Tetralogy of Fallot

Tetralogy of Fallot (TOF) is a combination of four congenital heart defects — ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy and overriding aorta — that change the way blood flows to the lungs and through the heart.

Surgeons at Norton Children’s Heart Institute, affiliated with the University of Louisville, repair tetralogy of Fallot (pronounced fah-LO) with open-heart surgery soon after birth or later in infancy. Some infants need more than one heart surgery.

Most babies recover from TOF and go on to lead full lives. Still, it’s a serious condition that will need regular follow-up visits with a heart specialist.

As the leading providers of pediatric heart care in Louisville and Southern Indiana, our specialists are experienced with successfully repairing tetralogy of Fallot.

The board-certified and fellowship-trained specialists at Norton Children’s Heart Institute have the skill and experience to provide a pinpoint diagnosis and develop a customized treatment plan for you and your child.

What is tetralogy of Fallot?

The four related conditions that make up tetralogy of Fallot are:

Ventricular septal defect

A ventricular septal defect is a hole in the wall that separates the ventricles, the two lower chambers of the heart. Because of the hole, the high-oxygen blood from the left ventricle and the low-oxygen blood from the right ventricle can mix. This can lead to either too little or too much blood flow going to the lungs.

Pulmonary stenosis

The stenosis is a narrowing of the valve that connects the right ventricle to the pulmonary artery that connects to the lungs.

With pulmonary stenosis, the heart has to work harder and there is less blood traveling to the lungs. Sometimes infants with TOF have pulmonary atresia instead, which is a complete closure of the pulmonary valve.

Right ventricular hypertrophy

Right ventricular hypertrophy (hi-PER-truh-fee) is a thickening of the muscular wall of the right ventricle. The thickened wall can partly block blood from flowing through the pulmonary valve.

Overriding aorta

This means the artery that carries high-oxygen blood to the body is out of place — arching over both ventricles instead of just the left. The misplacement allows some low-oxygen blood into the aorta and out to the body. Low-oxygen blood should pass through the pulmonary artery and the lungs to pick up oxygen before circulating to the body.

In most cases of tetralogy of Fallot, not enough blood goes to the lungs. This low-oxygen blood then circulates to the rest of the body. Babies with TOF often have a condition called cyanosis — a blue or purple tint to the skin, lips and fingernails.

If tetralogy of Fallot isn’t treated, a child may have:

  • Cyanosis that gets worse
  • “Spells” when blood oxygen levels become very low
  • Dizziness, fainting or seizures
  • A higher risk of endocarditis, an infection of the inner layer of the heart
  • High pressure in the right side of the heart that can cause an irregular heartbeat (arrhythmia)

Children whose TOF isn’t repaired usually become increasingly blue over time and have difficulty participating in sports and other physical activities. Most babies who have surgery to correct the defect do very well and can participate in normal activities.

Tetralogy of Fallot symptoms

Cyanosis is a very common sign. Healthy babies also sometimes have bluish skin around the mouth or eyes from prominent veins under the skin. Babies who have low oxygen levels in the blood usually have blue lips and tongues in addition to bluish skin.

A child with TOF might have sudden episodes of deep cyanosis, called “hypercyanotic spells” or “Tet spells,” during crying or feeding. Older children who have Tet spells will often instinctively squat down, which helps to stop the spell.

Other signs include:

  • Heart murmur
  • Fussiness
  • Tiring easily
  • Difficulty breathing
  • Rapid heartbeat (palpitations)
  • Fainting
  • “Clubbing,” when the skin or bones around the tips of the fingers become widened or rounded

The specific cause of tetralogy of Fallot isn’t always known. The TOF changes in a baby’s heart develop in the early weeks of pregnancy. In some cases, there are genetic causes of TOF — for example, children with Down syndrome or DiGeorge syndrome are more likely to have TOF. Someone born with TOF is more likely to have a child or sibling with it. Each year, roughly 1 out of every 2,500 babies born in the United States has the condition.

Tetralogy of Fallot diagnosis

Doctors might do several tests to find out if a baby has tetralogy of Fallot and to get more details about the baby’s heart and blood vessels, including:

  • Pulse oximeterA small sensor that clips onto the fingertip, toe or ear and measures how much oxygen is in the blood
  • Electrocardiogram (ECG or EKG)A test that records the electrical activity of the heart
  • EchocardiogramAn ultrasound picture of the heart that records the motion of blood through the heart and the direction and speed of blood flow
  • Chest X-ray: An image of the heart and surrounding organs
  • Cardiac catheterizationAn examination using a thin, flexible tube that is threaded through a vein in the leg or arm to the heart

Tetralogy of Fallot repair

The cardiothoracic surgeons at Norton Children’s Heart Institute repair tetralogy of Fallot through open-heart surgery soon after birth or later in infancy. The timing depends on the baby’s health and weight and severity of the defects.

The two surgical options are:

  • Complete repair:The surgeon widens the passageway between the right ventricle and the pulmonary artery to improve blood flow to the lungs. The ventricular septal defect (VSD) is patched.These repairs also fix the two remaining defects (overriding aorta and right ventricular hypertrophy). Because the right ventricle doesn’t have to work as hard to pump blood into the lungs, the thickness of the ventricle wall will decrease. The patched VSD prevents blood with low oxygen from flowing into the aorta.


  • Temporary or palliative surgery:Minor repairs can improve blood flow to the lungs. This usually is done only when a baby is too weak or small to have full surgery. The surgeon creates a secondary route for blood to travel to the lungs for oxygen by placing a shunt — a small tube — between a large artery branching off the aorta and the pulmonary artery.The full repair is done later when the baby grows stronger.

Why Norton Children’s Heart Institute?

Norton Children’s Heart Institute, affiliated with the University of Louisville, is a comprehensive pediatric heart surgery, heart failure and heart transplant program serving Kentucky, Southern Indiana and beyond.

The goal of the full-service Norton Children’s Heart Institute is to provide care for the child and the whole family. Our specialists are prepared to repair even the most complex congenital and acquired heart conditions.

Our heart team includes:

  • Pediatric cardiothoracic surgeons
  • Pediatric transplant surgeons
  • Pediatric cardiologists
    • Fetal cardiologists
    • Adult congenital heart cardiologists
    • Heart failure/heart transplant cardiologists
    • Pediatric electrophysiologists
    • Pediatric cardiac catheterization cardiologists
  • Pediatric cardiovascular anesthesiologists
  • Pediatric intensive care physicians
  • Cardiac critical care nurses
  • Critical care pharmacists
  • Family support team
  • Child life specialists
  • Rehabilitation specialists
  • Social workers
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