Tetralogy of Fallot
Tetralogy of Fallot (TOF) is a type of heart defect present at birth. Symptoms at birth may vary from none to severe.Later, there are typically episodes of bluish color to the skin known as cyanosis. When affected babies cry or have a bowel movement, they may develop a "tet spell" where they turn very blue, have difficulty breathing, become limp, and occasionally lose consciousness.Other symptoms may include a heart murmur, finger clubbing, and easy tiring upon breastfeeding.
The cause is typically not known.Risk factors include a mother who uses alcohol, has diabetes, is over the age of 40, or gets rubella during pregnancy.It may also be associated with Down syndrome. Classically there are four defects:
pulmonary stenosis, narrowing of the exit from the right ventricle
a ventricular septal defect, a hole between the two ventricles
right ventricular hypertrophy, thickening of the right ventricular muscle
an overriding aorta, which allows blood from both ventricles to enter the aorta
TOF is typically treated by open heart surgery in the first year of life. Timing of surgery depends on the baby's symptoms and size.The procedure involves increasing the size of the pulmonary valve and pulmonary arteries and repairing the ventricular septal defect. In babies who are too small, a temporary surgery may be done with plans for a second surgery when the baby is bigger.With proper care, most people who are affected live to be adults. Long-term problems may include an irregular heart rate and pulmonary regurgitation.
TOF occurs in about 1 in 2,000 newborns. Males and females are affected equally.It is the most common complex congenital heart defect accounting for about 10 percent of cases.
Tetralogy of Fallot results in low oxygenation of blood. This is due to a mixing of oxygenated and deoxygenated blood in the left ventricle via the ventricular septal defect (VSD) and preferential flow of the mixed blood from both ventricles through the aorta because of the obstruction to flow through the pulmonary valve. The latter is known as a right-to-left shunt.
Infants with TOF -a cyanotic heart disease- have low blood oxygen saturation. Blood oxygenation varies greatly from one patient to another depending on the severity of the anatomic defects.Typical ranges vary from 60% to around 90%. Depending on the degree of obstruction, symptoms vary from no cyanosis or mild cyanosis to profound cyanosis at birth.If the baby is not cyanotic then it is sometimes referred to as a "pink tet".Other symptoms include a heart murmur which may range from almost imperceptible to very loud, difficulty in feeding, failure to gain weight, retarded growth and physical development, labored breathing (dyspnea) on exertion, clubbing of the fingers and toes, and polycythemia. The baby may turn blue with breast feeding or crying.
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