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Tetralogy of Fallot

Medically Reviewed.Last updated on 07/06/2026.

Tetralogy of Fallot (ToF) is a congenital heart condition, which means it’s present at birth. ToF makes it hard to get enough oxygen to your body because of four issues in your heart’s structure. Surgery in infancy repairs the problems and helps blood flow better, but you’ll need lifelong follow-ups with a provider.

What Is Tetralogy of Fallot?

A normal heart compared to a heart with tetralogy of Fallot
A baby born with tetralogy of Fallot has four issues in their heart that cause problems with getting oxygen to their body.

Tetralogy of Fallot (ToF) is a rare type of congenital heart disease in which a baby has four defects in their heart at birth. These problems make it hard for your baby’s heart to send enough oxygen to their entire body. This matters because all the cells in a person’s body need oxygen to function.

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Normally, blood travels a specific route through your heart with every heartbeat. Because of the structural problems in a heart with ToF, some blood that doesn’t have oxygen in it can go out to your baby’s body.

Medicines and procedures can help your baby get relief during infancy.

A baby with tetralogy of Fallot has these four issues at the same time:

  1. Ventricular septal defect (VSD): A hole in the wall between your baby’s lower heart chambers lets blood without oxygen combine with blood that has oxygen in it.
  2. Pulmonary artery stenosis: A narrow pulmonary valve and main pulmonary artery keep your baby from getting enough blood through to their lungs with each heartbeat.
  3. Overriding aorta: The aorta and its valve are above and open to both ventricles because of a VSD. This allows blood without oxygen to go out to your baby’s body instead of going to their pulmonary artery and lungs to get oxygen.
  4. Ventricular hypertrophy: The wall of muscle around your baby’s right ventricle is too thick because it’s working harder than it should to make up for the heart’s other abnormalities.

Symptoms and Causes

Symptoms of tetralogy of Fallot

Tetralogy of Fallot symptoms in children can be mild to severe. Without treatment, they usually get worse.

Signs of ToF in children include:

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  • Fainting
  • Seizures
  • Not much desire to eat
  • Dizziness
  • Slow weight gain

ToF symptoms in an untreated adult may include:

  • A bluish tint to your skin (cyanosis)
  • Passing out
  • Exercise intolerance
  • Chest pain or heart palpitations

Tet spells

Without treatment for tetralogy of Fallot, babies can have spells when their oxygen level drops without warning during or after feeding, crying or pooping. These are called tet spells. Babies can have tet spells for a few minutes to several hours. Tet spells occur when babies’ activities worsen the mixing of the “blue” (deoxygenated) blood and “red” (oxygenated) blood.

Signs of a tet spell include:

  • Having very blue skin (cyanosis)
  • Having a limp body
  • Feeling very tired
  • Being restless
  • Not responding to a parent or caregiver
  • Losing consciousness
  • Having a hard time breathing
  • Having convulsions
  • Being unable to move one side of their body

After a child receives treatment, they shouldn’t have tet spells anymore. The “blue” blood and “red” blood can no longer mix, resulting in enough oxygen reaching different parts of their body.

Tetralogy of Fallot causes

When part of the wall in a baby’s heart doesn’t form the way it should, it causes the four ToF heart defects. Healthcare providers aren’t sure what causes this to happen.

Something in your child’s DNA may have changed, and that change rarely comes from a biological parent. A parent who’s had a heart abnormality since birth doesn’t normally pass it to their child. But the risk may be higher if both parents have the heart issue.

Risk factors

Tetralogy of Fallot disease tends to happen more often in babies who are male or have Down syndrome or DiGeorge syndrome.

Risk factors in the expectant mother that increase the risk for tetralogy of Fallot in the baby may include:

  • Having rubella or diabetes while pregnant
  • Drinking alcohol or lacking nutrition while pregnant
  • Being pregnant after age 40
  • Having a rare condition called phenylketonuria (a buildup of an amino acid)
How to lower your risk

Healthcare providers don’t know the cause of tetralogy of Fallot. But you may be able to reduce a fetus’ risk of ToF in these ways:

  • Don’t use tobacco products or drink alcoholic beverages while pregnant.
  • Avoid certain medicines during pregnancy.
  • If you have phenylketonuria, eat less protein.
  • Make sure your rubella vaccine is still working to keep you from getting rubella during pregnancy.
  • Manage diabetes if you have it.

Complications of this condition

Until a baby receives treatment, they struggle to get enough oxygen. But surgical repair can lead to other problems later. Complications from ToF and its treatment may include:

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  • Abnormal heart rhythm
  • Leaky heart valve
  • Enlarged aortic root
  • Heart failure
  • A higher number of red blood cells
  • Sinus infection
  • Blood clots
  • Brain abscess
  • Endocarditis (infection in your heart)
  • Slow development
  • Risk of miscarriage in pregnancy

Diagnosis and Tests

How doctors diagnose this condition

Your healthcare provider can diagnose tetralogy of Fallot disease during pregnancy or after your baby is born. They usually find ToF heart defects in a baby’s first few weeks or months of life. During prenatal tests, your provider may use a fetal echocardiogram to look at the fetal heart’s structure if the initial ultrasound looks suspicious.

A healthcare provider will listen to your child’s heart after birth. They’ll most likely hear a heart murmur if your child has ToF.

Tests a provider may use to diagnose tetralogy of Fallot include:

Management and Treatment

How is it treated?

Tetralogy of Fallot treatment includes medicine to ease symptoms and surgery to fix the issues. Three to six months after birth, your baby can have surgery to make blood move through their heart the way it should.

Tetralogy of Fallot repair

Repair options vary based on your child’s condition. If your baby is too small or weak for a full repair, their provider can do a simpler procedure first. This can relieve symptoms until a surgeon can do a more complete repair surgery.

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Tetralogy of Fallot repair procedures include:

  • Complete repair: A surgeon can make the pulmonary valve and the path to the pulmonary artery bigger so blood can more easily travel to the lungs. And they can patch the hole between the two ventricles.
  • BTT shunt procedure: A provider can put a shunt or tube between your child’s subclavian and pulmonary arteries to help blood get to their lungs.
  • Catheter procedure: A provider can put in a stent for better blood flow out of the right ventricle. They can also put a stent in the patent ductus arteriosus to keep it from closing so it can send more blood to the lungs.

Surgery for adults

Sometimes, a person reaches adulthood without having had any surgical repair. This isn’t common. Specialists recommend they have a complete surgical repair to prevent future complications or sudden death.

Many adults who undergo repair for a ToF heart defect don’t need further surgical treatment. But they should continue to follow up with an adult congenital heart disease specialist. It’s common for adults who undergo surgical correction in infancy to require more operations or procedures for the pulmonary valve.

When should my baby see a healthcare provider?

If your baby is having a severe tet spell, take them to the closest emergency room.

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If you’re an adult with ToF, you should go to the emergency room if you:

  • Have passed out
  • Are dizzy
  • Are short of breath
  • Have chest pain

After tetralogy of Fallot repair, your child will need regular visits with a provider who specializes in children’s hearts (pediatric cardiologist). Regular care will continue into adulthood.

Outlook / Prognosis

What can I expect if I have this condition?

With medical advances, the outlook for children with tetralogy of Fallot is better than it was in the past. Surgery is very effective in correcting structural defects and blood flow through the heart. With an experienced surgeon, surgical repair of the defect in adults has a very high success rate.

Most children who have surgery today to fix tetralogy of Fallot will have active lives. But people with repaired ToF typically have some limits on certain strenuous activities, like sports. Long-term survival after ToF repair is very good. Most people who undergo repair are alive 30 years later.

Some adults who had tetralogy of Fallot surgery as infants may develop issues that require medicines, medical care, surgery or even a transplant in adulthood. Adults should consult with their cardiologist before having surgery on a different part of their body and before becoming pregnant.

Is there anything I can do to help my child feel better?

Until your baby has surgery, you can help them through tet spells. When your baby has trouble breathing, push their knees to their chest (squatting position). This helps move more blood to their lungs.

It’s also helpful to make sure your child is drinking enough fluids and isn’t exerting themselves too much.

A note from Cleveland Clinic

Learning that your newborn has a heart problem can feel like a heavy weight to bear. But your healthcare team has helped other parents in this situation, and they can help you, too. Don’t be afraid to talk to a therapist if you feel stressed about caring for a child with tetralogy of Fallot. A counselor can also help children and teens who may feel like their classmates are ahead of them in development.

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Medically Reviewed.Last updated on 07/06/2026.

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References

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

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