Tetralogy of Fallot (TOF) is a combination of 4 heart defects. It is present at birth. These defects make it difficult for your child to get oxygen to the entire body.

The defects are:

  • Ventricular septal defect (VSD)—A hole in the heart. It is on a wall that separates the 2 lower chambers.
  • Overriding aorta—The aorta, which is the body's largest artery coming out of the left ventricle, partially covers or comes out of the right ventricle.
  • Pulmonary stenosis—The valve in the heart that allows blood to pass from the heart toward the lungs is too narrow.
  • Right ventricular hypertrophy—The muscle on the right side of the heart is too thick.

VSD and overriding aorta can decrease the amount of oxygen in the blood. This makes it difficult for the body to get the oxygen it needs. Pulmonary stenosis and right ventricular hypertrophy can make it difficult for blood to pass to the lungs. This will also decrease the amount of oxygen in the blood.


A child's heart develops very early in pregnancy. TOF is caused by a problem during this development. It is not known exactly why these problems happen. Some have been associated with genetics, mother's nutrition, or infections. Most have no known cause.

Ventricular Septal Defect
Ventral septal defect
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Risk Factors

Factors that may increase your child's chance of TOF include:

  • Family history
  • Mother's use of retinoic acid
  • Mother's use of oral fluconazole
  • Mother's alcohol use
  • Mother has infection with rubella
  • Pregnancy in mothers over 40
  • Maternal diabetes

Some people who have TOF also have a chromosome disorder. This may include Down syndrome , CHARGE syndrome, and VACTERL association.


For most, symptoms will appear during the first few weeks of life. For children with mild TOF, symptoms may not appear until much later. They may not show until your child or young adult becomes more active. Physical activity places more demand on the heart. A heart with TOF cannot keep up with the extra demand, causing symptoms. Without treatment, symptoms will continue to occur.

Symptoms may include:

  • Blue coloring of the skin and lips caused by a low oxygen level in the blood
  • Shortness of breath and rapid breathing caused by a low oxygen level in the blood
  • Older children may have shortness of breath and fainting spells when exercising
  • Clubbing of the fingers

In severe cases, a tetralogy spell may occur. This happens when the oxygen level in the blood drops suddenly. Symptoms include:

  • Lips and skin become very blue
  • Baby will become breathless and irritable
  • Baby may become sleepy or unconscious if low oxygen levels continue
  • Older children may squat with their knees on their chest to help recover from the breathlessness


A diagnosis of TOF is often made soon after birth. You will be asked about your child's symptoms and the mother's medical history. A physical exam will be done.

The doctor may begin tests based on your child's symptoms. A newborn with blue skin will often be given extra oxygen. If the oxygen does not help, a heart defect may be suspected. If the skin color is normal, the first clue is a loud heart murmur.

Images may be taken of your child's heart. This can be done with:

Heart problems may also be detected using cardiac catheterization .


Medications may be given to relieve symptoms. They may also help to prevent complications like a tetralogy spell.

The defects of the heart are treated with surgery. Surgical options include:

Temporary Operation

Small infants with severe TOF may not be strong enough for a complete repair surgery. A temporary operation will help increase the amount of oxygen in the blood. This will give the baby time to grow, get stronger, and prepare for a complete repair.

During this operation, a temporary, new path is made for the blood. The blood will be sent past the problems in the heart and go directly to the lungs. This will increase the amount of blood getting to the lungs. The oxygen in the blood will increase as a result.

Complete Repair

Most children with TOF have open-heart surgery within the first few years of life. The operation includes:

  • Closing the hole in the heart. A patch will be placed over the hole.
  • Improving the flow of blood from the heart to the lungs by one or more of the following:
    • Removing some of the thickened heart muscle on the right side of the heart
    • Repairing or replacing the valve that allows the blood to flow from the heart to the lungs
    • Increasing the size of the blood vessels that carry blood to the lungs

For some, a path is created between the heart and the blood vessels to the lungs.

In many cases, the surgery is successful. For some, further surgery may be needed. Long-term follow-up is always needed to detect recurring or new problems.


There are no current guidelines to prevent TOF.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 03/2018 -
  • Update Date: 05/07/2014 -