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Tetralogy of Fallot

Tetralogy of Fallot belongs to a category of birth defects known as conotruncal heart defects, or outflow tract defects.

What it is

This rare and complex defect is caused by the combination of 4 congenital heart defects:

  • Ventricular septal defect (VSD)
  • Pulmonary stenosis (PS)
  • Ventricular hypertrophy (an increase in the size of the right ventricle)
  • Overriding aorta (aorta lies directly over the VSD)

These defects affect the structure of the heart, causing oxygen-poor blood to flow out of the heart and to the body’s tissues. Babies with tetralogy of Fallot often experience cyanosis, or a blue tinge to the skin, because their blood doesn’t carry enough oxygen.

Symptoms

Cyanosis, usually developed within the first year of life by babies with tetralogy of Fallot, is recognizable by dusky blue coloring of the skin, lips and mucous membranes inside the mouth and nose and under the fingernails. Blue skin at birth is only observable in infants with severe obstruction of the right ventricle outflow. A small percentage of children will never turn blue at all, especially if the PS and/or VSD is small.

Between 20% and 70% of children with unrepaired tetralogy of Fallot experience spells of extreme blue color called hypercyanosis or “tet spells.” These usually occur in the first two to three years of life. During hypercyanosis or a tet spell, child becomes blue, has trouble breathing and may become extremely irritable or may faint. Hypercyanosis often takes place during feeding, crying, straining or when awakening in the morning.

Other symptoms of Tetralogy of Fallot include:

  • Heart murmurs – extra or unusual sound a doctor may hear while listening to the heartbeat
  • Delayed growth and development – puberty may be delayed in cases of untreated tetralogy
  • Poor weight gain
  • Clubbing – the widening or rounding of the skin or bone around the tips of the fingers
  • Tiring easily or panting with exertion
  • Ability to play only for a short time before sitting or lying down
  • Squatting – once able to walk, child may squat to catch his or her breath before carrying on with activity. Squatting causes less blood to move into the left ventricle and more out the pulmonary artery to the lungs.

Causes

Several studies have linked maternal use of anti-depressants to an increased risk of the infant being born with Tetralogy of Fallot. This means infants whose mothers took certain anti-depressants just before or during pregnancy are more likely to develop heart defects including Tetralogy of Fallot than unexposed babies. For more information, click any of the drug names below. Anti-depressants include:

Treatment

Babies born with this uncommon congenital defect require surgery to correct the four defective elements. Ideally, the operation is performed soon after birth or during infancy. Most children will receive intracardiac repair surgery.  Additional treatment and medications may be required throughout life, although people with repaired tetralogy of Fallot typically live relatively normal lives.

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