Tetralogy of Fallot



Tetralogy of Fallot (TOF) is a combination of 4 heart defects. It is present at birth. These defects make it difficult for your child to get oxygen to the entire body.The defects are:
  • Ventricular septal defect (VSD)—A hole in the heart. It is on a wall that separates the 2 lower chambers.
  • Overriding aorta—The aorta, which is the body's largest artery coming out of the left ventricle, partially covers or comes out of the right ventricle.
  • Pulmonary stenosis—The valve in the heart that allows blood to pass from the heart toward the lungs is too narrow.
  • Right ventricular hypertrophy—The muscle on the right side of the heart is too thick.
VSD and overriding aorta can decrease the amount of oxygen in the blood. This makes it difficult for the body to get the oxygen it needs. Pulmonary stenosis and right ventricular hypertrophy can make it difficult for blood to pass to the lungs. This will also decrease the amount of oxygen in the blood.


A child's heart develops very early in pregnancy. TOF is caused by a problem during this development. It is not known exactly why these problems happen. Some have been associated with genetics, mother's nutrition, or infections. Most have no known cause.
Ventricular Septal Defect
Ventral septal defect
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Risk Factors

Factors that may increase the risk of TOF include:
  • Family history
  • Mother's use of retinoic acid
  • Mother's use of oral fluconazole
  • Mother's alcohol use
  • Mother has infection with rubella
  • Pregnancy in mothers over 40
  • Maternal diabetes
Some people who have TOF also have a chromosome disorder. This may include Down syndrome, CHARGE syndrome, and VACTERL association.

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