by EBSCO Medical Review Board


Tetralogy of Fallot (TOF) is a combination of these four heart defects that are present at birth:

  • Ventricular septal defect (VSD)—A hole between the lower chambers of the heart
  • Overriding aorta—An aorta (blood vessel) that lies over the hole in the lower chambers
  • Pulmonary stenosis—A narrowing or thickening of the valve that connects the heart to the lungs
  • Right ventricular hypertrophy—A thickening of the muscle on the right side of the heart

TOF can decrease the amount of oxygen in the blood. This makes it hard for the body to get oxygen.


TOF is caused by a problem in the way a child's heart develops during pregnancy. It is not known this happens. Genes and the environment may play a role.

Ventricular Septal Defect
Ventral septal defect
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Risk Factors

TOF is more common in people who have other family members with TOF or other genetic disorders associated with it.

These things in the mother may raise the risk are:


Most babies have symptoms in the first few weeks of life. Children with mild TOF may not have problems until later.

Low oxygen levels in the blood may cause these problems:

  • Blue coloring of the skin and lips
  • Shortness of breath and rapid breathing
  • Being very tired
  • Fainting
  • Irritability
  • Clubbing of the fingertips in older children


TOF may be suspected before birth using prenatal screenings, such as:

The diagnosis may also be suspected based on a baby's health soon after birth.

An image will be taken to confirm the diagnosis. This can be done with an echocardiogram.


Medicine may be given to ease symptoms. Surgery will also be needed. Choices are:

Temporary Surgery

Small infants with severe TOF may not be strong enough for a complete repair surgery. Surgery is done to make a temporary, new path for the blood. The blood will be sent past the problems in the heart and go directly to the lungs. This will increase blood to the lungs. It will also raise oxygen in the blood.

Complete Repair

Most children with TOF have open-heart surgery within the first few years of life. It will:

  • Close the hole in the heart by putting a patch over it
  • Improve blood flow from the heart to the lungs by one or more of these methods:
    • 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 children, a path is created between the heart and the blood vessels to the lungs.


There are no current guidelines to prevent TOF.


American Heart Association 

National Heart, Lung, and Blood Institute 


About Kids Health—The Hospital for Sick Children 

Canadian Adult Congenital Heart Network 


Ma M, Maiwaring RD, Hanley FL. Comprehensive management of major aortopulmonary collaterals in the repair of tetraology of Fallot. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann. 2018;21:75-82.

Monaco M, Williams I. Tetralogy of Fallot: fetal diagnosis to surgical correction. Minerva Pediatr. 2012 Oct;64(5):461-470.

Seki M, Kuwata S, Kurishima C, et al. Report from the Japanese Society of Pediatric Cardiology and Cardiac Surgery Research Committee on Cardiovascular Function in Adult Patients with Congenital Heart Disease: Mechanism of aortic root dilation and cardiovascular function in patients with tetralogy of Fallot. Pediatr Int. 2016 Jan [Epub ahead of print].

Tetralogy of Fallot. American Heart Association website. Available at: Accessed April 13, 2020.

Tetralogy of Fallot in infants and children. EBSCO DynaMed website. Available at:  . Updated October 10, 2018. Accessed April 13, 2020.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 02/2020
  • Update Date: 04/13/2020