Tetralogy of Fallot

Tetralogy of Fallot involves four defects:



1. A large ventricular septal defect (VSD)

2. Pulmonary stenosis

3. Right ventricular hypertrophy

4. An overriding aorta   





Ventricular Septal Defect 



The heart has a wall that separates the chambers on its left side from those on its right side. This wall is called a septum. The septum prevents blood from mixing between the two sides of the heart.



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 to flow from the left ventricle into the right ventricle instead of flowing into the aorta, the main artery leading out to the body.

Pulmonary Stenosis  

This is a narrowing of the pulmonary valve and the passageway through which blood flows from the right ventricle to the pulmonary arteries. Normally, oxygen-poor blood from the right ventricle flows through the pulmonary valve into the pulmonary arteries and out to the lungs to pick up oxygen. In pulmonary stenosis, the heart has to work harder than normal to pump blood, and not enough blood can get to the lungs.

Right Ventricular Hypertrophy

This is when the right ventricle thickens because the heart has to pump harder than it should to move blood through the narrowed pulmonary valve. 

Overriding Aorta 

This is a defect in the location of the aorta. In a healthy heart, the aorta is attached to the left ventricle, allowing only oxygen-rich blood to go to the body. 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 can flow directly into the aorta instead of into the pulmonary artery to the lungs.