The Fontan procedure is a life-saving heart surgery designed for children born with only one working pumping chamber in their heart, transforming how blood flows through their body and allowing them to survive into adulthood.

What Is the Fontan Procedure?

The Fontan procedure is a type of open-heart surgery performed on children who were born with heart problems where only one ventricle, or pumping chamber, works properly. In a healthy heart, there are two lower chambers called ventricles. The right ventricle pumps blood to the lungs to pick up oxygen, while the left ventricle pumps oxygen-rich blood to the rest of the body. When a child is born with only one functioning ventricle, that single chamber must do the work of both, which puts tremendous strain on the heart and prevents the body from getting enough oxygen to function properly.^[1]

This surgery is usually the third and final procedure in a series of operations designed to help children with single ventricle heart defects. The Fontan procedure redirects blood flow so that oxygen-poor blood from the lower part of the body goes directly to the lungs without passing through the heart first. This means the single working ventricle only needs to pump oxygen-rich blood to the body, rather than trying to do two jobs at once.^[2]

The procedure was first performed in 1968 by Dr. Francis Fontan and Dr. Eugene Baudet in France, and has since evolved significantly. What began as a treatment for a specific condition called tricuspid atresia has now become a standard approach for many different types of single ventricle heart defects. Today, healthcare providers in the United States perform about 1,000 Fontan procedures each year, and an estimated 50,000 to 80,000 people worldwide have had this surgery.^[2][7]

Epidemiology

Single ventricle heart defects, which are the conditions that require a Fontan procedure, are rare. These defects occur in approximately 0.08 to 0.4 out of every 1,000 live births. This translates to roughly 5 out of every 100,000 births being affected by these complex heart problems.^[3][4]

Before the development of the Fontan procedure and the staged surgical approach that accompanies it, most children born with single ventricle defects would not survive childhood. Death in early childhood was typical for these patients. The introduction of this palliative surgery has dramatically changed outcomes, and survival to adulthood is now expected for many of these children.^[17]

The procedure is typically performed on children between 2 and 15 years of age, though most commonly it happens when children are between 3 and 5 years old. Some children may have the surgery before age 2, and others may have it done when they are 18 to 36 months old, depending on their individual circumstances and how well their heart and lungs have developed.^[1][2]

The success of the Fontan procedure is demonstrated by a growing population of adults living with this unique physiology. Most people who undergo the Fontan procedure can expect to live another 30 years or more after surgery, though this is not a cure and requires lifelong specialized medical care.^[2]

Causes

The need for a Fontan procedure arises from congenital heart defects, meaning heart problems that are present from birth. These defects occur during fetal development when the heart is forming in the womb. In normal heart development, the heart forms four chambers with specific valves and connections. When something goes wrong during this process, a child may be born with only one ventricle that functions properly, or with heart valves that didn’t develop correctly.^[2]

The Fontan procedure is used to treat several specific congenital heart conditions. The most common reason for needing this surgery is hypoplastic left heart syndrome, where the left side of the heart is severely underdeveloped. Other conditions that may require a Fontan procedure include tricuspid atresia, where the valve between the right upper and lower chambers is missing or didn’t form properly, and double outlet right ventricle, where both major blood vessels leaving the heart are connected to the right ventricle instead of being properly separated.^[1][2]

Additional heart defects that may lead to a Fontan procedure include hypoplastic right heart syndrome, pulmonary atresia with intact ventricular septum, congenitally corrected transposition of the great arteries, unbalanced atrioventricular canal defects, severe Ebstein’s anomaly, double inlet left ventricle, and heterotaxy syndrome where some organs aren’t in their normal locations.^[2]

The exact causes of why these congenital heart defects occur are not fully understood. They happen during the earliest weeks of pregnancy when the baby’s heart is forming. While most cases occur without a clear reason, some may be associated with genetic factors or environmental influences during pregnancy, though specific causes are rarely identified in individual cases.

Risk Factors

Not every child born with a single ventricle defect is a suitable candidate for the Fontan procedure. Healthcare providers must carefully evaluate each child to determine if they can safely undergo this surgery and benefit from it. Several factors influence whether a child is appropriate for the procedure.^[2]

The working ventricle must be strong enough to pump blood effectively to the entire body. If the single functioning ventricle is too weak or damaged, it may not be able to handle the increased workload that comes after the Fontan procedure. The heart muscle’s strength and pumping ability are carefully assessed before proceeding with surgery.

The lungs must be healthy enough to receive blood flow in a passive way, meaning without the force of a pumping ventricle pushing blood through them. The blood vessels in the lungs need to have low resistance, allowing blood to flow through easily. If the pulmonary vascular resistance, or the resistance in the lung blood vessels, is too high, blood won’t flow properly through the lungs, and the procedure won’t work as intended.^[3]

Timing is also a risk factor. The procedure must be done at the right age when the child’s heart and lungs have developed enough to handle the changes but before too much damage has occurred from the abnormal circulation. Healthcare providers use various tests and measurements to determine the optimal timing for each individual child.

Symptoms Before the Fontan Procedure

Children born with single ventricle heart defects typically show symptoms early in life, often as newborns. The most noticeable symptom is cyanosis, which is a bluish tint to the skin, lips, and nails. This blue color happens because the blood doesn’t have enough oxygen in it. Since the single ventricle is pumping a mixture of oxygen-rich and oxygen-poor blood to the body, the overall oxygen level in the blood is lower than normal.^[7]

Babies and young children with these heart defects may also show signs of congestive heart failure. This can include difficulty feeding, as eating requires significant energy and oxygen. These children may tire easily during feeding and may not gain weight properly. They may breathe faster than normal or seem to work harder to breathe, especially during activities that require exertion.^[7]

Poor growth and failure to thrive are common concerns. Because the body isn’t getting enough oxygen, all of the body’s systems struggle to function optimally. Children may be smaller than their peers and may not meet typical developmental milestones on schedule. They may have less energy for play and other activities compared to children with healthy hearts.

The body simply cannot thrive when it doesn’t receive adequate oxygen. Every cell in the body needs oxygen to produce energy and carry out its functions. When oxygen levels are chronically low, it affects growth, development, energy levels, and overall quality of life. This is why the staged surgeries, culminating in the Fontan procedure, are so important for these children.^[1]

Prevention

Because congenital heart defects that require a Fontan procedure develop before birth during fetal heart development, there are no known ways to prevent these conditions from occurring. The heart defects happen during the earliest weeks of pregnancy, often before a woman even knows she is pregnant. Unlike some health conditions that can be prevented through lifestyle changes or vaccinations, single ventricle heart defects are not preventable with current medical knowledge.

However, early detection and prompt treatment are crucial for the best outcomes. Prenatal ultrasound examinations can sometimes detect heart abnormalities before birth, allowing parents and doctors to prepare for the care the baby will need immediately after delivery. Some babies with single ventricle defects are born in specialized hospitals with pediatric heart surgery teams ready to provide immediate care.

After the Fontan procedure is completed, preventing complications becomes a key focus. Excellent dental hygiene is very important for keeping the heart healthy. Normal bacteria in the mouth can be harmful if they get into the bloodstream and reach the heart. The best way to protect the heart is by keeping the mouth and teeth healthy through regular brushing, flossing, and visiting the dentist at least once a year. Some patients are advised to take antibiotics before dental procedures to prevent infections.^[13]

Regular exercise is very important for keeping people with Fontan circulation healthy. Both the heart muscle and the breathing muscles help blood flow properly in people who have had this surgery. Stronger heart and breathing muscles make for better blood flow to the body overall. People with Fontan circulation should participate in regular exercise guided by their doctor, even though they may need to exercise at their own pace.^[13][19]

Following up regularly with a cardiologist who specializes in congenital heart disease is essential. These regular check-ups allow doctors to monitor how the heart and circulation are functioning and to detect any problems early before they become serious. Lifelong specialized medical care is necessary to maintain the best possible health after a Fontan procedure.

Pathophysiology

To understand how the Fontan procedure works, it helps to first understand normal heart function. In a healthy heart, oxygen-poor blood returns from the body to the right side of the heart through large veins. The right ventricle then pumps this blood to the lungs, where it picks up oxygen. The oxygen-rich blood returns to the left side of the heart, and the left ventricle pumps it out to the body. This system keeps oxygen-poor and oxygen-rich blood completely separated.^[2]

In children with single ventricle defects, this normal separation doesn’t exist. The single working ventricle must pump blood to both the lungs and the body. This means oxygen-poor and oxygen-rich blood mix together inside the heart. When this mixed blood is pumped to the body, it doesn’t contain as much oxygen as it should. The body’s tissues and organs don’t receive enough oxygen to function properly, leading to the symptoms these children experience.

The Fontan procedure fundamentally changes how blood flows through the body. During the surgery, the surgeon disconnects the inferior vena cava, which is the large vein bringing blood back from the lower part of the body, from the heart. This vein is then connected directly to the pulmonary artery, which carries blood to the lungs, using a tube called a conduit. This connection means that oxygen-poor blood from the lower body flows directly to the lungs without passing through the heart first.^[1][11]

Before the Fontan procedure, children typically have already had a Glenn procedure, which redirects oxygen-poor blood from the upper body directly to the lungs. After both procedures are completed, all oxygen-poor blood from the entire body goes directly to the lungs in a passive manner, without being pumped by a ventricle. The blood flows through the lungs simply because of pressure differences, not because a heart chamber is actively pumping it.^[2]

Once blood passes through the lungs and picks up oxygen, it returns to the heart. Now the single working ventricle only receives oxygen-rich blood, and it only has one job: to pump this oxygen-rich blood out to the body. There is no more mixing of oxygen-poor and oxygen-rich blood. This is called Fontan circulation, and it creates a unique physiology that exists nowhere else in nature.^[4]

Surgeons often make a small hole called a fenestration between the conduit and the right upper chamber of the heart during the Fontan procedure. This hole allows some blood to still flow back to the heart if pressures in the lungs become too high. It acts as a safety valve, preventing too much blood from flowing to the lungs right away and giving them time to adjust to the new circulation pattern. Doctors can close this fenestration later by doing a cardiac catheterization, a procedure where they thread a thin tube through blood vessels to reach the heart.^[1][11]

The Fontan circulation has both benefits and challenges. The main benefit is that the body now receives blood with much higher oxygen levels, which allows children to grow, develop, and be more active. However, because blood flows to the lungs passively rather than being actively pumped, the pressure in the veins throughout the body is higher than normal. This increased systemic venous pressure can affect multiple organ systems over time, including the liver, kidneys, and intestines.^[3][10]

The heart itself also functions differently after a Fontan procedure. The single ventricle must work harder than a normal left ventricle because it’s the only pumping chamber. Over many years, this extra workload can lead to heart muscle weakening or heart valve problems. The abnormal blood flow patterns can also increase the risk of abnormal heart rhythms, called arrhythmias, and blood clots forming inside the heart or blood vessels.^[10]

Life After the Fontan Procedure

After the Fontan procedure, children usually spend one to two weeks in the hospital recovering. During this time, they receive round-the-clock care and monitoring. They are given medicines to help the heart pump more effectively and improve blood flow. Many of these medicines will need to be continued at home for months or years, and some may be lifelong.^[1][11]

The care team teaches parents how to care for their child at home before discharge. Children can usually go home when they are feeding well, growing well, and gaining weight. Many children thrive and do well after heart surgery, though they will need specialized medical care for the rest of their lives.

Regular follow-up with a cardiologist who specializes in congenital heart disease is essential. These visits typically include electrocardiograms (EKGs) to check the heart’s electrical activity, echocardiograms to create ultrasound images of the heart’s structure and function, laboratory tests to check organ function, and occasional cardiac catheterizations to evaluate how well the circulation is working.^[1][11]

Despite the success of the Fontan procedure, it is important to understand that this surgery is not a cure. It is a palliative procedure, meaning it improves symptoms and quality of life but doesn’t fix the underlying heart defect. Long-term complications are common and can affect multiple organ systems. People who have had a Fontan procedure require ongoing specialized follow-up throughout their entire lives to keep them as healthy as possible for as long as possible.^[13]

Common long-term complications include heart rhythm problems, which may feel like skipped beats or a racing heart. Blood clots can form in the abnormal circulation and may require blood-thinning medications. Heart failure can develop if the single ventricle becomes too weak over time. Low blood oxygen levels may occur if the circulation isn’t working optimally. Kidney dysfunction can result from chronically elevated venous pressure. Liver congestion and even cirrhosis, or liver scarring, can develop because blood backs up in the liver. Some patients develop a condition called protein-losing enteropathy, where protein leaks from the intestines, causing swelling and other problems.^[10][13]

Women with Fontan circulation can become pregnant, though pregnancy is considered higher risk and requires specialized care. Discussing family planning and birth control methods with a congenital heart specialist is important. Some birth control methods are not safe for women with Fontan circulation. In general, progesterone-only birth control methods are preferred to reduce the risk of blood clots. Planned pregnancies with proper follow-up by specialized heart and obstetric doctors usually have better outcomes for both mother and baby.^[13]

Regular physical activity is strongly encouraged for people with Fontan circulation. Exercise helps strengthen both the heart and breathing muscles, which improves blood flow throughout the body. Studies have shown that higher rates of physical activity are associated with better heart function classification and improved quality of life. People with Fontan circulation should find an exercise activity they can do regularly, though they may need to exercise at their own pace. The type and intensity of exercise should be discussed with their congenital heart doctor.^[13][19]

Many people with Fontan circulation can be very active with few limitations. They can participate in school, work, and many recreational activities. However, recognizing and reporting new symptoms is important for maintaining long-term health. With proper medical care, regular monitoring, and healthy lifestyle choices, many people who have had the Fontan procedure can lead fulfilling lives well into adulthood.