A rare condition, tetralogy of Fallot is characterized by four related structural heart defects that are present at birth. These defects impact how the heart works and cause oxygen-poor blood to be pumped to the body. Your child’s tissues and organs don’t receive adequate oxygen and the skin may begin to look blue. Tetralogy of Fallot is often diagnosed in babies and toddler. Diagnosis may be delayed if your child has mild TOF and no symptoms. With early intervention, most children who have TOF can lead active lives.

Wellness & Prevention

  • During the first eight weeks of pregnancy, the heart grows from a hollow tube and the four structural heart problems that make up tetralogy of Fallot can develop. Some babies have other heart defects, too, such as atrial septal defect but the four defects of TOF include:
  • Pulmonary stenosis: A narrow pulmonary valve, which connects the right ventricle to the pulmonary artery, and a narrow area before and after the valve. Pulmonary stenosis restricts blood flow from the heart to the lungs.
  • Ventricular septal defect: An opening in the wall that separates the lower chambers (ventricles) of the heart. A ventricular septal defect allows oxygen-poor and oxygen-rich blood to mix. Oxygen-rich blood also flows backward into the right ventricle and the body doesn’t get enough oxygen.
  • Overriding aorta: The aorta is attached slightly to the right of the left ventricle where it is normally. An overriding aorta aligns with the ventricular septal defect and sends mixed blood to the body.
  • Right ventricular hypertrophy: Because the heart can’t pump properly, the right ventricle can become enlarged from overwork. The muscular wall of the ventricle thickens and may eventually stiffen and weaken.

Children who have tetralogy of Fallot can’t deliver enough oxygenated blood and the skin, lips and nails may look blue (cyanosis). After feeding, crying or becoming agitated, your child may suddenly experience severe cyanosis called tetralogy or “tet” spells. A tetralogy spell is triggered by a quick drop in the amount of oxygen in the blood. The decline may be caused by higher pressure in the lungs or a tighter passageway from the right ventricle to the pulmonary artery.

The exact cause of tetralogy of Fallot isn’t known but a baby’s risk may increase from viral illness, a genetic condition, poor maternal nutrition, fetal alcohol syndrome and the mother taking seizure medication.

Tetralogy of Fallot symptoms vary depending on the severity of the defects but may include:

  • Blue-tinged skin, lips and nails when the baby cries or feeds
  • Irritability
  • Lethargy
  • Pale, ashen skin
  • Cool, clammy skin
  • Tet spells
  • Poor growth
  • Trouble breathing or feeding
  • Heart murmur


Tetralogy of Fallot may be diagnosed soon after birth if your doctor notices a blue tinge to your baby’s skin or hears a heart murmur, the extra noise caused by turbulent blood flow. A pediatric cardiologist may confirm a TOF diagnosis using these tests:

  • Chest X-ray: Your pediatric cardiologist can see the size, shape and structure of your baby’s heart in a chest X-ray. Tetralogy of Fallot can make the right ventricle bigger than normal, giving the heart a characteristic boot shape.
  • Electrocardiogram (ECG or EKG): With each contraction of the heart, an electrocardiogram records the electrical activity. An ECG can show if the right ventricle or atrium is enlarged and if your baby has an irregular heartbeat, such as arrhythmia.
  • Echocardiogram: Using high-pitched sound waves, an echocardiogram creates a moving image of how the heart functions. An echocardiogram detects ventricular septal defects and evaluates the position of the aorta, the structure of the pulmonary valve and pulmonary artery and how the right ventricle functions.
  • Cardiac catheterization: A tiny catheter is inserted through a larger blood vessel and guided to the heart to measure blood pressure and oxygen levels in the heart and blood vessels. A dye may be injected through the tube to make the heart’s structure more visible in an X-ray.

TOF may also be diagnosed with an oxygen saturation test to measure oxygen in the bloodstream.


Tetralogy of Fallot is treated with surgery, typically before your baby turns 1, to repair the defects. Your pediatric cardiologist may recommend performing the surgery at 3 to 6 months old. A temporary shunt may be placed during an earlier procedure to improve function until your baby is old enough for more extensive surgery.

To repair tetralogy of Fallot, a pediatric cardiac surgeon places a patch over the ventricular septal defect, repairs or replaces the pulmonary valve and enlarges the pulmonary artery with a patch.


Most babies recover well after treatment for tetralogy of Fallot but there can be lifelong complications, such as an irregular heartbeat or restricted blood flow. Your pediatric cardiologist may recommend restrictions on activity and follow-up care for the rest of your child’s life.