Pediatric Heart Disease Fallot

Tetralogy of Fallot, a congenital heart defect that affects five out of every 10,000 births, actually refers to four different heart defects that are often found together (known in medical terms as co-morbid):

  • overriding aorta
  • pulmonary stenosis
  • right ventricular hypertrophy
  • ventricular septal defect.

Causes of Tetralogy of Fallot

Like many congenital birth defects, the cause of tetralogy of Fallot is unknown. However, genetics seem to play a role: A parent with congenital heart defects (heart defects a person is born with) has a higher than normal risk of having a child with tetralogy of Fallot. Chromosomal defects have also been linked to the presence of this heart defect. For example, children with Down’s syndrome are at a higher risk of suffering from tetralogy of Fallot.

This condition has also been linked to certain pregnancy events. The risk of a baby having tetralogy of Fallot increases if the pregnancy is characterized by any of the following:

  • maternal alcohol use
  • maternal diabetes
  • maternal rubella (German measles)
  • maternal substance abuse
  • poor maternal nutrition
  • use of seizure medications
  • viral illness during the pregnancy.

The risk of tetralogy of Fallot also increases as the age of the pregnant mother increases. Pregnancy after age 40 has an increased risk of producing a baby with heart defects.

Tetralogy of Fallot Birth Defects

The four birth defects that comprise tetralogy of Fallot are:

  • Overriding Aorta: This describes an enlarged aortic valve located directly over the ventricular septal defect. Overriding aortas allow oxygen-deficient blood to return to the body.
  • Pulmonary Stenosis: This defect refers to an obstruction blocking blood from flowing from the heart’s right ventricle to the pulmonary artery. Pulmonary stenosis prevents blood from getting to the lungs, leaving blood oxygen deficient.
  • Right Ventricular Hypertrophy: This abnormality is marked by an overexertion of the right ventricle. Because the other three disorders make it difficult for the right ventricle to pump blood to the lungs, the right ventricle works harder to compensate. Consequently, the ventricular walls become thicker, causing right ventricular hypertrophy.
  • Ventricular Septal Defect: This condition is marked by an opening in the wall, or septum, dividing the left and right ventricles. A ventricular septal defect allows oxygen-poor blood to flow back into the left ventricle and, therefore, back to the body without having been properly oxygenated.

Tetralogy of Fallot Symptoms

Like babies born with pulmonary stenosis, those born with tetralogy of Fallot may develop cyanosis. Cyanosis, a blue tint to the lips and fingernail beds, is caused by insufficient oxygen in the blood. Unless tetralogy of Fallot causes severe blood obstruction, cyanosis is not immediately observed after birth.

An open ductus arteriosus, a blood vessel present in unborn children, usually prevents quick detection of cyanosis. In the days immediately following birth, the ductus arteriosus slowly closes. However, before closing, blood gradually seeps through, allowing unoxygenated blood to mix with oxygenated blood. Symptoms of cyanosis only develop after the ductus arteriosis closes.

In addition to cyanosis, tetralogy of Fallot may produce such symptoms as:

  • cool or clammy skin
  • difficulty feeding
  • fussiness
  • irritability
  • paleness
  • poor weight gain
  • rapid breathing.

Tetralogy Spells

Babies with tetralogy of Fallot may also experience a set of symptoms that are known collectively as a tetralogy spell. Tetralogy spells occur when blood oxygen levels drop rapidly. During a tetralogy spell, the baby will develop severe cyanosis and “turn blue.” In addition, (s)he may exhibit:

  • difficulty breathing
  • extreme fussiness or irritability
  • limpness
  • seizures
  • sudden fatigue
  • unresponsiveness to voice or touch.

The reason for the sudden drop in blood oxygen levels that causes tetralogy spells is unknown. However, experts know that tetralogy spells are more likely to occur if the baby is upset. Anemia or a lack of fluids has also been associated with tetralogy spells.

A tetralogy spell is a medical emergency that requires immediate medical attention.

Diagnosing Tetralogy of Fallot

The first indications of tetralogy of Fallot are either cyanosis or a heart murmur in the weeks after birth. Either symptom suggests the possibility of a congenital heart defect and the need for further testing.

Echocardiology is most often used to diagnose tetralogy of Fallot. An echocardiogram uses sound waves to create an image of the heart. Echocardiology imaging can detect all four of the heart defects that comprise tetralogy of Fallot.

If a newborn suffers from severe cyanosis, (s)he should receive supplemental oxygen in case lung conditions are the cause of the cyanotic symptoms. If supplemental oxygen fails to relieve cyanosis, doctors then test for the presence of a congenital heart defect.

Tetralogy of Fallot Treatment

Surgical treatment to correct tetralogy of Fallot is essential. When treatment occurs depends on the child’s cyanotic symptoms and blood-oxygen levels. Children with mild symptoms may receive treatment six months after birth, giving the infants time to gain weight and strength. However, newborns with severe symptoms may require immediate surgical treatment.

Tetralogy of Fallot surgical treatment is an open-heart surgery that has the following goals:

  • to close the ventricular septal defect with a synthetic patch
  • to enlarge the narrowed pulmonary arteries
  • to remove obstructive muscle tissue in the right ventricle
  • to repair the pulmonary valve.

Post-Operative Follow-up

Presuming no secondary health problems, surgical treatment for tetralogy of Fallot has a very successful track record. In fact, 95 percent of infants with tetralogy of Fallot undergo successful surgery prior to their first birthday.

However, tetralogy of Fallot surgery does not completely repair heart defects. Most children have some degree of pulmonary insufficiency after surgery. Because the pulmonary valve does not close completely, blood can leak back into the right ventricle. Although most cases of pulmonary insufficiency have little effect on a patient’s overall health, some cases can become severe, requiring corrective surgery.

Long-term follow-up by a pediatric cardiologist is required after tetralogy of Fallot surgery. Along with limiting physical activity, some children may also require medication to help control heart function. These medications can include:

  • blood pressure medication
  • diuretics
  • medication to control arrhythmias (abnormal heartbeats)
  • medication to control heart contractions.

Both before and after surgery, children with tetralogy of Fallot are at higher than normal risk of contracting endocarditis, an infection of the heart muscle. To lower the risk of endocarditis, preventative antibiotics are prescribed before dental work and surgeries. Maintaining proper dental hygiene also lowers the risk of endocarditis.

Resources

American Heart Association (2007). Tetralogy of fallot. Retrieved September 4, 2007, from the AHA Web site: www.americanheart.org/presenter.jhtml?identifier=11071.

Cincinnati Children’s Hospital Medical Center (2006). Tetralogy of fallot (TOF). Retrieved September 4, 2007, from the Cincinnati Children’s Hospital Medical Center Web site: www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/tof.htm.

National Institutes of Health (n.d.). Tetralogy of Fallot. Retrieved September 4, 2007, from the National Heart, Lung, and Blood Institute Web site: www.nhlbi.nih.gov/health/dci/Diseases/tof/tof_causes.html.

U.S. National Library of Medicine (2007). Tetralogy of Fallot. Retrieved September 4, 2007, from the Medlineplus Web site:www.nlm.nih.gov/medlineplus/ency/article/001567.htm.