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 is typically episodes of bluish color to the skin (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. Tetralogy of Fallot (TOF) is a type of heart defect present at birth. Symptoms at birth may vary from none to severe. Later there is typically episodes of bluish color to the skin (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: 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. 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. It was initially described in 1671 by Niels Stensen. A further description was published in 1888 by the French physician Étienne-Louis Arthur Fallot, after whom it is named. The first total surgical repair was carried out in 1954. Tetralogy of Fallot results in low oxygenation of blood. This is due to: 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. Infants and children with unrepaired tetralogy of Fallot may develop 'tet spells'. These are acute hypoxia spells, characterized by shortness of breath, cyanosis, agitation, and loss of consciousness. This may be initiated by any event -such as anxiety, pain, dehydration, or fever- leading to decreased oxygen saturation or that causes decreased systemic vascular resistance, which in turn leads to increased shunting through the ventricular septal defect. Clinically, tet spells are characterized by a sudden, marked increase in cyanosis followed by syncope. Older children will often squat instinctively during a tet spell. This increases systemic vascular resistance and allows for a temporary reversal of the shunt. It increases pressure on the left side of the heart, decreasing the right to left shunt thus decreasing the amount of deoxygenated blood entering the systemic circulation.