72. What is the tetralogy of Fallot?

The tetralogy of Fallot is a rare congenital cyanotic heart condition that consists of the following:

1. Right ventricular hypertrophy
2. Ventricular septal defect
3. Overriding aorta (aorta displaced to the right, near the VSD)
4. Pulmonic valve stenosis (right ventricular outflow tract obstruction)

This results in a net right to left cardiac shunt. Depending on the severity of right ventricular outflow tract obstruction, symptoms may be present at birth or delayed into early childhood. Tetralogy of Fallot accounts for about 10% of all congenital heart defects. Surgery is required to repair the defect in most individuals. The Blalock-Taussig shunt (subclavian artery surgically attached to pulmonary artery) was initially used in 1945. Currently, surgery includes closing the VSD and enlargement of the right ventricular outflow tract (by relieving pulmonary stenosis). Chronic pulmonic regurgitation can result as a complication of repair.