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Tetralogy of Fallot (TOF)

What is tetralogy of Fallot?

Tetralogy of Fallot (TOF) is a set of 4 congenital heart defects that happen together. Tetralogy refers to the number 4. Congenital means that a baby is born with them. The set of 4 defects are:

  • Narrowing (stenosis) of the pulmonary artery. This is the artery that carries blood from the heart to the lungs to pick up oxygen.

  • Ventricular septal defect. This is an opening in the wall between the 2 lower chambers of the heart (right and left ventricles). 

  • Overriding aorta. The artery that carries oxygen-rich blood to the body (aorta) is shifted toward the right side of the heart. It should be on the left side. In this condition, the aorta sits over the ventricular septal defect.

  • Enlargement (hypertrophy) of the right ventricle. The right lower chamber of the heart (ventricle) is bigger than normal.

In a healthy heart, oxygen-poor (blue) blood returns to the right chamber of the heart (right atrium) from the body. Next, it travels through the tricuspid valve to the right ventricle of the heart. Then it’s pumped through the pulmonary valve to the pulmonary artery and into the lungs for oxygen. Oxygen-rich (red) blood comes back to the left upper chamber of the heart (left atrium) from the lungs. Then it passes through the mitral valve and into the left ventricle of the heart. Finally, it’s pumped through the aortic valve to the aorta and out to the body.

Some children with TOF may only have slightly lower than normal oxygen levels in their blood. These children have minimal narrowing of the pulmonary artery. They don’t usually have bluish skin (cyanosis). Other children with TOF will have low oxygen levels in their blood. These children have more severe narrowing of the pulmonary artery. They have bluish skin. This is from the low oxygen levels in their blood.

What causes tetralogy of Fallot?

Genes and family history may play a part in TOF. It may also be caused by Down syndrome or 22q11.2 deletion syndrome (DiGeorge syndrome). Most of the time, this heart defect happens by chance, with no cause.

What are the symptoms of tetralogy of Fallot?

Symptoms can show up a bit differently in each child. The most common symptom is a bluish color of the skin, lips, and nail beds. This may come on in sudden spells, called TET spells. It happens when blood oxygen level drops quickly. During the spell, babies may have a hard time breathing. They may also be tired and fussy. In the most severe cases, they may lose consciousness.

The symptoms of TOF may be similar to symptoms caused by other problems. Make sure that your child sees a healthcare provider for a diagnosis.

How is tetralogy of Fallot diagnosed?

Your child will need to see a heart doctor (pediatric cardiologist.) They will check your baby and listen to their heart and lungs. The details about your child’s heart murmur will also help the doctor make the diagnosis.

Tests may be done to confirm the diagnosis. The tests your child has depends on their age and condition, and the healthcare provider’s preferences.

Echocardiogram (echo)

An echo uses sound waves to make a moving picture of the heart and heart valves. This test will show structural changes caused by TOF.

Chest X-ray

A chest X-ray may show changes in the heart and lungs caused by TOF. The heart on an X-ray may be enlarged or have the shape of a boot.


This test records the electrical activity of the heart. It also shows abnormal rhythms (arrhythmias or dysrhythmias) and spots heart muscle stress. These issues may be caused by TOF.

Cardiac catheterization (cardiac or heart cath)

A cardiac catheterization gives detailed information about the structures inside the heart. In this test, a small, thin, flexible tube (catheter) is put into a blood vessel in your child’s groin. Then the healthcare provider guides it to your child’s heart. They will inject your child with contrast dye to see their heart more clearly. This test measures your child’s blood pressure and oxygen in the 4 chambers of the heart. It also measures blood pressure and oxygen in the pulmonary artery and aorta. Your child will get medicine to help them relax and prevent pain (sedation).

How is tetralogy of Fallot treated?

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

Some children will need a small tube called a shunt put into the pulmonary artery. This helps create stable pulmonary blood flow until a permanent repair can be done at a later age.

All children with TOF need to have surgery to fix it. Most children have it before they turn 1 year old. It’s often done around age 6 months. A team of heart surgeons will do your child’s surgery. To fix TOF, a surgeon may use a patch to close the ventricle septal defect (VSD). The surgeon will enlarge the right ventricular outflow tract. This can be done by removing excess heart muscle or using a patch to enlarge narrowed pulmonary arteries.

Fixing the heart defects will allow oxygen-poor blood to travel its normal route. This is through the pulmonary artery to the lungs to pick up oxygen.

What are possible complications of tetralogy of Fallot?

If left untreated, it can cause these problems:

  • Blood clots (which may be in the brain causing stroke)

  • Infection in the lining of the heart and heart valves (bacterial endocarditis)

  • Abnormal heart rhythms (arrhythmias)

  • Heart failure

  • Death

Living with tetralogy of Fallot

The heart doctor may give your child antibiotics to prevent infections after leaving the hospital. Your child may also need medicine before other surgeries or dental tests.

After surgery, your child may become tired easily and sleep more. Over time, most children are able to be active. Most children’s appetite and growth become normal soon after surgery. Some children who had surgery for TOF can have problems learning or growing normally.

Most children who have surgery for this condition will live healthy lives. They may need more surgeries throughout their lives. Your child might need a pulmonary valve replacement surgery when they are an adult. This will help prevent heart complications. These include enlargement of the right ventricle, abnormal heart rhythms, and heart failure. People who want to have children should be checked by a cardiologist before they get pregnant.

Ask your child's healthcare provider about your child’s outlook.

When should I call my child's healthcare provider?

Call your child’s healthcare provider if they have trouble breathing, eating, or being active.

Key points about tetralogy of Fallot

  • Tetralogy of Fallot is a set of 4 congenital heart defects. Children are born with this condition.

  • This condition causes problems with the heart’s ability to pump oxygen-rich blood to the body.

  • All children with TOF need to have surgery to fix it.

  • After surgery, most children will live healthy lives.

  • Most children who have had surgery for TOF will need more surgery when they are an adult.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Know the reason for the visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.

  • Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are and when they should be reported.

  • Ask if your child’s condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if your child does not take the medicine or have the test or procedure.

  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your child’s provider after office hours, and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.

Online Medical Reviewer: Dan Brennan MD
Online Medical Reviewer: Rita Sather RN
Online Medical Reviewer: Tracy C. Garrett RNC-NIC BSN
Date Last Reviewed: 9/1/2023
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