Tetralogy of Fallot
Tetralogy of Fallot (ToF) is a condition in which a baby has four abnormalities in their heart at birth. These issues make it hard for your baby’s heart to send enough oxygen to their entire body. This matters because your body needs oxygen to function.
Normally, your 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 child get relief during infancy.
Babies have these four issues with tetralogy of Fallot:
- Ventricular septal defect (VSD). A hole in the wall between your lower heart chambers lets blood without oxygen combine with blood that has oxygen in it.
- Pulmonary artery stenosis. A narrow pulmonary valve and main pulmonary artery keep you from getting enough blood through to your lungs with each heartbeat.
- Overriding aorta. Your 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 body instead of to your pulmonary artery and lungs to get oxygen.
- Ventricular hypertrophy. The wall of muscle around your right ventricle is too thick because it’s working harder than it should to make up for the heart’s other abnormalities.
This condition is rare. One out of 2,077 babies born in the U.S. each year has tetralogy of Fallot. But it’s one of the more common congenital heart disorders. Tetralogy of Fallot tends to happen more often in male babies. Healthcare providers also see ToF often in babies who have Down syndrome or other chromosome disorders.
Rarely, some people don’t get treatment in childhood and may develop issues in adulthood.
Symptoms of tetralogy of Fallot
ToF symptoms can be mild, moderate or severe. They usually get worse over time without treatment.
Tetralogy of Fallot symptoms in children include:
- Fainting (syncope)
- Seizures
- Not much desire to eat
- Dizziness
- Slow weight gain
If you didn’t get a diagnosis as a child, you may develop ToF symptoms as an adult. A lack of oxygen may give your skin a bluish tint (cyanosis). It also can make you likely to faint or have an inability to exercise (exercise intolerance). Some adults with tetralogy of Fallot experience chest pain or heart palpitations.
Tet spells
Babies who haven’t gotten treatment for tetralogy of Fallot can get “tet spells.” This happens when their oxygen level drops without warning while or after feeding, crying or pooping. Tet spells can be as short as a few minutes to as long as several hours. Your baby may sleep a lot after a tet spell.
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 for a short time
Healthcare providers aren’t sure what causes tetralogy of Fallot.
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 in the expectant mother that increase risk for tetralogy of Fallot in the baby may include:
- Having rubella or diabetes while pregnant
- Drinking beverages with alcohol or eating unhealthy foods while pregnant
- Being pregnant after age 40
- Having a rare condition called phenylketonuria (a buildup of an amino acid)
How to lower your risk
Although healthcare providers don’t know the cause of tetralogy of Fallot, you may be able to reduce a fetus’s risk of ToF in these ways:
- Don’t use tobacco products or drink beverages with alcohol while pregnant.
- Avoid certain medicines. Ask your provider for substitute medicines you can take 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.
Without tetralogy of Fallot surgery, symptoms usually get worse. Also, other health issues can happen with a ToF heart defect, like:
- A higher number of red blood cells
- Sinusitis (sinus infection)
- Blood clots
- Brain abscess
Your healthcare provider can diagnose tetralogy of Fallot during pregnancy or after your baby is born. They usually find ToF in the first few weeks or months of life. During prenatal tests, your healthcare provider may use a fetal echocardiogram to look at the fetal heart’s structure if the initial ultrasound looks suspicious.
Tests used to diagnose ToF after birth
During a physical exam, a healthcare provider will listen to your child’s heart. If they have ToF, their provider will most likely hear a heart murmur.
Tests a provider may use to diagnose tetralogy of Fallot may include:
- Pulse oximetry
- Echocardiogram
- Chest X-ray or cardiac CT (computed tomography)
- Electrocardiogram (EKG)
- Cardiac catheterization
How is ToF treated?
Tetralogy of Fallot treatment includes medicine to ease symptoms and surgery to fix the issues. As a first step in tetralogy of Fallot treatment, your child’s provider can give them beta-blockers (to improve blood flow) and extra oxygen. 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 depending on your child’s condition. If your baby is too small or weak for a full repair, their provider can do a simpler procedure until they can do the complete ToF repair. These techniques can relieve symptoms for a number of years — well into adulthood — until a provider can do a more complete repair surgery.
Tetralogy of Fallot repair procedures include:
- Complete repair. A surgeon can make the pulmonary valve and the path to the pulmonary artery bigger. And they can patch the hole between the two ventricles.
- BTT shunt procedure. Your provider can put a shunt or tube between your child’s subclavian and pulmonary arteries to help blood get to the 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.
Surgery for adults
Occasionally, 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.
To perform a complete repair, a surgeon who specializes in adult congenital heart disease closes the ventricular septal defect with a patch. They open the passageway out of the right ventricle and repair or replace the pulmonary valve. They enlarge the pulmonary arteries to both lungs. Sometimes, they place a tube between the right ventricle and the pulmonary artery to improve blood flow.
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 for regular monitoring.
Complications of ToF surgery
Complications of tetralogy of Fallot surgery (some of which may show up later) may include:
- Electrical disturbances. Having a patch on the VSD can block your atria from sending electrical signals to your ventricles. A pacemaker can correct this. With repaired ToF, you’re at risk for arrhythmias in your heart’s top and bottom chambers. You should get an evaluation for a syncopal episode.
- Residual ventricular septal defect. Sometimes, the ventricular septal defect doesn’t seal completely and there’s some leaking around the patch.
- Aneurysm. Patches that repair a ventricle can cause weak sections of the ventricle to bulge out, forming an aneurysm. There’s also an increased risk of aneurysms of the ascending aorta.
- Shunt issues. The shunts providers use for an initial repair can cause issues like narrowing (stenosis), high blood pressure in your pulmonary artery or excess volume load on the left side of your heart.
- Leaky valves. Your pulmonary, aortic or tricuspid heart valves can leak. Sometimes, a provider will need to replace the pulmonary valve.
With medical advances, the outlook for babies with tetralogy of Fallot is better than it was in the past. Surgical treatment is very effective in correcting structural defects and blood flow through the heart. With an experienced congenital heart disease surgeon, surgical repair of the defect in adults has a very high success rate.
Most babies who have surgery today to fix tetralogy of Fallot will have active lives. But people with repaired ToF typically have some restrictions on certain strenuous activities, like competitive sports. Long-term survival after ToF repair is very good. Most people who undergo repair are alive 30 years later. Without a repair, 1 out of 3 people with tetralogy of Fallot live to age 10.
Some adults who had tetralogy of Fallot surgery as infants may develop issues that require medicines, medical care or surgery in adulthood. Adults should consult with their cardiologist before having surgery on a different part of their body.
References
- American Heart Association. Tetralogy of Fallot (https://www.heart.org/en/health-topics/congenital-heart-defects/about-congenital-heart-defects/tetralogy-of-fallot). Accessed 3/13/2025.
- Cohen S, Earing MG. THE ADULT WITH REPAIRED TETRALOGY OF FALLOT. In: Daniels CJ, Zaidi AN, eds. Color Atlas and Synopsis of Adult Congenital Heart Disease. McGraw Hill; 2016.
- Dimopoulos K, Constantine. Right-Sided Lesions. In: Fuster V, Narula J, Vaishnava P, Leon MB, Callans DJ, Rumsfeld JS, Poppas A, eds. Fuster and Hurst’s The Heart. 15th ed. McGraw-Hill Education; 2022.
- Emani SM. The Heart: Congenital Diseases. In: Doherty GM, eds. Current Diagnosis & Treatment: Surgery. 16th ed. McGraw Hill; 2025.
- Merck Manual Consumer Version. Tetralogy of Fallot (https://www.merckmanuals.com/home/children-s-health-issues/birth-defects-of-the-heart/tetralogy-of-fallot). Last revised 4/2023. Accessed 3/13/2025.
- National Organization for Rare Disorders (U.S.). Tetralogy of Fallot (https://rarediseases.org/rare-diseases/tetralogy-of-fallot/). Last updated 8/18/2016. Accessed 3/13/2025.
- Tetralogy of Fallot. In: Crawford MH, Aras M, Sanchez JM, eds. Quick Dx & Rx: Cardiology. McGraw Hill; 2018.
- U.S. Centers for Disease Control and Prevention. About Tetralogy of Fallot (https://www.cdc.gov/heart-defects/about/tetralogy-of-fallot.html?CDC_AAref_Val=https://www.cdc.gov/ncbddd/heartdefects/tetralogyoffallot.html). Last updated 10/21/2024. Accessed 3/13/2025.
- van der Ven JPG, van den Bosch E, Bogers AJCC, Helbing WA. Current outcomes and treatment of tetralogy of Fallot (https://pubmed.ncbi.nlm.nih.gov/31508203/). F1000Res. 2019 Aug 29;8:F1000 Faculty Rev-1530. Accessed 3/13/2025.
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