by Kimberly Allen, RN
Tetralogy of Fallot (TOF) is the most commonly diagnosed congenital heart defect in the US. According to the CDC over 1,600 babies are born with Tetralogy of Fallot every year in the US. Tetralolgy of Fallot is also more common in boys than girls. Although TOF is a heart defect it has also been associated with other non-cardiac defects including cleft lip and cleft palate as well as craniofacial and other skeletal abnormalities. frequently children born with Down syndrome or DiGeorge syndrome will also have TOF.
Though the exact cause of TOF is unknown it occurs during fetal development. Therefore it is classified as a congenital birth defect. Most experts feel the development of TOF is a combination of genetic and environmental factors such as the mother having a viral illness like chicken pox during pregnancy or poor nutrition during pregnancy. Excess alcohol intake by the mother during pregnancy can also lead to the development of TOF. Children born to mothers over 40 years of age or if a parent has TOF also have a greater risk of developing TOF.
Because TOF leads to insufficient blood flow from the heart to the lungs to be oxygenated it is classified as a cyanotic heart disorder. Cyanotic means lacking in oxygen. Tetralogy of fallot is a combination of four separate heart defects that are all present at birth. The first is pulmonary valve stenosis. In PVS the flap or valve that separates the right ventricle in your heart from the pulmonary artery is narrowed. This impairs the blood flow from the heart to the lungs. Ventricular septal defect is another of the defects in TOF. In VSD there is an opening in the wall in your heart that separates the ventricles, which are the lower chambers in your heart. this opening allows the blood from the right ventricle, which is returning from delivering oxygen to the rest of your body on its way to the lungs to be re oxygenated, to flow through the opening into the left ventricle and mix with the blood returning from the lungs freshly oxygenated. The opening also allows the blood from the left ventricle to flow into the right ventricle causing a very inefficient oxygenation process. Another cardiac defect that is part of TOF is overriding aorta. The aorta, which is the main artery that takes the oxygenated blood from the heart to the body, normally branches off from the left ventricle. However, in this defect it is to the right a little and lies directly on top of the ventricular septal defect. This puts it in a position to receive blood from both the left and right ventricles. This mixes the blood without oxygen on it’s way to be re oxygenated with the blood from the left ventricle that has just returned freshly oxygenated. The final defect in the four defects that makes up TOF is right ventricular hypertrophy. Because the other defects especially pulmonary valve stenosis and ventricular septal defect impair the hearts pumping action the muscle has to work harder to pump the blood. This constant overworking of the muscle causes the wall of the right ventricle to become enlarged and thickened. As this condition worsens the heart may become weak and stiffen eventually leading to heart failure.
The symptoms of TOF vary depending on how severe the impairment of the blood flow from the right ventricle to the lungs. The most common symptom and usually the earliest is a bluish tint to the skin know as cyanosis, which is caused by low oxygen levels in the blood. You may also notice your child is short of breath, especially during feeding. Babies born with TOF almost always demonstrate failure to thrive syndrome, they tire easily and can be irritable.
Currently surgery is the only treatment for TOF that is effective. There are two types of surgery currently used to treat TOF. Intracardiac repair is a form of open heart surgery. This surgery is usually done during the first year of the child’s life. This surgical procedure involves placing a patch over the opening in the wall between the left and right ventricles as well as repairing and widening the pulmonary artery. The other surgical intervention is temporary surgery. Sometimes babies are born premature or are unable to gain sufficient strength for intracardiac surgery so the doctor will perform a temporary surgery to place a shunt between the aorta and the pulmonary artery to increase the blood flow to the lungs.
After your child’s cardiac defects have been repaired he/she will require ongoing care to assure the repairs are successful and monitor for any new problems that may develop.
Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to HealthAndFitnessTalk.com, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at firstname.lastname@example.org.