Tetralogy of Fallot

Tetralogy of Fallot is a relatively common anomaly, accounting for about 8% of congenital heart defects. This complex heart defect occurs in about 5 out of every 10,000 babies, affecting boys and girls equally. The four characteristic findings are: (1) malaligned ventricular septal defect (VSD), (2) pulmonary stenosis or atresia, (3) dextroposed overriding aorta, and (4) right ventricular hypertrophy. ^[1] The embryological defect is believed to be unequal division of the truncus arteriosus and conus cordis by the aorticopulmonary septum. Tetralogy of Fallot is the most common cause of "blue baby", but may not present in the newborn period, if pulmonary stenosis is not severe. In general, severity is dependent upon the degree of pulmonary stenosis. Without treatment, survival is about 50% at 2.5 years, and 10% at 20 years; however, with surgical treatment the majority of affected individuals live into adulthood.

Source: National Heart Lung and Blood Institute

Other Names

• Fallot's Tetralogy
• Pentalogy of Fallot (when an atrial septal defect is also present)

Heart with Tetralogy of Fallot

Ventricular septal defect

The heart has a wall that separates the chambers on its left side from those on its right side. This wall is called a septum. The septum prevents blood from mixing between the two sides of the heart.

A ventricular septal defect (VSD) is a hole in the part of the septum that separates the ventricles—the lower chambers of the heart. The hole allows oxygen‑rich blood to flow from the left ventricle into the right ventricle instead of flowing into the aorta, the main artery leading out to the body.

Pulmonary stenosis or atresia

This is a narrowing or of the pulmonary valve and the passageway through which blood flows from the right ventricle to the pulmonary arteries. Normally, oxygen-poor blood from the right ventricle flows through the pulmonary valve into the pulmonary arteries and out to the lungs to pick up oxygen. In pulmonary stenosis, the heart has to work harder than normal to pump blood, and not enough blood can get to the lungs. Pulmonary atresia occurs when the valve's orifice fails to develop.

Right ventricular hypertrophy

This is when the right ventricle thickens because the heart has to pump harder than normal to move blood through the narrowed pulmonary valve.

Overriding aorta

This is a defect in the location of the aorta. In a healthy heart, the aorta is attached to the left ventricle, allowing only oxygen-rich blood to go to the body. In tetralogy of Fallot, the aorta is between the left and right ventricles, directly over the VSD. As a result, oxygen‑poor blood from the right ventricle can flow directly into the aorta instead of into the pulmonary artery to the lungs.

Associated Anomalies

Associated anomalies are common:

• Patent foramen ovale (secundum atrial septal defect)
• Right-sided aortic arch with mirror-image branching (20%)

Signs and Symptoms

An important symptom of tetralogy of Fallot is cyanosis, or a bluish tint to the skin, lips, and fingernails caused by low levels of oxygen in the blood. Some babies will become very blue in response to an activity like crying or having a bowel movement caused by a sudden drop in the level of blood oxygen, this is called a tet spell. These infants may also:

• Have a hard time breathing
• Become very tired and limp
• Not respond to a parent's voice or touch
• Become very fussy
• Lose consciousness

Another common symptom is a heart murmur, which is an extra or unusual sound that a doctor can hear while listening to the heart during a physical exam. When a heart defect causes an abnormal flow of blood through the heart, it will make a certain sound. However, not all murmurs are signs of congenital heart defects, many healthy children have heart murmurs.

Normal growth and development depend on a normal workload for the heart and normal flow of oxygen-rich blood to all parts of the body. Babies who have tetralogy of Fallot may not gain weight or grow as quickly as children with healthy hearts because they tire easily while feeding. Also, children with this heart defect also may have “clubbing,” an abnormal, rounded shape to the skin or bone around the fingernails.

Causes

It is not known what causes most cases of tetralogy of Fallot and other congenital heart defects, but some conditions or factors during pregnancy may raise the risk of having a child with tetralogy of Fallot:

• Maternal stress ^[2]
• German measles (rubella) and some other viral illnesses
• Poor nutrition
• Overuse of alcohol
• Age (being older than 40)
• Diabetes

Heredity may also play a role in this heart defect. An adult with tetralogy of Fallot may have an increased chance of having a baby with this defect. Children with [[Genetic Disorders|genetic disorders, such as Down syndrome and DiGeorge syndrome, often have congenital heart defects, including tetralogy of Fallot.

Diagnosis

Signs and symptoms usually appear during the first weeks of life, and are usually seen by the doctor during a routine checkup. Some parents also notice cyanosis or poor feeding and bring the baby to the doctor. During the physical exam, the doctor:

• Listens to the baby's heart and lungs with a stethoscope.
• Looks for signs and symptoms, such as bluish color of skin and lips and rapid breathing.
• Looks at general appearance as some children with tetralogy of Fallot have a characteristic facial appearance because they have DiGeorge symdrome.

An echocardiogram/Doppler, will show the problems with the heart's structure and function. This test helps the cardiologist decide the best time to repair these defects, what type of surgery is needed, check a child's condition over time, and followup after the defect has been repaired. A Chest X-Ray is the other common exam used for diagnosis, characteristically there is a normal-sized, boot-shaped heart (coeur en sabot), it may show an enlarged right ventricle. Other tests that can be used are EKG, cardiac catheterization, and MRI.

Treatment

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 defects so the heart can work as normally as possible, the timing and type of surgery depend on the baby's health and weight, how severe the defects are, and how severe the symptoms are.^[3] In the United Stated there is an 85% survival into adulthood after surgical repair. ^[4]

Complete intracardiac repair

Surgery to repair tetralogy of Fallot is done to improve blood flow to the lungs and to make sure that oxygen-rich and oxygen-poor blood flows to the right places. The following are some of the goals of surgery:

• Widen the narrowed pulmonary blood vessels, widen or dilate the pulmonary valve, and enlarge the passageway from the right ventricle to the pulmonary arteries. These procedures improve blood flow to the lungs, allowing the blood to get enough oxygen to meet the body's needs.
• Close the ventricular septal defect (VSD), using a patch to cover the hole. 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 the lungs, it can return to a normal thickness. Fixing the VSD means that only oxygen-rich blood will flow out of the left ventricle into the aorta.Often there is a residual problem with a leaky pulmonary valve, known as pulmonary insufficiency, which may lead to another surgery later to replace the pulmonary valve.

The incision from the surgery usually heals in about six weeks. The surgeon or another member of the hospital staff will explain when it's okay to give the baby a bath, pick up the baby under the arms, and take the baby for his or her regular shots ([[Infant Immunization|immunizations).

Temporary or palliative surgery

In 1945 a successful palliative procedure called the Blalock-Taussig shunt was developed to temporarily improve blood flow to the lungs, postponing the complete repair until later in childhood. Some babies are too weak or too small to have the full repair and have temporary surgery first.

In the temporary procedure, the surgeon places a tube called a shunt between a large artery branching off the aorta and the pulmonary artery. One end of the shunt is sewn to the artery branching off the aorta, and 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. It is removed when the baby's heart defects are fixed during the full repair. The infant is given medicine to keep the shunt open until the complete repair is performed.

Living with Tetralogy of Fallot

Over the past few decades, the diagnosis and treatment of tetralogy of Fallot has greatly improved. As a result, the majority of children with this heart defect grow to adulthood. However, they need lifelong medical care from a specialist to make sure they stay as healthy as possible.

Feeding

Babies can tire while nursing or feeding, so small, frequent meals may be easier for the infant to handle. A supplement or an extra feeding can give the baby more calories, vitamins, or iron. The doctors will decide what extra nutrition the baby may need.

Tet spells (tetralogy episodes)

There are many ways to manage tetralogy spells:

• Bringing the infant's knees up tight against his or her chest (this is called the knee–chest position) or have the child squat down, this will increase blood flow to the lungs.
• Try to calm the child.
• Calling 9–1–1 if the symptoms don't improve right away.

Activity restrictions

Some children may need to limit certain types of exercise, it is important to discuss with the doctor the following things:

• Whether the child needs to restrict activity or exercise.
• Whether the child can play in organized sports, especially contact sports.

Routine medical care

Routine medical care includes the following:

• Seeing a pediatric cardiologist for heart checkups as directed.
• Seeing a pediatrician or family health care provider for routine exams.
• Making sure that the child takes medicines as prescribed.

Children with severe heart defects, like tetralogy of Fallot, are at increased risk for bacterial endocarditis. This is a serious infection of the heart valves or lining of the heart. Antibiotics may be required before medical and dental procedures (such as surgery or dental cleanings), which could allow bacteria to enter the bloodstream.

It is a good idea to work with health care providers to put together a packet with medical records and information that covers all aspects of the child's heart defect, including:

• Diagnosis
• Procedures or surgeries
• Prescribed medicines
• Recommendations about medical followup
• How to prevent complications
• Health insurance

Special needs for teenagers and adults

As children with tetralogy of Fallot grow up and become teens, it's important that they understand their heart defect, how it was treated, and what kind of care may still be needed. This understanding will help the teen take responsibility for his or her health. It also will help ensure a smooth transition from care by a pediatric cardiologist to care by a specialist in adult congenital heart disease.

Over time, people who have had surgery to repair tetralogy of Fallot may face a number of heart problems, such as:

Narrowing and leaking of heart valves

Heart valves make sure that blood flows only in one direction. If the valve doesn't seal tightly, blood can leak back into the originating chamber. This backward flow of blood is called regurgitation, and it can lead to symptoms and complications. The most frequent problem that occurs after tetralogy of Fallot repair is pulmonary regurgitation, or leaking from the pulmonary valve. An additional complication results from narrowing of the pulmonary valve over time, which reduces blood flow.

Arrhythmias

Arrhythmias, problems with the speed or rhythm of the heartbeat, also can occur. These can include ventricular tachycardia, atrial fibrillation, and atrial flutter. Medicines are used to control most of these arrhythmias, although on occasion a person may need a procedure or surgery to fix the problem.

Right ventricular aneurysms

The patches used during the repair surgery can create weakened areas in the ventricle that can bulge or “balloon” out. These aneurysms make it hard for the heart to function as well as it should. This problem must be repaired with surgery.

Residual ventricular septal defects

On occasion, a ventricular septal defect may still leak after it has been repaired. A second procedure may be required if the leak is large or is causing problems with the function of the right ventricle.

Coronary artery disease

As people with repaired tetralogy of Fallot approach middle age, they can develop coronary artery disease (CAD), just as adults without a heart defect can. Preventing CAD is especially important because any procedures, like coronary artery bypass grafting, that are done to relieve symptoms of CAD can cause complications in people with repaired tetralogy of Fallot.

Other considerations

Many women with repaired tetralogy of Fallot who become pregnant are able to have successful, full-term pregnancies while others may have difficult pregnancies. Women with tetralogy of Fallot who want to become pregnant (or who are pregnant) should consult specialists who take care of pregnant women with health conditions about the following issues:

• Health risks during pregnancy
• Medicines they can take during pregnancy
• Any new or worsening symptoms

Several laws protect the employment rights of people who have congenital heart defects. The Americans with Disabilities Act and the Work Incentives Improvement Act try to ensure fairness in hiring for all people, including those with health conditions such as heart defects.

Clinical Trials

• Current Research (ClinicalTrials.gov)

References

1. ↑ Shinebourne EA, Babu-Narayan SV, Carvalho JS. Tetralogy of Fallot: from fetus to adult. Heart. 2006 Sep;92(9):1353-9. Full text | PDF
2. ↑ Carmichael SL, Shaw GM, Yang W, Abrams B, Lammer EJ. Maternal stressful life events and risks of birth defects. Epidemiology. 2007 May;18(3):356-61. Abstract | Full Text | PDF
3. ↑ Aboulhosn J, Child JS. Management after childhood repair of tetralogy of fallot. Curr Treat Options Cardiovasc Med. 2006 Dec;8(6):474-83. Abstract
4. ↑ Murphy JG, Gersh BJ, Mair DD,et al., Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot. N Engl J Med. 1993 Aug 26;329(9):593-9. Abstract | Full Text

External Links

National Heart Lung and Blood Institute:

• Congenital Heart Defects
• NHLBI-Related Public Interest Organizations
• Pediatric Heart Network