Tetralogy of Fallot (TOF)

What is Tetralogy of Fallot?

The heart is made up of 4 chambers. The lower two equal sized chambers are called the ventricles. The upper two equal sized chambers the atria. In a normal heart the pulmonary artery arises from the right ventricle and the aorta from the left ventricle. These outflow tracts are of equal size and show forward flow. Babies born with Tetralogy of Fallot, often abbreviated to ToF, have less blood flowing to the lungs, meaning that the level of oxygen in their blood is low.

‘Tetralogy’ means four-fold. Tetralogy of Fallot (TOF) is a heart condition that is named after the French doctor Etienne-Louis Arthur Fallot who described it in 1888 and it features 4 main defects:

• Pulmonary stenosis – a narrowing at, or below, the pulmonary valve meaning blood has difficulty getting from the right ventricle to the pulmonary artery.
• Ventricular Septal Defect – a hole between the two lower ventricles of the heart. This means that blood can leak from one side to the other.
• The entrance to the aorta lies over this Ventricular Septal Defect, meaning that deoxygentated blood is pumped into the aorta (normal hearts should only have oxygenated blood in the aorta). This is called an over-riding aorta.
• The right ventricle becomes thickened as it forces blood into the narrowed pulmonary artery – called Right Ventricular Hypertrophy.

How can Tetralogy of Fallot be spotted?

TOF can be detected during the 20-week pregnancy scan.

If it is not detected during pregnancy, then the earlier it is detected, the better for your child. A heart murmur will often be present, and your baby can appear blue, particularly on the lips and tongue, inside the mouth, and on the hands. Their breathing may be rapid, and they won’t be gaining weight as they tire very easily when feeding.

Some babies with TOF may also have “spells” – caused by a sudden drop in the oxygen level of the blood. This causes the baby to become very blue, floppy and they may even lose consciousness. If you suspect your baby has had one of these ‘spells’, contact your doctor immediately.

How can it be treated?

Most babies diagnosed with Tetralogy of Fallot will not need immediate treatment so can be discharged as normal, soon after birth. However, your baby will need to have an operation to correct the problem –  usually when they are 6 to 12 months old.

Temporary

In some babies, a temporary shunt operation may be done first to provide adequate blood flow to the lungs. This is not open-heart surgery. The shunt is usually a small tube of synthetic material sewn between a body artery (or the aorta) and the pulmonary artery. A complete repair will need to be done later, at which point the shunt will be removed.

Complete repair

Open heart surgery to repair the heart will need to be done early in life, usually before the baby is 1-year-old. Your baby will need general anaesthetic and the use of a heart-lung machine.

During the operation, the surgeon will close the Ventricular Septal Defect by sewing a patch over it. Some of the thickened muscle around the right ventricle will be removed, thus increasing the amount of blood travelling to the lungs, and the narrow pulmonary valve will be widened.

Although the operation is often called a ‘repair operation’, it never makes the heart completely normal.

General advice/info for the future

Most children are completely well, active, and gaining weight a few days after surgery, and can be discharged within one week of their operation. Your baby will have a scar down the middle of the chest, and there will be small scars where drain tubes were used, but these will fade over time.

Your cardiologist will advise you about any restrictions on activity that you should be aware of as your baby grows up, but they should be able to live a full and active life.

Children will need regular follow-ups to make sure their condition is monitored closely.

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