Tetralogy of Fallot is a congenital heart defect. A congenital heart defect is a problem with the heart’s structure that’s present at birth. This type of heart defect changes the normal flow of blood through the heart.
Tetralogy of Fallot is a rare, complex heart defect that occurs in about 5 out of every 10,000 babies. It affects boys and girls equally.
To understand this defect, it’s helpful to know how a healthy heart works. The Diseases and Conditions Index How the Heart Works article describes the structure and function of a healthy heart.
Tetralogy of Fallot (TOF) is a cardiac anomaly that refers to a combination of four related heart defects that commonly occur together. The four defects are:
- Ventricular septal defect (VSD)
- Overriding aorta − the aortic valve is enlarged and appears to arise from both the left and right ventricles instead of the left ventricle as in normal hearts
- Pulmonary stenosis − narrowing of the pulmonary valve and outflow tract or area below the valve that creates an obstruction (blockage) of blood flow from the right ventricle to the pulmonary artery
- Right ventricular hypertrophy − thickening of the muscular walls of the right ventricle, which occurs because the right ventricle is pumping at high pressure