What causes tetralogy of Fallot?
Tetralogy of Fallot occurs due to improper development of the heart in the first 8 weeks of fetal growth. Tetralogy of Fallot results in decreased blood flow to the lungs and circulation of blue (unoxygenated) blood to the body tissues; both of these effects cause bluish skin (cyanosis), clubbing (bulging of the nailbeds) of the fingers and toes, shortness of breath, and
extreme fatigue.
Babies with tetralogy of Fallot are blue at birth (cyanosis). Sometimes the blue color appears only when they cry. They also have detectable heart murmurs. Infants with mild forms can have surgery postponed until they are older. Infants with more severe symptoms often have attacks of worsened cyanosis. During attacks, they turn very blue, have shortness of breath, and can faint. This usually occurs during heightened activity, such as crying.
Most of the time, this heart defect occurs sporadically (by chance), with no clear reason evident for its development. Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families. One genetic link that has been associated with tetralogy of Fallot, is a deletion, or tiny missing piece, of chromosone 22q11. This is present in a minority of patients but is thought to be more common in those with a severe form of tetralogy of Fallot, with pulmonary atresia. The condition is known as the 22q11 deletion and blood tests are available to detect it.
Environmental exposures, such as maternal abuse of alcohol during pregnancy, leading to fetal alcohol syndrome (FAS), is linked to tetralogy of Fallot. Mothers who take medications to control seizures and mothers with phenylketonuria (PKU) are also more likely to have a baby with tetralogy of Fallot. |
