Tetralogy of Fallot TOF is a cardiac anomaly that refers to a combination of four related heart defects that commonly occur together. The four defects are:. A small percentage of children with tetralogy of Fallot may also have additional ventricular septal defects, an atrial septal defect ASD or abnormalities in the branching pattern of their coronary arteries.
Some patients with tetralogy of Fallot have complete obstruction to flow from the right ventricle, or pulmonary atresia. Tetralogy of Fallot may be associated with chromosomal abnormalities, such as 22q11 deletion syndrome.
The pulmonary stenosis and right ventricular outflow tract obstruction seen with tetralogy of Fallot usually limits blood flow to the lungs. When blood flow to the lungs is restricted, the combination of the ventricular septal defect and overriding aorta allows oxygen-poor blood "blue" returning to the right atrium and right ventricle to be pumped out the aorta to the body. This "shunting" of oxygen-poor blood from the right ventricle to the body results in a reduction in the arterial oxygen saturation so that babies appear cyanotic , or blue.
The cyanosis occurs because oxygen-poor blood is darker and has a blue color, so that the lips and skin appear blue. The extent of cyanosis is dependent on the amount of narrowing of the pulmonary valve and right ventricular outflow tract.
A narrower outflow tract from the right ventricle is more restrictive to blood flow to the lungs, which in turn lowers the arterial oxygen level since more oxygen-poor blood is shunted from the right ventricle to the aorta. Tetralogy of Fallot is most often diagnosed in the first few weeks of life due to either a loud murmur or cyanosis. Babies with tetralogy of Fallot usually have a patent ductus arteriosus at birth that provides additional blood flow to the lungs, so severe cyanosis is rare early after birth.
As the ductus arteriosus closes, which it typically will in the first days of life, cyanosis can develop or become more severe. The degree of cyanosis is proportional to lung blood flow and thus depends upon the degree of narrowing of the outflow tract to the pulmonary arteries. Rapid breathing in response to low oxygen levels and reduced pulmonary blood flow can occur. The heart murmur, which is commonly loud and harsh, is often absent in the first few days of life.
The arterial oxygen saturation of babies with tetralogy of Fallot can suddenly drop markedly. This phenomenon, called a "tetralogy spell," usually results from a sudden increased constriction of the outflow tract to the lungs so that pulmonary blood flow is further restricted.
The lips and skin of babies who have a sudden decrease in arterial oxygen level will appear acutely more blue. Children having a tetralogy spell will initially become extremely irritable in response to the critically low oxygen levels, and they may become sleepy or unresponsive if the severe cyanosis persists. Fox, G. Devendra, S. Hart et al. Shinebourne, S. Babu-Narayan, and J. Mahle, G. Martin, R. Beekman III et al. Liberman, K. Getz, A. Lin et al.
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View at: Google Scholar M. Tannheimer, C. Fusch, D. Bailliard and R. View at: Publisher Site Google Scholar. More related articles. Download other formats More. Normally the upper piece fuses with the lower piece during development of the heart in the womb to form an intact wall. With tetralogy of Fallot, the upper wall gets out of alignment with the lower portion of the wall during development of the heart.
It swings foward, towards the pulmonary valve, and thus creates obstruction or narrowing in blood flow out to the lungs. Tetralogy of Fallot is a cyanotic heart defect. The term cyanosis means a bluish discoloration of the skin. The cause of cyanosis is a lower than normal blood oxygen level.
Patients with tetralogy of Fallot are at risk for cyanosis because the narrowing of blood flow to the lungs in combination with a VSD or hole allows blood in many instances to bypass the lungs and go directly up to the body. The severity of cyanosis, and therefore the severity of symptoms, is determined by how the severity of pulmonary stenosis. Patients with more severe pulmonary stenosis are usually very cyanotic at birth and often need immediate attention.
Patients with less significant pulmonary stenosis may have a normal or near-normal blood oxygen levels and may be seemingly fine at birth and for several months thereafter. One of the risks of tetralogy of Fallot is what are called tet spells. A tet spell is an episode in which a child or infant becomes extremely blue and frequently agitated and out of breath. Sometimes, depending on the severity of the defects and symptoms, tetralogy of Fallot is not detected until adulthood.
All babies who have tetralogy of Fallot need corrective surgery. People with tetralogy of Fallot need regular doctor's checkups for the rest of their life and may have activity restrictions.
Tetralogy of Fallot symptoms vary, depending on the amount of blood flow that's blocked. Signs and symptoms may include:. Sometimes, babies who have tetralogy of Fallot will suddenly develop deep blue skin, nails and lips after crying or feeding, or when agitated. These episodes are called tet spells. Tet spells are caused by a rapid drop in the amount of oxygen in the blood. Tet spells are most common in young infants, around 2 to 4 months old.
Toddlers or older children might instinctively squat when they're short of breath. Squatting increases blood flow to the lungs.
If your baby becomes blue cyanotic , place your baby on his or her side and pull your baby's knees up to his or her chest. This helps increase blood flow to the lungs. Call or your local emergency number immediately. Tetralogy of Fallot occurs as the baby's heart is developing during pregnancy. Usually, the cause is unknown.
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