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:

  1. A hole between the ventricles or the lower chambers of the heart, called a ventricular septal defect (VSD).
  2. A blockage or kink in the pulmonary artery where blood flows from the heart to the lungs.
  3. The aorta, the largest blood vessel, lies over the hole (VSD) in the lower chambers of the heart.
  4. 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.

See why our outcomes make us one of the top heart hospitals

Get to know our pediatric experts.

Michael Di Maria, MD

Michael Di Maria, MD

Cardiology - Pediatric, Pediatrics

Joseph Kay, MD

Joseph Kay, MD

Cardiology, Cardiology - Pediatric

Jessica Church, APN

Jessica Church, APN

Certified Pediatric Nurse Practitioner

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Mark Farina, PA-C, MS

Mark Farina, PA-C, MS

Physician Assistant

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Children's Colorado in the news

9News

Adults find treatment for congenital heart disease at Children’s Colorado

July 3, 2019

Born with a congenital heart defect, Chris Dini now works as a firefighter in Fort Collins. Though he’s now 38, he still receives treatment at Children’s Colorado. Joseph Kay, MD, wants more teens and adults with congenital heart disease to know they need specialized care as they age.