior vena cava (IVC) and superior vena cava (SVC) to the pulmonary arteries without passing through the morphologic right ventricle; i.e., the systemic and pulmonary circulations are placed in series with the functional single ventricle. The procedure was initially performed in 1968 by Francis Fontan and Eugene Baudet from Bordeaux, France, published in 1971, simultaneously described in 1971 by Guillermo Kreutzer from Buenos Aires, Argentina, and finally published in 1973.

Indications

The Fontan Kreutzer procedure is used in pediatric patients who possess only a single functional ventricle, either due to lack of a heart valve (e.g. tricuspid or mitral atresia), an abnormality of the pumping ability of the heart (e.g. hypoplastic left heart syndrome or hypoplastic right heart syndrome), or a complex congenital heart disease where a bi-ventricular repair is impossible or inadvisable. The surgery allows blood to be delivered to the lungs via central venous pressure rather than via the right ventricle. 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 Kreutzer 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 (The original Fontan's Technique)
* Atriopulmonary connection (the original Kreutzer's Technique)
* Intracardiac total cavopulmonary connection (lateral tunnel) (described by Marc De Leval and Aldo Castañeda, separately)
* Extracardiac total cavopulmonary connection (described by Carlo Marceletti and Francisco Puga for Heterotaxy Syndrome)

Approach

The Fontan is usually done as a two staged repair.

The first stage, also called a ''Bidirectional Glenn procedure'' or ''Hemi-Fontan'' (see also Kawashima procedure), 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 (e.g. a Blalock Taussig or a Sano shunt created during a Norwood procedure, a patent ductus arteriosus or a pulmonary artery banding). The superior vena cava (SVC), which carries blood returning from the upper body, is disconnected from the heart and instead redirected into the pulmonary arteries. The inferior vena cava (IVC), 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 (driven only by the pressure that builds up in the veins). 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 (fluid building up around the lungs). 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 relieve 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 and other complications of Fontan-Associated Liver Disease. Screening protocols and treatment standards are emerging in the light of these discoveries.

The Fontan procedure is palliative — not curative — but more than 80% of the cases can result in normal or near-normal growth, development, exercise tolerance, and good quality of life. However, 10% or more of patients may 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. New approaches to the management of failing Fontans or other clinical deterioration have included lymphatic decompression surgical procedures & intervention, Ventricular assist devices or other mechanical support therapies as either bridge to transplantation or destination therapies.

Because of structural and electrochemical changes related to scarring after the procedure, arrhythmias are common. Pacemakers are placed in as many as 7% of patients who undergo the Fontan procedure. While the need for pacemakers may be related to the underlying cardiac anomaly, there is sufficient evidence that the surgery itself lead to the need for cardiac pacing.

History

The Fontan procedure was initially described in 1971 by Dr. Francis Fontan (1929–2018) 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 ( Blalock-Taussig shunt) or the superior vena cava and the pulmonary artery (Glenn shunt). 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 (b. 1934) 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 defect to serve as a pop-off valve for the circulation.

References

External links

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{{DEFAULTSORT:Fontan Procedure
Cardiac surgery
Congenital heart defects
Pediatric surgical procedures
Thoracic surgical procedures