Tetralogy of Fallot is a congenital heart defect. This is a problem with the heart's structure that's present at birth. Congenital heart defects change the normal flow of blood through the heart.
Tetralogy of Fallot is a rare, complex heart defect. It occurs in about 5 out of every 10,000 babies. The defect affects boys and girls equal
Tetralogy of Fallot involves four heart defects:
- A large ventricular septal defect (VSD)
- Pulmonary stenosis
- Right ventricular hypertrophy
- An overriding aorta
Ventricular Septal Defect
The heart has an inner wall that separates the two chambers on its left side from the two chambers on its right side. This wall is called a septum. The septum prevents blood from mixing between the two sides of the heart.
A VSD is a hole in the septum between the heart's two lower chambers, the ventricles. The hole allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood from the right ventricle.
This defect involves narrowing of the pulmonary valve and the passage from the right ventricle to the pulmonary artery.
Normally, oxygen-poor blood from the right ventricle flows through the pulmonary valve and into the pulmonary artery. From there, the blood travels to the lungs to pick up oxygen.
In pulmonary stenosis, the pulmonary valve cannot fully open. Thus, the heart has to work harder to pump blood through the valve. As a result, not enough blood reaches the lungs.
Right Ventricular Hypertrophy
With this defect, the muscle of the right ventricle is thicker than usual. This occurs because the heart has to work harder than normal to move blood through the narrowed pulmonary valve.
This defect occurs in the aorta, the main artery that carries oxygen-rich blood from the heart to the body. In a healthy heart, the aorta is attached to the left ventricle. This allows only oxygen-rich blood to flow to the body.
In tetralogy of Fallot, the aorta is located between the left and right ventricles, directly over the VSD. As a result, oxygen-poor blood from the right ventricle flows directly into the aorta instead of into the pulmonary artery.
With tetralogy of Fallot, not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows to the body.
Cross-Section of a Normal Heart and a Heart With Tetralogy of Fallot
Figure A shows the structure and blood flow inside a normal heart. Figure B shows a heart with the four defects of tetralogy of Fallot.
Babies and children who have tetralogy of Fallot have episodes of cyanosis. Cyanosis is a bluish tint to the skin, lips, and fingernails. It occurs because the oxygen level in the blood leaving the heart is below normal.
Tetralogy of Fallot is repaired with open-heart surgery, either soon after birth or later in infancy. The timing of the surgery will depend on how narrow the pulmonary artery is.
Over the past few decades, the diagnosis and treatment of tetralogy of Fallot have greatly improved. Most children who have this heart defect survive to adulthood. However, they'll need lifelong medical care from specialists to help them stay as healthy as possible.
What Are the Signs and Symptoms of Tetralogy of Fallot?
Cyanosis is an important sign of tetralogy of Fallot. Cyanosis is a bluish tint to the skin, lips, and fingernails. Low oxygen levels in the blood cause cyanosis.
Babies who have unrepaired tetralogy of Fallot sometimes have "tet spells." These spells happen in response to an activity like crying or having a bowel movement.
A tet spell occurs when the oxygen level in the blood suddenly drops. This causes the baby to become very blue. The baby also may:
- Have a hard time breathing
- Become very tired and limp
- Not respond to a parent's voice or touch
- Become very fussy
- Pass out
In years past, when tetralogy of Fallot wasn't treated in infancy, children would get very tired during exercise and could faint. Now, doctors repair tetralogy of Fallot in infancy to prevent these symptoms.
Another common sign of tetralogy of Fallot is a heart murmur. A heart murmur is an extra or unusual sound that doctors might hear while listening to the heart.
The sound occurs because the heart defect causes abnormal blood flow through the heart. However, not all heart murmurs are signs of congenital heart defects. Many healthy children have heart murmurs.
Babies who have tetralogy of Fallot may tire easily while feeding. Thus, they may not gain weight or grow as quickly as children who have healthy hearts. Also, normal growth depends on a normal workload for the heart and normal flow of oxygen-rich blood to all parts of the body.
Children who have tetralogy of Fallot also may have clubbing. Clubbing is the widening or rounding of the skin or bone around the tips of the fingers.
How Is Tetralogy of Fallot Diagnosed?
Doctors diagnose tetralogy of Fallot based on a baby's signs and symptoms, a physical exam, and the results from tests and procedures.
Signs and symptoms of the heart defect usually occur during the first weeks of life. Your infant's doctor may notice signs or symptoms during a routine checkup. Some parents also notice cyanosis or poor feeding and bring the baby to the doctor. (Cyanosis is a bluish tint to the skin, lips, and fingernails.)
If your child has tetralogy of Fallot, a pediatric cardiologist and pediatric cardiac surgeon may be involved in his or her care.
A pediatric cardiologist is a doctor who specializes in diagnosing and treating heart problems in children. Pediatric cardiac surgeons repair children's heart defects using surgery.
During a physical exam, the doctor may:
- Listen to your baby's heart and lungs with a stethoscope.
- Look for signs of a heart defect, such as a bluish tint to the skin, lips, or fingernails and rapid breathing.
- Look at your baby's general appearance. Some children who have tetralogy of Fallot also have DiGeorge syndrome. This syndrome causes characteristic facial traits, such as wide-set eyes.
Diagnostic Tests and Procedures
Your child's doctor may recommend several tests to diagnose tetralogy of Fallot. These tests can provide information about the four heart defects that occur in tetralogy of Fallot and how serious they are.
Echocardiography (echo) is a painless test that uses sound waves to create a moving picture of the heart. During the test, the sound waves (called ultrasound) bounce off the structures of the heart. A computer converts the sound waves into pictures on a screen.
Echo allows the doctor to clearly see any problem with the way the heart is formed or the way it's working.
Echo is an important test for diagnosing tetralogy of Fallot because it shows the four heart defects and how the heart is responding to them. This test helps the cardiologist decide when to repair the defects and what type of surgery to use.
Echo also is used to check a child's condition over time, after the defects have been repaired.
An EKG is a simple, painless test that records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through the heart.
This test can help the doctor find out whether your child's right ventricle is enlarged (ventricular hypertrophy).
Chest X Ray
A chest x ray is a painless test that creates pictures of the structures in the chest, such as the heart and lungs. This test can show whether the heart is enlarged or whether the lungs have extra blood flow or extra fluid, a sign of heart failure.
For this test, a small sensor is attached to a finger or toe (like an adhesive bandage). The sensor gives an estimate of how much oxygen is in the blood.
During cardiac catheterization, a thin, flexible tube called a catheter is put into a vein in the arm, groin (upper thigh), or neck. The tube is threaded to the heart.
Special dye is injected through the catheter into a blood vessel or one of the heart's chambers. The dye allows the doctor to see the flow of blood through the heart and blood vessels on an x-ray image.
The doctor also can use cardiac catheterization to measure the pressure and oxygen level inside the heart chambers and blood vessels. This can help the doctor figure out whether blood is mixing between the two sides of the heart.
How Is Tetralogy of Fallot Treated?
Tetralogy of Fallot is repaired with open-heart surgery, either soon after birth or later in infancy. The goal of surgery is to repair the four defects of tetralogy of Fallot so the heart can work as normally as possible. Repairing the defects can greatly improve a child's health and quality of life.
The pediatric cardiologist and cardiac surgeon will decide the best time to do the surgery. They will base their decision on your baby's health and weight and the severity of the defects and symptoms.
Some teenagers or adults who had tetralogy of Fallot repaired in childhood need additional surgery to correct heart problems that develop over time. For more information, go to "Living With Tetralogy of Fallot."
Types of Surgery
Complete Intracardiac Repair
Surgery to repair tetralogy of Fallot improves blood flow to the lungs. Surgery also ensures that oxygen-rich and oxygen-poor blood flow to the right places.
The surgeon will:
- Widen the narrowed pulmonary blood vessels. The pulmonary valve is widened or replaced. Also, the passage from the right ventricle to the pulmonary artery is enlarged. These procedures improve blood flow to the lungs. This allows the blood to get enough oxygen to meet the body's needs.
- Repair the ventricular septal defect (VSD). A patch is used to cover the hole in the septum. This patch stops oxygen-rich and oxygen-poor blood from mixing between the ventricles.
Fixing these two defects resolves problems caused by the other two defects. When the right ventricle no longer has to work so hard to pump blood to the lungs, it will return to a normal thickness. Fixing the VSD means that only oxygen-rich blood will flow out of the left ventricle into the aorta.
The incision (cut) that the surgeon makes to reach the heart usually heals in about 6 weeks. The surgeon or a hospital staff member will explain when it's okay to give your baby a bath, pick him or her up under the arms, and take your baby for regular shots (immunizations).
Temporary or Palliative Surgery
It was common in the past to do temporary surgery during infancy for tetralogy of Fallot. This surgery improved blood flow to the lungs. A complete repair of the four defects was done later in childhood.
Now, tetralogy of Fallot usually is fully repaired in infancy. However, some babies are too weak or too small to have the full repair. They must have temporary surgery first. This surgery improves oxygen levels in the blood. The surgery also gives the baby time to grow and get strong enough for the full repair.
For temporary surgery, the surgeon places a tube between a large artery branching off the aorta and the pulmonary artery. The tube is called a shunt. One end of the shunt is sewn to the artery branching off the aorta. The other end is sewn to the pulmonary artery.
The shunt creates an additional pathway for blood to travel to the lungs to get oxygen. The surgeon removes the shunt when the baby's heart defects are fixed during the full repair.
After temporary surgery, your baby may need medicines to keep the shunt open while waiting for the full repair. These medicines are stopped after the surgeon removes the shunt.