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.