Tetralogy of Fallot

Definition:

A congenital defect of the heart consisting of 4 abnormalities that results in insufficiently oxygenated blood pumped to the body.

Causes, incidence, and risk factors:

The cause of most congenital heart defects is unknown. Prenatal factors that are associated with a higher than normal incidence of the disease include maternal rubella or other viral illnesses during pregnancy, poor prenatal nutrition, maternal alcoholism, mother over 40 years old, and diabetes. There is a higher incidence of Tetralogy of Fallot in children with Down syndrome.

Tetralogy of Fallot is classified as a cyanotic heart defect because the condition results in insufficiently oxygenated blood pumped to the body, which leads to cyanosis (a bluish-purple coloration to the skin) and shortness of breath. The classic form of Tetralogy includes 4 defects within the heart structures: ventricular septal defect (hole between the right and left ventricles); narrowing of the pulmonary (lung) valve; displaced aorta; and thickened wall of the right ventricle. There is flow of unoxygenated blood into general circulation, and a decreased blood flow to the lungs, which compounds the cyanotic condition. At birth, infants do not show the signs of the cyanosis but later may develop episodes of bluish skin from crying or feeding (called "Tet spells"). Tetralogy of Fallot occurs in approximately 50 out of 100,000 infants. It is the 2nd most common cause of congenital cyanotic heart disease in infants.