Heterotaxy Syndrome?

taken from Children’s Hospital of Philadelphia’s website (www.chop.edu)

Heterotaxy syndrome is a rare birth defect that involves the heart and other organs. The beginning of the word (hetero-) means “different” and the end (–taxy) means “arrangement.”

In heterotaxy syndrome, paired organs, such as the lungs or kidneys, are often mirror images of one another instead of having the unique characteristics of right and left that are normally present.

There are different forms of heterotaxy. All usually involve heart defects, of varying type and severity. In addition, organs such as the stomach, intestines, liver and lungs may be in abnormal places in the chest and abdomen. The intestines may have malrotation, which is when the loops of bowel are lined up incorrectly. With this problem the bowel can twist on itself (volvulus), so many children with malrotation need abdominal surgery to correct it. Some children with heterotaxy can have a very serious condition of the liver called biliary atresia. This also may require surgical intervention. There may also be irregularities with the skeleton, central nervous system and urinary tract.

The spleen may not work correctly or may be missing entirely. This can cause many problems, because the spleen helps the body fight infections. When the spleen is missing or doesn’t work correctly, patients have a more difficult time recovering from surgeries or infections. (Patients with heterotaxy may require multiple surgeries.) In some cases, there may be a functioning spleen, but it may be divided into several smaller spleens (polysplenia).

Sometimes children with heterotaxy have dextrocardia. This means the heart is in the right chest instead of the left chest.

Here are general descriptions of two types of heterotaxy. The morphology (structure) of the heart varies from child to child. The Cardiac Center team will explain your child’s heart structure to you in detail. Types of heterotaxy include:

  • Asplenia or right atrial isomerism: Children with this condition have multiple heart defects. They may have septal defects (holes between the tissue dividing the two sides of the heart) and problems with heart valves, particularly the pulmonary valve. They may also have abnormalities of the blood returning from the lungs to the heart (anomalous pulmonary venous connection). The spleen may be absent (asplenia), and the liver and other organs may be on the wrong side of the body.
  • Polysplenia or left atrial isomerism: Children with this condition may have septal defects (holes between the tissue dividing the two sides of the heart) as well as problems with heart valves and the heart’s electrical system. Some children with this problem have complete heart block, which is when the upper-chamber electrical system does not communicate with the lower-chamber electrical system. Most children require pacemakers for this problem. The spleen may be absent, or there may be several small spleens (polysplenia), instead of one spleen.

What do the terms “right atrial isomerism” and “left atrial isomerism” mean? The heart has tiny pouches, one on each of the two upper chambers, called atrial appendages. In a normal heart, the left atrial appendage looks different than the right. In heterotaxy, the two appendages look similar. “Isomerism” means mirror images. Hence the terms “right atrial isomerism” and “left atrial isomerism.”


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