Medical Definition of Tetralogy of Fallot

Reviewed on 3/29/2021

Tetralogy of Fallot: A combination of four heart defects that are present at birth and account for about 10 percent of all congenital heart disease:

  • Ventricular septal defect (VSD)A hole between the two bottom chambers, the ventricles, of the heart that permits oxygen-poor blood from the right ventricle to mix with oxygen-rich blood from the left ventricle.
  • Pulmonary stenosisNarrowing of the outlet to the pulmonary artery area with an abnormal pulmonary valve impeding blood flow from the right ventricle to the lungs.
  • Right ventricular hypertrophy (RVH)Thickening and enlargement of the muscle of the right ventricle.
  • Overriding aortaA case in which the aorta overrides or straddles the wall (the septum) between the ventricles, permitting oxygen-poor blood to flow through the VSD into the aorta.

Open-heart surgery is done on patients with tetralogy of Fallot in infancy or early childhood. Untreated tetralogy of Fallot is usually fatal before age 20. With open-heart surgery, the patient has an excellent chance of survival.


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