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Heterotaxy Syndrome

What is Heterotaxy Syndrome?

The term Heterotaxy syndrome is derived from two words – HETERO (means “different”) and TAXY (means “arrangement”). Heterotaxy syndrome is a congenital rare defect that can affect many organs, including heart, liver and other organs. In Heterotaxy syndrome, the defective arrangement of a specific organ or more than one organs is involved.

The involve organ or organs mainly present in the chest and/or abdominal cavity. Inside the uterus, incorrect rotation along with the body axis of the developing fetus is the main causative factor to generate Heterotaxy syndrome. Depending upon the organ involvement Heterotaxy syndrome is divided into several types. The severity of the condition also depends upon the organ involvement.

For example, normally heart is located at the left side of the chest cavity, but in Heterotaxy syndrome, the heart may present on the right side. The sign and symptoms of same organ involvement could give varied severity. Like a child with heart abnormal location may provide severe symptoms with an increased risk of fatal outcome, however, some children have mild to negligible symptoms. Therefore, the patients with Heterotaxy syndrome are unique. Apart from, cardiac problem, lung complication, immunity disorders are also common in Heterotaxy syndrome^1,2,3.

Possible Organ Involvement/Causes

There are several possible risks of organ involvement in Heterotaxy syndrome.

The altering rotation of intestine can cause incorrect positioning of bowel loop. Volvulus is a condition, in which bowel can twist on itself and that can corrective by surgical intervention.
Skeletal system irregularity, central nervous system abnormality, and malformation of the urinary tract are also possible organ involvement in Heterotaxy syndrome.
In some children, incorrect spleen functionality may appear, whereas some completely lost their spleen. The spleen is a major defensive organ and assist in infection protection and boosting immunity. Therefore, spleen involvement in Heterotaxy syndrome causes deficit defensive mechanism, which leads to compromised immune system, increase susceptibility towards infection and delay wound healing after surgical intervention (as patients having Heterotaxy syndrome need to different corrective surgeries). In some children, though spleen functionality does not compromise, but multiple smaller sized spleens present (polysplenia).
In Heterotaxy syndrome, the altering positioning of heart from left to right direction is termed as dextrocardia syndrome. Furthermore, clinically heart abnormality in Heterotaxy syndrome is broadly classified depending upon the morphological alteration of the heart.

Types

There are two types of heart problem – Right atrial isomerism and Left atrial isomerism.

Right Atrial Isomerism

In this condition, multiple heart defects are present in affected children. The included defects include septal defects and cardiac valve abnormality. The septum is acted as a divider of heart and provide right and left chambers. The pulmonary valve abnormality is a major concern of cardiac valve abnormality, which causes abnormal returning of blood from the lungs to the cardiac chamber.

This problem usually occurs due to the anomalous connection of pulmonary venous system. In associated with a heart defect, it may also involve nonappearance of the spleen (asplenia), along with liver and other organs may wrongly position in the body cavity.

Left Atrial Isomerism

In this condition, the included heart defects include septal defects, cardiac valve abnormality and the abnormal electrical system of the heart. In some severe case, complete cardiac block obtains, in which the electrical system between upper and lower chamber does not communicate.

Insertion of pacemaker through surgical intervention often require solving the problem. Along with this, it may also involve nonappearance of the spleen (asplenia), or instead of the single spleen, multiple small spleens (polysplenia) may present^1,3.

Prevalence

The exact prevalence of the Heterotaxy syndrome is unknown, but it is estimated that approximately 1 in 8,000-25,000 live births has Heterotaxy syndrome, which indicates it is a very rare disorder^1,2,3.

Symptoms

The following are some abnormality, which considered as symptoms of Heterotaxy syndrome. Most of these symptoms are noticeable just after birth. The included symptoms are

Cyanosis of skin, which is marked as bluish skin color, lips and in the nail beds. These symptoms appear due to deficit systemic oxygen supply and considered as cyanotic congenital heart disease.
Breathing difficulty and cardiac failure occur due to excessive blood flow to lungs.
Underweight childbirth, difficulty in weight gain and rapid breathing. All these symptoms indicate stomach, liver, intestine and lungs abnormality.
Frequent incidence of infection due to deficit functionality of spleen.
Poor eyesight
Language dominance
Strong right-handedness
Clubbing^1,2,3,5

Diagnosis

The following diagnostic tests are performed in Heterotaxy Syndrome. These are

Chest X-ray
Electrocardiogram (ECG) is a recording process of cardiac electrical activity
Echocardiogram (“echo”): In this process images of heart are created by sound waves
Cardiac MRI: cardiac abnormality is detected by three-dimensional image
Cardiac catheterization is conducted for detecting the heart block^1,3,4

Treatment

The treatment approach depends on the complexity of the symptoms and range of organ abnormality involves.

Heterotaxy Syndrome affected patients with left atrial isomerism need surgical interventions to repair septal defects. Pacemaker insertion can assist to control abnormal heart rhythms. However, both right atrial isomerism and left atrial isomerism to require several cardiac surgeries to correct the abnormalities. The included surgical processes include Norwood procedure, Glenn operation or hemi-Fontan, and the Fontan procedure. Fontan circulation procedure is conducted to correct circulatory system of the heart. along with this cardioprotective drugs are also prescribed to prevent heart failure^1,3,5.

Life expectancy & Survival Rate

A Severe cardiac complication associated with Heterotaxy Syndrome is a major cause of short life span of the affected children. Only 10 percent of children with severe complex heart disease can survive until their second year. Medical advancement including surgical intervention assists in increasing the life expectancy and survival rate.

A vast range of antibiotics, penicillin, amoxicillin etc. assist in treating a variety of infections and increasing the lifespan of the Heterotaxy Syndrome affected children. However, children with mild or negligible symptoms can survive with normal life span^1,3.

References

Heterotaxy Syndrome (Isomerism); Retrieve from http://www.chop.edu/conditions-diseases/heterotaxy-syndrome-isomerism
heterotaxy syndrome; Genetic Home References; Retrieve from https://ghr.nlm.nih.gov/condition/heterotaxy-syndrome
Heterotaxy Syndrome Symptoms & Causes; Retrieve from http://www.childrenshospital.org/conditions-and-treatments/conditions/heterotaxy-syndrome/symptoms-and-causes
Dr Ayush Goel, Dr Yuranga Weerakkody et.al. Heterotaxy syndrome; Radiopaedia.org https://radiopaedia.org/articles/heterotaxy-syndrome
Heterotaxy Syndrome; http://www.chd-uk.co.uk/types-of-chd-and-operations/heterotaxy-syndrome/