Tetralogy of Fallot

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.



Tetralogy of Fallot involves four heart defects:

A large ventricular septal defect (VSD)
Pulmonary stenosis
Right ventricular hypertrophy
An overriding aorta

* Ventricular Septal Defect

A VSD is a hole in the part of the septum that separates the ventricles, the lower chambers of the heart. The hole allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood from the right ventricle.

* Pulmonary Stenosis

This defect is a narrowing of the pulmonary valve and the passage through which blood flows from the right ventricle to the pulmonary artery.In pulmonary stenosis, the heart has to work harder than normal to pump blood, and not enough blood reaches the lungs.

* Right Ventricular Hypertrophy

This defect occurs if the right ventricle thickens because the heart has to pump harder than it should to move blood through the narrowed pulmonary valve


* Overriding Aorta

In tetralogy of Fallot, the aorta is between the left and right ventricles, directly over the VSD. As a result, oxygen-poor blood from the right ventricle flows directly into the aorta instead of into the pulmonary artery to the lungs.

Together, these four defects mean that not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows out to the body.