Tetralogy of Fallot: Tetralogy of Fallot is combination of four defects of the heart which occur by birth (congenital heart disease). There is a large defect in the wall between the left and right ventricles (ventricular septal defect), aorta overriding the defect, thickening of the wall of the right ventricle (right ventricular hypertrophy) and narrowing of outflow of the right ventricle (pulmonary stenosis). This results in reduced blood supply to the lungs and mixing of deoxygenated and oxygenated blood in the ventricles. As a result oxygen content of blood flowing to the different organs of the body is reduced. This leads to blue color (cyanosis) and these babies are called ‘blue babies’. It is the commonest form of cyanotic congenital heart disease for which survival to adult life is possible.
What symptoms can occur in a child with Tetralogy of Fallot?
Most striking feature is the is bluish color, more prominent in fair skinned individuals. The intensity of the color may vary from time to time and depending on the severity of obstruction of blood flow to the lungs. Episodic worsening of blue color, often with rapid breathing and sometimes with fits is called cyanotic spells or Tet spells (short for Tetralogy). It may occur after a bout of crying or other form of exertion.
Another important feature seen in older children is squatting after exertion. Squatting compresses the blood vessels of the legs (veins) and prevents return of blood with lower oxygen content flowing from exercising muscles of the legs to the heart. Compression of the arteries (blood vessel carrying oxygenated blood) to the legs increases the resistance to the pumping of the left ventricle. Increasing pressure in the left ventricle reduces the passage of blood from right ventricle to the left ventricle across the ventricular septal defect. This allows more blood from the right ventricle to reach the pulmonary artery (blood vessel to the lung) for oxygenation.
How can Tetralogy of Fallot be treated?
Tetralogy of Fallot needs early surgical repair. But timing of surgery depends on the health status of the baby and the level of expertise available in the treating center. In advanced centers surgery is possible on the first day of life itself, in selected cases. When an early repair is not feasible some temporary shunt surgeries can be done as a palliative procedure and a definitive procedure carried out later. Occurrence of cyanotic spells can be prevented to some extend by giving medications. Palliative procedures done using X-ray fluoroscopic guidance in the cardiac catheterization laboratory are also done in some centers. These procedures have the advantage of avoiding a major surgery in a sick new born baby and buys time for the major surgery. Major surgery can be done with better safety when the medical status of the baby is better after an initial palliative procedure.
How is Tetralogy of Fallot confirmed?
When it is suspected on physical examination, it is most often confirmed by ultrasound examination of the heart (echocardiography). Being a non-invasive test available in most major hospitals, it is easy to perform. Sometimes the baby may be uncooperative and we may have to wait till natural sleep occurs. Alternatively cautious use of sedative medication may be needed to complete the study.