Heterotaxy syndrome is a disorder that results in certain organs forming on the opposite side of the body. For example, instead of the heart normally forming on the left side of the chest, it will be located on the right side. Heterotaxy has been known to affect the development of the heart, liver, lungs, intestines, and spleen. Babies with Heterotaxy syndrome are usually first identified because they have structural problems with their hearts or livers.
Heterotaxy syndrome is equally common in boys and girls and can occur in all ethnic groups. For every 1,000,000 babies born, 4 of them will have Heterotaxy syndrome. Rarely, Heterotaxy can only affect the boys in some families.
Heterotaxy, or Situs Ambiguous, is a rare congenital defect in which the major visceral organs are distributed abnormally within the chest and abdomen. The normal position of the organs is known as Situs Solitus. Situs Inversus is a condition in which the usual positions of the organs are reversed from left to right as a mirror image of the normal condition. If these are the two extreme positions on a continuum of asymmetric thoracic and abdominal organ formation, Situs Ambiguous (Heterotaxy) covers everything in between.
Heterotaxy is a term used to describe two groupings of congenital heart defects that generally involve a looping defect, Dextrocardia. In addition to several anomalies in the heart, the liver of a person with Heterotaxy is generally midline, instead of placed on one side of the body. The most significant indicator of Heterotaxy is the presence of a number of small spleens, Polysplenia, or the total absence of a spleen, Asplenia. Heterotaxy is split into two types, Left Atrial Isomerism and Right Atrial Isomerism, sometimes called Ivemark’s Syndrome.
Left Atrial Isomerism is generally associated with Polysplenia. This form of Heterotaxy is less severe than Ivemark’s because these multiple tiny spleens tend to do some of the work of a regular spleen. Often, ventricular septal defects and pulmonary stenosis are present, but these two conditions, unless severe, can usually be repaired in one surgery. Surgical repairs for Left Atrial Isomerism are usually not necessary right after birth. Surgeons generally elect to repair the heart’s defects during the first five years of life. Diagnosis of Dextrocardia is usually made during routine sonograms, but prior to birth it is difficult to determine whether a spleen or multiple spleens exist, because they cannot be visualized easily. After birth, a blood test can determine splenic function to confirm diagnosis of Polysplenia associated with Heterotaxy.
Right Atrial Isomerism is one of the more difficult heart anomalies to treat. This form of Heterotaxy is marked by multiple defects in addition to Asplenia. The most prominent defect is complete atrioventricular canal defect. The septum between the ventricles usually has a large hole, allowing blood to mix. Additionally, the septum between the atria may never have formed, and the atria are generally undersized. Extreme pulmonary stenosis and Transposition of the Great Arteries may also be present. As well, the pulmonary veins may drain on the wrong side, depriving the heart of oxygen-rich blood. These multiple defects usually require surgery soon after birth, and generally the surgery must be done in stages, as with the Fontan procedure. Surgery to correct Right Atrial Isomerism is complicated by Asplenia. Lack of a spleen means a much greater risk of post-operative infection.
Classically, Heterotaxy comprises of:
- Cardiac looping malformations – commonly Fallot’s Tetralogy, Transposition of the Great Vessels, Pulmonary Valve Stenosis, and ventricular and atrial septal defects.
- Deranged abdominal organ asymmetry – the stomach and spleen are particularly prone to isolated reversal, and the stomach, liver, and a single adrenal gland are occasionally found in the midline.
- Organ malformations – chiefly Asplenia-Polysplenia, and more rarely a failure of the head of the pancreas to form, and horseshoe adrenals and kidneys.
Types
The following are included in the list of Heterotaxy Syndromes:
- Asplenia refers to the absence of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced splenic functioning, but not as severely affected as with asplenism.
- Polysplenia is a congenital disease manifested by multiple small accessory spleens. There are frequent associated congenital anomalies all related to deviations in the development of anatomical asymmetries in early embryonic stages. These conditions considered together are called “polysplenia syndrome”.
- Ivemark syndrome, also known as Right Atrial Isomerism, is an uncommon congenital disorder characterized by asplenia or polysplenia, a poorly formed cardiovascular system, and having one’s organs misoriented or on the wrong side of the body.
- Dextrocardia is the heart being situated on the right side of the body. Dextrocardia Situs Inversus refers to the heart being a mirror image situated on the right side.
- Kartagener Syndrome (KS), is a rare, ciliopathic, autosomal recessive genetic disorder that causes a defect in the action of the cilia lining the respiratory tract (lower and upper, sinuses, Eustachian tube, middle ear) and fallopian tube. When accompianied by the combination of situs inversus (reversal of internal organs), chronic sinusitus, and bronchiectasis, it is known as Kartagener Syndrome.
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.
Treatment
Children with Heterotaxy syndrome and heart disease will need medications to help prevent heart failure in addition to surgery to correct the abnormalities. The type of heart surgery performed will be based on each child’s particular heart problems. Children with Heterotaxy are also at increased risk of having irregular electrical signals in their heart tissue and may need a pacemaker later in life. If the intestines are twisted incorrectly, surgery will be needed to place the intestines into the proper position to prevent any blockage. When biliary atresia occurs, a liver transplant is often required. If the spleen isn’t functioning properly, children with Heterotaxy may need to take daily antibiotics and receive special vaccinations to protect them from certain infections.
Source: Wikipedia and WiseGeek.com
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