Tetralogy of Fallot


Tetralogy of Fallot (te-tral-uh-jee; fa-loh) is a rare, complex series of four congenital (present at birth) heart defects that occur while your baby is still growing inside the womb.

According to the American Heart Association, congenital heart defects (present at birth) are the most common type of birth defect. They affect 8 out of every 1,000 newborns. Each year, more than 35,000 babies in the United States are born with congenital heart defects. 

Although the condition is rare, Tetralogy of Fallot (TOF) is the most common congenital (present at birth) heart defect causing a “blue baby.” According to the National Heart, Lung, and Blood Institute (NHLBI), TOF affects roughly 5 out of every 10,000 babies. The defect is found equally among boys and girls.

Causes of Tetralogy of Fallot

Causes of Tetralogy of Fallot

Tetralogy of Fallot includes:

  1. Ventricular septal defect – A hole in the wall (septum) that separates the heart’s lower chambers (ventricle), allowing mixing of blood between the right and left side of the heart
  2. Overriding aorta – Enlarged aortic valve that appears to arise from both the left and right ventricles (instead of from the left ventricle only in a normal heart)
  3. Pulmonary valve stenosis – Narrowing of the pulmonary valve, which obstructs the blood flow from the right ventricle to the lungs
  4. Right ventricular hypertrophy – Thickening of the muscular walls in the right ventricle that occurs when right ventricle is pumping against high pressure


Like many congenital heart defects, the cause of TOF is largely unknown, but many factors during the mother’s pregnancy seem to be involved, including:

  • Alcoholism
  • Mother who is over 40 years old
  • Poor nutrition during pregnancy
  • Rubella (German measles) or other viral illnesses during pregnancy

Children with TOF also are more likely to have chromosome disorders, such as DiGeorge syndrome (a condition that causes heart defects, low calcium levels, and poor immune function), or Down syndrome.

Symptoms of Tetralogy of Fallot

Symptoms of Tetralogy of Fallot

TOF causes low oxygen levels in the blood, which can cause your baby’s skin to have a bluish-purple color (cyanosis). This coloring often gets worse when your baby is upset.

Another common sign of TOF is a heart murmur. A heart murmur is an extra or unusual sound that a doctor might hear while listening to the heart. The sound occurs because the heart defect causes abnormal blood flow through the heart.

Other symptoms include:

  • Clubbed fingers (tissue enlargement around the fingernails)    
  • Passing out
  • Poor development
  • Squatting during episodes of cyanosis


Diagnosis and Treatment Options

Diagnosis and Treatment Options

TOF usually is diagnosed based on the above signs and symptoms, a physical exam, and the results from tests and procedures. During a physical exam, your doctor will listen to your baby’s heart and lungs to check for a murmur and will evaluate your baby’s general appearance to look for signs of a heart defect, such as a bluish tint to the skin, lips, or fingernails and rapid breathing.

If your doctor finds any signs of TOF, your baby likely will undergo additional testing. Tests that your doctor may order include a chest x-ray, echocardiogram (echo), electrocardiogram (EKG), pulse oximetry, or cardiac catheterization. For more information on these tests, visit our common diagnostic tests page.

The only treatment for TOF is open heart surgery. 

Illustration of repaired TOF

Illustration of a heart with a repaired VSD. Illustration by Steven P. Goldberg, MD


Timing of treatment varies, but the more common approach is to wait until your child is about 3-6 months old.

Some babies with TOF can have very low blood oxygen levels soon after birth. If your baby is too weak or too small to have full repair at this stage, the surgeon may perform an initial surgery (shunt procedure) to help increase blood flow to the lungs and give him or her time to grow and get strong enough for the full repair. Complete corrective surgery is done later in life.

Be sure to speak with your baby’s doctor about what you should expect during and after the surgery. You can print these sample questions to use as a basis for discussion with the doctor.

Expected outcomes: The Society of Thoracic Surgeons (STS) Congenital Heart Surgery Database shows an expected outcome of 1.1% mortality for isolated Tetralogy of Fallot. Outcomes will vary across different programs. It is appropriate to inquire about the outcomes of a surgical group or surgeon during your consultation.


The only treatment for TOF is open heart surgery. During the operation, the cardiothoracic surgeon will use a patch to cover the hole in the septum. This patch stops oxygen-rich (red) blood and oxygen-poor (blue) blood from mixing together.

The cardiothoracic surgeon also will enlarge the passage from the right ventricle to the pulmonary artery. At the time of surgery, your child’s native pulmonary valve (which guards the blood flow from the right ventricle to the lungs) will be assessed. Sometimes, the valve is very underdeveloped and will need to be removed in order to improve blood flow from the right ventricle to the lungs.



Without surgery, TOF can be fatal and most people die by age 20.

After surgery, your baby will require continued follow-up care. The doctor will schedule routine checkups to make sure that the procedure was successful and monitor for any new problems.

Child receiving follow-up care

Most children with successful complete repair will not have any activity restrictions as they grow older.

Sometimes, patients who had an operation to repair TOF in childhood need additional surgery as they age. Most often, this procedure is undertaken to reduce leakage of blood back into the right ventricle, and more frequently is required in children whose native pulmonary valve was not usable at the time of the initial repair.

Your child may be required to take antibiotics during dental procedures to prevent infections that may cause inflammation of the heart (endocarditis). Preventive antibiotics are almost always recommended for people who have artificial valves or who’ve had repair with prosthetic material. Be sure to ask your doctor about what is right for your child.

Tetralogy of Fallot patient 3-years post-surgery Patient with Tetralogy of Fallot 4 years after pulmonary valve replacement surgery 


Reviewed by: Ram Kumar Subramanyan, MD, PhD
December 2017