Tetralogy of Fallot


Tetralogy of Fallot (TOF) is a complex congenital heart condition that involves four defects in the heart’s structure. These defects change the normal flow of blood through the heart, causing oxygen-poor blood to flow out of the heart and into the body.

The condition occurs during the first eight weeks of pregnancy when the fetal heart fails to develop correctly.

Tetralogy of Fallot requires heart surgery within the first year of life. For our fetal cardiology program patients, surgery is performed at Texas Children’s Heart Center, ranked #1 in the nation for pediatric cardiology and heart surgery by U.S. News and World Report.

One Condition, Four Defects

The name tetralogy of Fallot comes from the Greek word for four – “tetra” – and the French physician, Étienne-Louis-Arthur Fallot, who first described the condition. 

The four heart defects that make up this complex condition include:

  1. Ventricular septal defect (VSD) – an abnormal opening in the wall between the two lower chambers of the heart (left and right ventricles). This opening allows blood from each side of the heart – oxygen-rich and oxygen-poor blood – to mix together. As a result, the blood isn’t as high in oxygen as it should be.
  2. Pulmonary stenosis (PS) – a narrowed area within the main pulmonary artery, at, above or below the pulmonary valve, reducing blood flow to the lungs.
  3. Malpositioned or overriding aorta – the entrance to the aorta, the large artery that takes blood out to the body, is positioned over both ventricles instead of the left ventricle, causing blood to flow into the aorta from both the right and left ventricle, further diluting the oxygen supply in the blood.
  4. Ventricular hypertrophy – an overly muscular (enlarged) right ventricle, caused by the heart having to work harder than normal to pump enough oxygenated blood out into the body.

How will tetralogy of Fallot affect my baby?

In a normal heart, oxygen-poor (blue) blood flows to the right side of the heart, where it is pumped through the pulmonary valve and into the lungs to receive more oxygen.

In babies with tetralogy of Fallot, the pulmonary stenosis defect (narrowed area within the main pulmonary artery) makes it harder for blood to flow out of the right side of the heart. This causes oxygen-poor blood to travel across the heart, through the ventricular septal defect (VSD) into the left ventricle, and then out into the aorta, which distributes the blood to the rest of the body.

When the aorta carries this “mixed” (oxygen-poor and oxygen rich) blood out into the body, less oxygen is available to the tissues, causing cyanosis – blue or purple coloration of the skin or mucous membranes such as the lips or mouth, also known as “blue baby syndrome.”

Babies born with severe tetralogy of Fallot may suddenly develop deep blue skin, nails and lips after crying, feeding or a bowel movement. These episodes are called “tet spells.” Tet spells are caused by a rapid drop in the amount of oxygen in the blood. They are most common in young infants, around 2 to 4 months old.

Some babies with tetralogy of Fallot may have other heart defects, such as a hole in the wall between the heart’s upper chambers (atria), known as an atrial septal defect.

In rare cases, children with tetralogy of Fallot may have a complete blockage of the pulmonary valve, with no connection between the right side of the heart and the lungs. This is known as tetralogy of Fallot with pulmonary atresia.

Cause and Prevalence

Tetralogy of Fallot is rare, occurring in approximately 5 out of every 10,000 babies.

The cause of the condition is typically unknown. It may be more common with certain chromosomal abnormalities such as Down’s or DiGeorge’s syndromes, or in women who contract certain infections during pregnancy, such as rubella.

Heredity may also play a role, with those born with tetralogy of Fallot more likely to have a child with the condition.

Testing and Diagnosis

Tetralogy of Fallot may be diagnosed during a routine pregnancy ultrasound or in some cases after the baby is born.

If a heart defect is detected during pregnancy, you may be referred to a fetal center for a comprehensive evaluation and specialized care.

At Texas Children’s Fetal Center, we arrange for you to meet with a team of specialists experienced in diagnosing and treating congenital heart defects, including maternal-fetal medicine physicians, cardiologists, neonatologists, genetic counselors, and fetal imaging experts.

You will undergo additional testing, including a fetal echocardiogram, to help us gain more information about the structure and function of your baby’s heart.  

Following a thorough evaluation and assessment, our specialists will meet with you about the results, answer any questions you have, and provide treatment recommendations based on the unique needs of your baby and your pregnancy.

Treatment During Pregnancy

Mother and baby will be closely monitored throughout pregnancy, with regular ultrasounds to assess fetal growth and development.

Because the fetus is getting oxygen through the placenta during pregnancy, treatment isn’t required until after the baby is born. At birth, heart function becomes critical as the baby transitions to receiving oxygen from their lungs. The baby’s oxygenated blood supply will be compromised due to the heart defects. Heart surgery is required within the first year of life.

A diagnosis during pregnancy enables your family and your healthcare team to plan ahead for the special care and treatment needs your baby will have at birth, optimizing long-term outcomes.


Because tetralogy of Fallot is a potentially life-threatening condition, delivery should take place at a facility with the highest quality congenital heart program, ensuring the expertise and resources required at birth to treat this complex congenital heart defect, including an advanced neonatal intensive care unit (NICU) and specialists available should heart surgery be required.

Our fetal center specialists work closely with Texas Children’s Heart Center, seamlessly transitioning your baby’s care at delivery to this national leader in pediatric cardiology and heart surgery.

Following delivery at Texas Children’s Pavilion for Women, newborns are transferred to Texas Children’s level IV neonatal intensive care unit (NICU), the highest level of care available for premature and critically-ill newborns.

To prepare your family for this birth, Texas Children’s Fetal Center offers a family-centered class designed specifically for caregivers and parents whose babies have received a prenatal diagnosis and will be hospitalized in intensive care after birth. Learn more about Preparing For Your Newborn’s Hospitalization.

Testing After Birth

Additional testing may be recommended after birth to gain more information about the four heart defects, any additional issues, and the severity of your baby’s condition.

Testing after birth may include:

  • Chest x-ray
  • Complete blood count (CBC)
  • Echocardiogram
  • Electrocardiogram (EKG)
  • Cardiac catheterization

Surgery After Birth

Treatment for tetralogy of Fallot is open heart surgery in the first year of life to repair the defects. The goal is to allow blood to flow properly through the heart, with normal oxygen levels in the blood.

At Texas Children’s Heart Center, our surgical approach is tailored around your baby’s age, anatomy and symptoms. This individualized approach enables us to repair the defects and preserve critical parts of the heart’s structure, optimizing your child’s cardiac function long-term.

Based on our team’s assessment, surgery will be undertaken in either one or two stages during the first year of life.

Temporary shunt. If the baby is too small or too weak for open heart surgery, the first stage of treatment may be a temporary shunt procedure to increase blood flow to the lungs while allowing the infant time to grow and get strong enough to undergo a full repair.

In this procedure, known as a Blalock-Taussig shunt, a small shunt (tube) is temporarily placed between the aorta and pulmonary artery to provide adequate blood flow to the lungs. The shunt is removed when surgery is performed to repair the heart defects.

Complete tetralogy of Fallot repair. During this open heart surgery:

  • The abnormal opening (VSD) between the lower chambers of the heart is closed with a patch to prevent right-to-left blood flow (the mixing together of oxygen-rich and oxygen-poor blood between the ventricles).
  • The right ventricular outflow tract (pulmonary artery/valve) is widened to improve blood flow to the lungs.
tetralogy of fallot


Repairing these two defects resolves the issues caused by the remaining two defects.

For babies who also have pulmonary atresia, a new valve will be inserted to connect the right ventricle to the lung artery.

Long-Term Care and Outcomes

With specialized medical care and surgery, most children with tetralogy of Fallot live relatively normal lives and survive to adulthood.

Life-long monitoring by cardiologists experienced in the treatment of congenital heart defects is a critical component of care for babies born with tetralogy of Fallot.

At Texas Children’s Heart Center, our pediatric cardiologists will follow your child through adolescence, seamlessly transitioning their care at adulthood to our Adult Congenital Heart Disease (ACHD) program

Texas Children’s – #1 in the Nation for Pediatric Cardiology and Heart Surgery

Texas Children’s Pavilion for Women and Texas Children’s Fetal Center are nationally recognized centers for the care of fetuses and infants with congenital heart defects, providing mother and baby expert maternal, fetal and pediatric care all in one location.

Our Fetal Cardiology Program is a collaboration between our Fetal Center and Texas Children’s Heart Center, ranked #1 in the nation for pediatric cardiology and heart surgery by U.S. News & World Report.

Through this multidisciplinary team of experts, we offer comprehensive fetal cardiac care for babies with congenital heart defects, including diagnosis, counseling, delivery planning and seamless transition at birth to Texas Children’s Heart Center, a pioneer in the care of children’s hearts with outcomes among the best in the nation.

In the News

Patient Stories


Other Resources

Volumes and Outcomes

The Congenital Heart Surgery Division at Texas Children’s Heart Center performs an average of 30 tetralogy of Fallot repairs each year with a survival rate of nearly 99%. 

Research and Clinical Trials

Texas Children’s, together with our partner institution Baylor College of Medicine, constantly strives to seek new and better treatments for babies with congenital heart defects.

For more information, please contact the Cardiovascular Clinical Research Core at 832-826-2064 or email sandrea@texaschildrens.org.

Learn more about our fetal cardiology research.