Tetralogy of Fallot
Tetralogy of Fallot is the most common type of cyanotic congenital heart disease. This condition has four related heart defects that are together. The four defects are:
1. Ventricular septal defect (VSD), which is a hole in the heart between the right ventricle and left ventricle.
2. Overriding aorta. The aorta is enlarged and rises from both the left and right ventricles instead of the left ventricle as found in normal hearts.
3. Pulmonary stenosis. There is a thickened pulmonary valve that does not open all the way. In addition, there is usually obstruction below the valve as well as above the valve.
4. Right ventricular hypertrophy. This is a thickening of the right ventricular muscle that occurs because the right ventricle is pumping at high pressure.
A small percentage of children with Tetralogy of Fallot may also have associated heart defects. There might be a hole or opening between the heart’s upper chambers called a patent foramen ovale or an atrial septal defect.
Tetralogy of Fallot occurs during pregnancy when the baby’s heart is developing. The reasons for Tetralogy of Fallot are considered multifactorial. The cause remains unknown in many cases. Some factors may increase the risk of this condition. These factors may include genetic disorders (Down syndrome, DiGeorge, CHARGE, VACTERL), alcoholism, poor nutrition, and others. A child born to a parent who has Tetralogy of Fallot has a higher incidence of having a similar condition or other congenital heart defect.
The most common symptom associated with Tetralogy of Fallot is a bluish coloration of the skin caused by unoxygenated blood (cyanosis). In a smaller percentage of patients who have less severe pulmonary stenosis, cyanosis may not be visible (pink Tetralogy). These patients may present with signs of heart failure. Therefore, symptoms of Tetralogy of Fallot vary, depending on the extent of pulmonary stenosis. Symptoms may include:
Bluish coloration of the skin (cyanosis). Bluish coloration of the nail beds.
Fainting, especially while crying, crawling, first thing in the morning or upon awakening.
Clubbing of fingers and toes (round shaped fingertips).
Shortness of breath, rapid breathing, feeding difficulties, poor weight gain, tiring easily, irritability, seizures, and weakness.
Hypoxic Spells (Tet spells):
Infants with Tetralogy of Fallot may suddenly develop deep blue skin, nails, and lips after crying, feeding, crawling, or upon awakening. In addition, they may develop rapid and difficult breathing. These episodes are called “hypoxic spells” or “Tet spells” and result from a rapid drop in the amount of oxygen in the blood. It is considered an emergency situation and you must call 911. There is a risk of fainting and even sudden death. The baby should be held in a knee-on-chest position and calmed down to prevent further crying. Place the child on his/her side and pull the knees up to the chest (knee-on-chest position).
Patients with Tetralogy of Fallot usually have a loud murmur that tends to disappear during hypoxic or Tet spells.
Tests include an electrocardiogram, echocardiogram, and chest X-ray. The echocardiogram is used to diagnose Tetralogy of Fallot and assessing holes and obstructions inside the heart. This test may help detect other associated heart defects. A chest x-ray may show a “boot-shaped” heart, decreased blood in the lungs, and other abnormalities such as a right aortic arch and absent thymus.
Patients with Tetralogy of Fallot may have other heart defects including a right aortic arch, coronary abnormalities, PDA, ASD, persistent left superior vena cava, AP window, additional ventricular septal defects, absent pulmonary valve, coarctation of the aorta, interrupted aortic arch, and others.
Infants with Tetralogy of Fallot will need close follow up and serial echocardiograms as well as measurement of their oxygen level in the blood (pulse oximeter). Parents should be trained in CPR, be educated in congestive heart failure (CHF), and hypoxic spells. Most patients will develop a progressive cyanosis (blue skin) and will require earlier heart surgery. All infants with Tetralogy of Fallot will need surgery. Timing of the surgery depends on the severity of symptoms. Elective surgery is usually performed around six months of age. Without surgery, the baby will not grow or develop properly. Infants are at increased risk of serious complications such as endocarditis, stroke (brain abscess), and sudden death.
The heart surgery for Tetralogy of Fallot is not curative. In severe cases, the infant may require a palliative shunt (conduit between the aorta and pulmonary artery) prior to open heart surgery. This is usually done in babies who are born very prematurely or have very under-developed (hypoplastic) pulmonary arteries.
During open heart surgery, the surgeon places a patch over the ventricular septal defect (hole) to close the hole between the right and left ventricle. The pulmonary stenosis is relieved by opening up the pulmonary valve and excising any muscle bundle under the valve. A transannular patch may be necessary in order to enlarge the pulmonary outflow and pulmonary arteries.
After the surgery, most babies will have some degree of pulmonary stenosis (obstruction) and pulmonary regurgitation. The infant will require continuing cardiology care. Many patients will require one or two heart medications. Serial echocardiograms are usually performed to monitor the heart size and function as well as the degree of pulmonary stenosis and pulmonary regurgitation.
The surgical mortality is fairly low, less than 3%, depending on several factors. About 15% of patients will require another surgery within 10 years, mainly those with a transannular patch or pulmonary conduit. Lifetime expectancy is pretty good as almost 90% of patients are alive 30 years after their first surgery.
About 25% of patients with Tetralogy of Fallot may have genetic abnormalities that may affect other organs and mental IQ. One-fourth of patients may have attention deficit disorder, academic problems, psychological disorders, aggressive behavior, as well as neurologic or motor abnormalities. About one-fifth of patients with Tetralogy of Fallot may develop arrhythmias. The arrhythmias may include slow heartbeats and fast heartbeats, which may originate in any heart chamber. Some patients with arrhythmias may require medical treatment or ablation. In patients with Tetralogy of Fallot, only athletes with an excellent repair may be allowed to participate in most competitive sports. Patients with marked pulmonary regurgitation, arrhythmias, residual holes, or high pressures in the right ventricle may be able to be cleared to participate in low-intensity sports.
Patients with this heart defect may be at risk of endocarditis, so optimal dental hygiene and semiannual dental appointments are strongly recommended. Preventive antibiotics (SBE prophylaxis) may be necessary, especially for those with artificial valves and a residual leak in the VSD patch.
Overall, patients with repaired Tetralogy of Fallot, are considered low-risk for pregnancy. Plans for pregnancy should be discussed in advance with Dr. Villafañe, as other cardiovascular tests may be required to assess potential risks and to make any pertinent changes in medications. Some heart medications can cause severe problems for a fetus and may need to be stopped before becoming pregnant. Infants born to parents with Tetralogy of Fallot have a higher risk for similar or other congenital heart defects. Complications during pregnancy may include irregular heartbeats, congestive heart failure, miscarriages, stroke, endocarditis, and low blood pressure. Mortality is low, at less than 1% to 5%.