Tetralogy of Fallot (TOF)

Anatomy of the heart, normal

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 eight weeks of pregnancy. These problems include the following:

  • 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 four heart problems. The fourth problem is that the right ventricle becomes enlarged as it tries to pump blood past the obstruction into the pulmonary artery.

Anatomy of a heart with tetralogy of Fallot

Normally, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped through the aorta out to the body.

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 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

Prevention & Risk Treatment

Prevention & Risk Treatment

What causes tetralogy of Fallot?

Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families.

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 sporadically (by chance), with no clear reason evident 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. Symptoms may include:

  • 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, and quickly becomes more obvious.
  • 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 decreasing amount of oxygen available 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.

Diagnosis

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.

A pediatric cardiologist specializes in the diagnosis and medical management of congenital heart defects, as well as heart problems that may develop later in childhood. The cardiologist will perform a physical examination, listening to the heart and lungs, and make other observations that help in the diagnosis. The location within the chest that the murmur is heard best, as well as the loudness and quality of the murmur (such as, harsh or blowing) will give the cardiologist an initial idea of which heart problem your child may have. Diagnostic testing for congenital heart disease varies by the child's age, clinical condition, and institutional preferences. Some tests that may be recommended include the following:

  • Chest X-ray. A diagnostic test that uses X-ray beams to produce images of internal tissues, bones, and organs onto film.
  • Electrocardiogram (ECG or EKG). A test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle stress.
  • Echocardiogram (echo). A procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and heart valves. 
  • Cardiac catheterization. A cardiac catheterization is an invasive procedure that gives very detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin, and guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, as well as the pulmonary artery and aorta. Contrast dye is also injected to more clearly visualize the structures inside the heart.
Children's Team

Children's Team

Providers

Our Stories

Our Stories

Patient story

Alexis's Story

"She likes to show off her scar and tell whoever listens that Children's National fixed her heart."

Charlotte's Story

"It is a little scary to see your baby with tubes, lines, gauze, and all of the other medical gear occupying their body, but once the nurses explain what it all does and how it helps your baby, you will feel much better."

Camdyn's Story

"The nurses, techs, and doctors at Children's National were absolutely amazing. They were always professional, compassionate, and kind. Each person there touched us in ways that are unimaginable."

Jax's Story

"I know this is a scary time for you. But it's okay: you have Children's National."

Patient story

Derek's Story

"The doctors and nurses at Children's have always done everything that they can to make my experiences pleasant. In a sense, many have become an extension of my family."

Patient story

Alex's Story

"He is proud of his scar. He likes to tell people he is special and when they ask him why, he will tell them he had a bad heart and the doctors at Children's National made it all better."

Matthew R.'s Story

"It is overwhelming for any parent with children of any age to have to experience something like this. Now that I am and have gone through the experience I cannot thank Children's National enough for its kindness, professionalism, and knowledge."

Departments

Departments

Cardiac Imaging

Learn more about the advanced cardiac imaging procedures we use to diagnose infants and children in our Heart Institute.

Cardiology

Children’s National Heart Institute, an international leader in comprehensive cardiac care for infants, children, and adults.

Washington Adult Congenital Heart Program (WACH)

The Washington Adult Congenital Heart Program meets the unique needs of adult patients with congenital heart disease by providing all the necessary resources and highly sophisticated care in a central location.

Fetal Heart Program

When your baby needs the most advanced cardiac care, Children’s National Heart Institute is the preeminent provider of fetal cardiac services in the Washington, DC, metropolitan area.

Cardiac Surgery

Learn more about the comprehensive, expert care we provide for infants and children in our heart surgery program.

Invest in future cures for some of life's most devastating diseases

See other ways to give

Run or walk with us on September 13th and help local kids!

Race for Every Child Logo Register now

Scott's Story

"You should know that your child is being cared for at the finest children's hospital in the world and he or she could not be in better hands."

Read More of Scott's Story