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Tetralogy of FallotTetralogía de Fallot

Tetralogy of Fallot

What is tetralogy of Fallot?

Tetralogy of Fallot (TOF or "TET") is a condition of several related congenital (present at birth) defects that occur due to abnormal development of the fetal heart during the first 8 weeks of pregnancy. These problems include the following:

Anatomy of the heart, normal
Click Image to Enlarge

  • Ventricular septal defect (VSD). An opening in the ventricular septum, or dividing wall between the two lower chambers of the heart known as the right and left ventricles.

  • Pulmonary (or right ventricular outflow tract) obstruction. A muscular obstruction in the right ventricle, just below the pulmonary valve, that decreases the normal flow of blood. The pulmonary valve may also be small.

  • Overriding aorta. The aorta is shifted towards the right side of the heart so that it sits over the ventricular septal defect.

"Tetralogy" refers to 4 heart problems. The fourth problem is that the right ventricle becomes thickened as it tries to pump blood past the obstruction into the pulmonary artery.

Anatomy of a heart with tetralogy of Fallot
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In tetralogy of Fallot, the direction of blood flow within the heart varies, and is largely dependent on the size of the ventricular septal defect, and how severe the obstruction in the right ventricle is.

  • With mild right ventricle obstruction, very little of the oxygen-poor (blue) blood in the right ventricle will pass through the VSD to the left ventricle, mix with the oxygen-rich (red) blood there, and then flow into the aorta. The majority of the oxygen-poor (blue) blood will go by its normal route to the lungs. These children may have oxygen levels that are only slightly lower than usual, and do not appear blue.

  • With more serious obstruction in the right ventricle, it is harder for oxygen-poor (blue) blood to flow into the pulmonary artery, so more of it passes through the VSD into the left ventricle, mixing with oxygen-rich (red) blood, and then moving on out to the body. These children will have lower than normal oxygen levels in the bloodstream, and may appear blue, especially whenever the pressure in the right ventricle is very high and large amounts of oxygen-poor (blue) blood passes through the VSD to the left side of the heart.

According to the National Heart, Lung, and Blood Institute, tetrology of Fallot affects about 5 of every 10,000 babies and occurs equally in boys and in girls. It is one of the most common congenital abnormalities of the heart that requires intervention in the first year of life 

What causes tetralogy of Fallot?


Maternal abuse of alcohol during pregnancy, leading to fetal alcohol syndrome, is linked to tetralogy of Fallot. Mothers who take medications to control seizures and mothers with phenylketonuria are also more likely to have a baby with tetralogy of Fallot.

Tetrology of Fallot may also occur as part of a syndrome like Down syndrome or DiGeorge syndrome. 

Most of the time, this heart defect occurs by chance, with no clear reason for its development.

Why is tetralogy of Fallot a concern?

The amount of oxygen-poor (blue) blood that passes through the VSD to the left side of the heart varies. If the right ventricle obstruction is severe, or if the pressure in the lungs is high, a large amount of oxygen-poor (blue) blood passes through the VSD, mixes with the oxygen-rich (red) blood in the left ventricle, and is pumped to the body. The more blood that goes through the VSD, the less blood that goes through the pulmonary artery to the lungs, and the less oxygen-rich (red) blood that returns to the right side of the heart. Soon, nearly all the blood in the left ventricle is oxygen-poor (blue). This is an emergency situation, as the body will not have enough oxygen to meet its needs.

Some situations, such as crying, increase the pressure in the lungs temporarily, and increasing blueness might be noted as a baby with tetralogy of Fallot cries. In other situations, the pathway from the right ventricle to the pulmonary artery becomes tighter, preventing much blood from passing that way, and allowing oxygen-poor (blue) blood to flow through the VSD into the left heart circulation. Both of these situations are nicknamed "TET spells." Sometimes, steps can be taken to lessen the pressure or the obstruction, and allow more blood to flow into the lungs and less through the VSD. These steps, however, are not always effective.

What are the symptoms of tetralogy of Fallot?

The following are the most common symptoms of tetralogy of Fallot. However, each child may experience symptoms differently.

  • Because large amounts of oxygen-poor (blue) blood can flow to the body under certain circumstances, one of the symptoms of tetralogy of Fallot is blueness (blue color of the skin, lips, and nail beds) that occurs with such activity as crying or feeding.

  • Some babies do not have noticeable cyanosis (blue color of the skin, lips, and nailbeds), but may instead be very irritable or lethargic due to a reduced amount of oxygen in the bloodstream.

  • Some children become pale or ashen in color, and may have cool, clammy skin.

Any of these can be symptoms of tetralogy of Fallot. The symptoms of tetralogy of Fallot may resemble other medical conditions or heart problems. Always consult your child's doctor for a diagnosis.

How is tetralogy of Fallot diagnosed?

Your child's doctor may have heard a heart murmur during a physical examination, and referred your child to a pediatric cardiologist for a diagnosis. In this case, the heart murmur is caused by the turbulence of blood flowing through the obstruction from the right ventricle to the pulmonary artery. Symptoms your child exhibits will also help with the diagnosis.


  • Chest X-ray. A diagnostic test that uses X-ray beams to produce images of internal tissues, bones, and organs onto film.


  • Echocardiogram (echo). A procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor to produce a moving picture of the heart and heart valves.


How is tetralogy of Fallot treated?

Specific treatment for tetralogy of Fallot will be determined by your child's doctor based on:

  • Your child's age, overall health, and medical history

  • Extent of the condition

  • Your child's tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

Tetralogy of Fallot is treated by surgical repair of the defects. A team of cardiac surgeons does the surgery, usually before an infant is 1 year old. In many cases, the repair is made around 6 months of age, or even a little earlier. Repairing the heart defects will allow oxygen-poor (blue) blood to travel its normal route through the pulmonary artery to receive oxygen.


  • The ventricular septal defect is closed with a patch.

  • The obstructed pathway between the right ventricle and the pulmonary artery is opened and enlarged with a patch. If the pulmonary valve is small, it may be opened as well.

Care for your child in the hospital

Children will spend time in the intensive care unit (ICU) after tetralogy of Fallot repair. During the first several hours after surgery, your child will be very drowsy from the anesthesia that was used during the operation, and from medications given to relax him or her and to help with pain. As time goes by, your child will become more alert.


  • Ventilator. A machine that helps your child breathe while he or she is under anesthesia during the operation. A small, plastic tube is guided into the windpipe and attached to the ventilator, which breathes for your child while he or she is too sleepy to breathe effectively on his or her own. After a tetralogy of Fallot repair, children will benefit from remaining on the ventilator for up to several days so they can rest.










Caring for your child at home


After surgery, older children usually have a fair tolerance for activity. Your child may become tired easily, and sleep more right after surgery, but, within a few weeks, your child should be fully recovered.

Long-term outlook

Most children who have had a tetralogy of Fallot surgical repair will live healthy lives. Activity levels, appetite, and growth will return to normal in most children soon after surgery . Your child's cardiologist may recommend that antibiotics be given to prevent bacterial endocarditis after discharge from the hospital.

After initial repair of tetralogy of Fallot, pulmonary valve replacement may be indicated in the second or third decade of life to prevent complications, such as enlargement of the right ventricle, abnormal heart rhythms, and heart failure. For women wishing to have children, preconception evaluation by echocardiogram and/or magnetic resonance imaging (MRI) is recommended.

Consult your child's doctors regarding the specific outlook for your child.

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