Tetralogy of fallot causes


 * Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org], Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
Both environmental and genetic factors appear to be involved in the development of Tetralogy of Fallot.

Embrylogy
Embryologic studies show that Tetralogy of Fallot is a result of anterior malalignment of the conal septum, resulting in the clinical combination of a ventricular septal defect (VSD), pulmonary stenosis, and an overriding aorta. Right ventricular hypertrophy is secondary to this combination of abnormalities, which causes resistance to blood flow from the right ventricle.

Potential Environmental Causes or Influences
Factors that increase the risk for this condition during pregnancy include:
 * Alcoholism in the mother
 * Diabetes
 * Pregnancy after the age of 40
 * Poor nutrition during pregnancy
 * Rubella or other viral illnesses during pregnancy
 * Phenylketonuria (PKU) in the mother
 * Fetal hydantoin syndrome
 * Fetal carbamazepine syndrome

Genetic Causes

 * There is a high incidence of chromosomal disorders in children with Tetralogy of Fallot
 * Tetralogy of Fallot is associated with:
 * Down syndrome
 * diGeorge syndrome (a 22q11.2 deletion, a condition associated with heart defects, hypocalcemia, and immune deficiency)


 * A gene polymorphism at the methylene tetrahydrofolate reductase (MTHFR) region has been associated with tetralogy of Fallot