Tetralogy of Fallot

Tetralogy of Fallot
What is Tetralogy of Fallot?
Tetralogy of Fallot is a congenital heart defect (one which is present at birth.) In fact, it is one of the most common congenital heart defects. It affects approximately 5 in 10,000 live births. Fallot was the name of the doctor who discovered this condition and the word tetralogy relates to the four main features associated with this heart condition.
The Four Defects:
The main four abnormalities in TOF are:

  1. Pulmonary Stenosis
  2. Ventricular Septal Defect
  3. Overriding Aorta
  4. Right Ventricle Hypertrophy

Pulmonary Stenosis:
Pulmonary Stenosis is where there is an obstruction to the flow of blood from the right ventricle into the pulmonary artery caused by one or more points of narrowing. It can also be caused by the pulmonary valve being too narrow or being unable to open fully. Therefore, the blood flowing out of the right ventricle is reduced.
Ventricular Septal Defect:
A ventricular septal defect is where there is a hole between the right and left ventricles. This leads to the mixing of oxygenated blood from the left ventricle and deoxygenated blood from the right ventricle. Consequently, blood is only somewhat oxygenated and therefore not enough oxygen reaches the child’s respiring tissues.
Overriding Aorta:
This is where the aorta is enlarged and positioned above the ventricular septal defect rather than attached to the left ventricle. Thus, oxygen-poor blood from the right ventricle is able to enter the systemic circulation (circulation of blood from the heart to the body and back) more easily.
Right Ventricle Hypertrophy:
Right Ventricle Hypertrophy means that the walls of the right ventricle have become thicker. This is due to the pulmonary artery narrowing and so the muscle thickens (hypertrophies) in order to develop sufficient pressure to pump blood through the narrower artery.
The above four malformations result in a few symptoms listed below.

  • Cyanosis – bluish colour of the skin, lips and nails caused by low levels of oxygen.
  • A Heart Murmur
  • High breathing rate
  • Poor feeding and difficulty gaining weight
  • Clubbing of the fingers

Cyanosis is one indication of a heart problem. Once a new-born is seen to be cyanotic they are supplied with extra oxygen and if there is an improvement in oxygen levels then the medical staff would know that something is wrong with the lungs. However, if the oxygen levels don’t improve then the problem is cardiac.
After establishing that it’s cardiovascular the heart would then be listened to. A heart murmur would be found and so an echocardiogram would be carried out. This would reveal the four defects associated with tetralogy of Fallot and subsequently a diagnosis would be reached.
Treatment and Complications:
Tetralogy of Fallot is treated by open heart surgery and has a 98% survival rate. Some cases require surgery soon after birth whereas some require surgery 3-6 months after birth, depending on the severity of the condition. The heart is stopped and opened and a heart bypass machine performs the role of the heart for the duration of the operation. The ventricular septal defect would be closed using a patch and therefore blood will be prevented from shunting. The pulmonary valve would be widened or replaced and the pulmonary artery would be widened by removing (resecting) obstructive muscle tissue.
The main complications of this treatment are:

  • Tachycardia – a fast heart rate
  • Narrowing of the Pulmonary Artery once again
  • Narrowing of the Pulmonary Valve
  • Leaking of the Pulmonary Valve
  • Infective Endocarditis – an infection of the inner layer of the heart (endocardium).

The outlook of most patients is very good. They start to gain weight shortly after surgery and can lead normal active lives. On the other hand, they will be left with a scar down the middle of their chests and it would be necessary for them to regularly attend check-ups with a cardiologist.

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