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.”

Signs and Symptoms
Babies with Heterotaxy can have symptoms that start shortly after birth from any of the organs listed above. The heart is involved about 80%
of the time and the first thing that may be seen is a blue color to the skin (cyanosis) that most commonly is found on the lips and under the
fingernails. Over time, your baby may develop poor feeding, fast breathing, increased sweating when they eat, or poor weight gain. All of these
findings are signs that the heart is not able to pump enough blood to the body to meet its needs and is called “heart failure.” Sometimes your
doctor might hear an unusual heart beat or an extra sound when they listen to the heart (heart murmur). Heterotaxy can also affect the liver and
intestine. Biliary atresia is due to a failure of the bile ducts in the liver to form correctly and can cause jaundice (a yellow color of the skin). If
the intestines are abnormally positioned inside the body, then it is more likely for the intestine to get blocked and your baby may have vomiting
or swelling of their stomach when they eat. When the spleen is involved your child can have either no spleen (asplenia) or many little spleens
(polysplenia). Even if there are many little spleens, sometimes they don’t work well enough to help fight off certain types of infections.

Possible Causes
The exact cause of Heterotaxy is not known, but the symptoms result from the way that the internal organs turn into position during
fetal development. This rotation can be affected by many different factors including: infection, genetics, or exposures to certain chemicals.
There are a few reports of families having several members with Heterotaxy, but the exact cause has not been identified yet.

Diagnosis
Making the diagnosis of Heterotaxy syndrome involves an ultrasound of the heart (echocardiogram) that will allow a pediatric
cardiologist to best see the structures of your child’s heart. An electrocardiogram (EKG) is usually done to ensure there are no heart rhythm
problems. An x-ray can help to evaluate the heart size and look for what side the abdominal organs and heart are on. The intestines can also be
twisted incorrectly and an upper gastrointestinal series should be done to look for this. A liver-spleen scan should also be done to check for a
functioning spleen. Finally, a cardiac catheterization procedure may be needed for a more detailed view of the child’s heart structures in
preparation for corrective surgery.