Tetralogy of Fallot
Named for the French physician who first described it in 1888, tetralogy of Fallot is a type of heart defect that is present at birth (congenital heart disease). According to the American Heart Association, it occurs in less than 5 out of 10,000 babies. It involves a tetralogy (a complex of four conditions) that includes: Ventricular septal defect (VSD). A hole in the wall (septum) between the heart’s two lower chambers (the ventricles). The VSD is the prime defect with tetralogy of Fallot and leads to all the other conditions seen. This particular VSD however is different than most other VSDs in that its position is shiftCongenital heart disease is any heart abnormality, defect or malformation present from birth.ed in such a way that there is a tendency for much of the blood from the right ventricle to be shunted toward the left ventricle. This tendency to have the blood criss-cross at the VSD results in a significant amount of oxygen poor blood being pumped out to the body without going to the lungs first. Hypertrophy (enlargement and thickening) of the right ventricle. An enlargement of the muscle tissue of the right ventricle due to overexertion, usually as a result of increased blood flow to the right side of the heart (caused by the VSD) and by blockage of the blood being pumped out to the lungs. Much of the hypertrophy is secondary to the unusual location of the VSD causing some of the muscle bundles in the right ventricle to abnormally thicken. This will block the channel through which the right ventricle pumps blood out to the lungs. Pulmonary stenosis. A narrowing (stenosis) of the pulmonary valve or the channel in the right ventricle leading to the pulmonary valve. This narrowing decreases the amount of oxygen-poor blood from the right ventricle that can travel through the pulmonary artery to the lungs. Thus, there is a decreased blood flow to the lungs. Displaced, deviated or overriding aorta. This is another effect of the location of the VSD. Instead of opening into the left ventricle, which pumps oxygen-rich blood into the aorta, the main artery out to the body opens into both the right and left ventricle. This allows excess blood in the right ventricle (usually as a result of pulmonary stenosis) to be pumped out to the body. Because the body is receiving so much oxygen-poor blood, the skin of the child often has a bluish tint (cyanosis, or blue baby when occurring in infants). Prenatal heart circulation is different than adults and the heart continues to evolve after birth. The combination of these four heart defects lead to reduced blood flow to the lungs because less oxygen-poor blood can squeeze through the pulmonary valve to get to the lungs, and more oxygen-poor blood is pumped to the tissues of the body.
One of the most obvious symptoms of tetralogy of Fallot is a bluish tint to the skin (cyanosis, or blue baby when occurring in infants) of a baby or young person. The skin, lips, fingernails and tongue are often blue or otherwise discolored, especially after exertion (which for babies is most often during feeding time). The condition may also cause periods of profound cyanosis, when the outflow of blood from the right ventricle is nearly blocked. These are called tet spells, and should be treated immediately. Blue Baby Other symptoms include:
- Difficult feeding
- Low weight gain
- Shortness of breath, dyspnea and/or fatigue, especially after exercise or exertion
- Slow growth and development in the first five years
- Clubbed fingers if not corrected in the first few years of life (this is rarely seen nowadays)
In some cases, infants with tetralogy of Fallot have other defects, such as a patent ductus arteriosus, that may temporarily allow oxygen-rich blood to circulate the body. This may reduce the appearance of symptoms in the early stages of life.
Like many other types of congenital heart disease, there is no known prevention for tetralogy of Fallot. However, some risk factors that have been linked to a higher occurrence of this defect. They include:
- Maternal viral infection during pregnancy, especially with rubella (German measles)
- Maternal alcoholism
- Poor prenatal nutrition
- Mother’s age (if over 40)
- Presence of Down syndrome
- Other genetic or chromosome abnormalities, especially defects with chromosome 22
- Parent with tetralogy of Fallot
Most commonly, tetralogy of Fallot is discovered early in life when symptoms, such as cyanosis, or the presence of a heart murmur, indicate the possibility of a heart defect. A physician uses a stethoscope to listen for a heart murmur during a physical examination. Any suspicious sounds will prompt the physician to order tests, which may include:
Echocardiogram of the heart. This ultrasound test uses sound waves to track the structure and function of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation), blockage (stenosis), or deformity. During this test, a Doppler ultrasound may also be done to evaluate blood flow. This is the definitive test to diagnose tetralogy of Fallot.
Electrocardiogram (EKG). An EKG is a recording of the heart’s electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine helps detect heart irregularities, disease and damage by measuring the heart’s rhythms and electrical impulses. This test is only slightly helpful in the diagnosis of this condition as it is very non-specific. * Blood tests. Tests that reveal oxygen levels and blood cell counts. Blood tests may also be used to test for a frequently associated chromosome abnormality involving chromosome 22.
Chest x-ray. A radiation-based imaging that offers the physician a picture of the general size, shape, and structure of the heart and lungs. This may reveal congestion or enlargement of the heart muscle, which could be a sign of a heart defect. It may also help in demonstrating the decreased blood flow to the lungs in many of these babies.
Cardiac catheterization. A common, minimally invasive procedure in which a physician inserts a small tube called a catheter into a patient’s blood vessels and advances the tube toward the heart. This procedure allows the cardiologist to take special x-ray of the inside of the heart and blood vessels, which gives a clear picture of the structures in the patient’s heart. It also allows for the measurement of function of the various cardiac structures. This is rarely necessary nowadays for a diagnosis of tetralogy of Fallot. In some cases, tetralogy of Fallot is diagnosed soon after birth. Newborns with severe cyanosis at birth are usually given supplemental oxygen to rule out lung defects as the cause of poor oxygen circulation – supplemental oxygen improves the symptoms of newborns with lung defects. This is called a hyperoxia test. Newborns who remain cyanotic during the hyperoxia test may require further testing to diagnose the nature of their heart defect. In some other cases, the defect may be diagnosed during pregnancy when the components of the defect are seen on a routine ultrasound.
Surgery is the only treatment to repair this heart defect. Depending upon the severity of the defect, surgery may be performed any time between birth and the first few years of life. Also, the longer the heart muscles, tissues and vessels operate in the presence of these defects, the more long-term (even post-surgery) damage they will sustain. Although surgery used to be performed routinely in the first few years of life, the current approach in the United States is to plan on surgical correction in the first few weeks to months of life. Once the defect is detected, surgery usually has a high success rate. Conversely, choosing not to have the surgery results in a high risk of death before age 20. During corrective surgery, the pulmonary valve is widened to increase blood flow, and the ventricular septal defect is closed or patched in such a way that all the blood flow from the left ventricle is pumped out to the aorta. Some of the thickened muscle in the right ventricle may need to be removed to allow for the blood to be pumped from the right ventricle out to the pulmonary artery. Synthetic material may need to be inserted to enlarge narrowed areas of the right ventricle, the pulmonary valve, and the pulmonary arteries. Sometimes a palliative surgery (to relieve symptoms temporarily but not to fix the defect) is done before the corrective surgery to fix the defect. A palliative surgery is usually performed when the child’s heart structures have not developed enough for surgery to make a full correction. Palliative surgery relieves symptoms until the child has grown enough for a corrective surgery to be done. It may also be necessary if the baby is born very prematurely and the risk of open heart surgery us too great. Palliative surgery involves the creation of a systemic-pulmonary shunt to redirect the blood flow. A systemic-pulmonary shunt is designed to detour some of the blood from the aorta (which is getting blood from both the left and right ventricles) to the pulmonary artery (which is getting very little blood). The pulmonary artery then carries the blood to the lungs, as it does normally. This increases blood flow to the lungs, which can then supply the body with more oxygen-rich blood and reduce the child’s bluish skin tone (cyanosis). A number of types of shunts (e.g., a Blalock-Taussig shunt) may be used for this type of palliative surgery. Before any type of surgery, there are immediate ways to relieve some symptoms, including:
- Feeding children slowly and more often. Smaller meals require less initial effort, as well as less digestive effort.
- Anticipating the child’s needs and fears, and helping to reduce anxiety, sadness (e.g., crying) and anger.
- Putting the child in a knees-to-chest position on his or her side during episodes of blue skin.
- Sometimes medications such as beta-blockers are used to relax the thickened right ventricular muscle so that it is easier for blood to be pumped to the lungs as the degree of cyanosis is decreased.
According to the American Heart Association, patients who have undergone surgical repair of tetralogy Fallot can also expect:
- Possible restrictions on some physical activity such as certain competitive sports, as recommended by their cardiologist.
- A possible eventual decline in functioning of heart muscle, necessitating medications such as diuretics or other antihypertensives.
- An increased risk of abnormal heart rhythms (arrhythmias), which can cause dizziness or fainting (syncope) and may require medication or surgery.
- A possible increased risk of a difficult pregnancy in some women who were born with tetralogy of Fallot. There is also an increased risk of giving birth to a child with tetralogy of Fallot if a parent was born with it.
- Further surgery to insert an artificial or replacement pulmonary valve, replace or repair the pulmonary artery, or enlarge the attachments to the pulmonary arteries supplying the right and left lungs.
- Probable need for special education and care services if there are other birth defects.
Tetralogy of Fallot, like almost all forms of congenital heart disease, will require the patients to be evaluated on a regular basis by cardiologists familiar with congenital heart disease for their entire life. However, research has shown that many adults with congenital heart defects such as tetralogy of Fallot do not receive regular cardiac care. The U.S. National Institutes of Health (NIH) is considering requests from cardiologists to establish a national registry of such patients to improve care.