Children's Hospital Colorado

Tetralogy of Fallot (TOF)

Tetralogy of Fallot is a congenital heart defect that involves the incorrect formation of the septum (partition) between the right and left ventricles. This condition results in mixing oxygen-rich and oxygen-poor blood across the ventricular septal defect, which causes an overall decrease in the amount of oxygen in the blood.

It is called tetralogy of Fallot because "tetralogy" means "four" in Greek and there are four defining features of this heart defect.

The four heart problems that make up tetralogy of Fallot include:

  • A hole between the ventricles or the lower chambers of the heart, called a ventricular septal defect (VSD)
  • A blockage or kink in the pulmonary artery where blood flows from the heart to the lungs
  • The aorta, the largest blood vessel, lies over the hole (VSD) in the lower chambers of the heart
  • The muscle surrounding the lower right chamber is too thick

Some patients may also have a complete blockage from the right ventricle (called pulmonary valve atresia). Pulmonary valve stenosis, or the pulmonary valve's inability to open properly, is also seen in babies with tetralogy of Fallot. This defect usually limits blood flow to the lungs, resulting in lower oxygen levels in the baby's body after birth.

What causes tetralogy of Fallot?

Tetralogy of Fallot is a congenital heart condition, meaning children are born with it. The cause of the condition is not known. In some situations, it may be associated with certain genetic syndromes like DiGeorge syndrome, also known as 22q11.2 deletion syndrome.

Children usually show symptoms of the condition and are diagnosed shortly after birth. With treatment, kids with tetralogy of Fallot can lead normal, healthy lives. However, if your child has tetralogy of Fallot, he or she will need follow-up care to monitor any changes in the heart.

Learn more about our nationally-ranked Heart Institute for the treatment of this condition.

What are signs and symptoms of tetralogy of Fallot in kids?

Children with this heart condition often have a blue tint to their skin, lips and fingernails. This is called "cyanosis" and means that not enough oxygen-rich blood is reaching the child’s body.

Sometimes, a baby only shows signs of cyanosis after crying or feeding. These episodes are called “Tet spells.”

Other tetralogy of Fallot symptoms include:

  • Trouble feeding
  • Poor growth and weight gain
  • Fainting
  • Clubbed fingers

If your child is having any of these symptoms, especially cyanosis, contact your doctor immediately.

Learn more about our nationally-ranked Heart Institute for the treatment of this condition.

How do doctors diagnose tetralogy of Fallot before birth?

Prenatal ultrasound is used to identify babies with tetralogy of Fallot early in pregnancy. Prenatal diagnosis is important because babies with this heart condition may have additional organ or chromosomal abnormalities, such as 22q11.2 deletion syndrome.

How do doctors diagnose Tetralogy of Fallot after birth?

If your doctor suspects your child has a congenital heart defect, he or she will want to do more tests to examine the heart. These tests will help your cardiologist identify the problem affecting your child and allow the cardiac team to create a treatment plan.

Other tests that help cardiologists diagnose tetralogy of Fallot are:

How is tetralogy of Fallot treated?

Surgery is the only definitive treatment for tetralogy of Fallot and babies diagnosed with this conditions will require heart surgery after birth to correct the heart defect. At Children's Hospital Colorado's Heart Institute, our doctors will likely schedule your child's surgery before he or she turns 1 year old.

Babies with milder forms of the condition may not require surgery for a few months after birth. However, babies with severe pulmonary valve stenosis or complete obstruction of the pulmonary valve will most likely require surgery as newborns.

What should I expect from surgery?

During surgery to repair tetralogy of Fallot, a pediatric cardiac surgeon will fix the hole between the ventricles (the ventricular septal defect) using a patch. The surgeon will also widen the pulmonary artery and fix any problems with the pulmonary valve. This repair will help more blood reach the lungs. The entire procedure is known as intra-cardiac repair.

If your child is too ill or too small for intra-cardiac repair, surgeons will use a temporary solution, called a shunt. This is a bypass from the aorta to the pulmonary artery, which will increase blood flow to the lungs until your child is big enough for the final procedure.

Your pediatric cardiologist at the Heart Institute will want to monitor your child for many years after the surgery to make sure there are no changes in your child’s heart.

Learn more about heart surgery for the treatment of tetralogy of Fallot.


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