Definition of Tetralogy of Fallot

Tetralogy of Fallot: A combination of four heart defects that are present together at birth, accounting for about 10% of all congenital heart disease.

The four defects that constitute the tetralogy of Fallot are:

• Ventricular septal defect (VSD) -- A hole between the two bottom chambers, the ventricles, of the heart permitting oxygen-poor blood from the right ventricle to mix with oxygen-rich blood from the left ventricle.
• Pulmonary stenosis -- Narrowing of the outlet to the pulmonary artery area with an abnormal pulmonary valve impeding blood flow from the right ventricle to the lungs.
• Right ventricular hypertrophy (RVH) -- Thickening and enlargement of the muscle of the right ventricle.
• Overriding aorta -- The aorta overrides or straddles the wall (the septum) between the ventricles, permitting oxygen-poor blood to flow through the VSD into the aorta.

Children with tetralogy of Fallot have "blue" spells. These occur because the blood getting to the lungs is vastly reduced so that there is not enough oxygen reaching the body. The hole between the ventricles and the narrowed pulmonary outlet seriously hinder the flow of blood to the lungs; these defects also keep the level of oxygen in the blood too low, causing cyanosis - a blue tint to the skin. This is most noticeable with the exertion of feeding. Ways to relieve some of the symptoms include:

• Feed the child slowly and more often. Smaller meals require less effort.
• Anticipate the child's needs and fears and help to reduce anxiety, crying, and anger.
• Put the child in a knees-to-chest position on his or her side during blue spells.

Open-heart surgery is done in infancy or early childhood. Two surgeries may be done: one to palliate (ease) the situation by lessening the symptoms by increasing blood flow to the lungs and another surgery to correct the situation by repairing the underlying defects. Untreated tetralogy of Fallot is usually fatal before age 20. With open-heart surgery, there is an excellent chance of survival

History: Tetralogy of Fallot was described in 1846 by the English physician Thomas Bevill Peacock who wrote: "In this case there existed extreme contraction of the orifice of the pulmonary artery, with a deficiency in the interventricular septum, and the aorta arose in part from the right ventricle.... The heart was taken from a child two years and five months old, who had exhibited well-marked symptoms of cyanosis, which commenced three months after birth." (Ref.: Trans Path Soc London. 1846-7; 1:25)

The French physician Etienne-Louis Fallot gave a detailed description of the "maladie bleu" in 1888. He showed that it could be diagnosed before death, and that these multiple cardiac defects were common rather than rare. The eponym "tetralogy of Fallot" persists despite the fact that Fallot candidly acknowledged the fact that he was by no means the first to discover the disease.

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