Tetralogy of Fallot

What is Tetralogy of Fallot?

(© Competence Network for Congenital Heart Defects)

Etienne Fallot was a French doctor who first spotted this particular type of heart condition. Tetralogy means fourfold – there are four defects found together.

The four problems are:

1. Sub-Pulmonary stenosis

Pulmonary means ‘of the lungs’. Stenosis means narrowing. Sub-Pulmonary stenosis is a narrowing below the pulmonary valve.  This means that blood has difficulty getting from the right ventricle into the pulmonary artery.

2. Ventricular Septal Defect (VSD)

Ventricular means ‘of the ventricles’ - the pumping chambers of the heart. Septal means ‘of the septum’ – the wall between the right and left sides of the heart. Defect means a hole. So a VSD is a hole in the wall between the ventricles.  This means that blood can leak from one side to the other.

3. Over-riding aorta

The entrance to the aorta, which should only take red (oxygenated) blood round the body, lies over the VSD. This allows the right ventricle to pump some blue (deoxygenated) blood directly into the aorta through the VSD.

4. Thick right ventricle

The right ventricle becomes thickened as it works harder to force blood into the narrowed pulmonary artery.

Other conditions

Tetralogy of Fallot is sometimes part of a syndrome, such as Down’s Syndrome or 22q11 deletion (Di George Syndrome).


Tetralogy of Fallot (ToF) can sometimes be seen on a scan during pregnancy. It may also be diagnosed after birth if your baby is showing symptoms.

ToF will normally cause your baby to become more blue (cyanosed). They may also get breathless quickly and need to breathe rapidly. Occasionally babies with ToF will experience a ‘tetralogy spell’ – increased blueness and fainting - caused by a rapid drop in the amount of oxygen in the blood.

The sound of blood moving through the narrow pulmonary valve can also be heard as a heart murmur. When a heart murmur is heard the tests used can be:


All children with ToF will need heart surgery at some point in their lives to treat the condition. Sometimes, however, your child may first need to undergo temporary treatment to increase the amount of blood getting to the lungs.

There are two ways of increasing the amount of blood reaching the lungs:

1. Shunt

One way of increasing blood flow to the lungs is by creating a bypass between the aorta and the pulmonary artery (a BT shunt). This operation is carried out through the side of the chest, and the heart doesn’t have to be stopped.

2. Balloon dilation

Another way of increasing blood to the lungs is to use a balloon catheter. A balloon is inserted from a vein in the groin into the narrow part of the pulmonary artery, and then inflated, so stretching the pulmonary valve and part of the opening below it. This does not leave any scars.

Open heart surgery

The aim of the operation is to make the circulation of blood through the heart and lungs normal. To do this the heart will need to be stopped and opened, so a heart bypass machine will take over the job that the heart normally does.

During the surgery, a patch is put over the VSD to close the hole between the ventricles. The narrow area around the pulmonary valve is also enlarged to increase blood flow to the lungs.

After surgery

Cases of ToF can be more complicated than this description, so there cannot be guarantees of how well your child will do.

Some of the following problems can occur after surgery or later in life:

  • It is not uncommon for a child to pick up an infection, such as a chest infection or infected wound, while undergoing treatment.
  • Your child may develop a very fast heart rate which can need medicine to keep it stable.
  • The pulmonary valve may leak, which, when severe, may need repair or replacing.

But most children are completely well, active, and gaining weight a few days after surgery. Your child will have a scar down the middle of the chest, and there will be small scars where drain tubes were used. These fade very rapidly in most children, but they will not go altogether. Smaller scars on the hands and neck usually fade away to nothing.

After the first year, your child will be monitored infrequently by a cardiologist.

Author(s): Children’s Heart Federation
Last updated: 2010-04-08