Tetralogy of Fallot
What is tetralogy of Fallot?
Tetralogy of Fallot (fuh-LOE) is a combination of four different birth defects in the heart.
A healthy heart is a strong, muscular pump that pushes blood through the circulatory system to carry oxygen and nutrients to the body. The heart has four chambers -- two on the right and two on the lef. Blood is pumped through these chambers and regulated by valves that open and close like tiny doors, so that blood can move in only one direction.
After its trip through the body to deliver oxygen, blood is a blue color because it's no longer oxygen-rich. The blue blood returns to the heart through the right chambers and is pumped through the pulmonary artery into the lungs. In the lungs, it picks up more oxygen and becomes bright red. It then goes back through the pulmonary vein to the left chambers and is pumped through the aorta and out into the body again.
If your child has tetralogy of Fallot, it means the following defects are present:
- Ventricular septal defect (VSD): This is a hole in the wall between the heart's right and left ventricles (pumping chambers).
- Overriding aorta: This means the aorta is located above the ventricular septal defect, to the right of where it should normally be.
- Pulmonary valve stenosis: This is a narrow place in the pulmonary valve (between the right ventricle and pulmonary artery) that forces the heart to pump harder to push blood through it.
- Right ventricular hypertrophy: Because the heart must work so hard to pump blood through the narrowed pulmonary valve, the muscle wall of the right ventricle may become enlarged and weakened.
Together, these four defects reduce blood flow to the lungs and allow oxygen-poor (blue) blood to be pumped out to the whole body. As a result, the body does not have enough oxygen to meet its needs, and breathing becomes difficult.
What causes tetralogy of Fallot?
Tetralogy of Fallot's exact cause is unknown. The condition occurs during the first eight weeks of fetal growth, when the baby's heart is developing.
Although there is usually no clear reason for the development of tetralogy of Fallot, some risk factors have been identified. These include a viral illness (such as measles) in the mother during pregnancy, a genetic disorder in the mother, alcohol abuse or poor nutrition during pregnancy, or a case of tetralogy of Fallot in either parent.
Tetralogy of Fallot accounts for 9-14% of all congenital (from birth) heart defects. It occurs in two to five out of every 10,000 live births. It appears equally in boys and girls. Babies born with Down syndrome or fetal alcohol syndrome are at greater risk of having tetralogy of Fallot.
What are the signs and symptoms of tetralogy of Fallot?
Tetralogy of Fallot is usually diagnosed during infancy. Occasionally, babies with tetralogy of Fallot develop a deeper blue color to their skin, lips, or nails after waking up, crying or feeding. These episodes, nicknamed "Tet spells," are caused by a rapid drop in the blood's oxygen level. The symptoms of tetralogy of Fallot vary for each child, but may include:
- Cyanosis: A blue tone to the skin, lips, or nails
- Pale, cool or clammy skin
- Difficulty breathing
- Fainting, seizures or loss of consciousness
- An abnormal, club-like shape of the fingers or toes
- Poor appetite and poor weight gain
- Unusual tiredness or irritability
Your baby's doctor may also suspect tetralogy of Fallot if he or she hears a heart murmur — an abnormal whooshing noise, heard through a stethoscope exam, which may indicate a problem with blood flow. Most heart murmurs are called "innocent heart murmurs." Children with innocent heart murmurs do not have a heart defect and do not experience heart problems. However, if a heart murmur is present along with other symptoms, your doctor may want to investigate further by ordering other tests.
Depending on the severity of the case, tetralogy of Fallot may also be diagnosed later in childhood. One sign of the condition in toddlers or older children is that they sometimes crouch low to the ground when they have trouble breathing, in order to increase blood flow to the lungs.
How is tetralogy of Fallot diagnosed?
A clear diagnosis is the first step to treatment. A pediatric cardiologist (a children's heart doctor) can use several tests to confirm your child's diagnosis. These tests may include:
- Chest X-ray: A beam of electromagnetic energy creates images on film that show the inside structures of your baby's body. Tetralogy of Fallot may show up on X-ray films as a "boot-shaped" heart due to the enlargement of the right ventricle.
- Complete blood count: This test measures the number of each type of cell in the blood. Babies with tetralogy of Fallot may have a high red blood cell count (called "erthrocytosis") as the body attempts to increase its blood oxygen level.
- Cardiac Magnetic Resonance Imaging (MRI): This test produces a three-dimensional image of the heart so you're your child's doctors can examine blood flow and functioning of the heart as it is working.
- Electrocardiogram (ECG or EKG): This test, conducted by attaching patches with wires (electrodes) to your baby's skin, records the heart's electrical activity. It will show if there are abnormal heart rhythms (arrhythmias or dysrhythmias) and/or stress on the heart muscle.
- Echocardiogram (Echo): This test uses sound waves to make a moving image of the heart on a video screen. It is similar to an ultrasound and can diagnose tetralogy of Fallot by showing the structure and position of the parts of the heart.
- Cardiac catheterization: During this procedure, your doctor inserts a thin flexible tube (a catheter) into a blood vessel in the groin, then guides it up to the inside of the heart. A dye injected through the catheter makes the heart structures visible on x-ray pictures. The catheter also measures blood pressure and oxygen levels.
How is tetralogy of Fallot treated?
With early diagnosis and corrective surgery, most children with tetralogy of Fallot will live healthy lives. After surgery, most children's activity levels, appetite and growth will eventually return to normal.
Once diagnosed with tetralogy of Fallot, your baby will need surgery to repair defects in his or her heart, usually within the first year of life. Without it, your baby may not grow and develop properly, and will be at risk of serious complications, death or disability.
The type of surgery may vary, depending on your child's individual needs. Typically, the surgeon closes the hole between the heart's ventricles, repairs the narrowed pulmonary valve, and opens up the pulmonary arteries to increase needed blood flow to your baby's lungs.
Occasionally, a prematurely born baby or a baby with underdeveloped pulmonary arteries may need a temporary surgery before the main surgery. Doctors will create a bypass (a shunt) between the aorta and pulmonary artery. This bypass increases blood flow to the lungs. When your baby is ready for a full surgical repair, the shunt will be removed.
After surgery, your baby will need continuing care. Your doctor will schedule regular check-ups to make sure that the procedure was successful and to monitor for any complications or new problems. Your doctor may also recommend that your child limit physical activity or take antibiotics to prevent infections.
About treatment for tetralogy of Fallot at Children's
Tetralogy of Fallot is treated through Children's cardiovascular program one of the largest and oldest pediatric cardiovascular programs in the region. Team members consistently achieve treatment results that are among the best in the nation. Each year, care is provided for thousands of the region¹s sickest children with heart conditions, including fetuses, newborns, infants, children, adolescents, and adult, long-term patients with pediatric cardiovascular conditions.
For more information, please call Children's Heart Clinic at 1-800-938-0301.
(From Pritchet & Hull Assoc., Inc.)
Heart with tetralogy of Fallot
(From Pritchet & Hull Assoc., Inc.)