Fontan Procedure

Introduction

If your child has been recommended for the Fontan procedure, or has already had it, you are part of a long and carefully planned treatment journey. Most families reading this have spent years inside the world of pediatric cardiology — scans before birth, surgery in the first weeks of life, a second surgery in infancy, and now a third operation that completes the staged pathway. The Fontan is rarely a surprise. It is the planned destination that the earlier surgeries were preparing for.

The Fontan procedure is the final stage of surgical management for children born with a heart that has only one effective pumping chamber, a group of conditions called single-ventricle physiology. It does not rebuild the heart into a normal two-pump heart — that is not possible when one ventricle is too small or absent. Instead, it creates a different way for blood to circulate, one that allows the single ventricle to focus on pumping oxygen-rich blood to the body while oxygen-poor blood flows passively to the lungs.

This guide is written for parents. It explains what the Fontan procedure is, where it sits within the wider staged pathway, what happens during surgery and in the intensive care unit afterwards, what recovery looks like at home, and — just as importantly — what life with Fontan circulation involves over the years and decades that follow. Children who have had a Fontan today are growing up, going to school, playing, and reaching adulthood in greater numbers than ever before. They also need careful, lifelong follow-up with cardiologists who understand single-ventricle hearts.

What Is the Fontan Procedure?

The Fontan procedure is an open-heart operation that connects the large veins returning blood from the body directly to the arteries leading to the lungs, bypassing the heart on the return side of the circulation. After a Fontan, blood flows from the body to the lungs without being pumped — it moves passively, driven by pressure differences and the mechanics of breathing.

To understand why this is needed, it helps to picture how a normal heart works. A healthy heart has two pumping chambers, called ventricles. The right ventricle pumps oxygen-poor blood from the body to the lungs. The left ventricle pumps oxygen-rich blood from the lungs to the body. The two circulations run side by side, separated.

In single-ventricle conditions, only one of these ventricles can do its job properly. The other is too small, missing, or structurally unable to pump effectively. Without surgery, oxygen-rich and oxygen-poor blood mix inside the heart, and the single working ventricle has to do twice the work. Babies with these conditions are often visibly blue (cyanotic), and the heart tires under the strain.

The Fontan rearranges the plumbing so that the two streams of blood — oxygen-poor blood from the body and oxygen-rich blood from the lungs — no longer mix. The single ventricle pumps only oxygen-rich blood to the body, and oxygen-poor blood from the body travels straight to the lungs through the new connections. The resulting circulation is called Fontan circulation or Fontan physiology, and the heart and body adapt to it over time.

The Staged Pathway: Where the Fontan Fits

Stage 1: The Newborn Operation

In the first days or weeks of life, babies with single-ventricle conditions usually need an early operation to balance the blood flow between the body and the lungs. The exact procedure depends on the underlying defect. For babies with hypoplastic left heart syndrome, this is typically the Norwood procedure. For other conditions, it may be a shunt operation (such as a modified Blalock-Taussig-Thomas shunt) or a band placed around the pulmonary artery to control lung blood flow. The goal at this stage is survival and stable oxygen levels, not a finished result.

Stage 2: The Glenn or Hemi-Fontan

Between roughly four and six months of age, most children have a second operation called the bidirectional Glenn (or, in some centres, the hemi-Fontan). In this operation, the superior vena cava — the large vein bringing blood back from the head and upper body — is disconnected from the heart and joined directly to the pulmonary artery. From this point on, blood from the upper body flows passively to the lungs.

After the Glenn, the single ventricle does less work, oxygen levels usually improve, and the lung blood vessels are protected from high pressure. The lower half of the body, however, still drains into the heart and mixes with the oxygen-rich blood, so the child remains somewhat blue.

Stage 3: The Fontan Completion

The Fontan procedure completes the rearrangement begun by the Glenn. The inferior vena cava — the large vein bringing blood back from the lower body — is also redirected to the pulmonary artery. After the Fontan, all oxygen-poor blood from both the upper and lower body flows to the lungs without passing through the heart. The single ventricle now pumps only oxygen-rich blood to the body.

The Fontan is usually performed between the ages of two and four years, though the exact timing depends on the child’s growth, oxygen levels, ventricular function, and the pressures and anatomy of the lung blood vessels. Some centres prefer slightly earlier or later timing based on local experience.

Conditions Treated with the Fontan Pathway

The Fontan pathway is used for a range of complex congenital heart defects in which only one ventricle can pump effectively. These include:

• Hypoplastic left heart syndrome (HLHS) — the left ventricle and structures on the left side of the heart are severely underdeveloped.
• Tricuspid atresia — the valve between the right atrium and right ventricle did not form, and the right ventricle is usually small.
• Pulmonary atresia with intact ventricular septum — the valve from the right ventricle to the lungs is closed, and the right ventricle is often too small to use.
• Double inlet left ventricle — both atria empty into a single ventricle.
• Unbalanced atrioventricular septal defect — the central valves and walls of the heart did not form evenly, leaving one ventricle dominant.
• Other complex single-ventricle anatomies, including some forms of heterotaxy syndrome and double outlet right ventricle with unbalanced ventricles.

In each of these conditions, the cardiac team makes an early decision about whether two-ventricle repair is possible. When it is not, the staged single-ventricle pathway — ending in the Fontan — becomes the plan.

Who Is a Candidate for the Fontan?

Not every child with single-ventricle anatomy is suited to a Fontan completion at every point in time. Before recommending the Fontan, the cardiac team performs a detailed evaluation to confirm that the child’s circulation is ready. The key factors they assess include:

• Pulmonary artery pressure and resistance. Because blood will flow through the lungs without a pump, the lung blood vessels must be low-pressure and relaxed. High pulmonary pressure is one of the strongest reasons to delay or avoid the Fontan.
• Ventricular function. The single ventricle must squeeze well and relax well between beats. Weak or stiff ventricles raise the risk of Fontan failure.
• Valve function. The valve guarding the single ventricle (the atrioventricular valve) should not leak heavily. Significant leakage may need to be addressed at the time of surgery.
• Anatomy of the pulmonary arteries. The arteries to both lungs should be well-grown and free of narrowing.
• General health. Adequate growth, good nutrition, absence of active infection, and stable lung function all matter.

This assessment usually involves echocardiography, cardiac catheterisation (a study in which thin tubes are passed into the heart to measure pressures), and often cardiac MRI or CT. The cardiac catheterisation in the months before the Fontan is one of the most important tests, because it gives direct measurements of pulmonary pressures that scans cannot provide.

Alternatives and Decisions Along the Pathway

For a child with single-ventricle anatomy who has already had a Norwood and a Glenn, there are essentially three forward paths: completing the Fontan, remaining at the Glenn stage indefinitely, or considering heart transplantation. The cardiac team weighs these options based on the child’s individual heart and circulation.

• Fontan completion is the standard final step for children whose evaluation shows favourable pulmonary pressures and ventricular function. It separates the circulations and usually improves oxygen levels significantly.
• Staying at the Glenn stage may be considered if pulmonary pressures or ventricular function are not favourable enough for a successful Fontan. Some children remain at this stage for a long time while the team monitors and tries to improve the factors that are limiting them.
• Heart transplantation may be considered when neither completing nor maintaining the Fontan offers a good long-term outlook — for example, when ventricular function is very poor, or later in life if Fontan circulation begins to fail.

The choice between these is a clinical decision made together by the cardiology and surgical teams in conversation with the family, based on detailed studies of the child’s heart.

Types of Fontan Operation

Extracardiac Conduit Fontan

In the extracardiac Fontan, the surgeon places a tube-shaped graft (the conduit) outside the heart, connecting the inferior vena cava to the pulmonary artery. The advantage of this approach is that very little surgery is done inside the heart itself, which may reduce the risk of certain types of abnormal heart rhythms later in life. It is currently the most common modern technique.

Lateral Tunnel Fontan

In the lateral tunnel Fontan, a patch is sewn inside the right atrium to create a channel that directs blood from the inferior vena cava to the pulmonary artery. Part of the wall of the right atrium forms one side of this tunnel. The lateral tunnel can grow somewhat with the child, which is one reason some centres prefer it.

Fenestration

In either approach, the surgeon may create a small opening — a fenestration — between the new Fontan pathway and the heart itself. This acts as a pressure release valve in the early weeks after surgery. If pressures in the Fontan circuit rise too high, a small amount of blood can escape across the fenestration, keeping the system stable. Fenestrations often close on their own or are closed later in a catheterisation procedure once the circulation has settled. Whether or not to fenestrate is a decision the surgical team makes based on the child’s risk profile.

Preparing for the Fontan

Preparation for the Fontan happens over months rather than days. By the time surgery is scheduled, the cardiac team has built a detailed picture of the child’s circulation. In the weeks leading up to the operation, families can expect:

• A pre-Fontan cardiac catheterisation to measure pulmonary artery pressures and check the anatomy. Sometimes interventions such as opening narrowed vessels are done during this same study.
• Echocardiography and often cardiac MRI to assess ventricular function, valve function, and the size of the pulmonary arteries.
• Blood tests including liver and kidney function, blood counts, and clotting studies.
• Dental and infection screening, because any source of infection in the body can become serious in the perioperative period.
• Nutritional assessment, since adequate weight gain and protein levels improve healing.
• Vaccinations brought up to date well before surgery.
• Detailed consultations with the surgeon and cardiologist, in which the operation, the early recovery, and the long-term outlook are explained.

Parents are usually asked to stop certain medications before surgery and given specific fasting instructions for the night before. The surgical and anaesthetic teams will walk you through these details.

What Happens During the Operation

1. Anaesthesia and monitoring. Your child is given anaesthetic medication and connected to monitors that track heart rhythm, blood pressure, oxygen levels, and brain activity. Intravenous lines are placed.
2. Chest access. The surgeon opens the chest through the breastbone (sternum), usually along the same incision line as the previous surgeries.
3. Cardiopulmonary bypass. In many cases, the heart and lungs are temporarily supported by a heart-lung machine while the new connections are made. Some centres are able to perform parts of the operation without the heart-lung machine, depending on technique and anatomy.
4. Creating the Fontan connection. Either a conduit (extracardiac approach) or a tunnel inside the heart (lateral tunnel approach) is constructed to route blood from the inferior vena cava to the pulmonary artery.
5. Fenestration, if planned. A small opening between the new pathway and the heart is created if the team has decided this is appropriate.
6. Additional repairs, if needed. Sometimes the surgeon also repairs a leaking valve, enlarges a narrowed pulmonary artery, or addresses other issues at the same time.
7. Coming off bypass and closing. Once the new circulation is working and the team is satisfied with pressures and function, the heart-lung machine is gradually withdrawn. Drainage tubes are placed to remove fluid from around the heart and lungs, and the chest is closed.

Recovery in the Hospital

The Intensive Care Phase

The first days after a Fontan are spent in the PCICU, where children are monitored closely as the new circulation adapts. The team focuses on keeping the pressures in the Fontan circuit low, ensuring blood flows easily through the lungs, and managing fluid balance carefully.

In the early hours, your child will usually be supported by a breathing machine (ventilator). Coming off the ventilator is an important early step because spontaneous breathing actually helps draw blood through the Fontan pathway. The team will often extubate (remove the breathing tube) earlier than after other heart surgeries for this reason.

Chest drains remove fluid from around the lungs and heart. Some fluid leakage is expected. When drainage stays high for many days — called prolonged pleural effusions — it is one of the most common reasons hospital stays after a Fontan are longer than after other heart surgeries.

Other features of this phase include:

• Careful management of intravenous fluids to avoid both dehydration and overload.
• Pain control with appropriate medications.
• Anticoagulation (blood thinning), usually starting in the first days after surgery, because the slow-moving Fontan circulation has a higher tendency to form clots.
• Gradual reintroduction of feeding.
• Early mobilisation as soon as it is safe, because movement helps blood flow through the new circuit.

Most children spend several days to about a week in the PCICU, followed by additional time on the cardiac ward. The total hospital stay after a Fontan is commonly around two to three weeks but can be longer if drainage persists or other issues arise.

Going Home

Before discharge, the team will confirm that oxygen levels are stable, drainage has settled, feeding is going well, and your child is comfortable on oral medications. You will be given:

• A schedule of medications, often including a blood thinner, diuretics, and sometimes a medication to help the heart pump or relax.
• Guidance on wound care for the chest incision.
• Activity restrictions, particularly avoiding chest-strain activities for several weeks while the breastbone heals.
• Warning signs that should prompt a call to the cardiac team or a return to hospital.
• A follow-up appointment, usually within one to two weeks of discharge.

Recovery at Home

The first weeks at home are a transition period. Children are often more tired than usual, may eat less than before for a time, and may need extra naps. Most children gradually return to their baseline energy over four to eight weeks. Oxygen saturation usually rises noticeably compared with before the Fontan, often into the low- to mid-90s.

Things to expect and watch for at home include:

• Chest healing. The breastbone takes about six weeks to heal. During this period, children should avoid pulling, pushing, lifting, or carrying heavier objects, and avoid rough play.
• Appetite and growth. Appetite often dips for a while and then rebounds. Steady growth over the following months is a good sign.
• Energy. Tiredness improves gradually. School-aged children typically return to school part-time within a few weeks and full-time within one to two months.
• Medications. Stick closely to the prescribed schedule, especially blood thinners, and never stop a medication without talking to the cardiology team.
• Wound checks. Some redness around the scar can be normal, but spreading redness, swelling, discharge, fever, or a scar that feels unstable should be reported promptly.

It is normal for parents to feel anxious during this period, particularly after such a long pre-surgery preparation. Many families find that joining a support group for parents of children with single-ventricle hearts helps.

Risks and Complications

The Fontan is a major operation on a heart with complex anatomy, and it carries real risks. The cardiac team will discuss these with you in detail. Broadly, complications can be grouped into those that occur in the early period and those that may develop years later.

Early Complications

• Prolonged pleural effusions — ongoing fluid drainage from the chest, the most common reason for extended hospital stay.
• Low cardiac output — difficulty maintaining adequate circulation in the first days, sometimes requiring extra support.
• Heart rhythm disturbances — both fast and slow abnormal rhythms can occur, occasionally needing temporary or permanent pacing.
• Bleeding — requiring transfusion or, less often, return to the operating room.
• Infection — of the wound, lungs, or bloodstream.
• Stroke or blood clots — the reason anticoagulation is started early.
• Failed Fontan — in a small number of cases, the circulation does not adapt as hoped, and the team may need to take down the connections or consider further interventions.

Later Complications

Even when the early recovery goes well, Fontan circulation creates long-term pressures inside the body that can lead to specific late issues. These do not happen to every child, and modern management aims to detect them early.

• Arrhythmias. Abnormal heart rhythms become more common over time and may require medication, catheter procedures, or pacemakers.
• Protein-losing enteropathy (PLE). A condition in which protein leaks out of the body through the gut, causing swelling and other problems. It is uncommon but serious when it occurs.
• Plastic bronchitis. A rare condition in which thick casts form in the airways and cause coughing or breathing problems.
• Fontan-associated liver disease. Over years, the higher pressures in the veins draining the liver can cause the liver to become scarred. Regular liver monitoring is now a standard part of follow-up.
• Thromboembolism. The slow-moving Fontan circulation has a higher tendency to form clots, which is why blood thinning is used long-term.
• Ventricular dysfunction over time. The single ventricle may eventually weaken, sometimes leading to a discussion of advanced therapies including transplantation.
• Cyanosis from collaterals. Small abnormal blood vessels may grow over time and allow oxygen-poor blood to bypass the lungs, lowering oxygen levels.

The AHA scientific statement on Fontan circulation, and similar guidance from major cardiology societies, emphasises that lifelong specialist follow-up is what makes early detection of these issues possible.

Life After the Fontan

Activity, School, and Daily Life

Most children with a well-functioning Fontan are able to return to school and to most childhood activities. Energy levels are usually better after the Fontan than before, because the circulation is more efficient and oxygen saturation is higher.

Cardiologists generally encourage children with Fontan circulation to be active. Regular, moderate activity supports the muscle pump in the legs, which actually helps blood return to the lungs. The kind and intensity of exercise that is appropriate varies from child to child, and the cardiology team will give individualised guidance — usually permitting recreational sport while discouraging extreme competitive or contact activities.

Medications

Children with Fontan circulation often stay on long-term medication, which may include:

• Anticoagulation (blood thinning), such as aspirin or warfarin, depending on age, risk factors, and centre practice.
• Medications that support the heart and lower blood pressure, such as ACE inhibitors.
• Diuretics to control fluid balance.
• Pulmonary vasodilators in some cases, to keep blood flowing easily through the lungs.

The exact combination is tailored to the individual child and may change over time.

Infections, Dental Care, and Vaccinations

Children with congenital heart disease are at higher risk from certain infections. Routine childhood vaccinations are important, and additional vaccines such as influenza and others may be recommended by the cardiology team. Dental hygiene matters: dental infections can spread to the heart (endocarditis). Antibiotics before certain dental procedures may be advised, following standard cardiology guidance.

Diet, Travel, and Daily Considerations

• A balanced diet supports growth and helps maintain healthy weight, which matters for Fontan function.
• Adequate hydration is important because dehydration can lower blood flow through the lungs.
• Air travel is usually safe but should be discussed with the cardiology team, particularly for long flights.
• High altitudes can affect oxygen levels and are worth discussing in advance.

Long-term Management and Ongoing Care

Fontan circulation requires lifelong specialist follow-up. Children who have had a Fontan grow into teenagers and adults with congenital heart disease, and the care team evolves with them. Major cardiology societies recommend that children and adults with Fontan circulation be followed by clinicians who specifically care for congenital heart disease.

• Regular cardiology reviews, often every six to twelve months once the child is stable.
• Echocardiography at each review to look at ventricular function, valve function, and the Fontan pathway.
• Periodic cardiac MRI to assess the heart and pathway in more detail than ultrasound allows.
• Liver assessment — blood tests, ultrasound, and sometimes more detailed imaging — on a regular schedule, because of the risk of Fontan-associated liver disease.
• Holter or other rhythm monitoring when there are concerns about arrhythmia.
• Periodic cardiac catheterisation when more detailed information is needed, or to close a fenestration, open a narrowing, or close abnormal collateral vessels.
• Transition planning in adolescence, so that as the child approaches adulthood they are gradually introduced to an adult congenital heart disease team.

If problems develop — arrhythmias, a leaking valve, a narrowed pathway, declining ventricular function, liver issues — treatments are available. These range from medication adjustments and catheter interventions to additional surgery and, in some cases, consideration of heart transplantation. The trajectory is not the same for every child, and many do extremely well for many years.

Outcomes Over Time

The Fontan operation has transformed the outlook for children born with single-ventricle hearts. Conditions that were once uniformly fatal in early childhood are now compatible with growing up, going to school, and reaching adulthood. With improvements in surgical technique, intensive care, anticoagulation, and long-term follow-up, the proportion of Fontan patients reaching adolescence and adulthood has increased substantially over recent decades.

It is important, though, to be honest about what the Fontan is and is not. It is not a cure. It does not give a child a normal two-pump heart. The Fontan circulation is a workable but imperfect substitute, and the late complications described earlier are part of why specialist follow-up matters so much. Outcomes also depend on the specific underlying anatomy, the function of the single ventricle, and how the body adapts over time.

The most accurate way to think about your own child’s outlook is in conversation with the cardiac team that knows their heart in detail. They can give a more individualised picture than any general figures can.

Frequently Asked Questions

Is the Fontan procedure a cure?

No. The Fontan does not rebuild the heart into a normal two-pump heart. It rearranges the circulation so that the single ventricle can work more efficiently. It is best thought of as a long-term management strategy that allows children to grow and thrive, with ongoing specialist follow-up.

At what age is the Fontan usually performed?

The Fontan is most often performed between the ages of two and four years, after the earlier-stage operations (the newborn operation and the Glenn). Some centres operate slightly earlier or later. The exact timing depends on the child’s growth, oxygen levels, ventricular function, and the pressures inside the lung blood vessels.

Why is my child still slightly blue before the Fontan even after the Glenn?

After the Glenn, blood from the upper body flows directly to the lungs, but blood from the lower body still returns to the heart and mixes with oxygen-rich blood. This mixing is what keeps oxygen saturation lower than normal. The Fontan completes the rearrangement so that blood from the lower body also goes directly to the lungs, which is why oxygen levels typically rise after a Fontan.

Can children with a Fontan play sports?

Many children with a well-functioning Fontan are encouraged to be active and to take part in recreational sport. Regular moderate activity helps the muscles in the legs pump blood back toward the lungs. High-intensity competitive sports and contact sports are usually discouraged. The cardiology team will give specific advice tailored to your child.

Will my child need blood thinners forever?

Most children with a Fontan are kept on some form of anticoagulation long-term because the slow-moving Fontan circulation has a higher tendency to form blood clots. The specific medication, dose, and duration are individual decisions made by the cardiology team.

What is a fenestration and will it close?

A fenestration is a small opening sometimes created during the Fontan to act as a pressure release valve in the early recovery period. Many fenestrations close on their own over time, and some are closed later during a cardiac catheterisation if the child’s circulation has adapted well and the opening is no longer needed.

Could my child ever need a heart transplant?

For some children, Fontan circulation eventually becomes inadequate, often years or decades later, and heart transplantation may be considered. This is not the path for every child. Decisions about transplantation are made by specialised teams when and if the situation arises. Many people with Fontan circulation never reach this point.

How often will follow-up appointments be needed?

In the first year after the Fontan, follow-up is frequent. Once the circulation is stable, most children are seen every six to twelve months, with echocardiograms at each visit and additional tests such as MRI, liver assessment, and catheterisation done periodically. Follow-up continues for life and transitions to an adult congenital heart disease team during adolescence.

Can children with a Fontan attend school normally?

Yes. Most children with a well-functioning Fontan attend regular school and follow a normal curriculum. Some may need accommodations for tiredness, time off for hospital visits, or guidance around physical education. Letting the school know about your child’s heart condition and any medications — especially blood thinners — is sensible.

Conclusion

The Fontan procedure is the final, completion-stage operation in a carefully planned pathway for children born with single-ventricle hearts. It does not create a normal heart, but it creates a workable circulation that allows children who once had no surgical options to grow up, attend school, play, and reach adulthood. The operation itself is only one chapter of a longer story that begins before birth and continues into adult life.

For families, the most important things are understanding the staged pathway your child is on, having a clear plan for follow-up with a team experienced in single-ventricle hearts, knowing the signs and symptoms that should prompt review, and supporting your child to live as active and ordinary a childhood as possible within the boundaries the heart allows. The future for children with Fontan circulation continues to improve with advances in surgery, imaging, medication, and long-term care — and most of all, with the careful, lifelong partnership between families and the cardiology teams who walk this path with them.