What exactly happens in ToF ?

It is quite difficult to explain (so please excuse me if I seem vague), but there are basically TWO major problems with ToF.

What is Veno-arterial mixing ?

In ToF, and a few other defects too, the "impure" blood returning through the veins to the right ventricle mixes with the arterial blood. This mixing decreases the amount of oxygen in the blood reaching the aorta. Blood from the aorta reaches all organs of the body. So all organs - brain, kidneys, liver, muscles - now get a lesser amount of oxygen, which is the life-giving gas. As a result, they are not able to work normally. In older children, this is shown by a limitation in work and play. Children with ToF cannot play strenuous games. They often "squat" down in a typical position after some time to relieve their giddiness and tiredness.
Other problems also exist. Due to a narrow pulmonary valve, less blood enters the blood vessels of the lung - the pulmonary arteries. Because of this low blood flow, these arteries do not grow in size as the child grows older. In severe cases, the pulmonary arteries may not develop at all, and may be absent. This condition is called Pulmonary Atresia. The size and development of the pulmonary artery is very important in deciding about the timing of an operation, and the choice of procedure.
Another complication is Paradoxical Embolism. Strokes and infection of the brain (called Cerebral Abscess) can occur because of this.
By far the most dangerous complication of ToF is the CYANOTIC SPELL. During a cyanotic spell, the child develops very rapid deep breathing and sweating. The bluish color becomes deeper. The child may become limp and lose consciousness. Seizures - or "fits" - may also occur. Rarely, a spell may be fatal. This is why the presence of multiple frequent spells makes early surgery necessary. Spells occur most frequently in the first six months of life. They most often occur after feeding or crying, especially when the child has just woken up from deep sleep.

What causes a spell ?

There may be "spasm" or contraction of a band of muscle in the right ventricle just under the pulmonary valve. When this muscle contracts, it further narrows the channel for blood flow into the lungs. As a result, oxygen delivery becomes further reduced. This causes a spell. Luckily, after some time, this muscle relaxes. Once again, blood flow into the lungs is restored, and oxygen supply increases. The spell is "broken".

What happens if ToF is untreated ? Find out .....

 

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