Tetralogy of Fallot (TOF) is a type of heart defect present at birth. Symptoms include episodes of bluish color to the skin. 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. 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. 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 surgical repair was carried out in 1954.
Tet spells may be treated with beta-blockers such as propranolol, but acute episodes require rapid intervention with morphine or intranasal fentanyl to reduce ventilatory drive, a vasopressor such as phenylephrine, or norepinephrine to increase systemic vascular resistance, and IV fluids for volume expansion.
Oxygen (100%) may be effective in treating spells because it is a potent pulmonary vasodilator and systemic vasoconstrictor. This allows more blood flow to the lungs by decreasing shunting of deoxygenated blood from the right to left ventricle through the VSD. There are also simple procedures such as squatting and the knee chest position which increase systemic vascular resistance and decrease right-to-left shunting of deoxygenated blood into the systemic circulation.
The condition was initially thought untreatable until surgeon Alfred Blalock, cardiologist Helen B. Taussig, and lab assistant Vivien Thomas at Johns Hopkins University developed a palliative surgical procedure, which involved forming a side to end anastomosis between the subclavian artery and the pulmonary artery. This first surgery was depicted in the film Something the Lord Made. It was actually Helen Taussig who convinced Alfred Blalock that the shunt was going to work. This redirected a large portion of the partially oxygenated blood leaving the heart for the body into the lungs, increasing flow through the pulmonary circuit, and greatly relieving symptoms in patients. The first Blalock-Thomas-Taussig shunt surgery was performed on 15-month-old Eileen Saxon on November 29, 1944 with dramatic results.
The Potts shunt and the Waterston-Cooley shunt are other shunt procedures which were developed for the same purpose. These are no longer used.
Currently, Blalock-Thomas-Taussig shunts are not normally performed on infants with TOF except for severe variants such as TOF with pulmonary atresia (pseudotruncus arteriosus).
Total surgical repair
The Blalock-Thomas-Taussig procedure, initially the only surgical treatment available for tetralogy of Fallot, was palliative but not curative. The first total repair of tetralogy of Fallot was done by a team led by C. Walton Lillehei at the University of Minnesota in 1954 on an 11-year-old boy.Total repair on infants has had success from 1981, with research indicating that it has a comparatively low mortality rate.
Total repair of tetralogy of Fallot initially carried a high mortality risk, but this risk has gone down steadily over the years. Surgery is now often carried out in infants one year of age or younger with less than 5% perioperative mortality. The open-heart surgery is designed to relieve the right ventricular outflow tract stenosis by careful resection of muscle and to repair the VSD with a Gore-Tex patch or a homograft. Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy.