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Tetralogy of Fallot

(TOF)

Definition

Tetralogy of Fallot (TOF) is a combination of four heart defects. It is present at birth. These defects make it difficult for your child to get oxygen to the entire body.
The four defects are:
  • Ventricular septal defect (VSD) —A hole in the heart. It is on a wall that separates the two lower chambers.
  • Overriding aorta—The aorta, which is the body's largest artery, comes out of the left ventricle, but 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.

Causes

A child's heart develops very early in pregnancy. Tetralogy of fallot 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 the risk of TOF include:
  • Family history
  • Mother's use of retinoic acid
  • 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.

Symptoms

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 can not keep up with the extra demand. This will make symptoms appear. 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

Diagnosis

A diagnosis of TOF is often made soon after birth. The doctor will ask 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.

Treatment

Medications may be given to relieve symptoms. They may also help to prevent complications like the 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.

Prevention

There are no guidelines for preventing TOF.

RESOURCES

American Heart Association http://www.heart.org

National Heart, Lung, and Blood Institute http://www.nhlbi.nih.gov

CANADIAN RESOURCES

About Kids Health http://www.aboutkidshealth.ca

Canadian Adult Congenital Heart Network http://www.cachnet.org

References

Tetralogy of fallot. American Heart Association website. Available at: http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Tetralogy-of-Fallot%5FUCM%5F307038%5FArticle.jsp . Updated March 30, 2012. Accessed May 20, 2013.

Tetralogy of fallot. Cincinnati Children's Hospital website. Available at: http://www.cincinnatichildrens.org/health/t/tof/ . Updated October 2012. Accessed May 20, 2013.

Tetralogy of fallot in infants and children. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed . Updated December 20, 2012. Accessed May 20, 2013.

What is tetralogy of fallot? National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health/health-topics/topics/tof/. Accessed May 20, 2013.

Revision Information

  • Reviewer: Michael Woods
  • Review Date: 05/2013 -
  • Update Date: 05/20/2013 -

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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