Tetralogy of Fallot


Tetralogy of Fallot (ToF) is a complex form of rare congenital heart disease that changes the normal flow of blood through the heart. Because not enough blood is pumped to the lungs to be oxygenated, oxygen-poor blood flows to the body. Four main heart defects are associated with this disease:

  • Ventricular septal defect (VSD)
  • Override of the aorta over the VSD
  • Right ventricular outflow tract obstruction (pulmonary stenosis)
  • Right ventricular hypertrophy


The cause of tetralogy of Fallot is not always known. Heredity may be responsible. Also, those who have genetic disorders such as Down syndrome or DiGeorge syndrome often have tetralogy of Fallot as well as congenital heart defects.



Tetralogy of Fallot has varying degrees of right ventricular outflow obstruction. This can cause:

  • Cyanosis (bluish discoloration of the skin caused by lack of oxygen in the bloodstream)
  • Heart murmurs
  • “Clubbing” (skin or bone around the fingertips becomes enlarged)
  • "Tet spells," which occur when the oxygen level in the blood suddenly drops. These are:
    • Difficulty in breathing
    • Becoming very tired and limp
    • Not responding to a parent's voice or touch
    • Tiring easily while feeding
    • Slow weight gain
    • Becoming very fussy
    • Fainting


While a woman is pregnant, German measles (rubella), other viruses or diabetes may cause this syndrome. Pregnancy after age 40 increases the risk, as does poor nutrition or alcohol abuse. A parent who has tetralogy of Fallot has more chance of having a child with this heart defect.



Your child should be seen by a pediatric cardiologist and pediatric cardiologist surgeon. A physical exam will include listening to the baby’s heart with a stethoscope. The following tests may be used to diagnose the defect:

  • Echocardiography (echo)
  • EKG (electrocardiogram)
  • Chest X-ray
  • Pulse oximetry (using a sensor attached to a finger or toe to measure blood oxygen)
  • Cardiac catheterization


Treatment of tetralogy of Fallot usually requires at least one open-heart surgery before the first year of life. Lifelong surveillance is required due to the increased incidence of arrhythmia, exercise intolerance and reduced right ventricular function. Periodic assessment is warranted to assess the health of the right ventricle. Later on in life, most patients will require a pulmonary valve replacement. While usually performed surgically, pulmonary valve placement is becoming available in the cardiac catheterization laboratory, thanks to newer technologies.

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