Transposition of the Great Arteries

Transposition of the Great Arteries

Transposition of the great arteries (TGA) refers to the congenital heart problem found in newborn babies in which two main arteries; the aorta and pulmonary artery are transposed or switched their original positions. These two main arteries are responsible to carry blood out of the heart.

When anomaly exists in these two great arteries; a) aorta is connected to the right ventricle (right-sided pumping chamber), instead of left and b) pulmonary artery is connected to the left ventricle (left-sided pumping chamber) instead of right. It is a cyanotic heart defect in which oxygen level is decreased in the blood that the heart pumps and moves to the other body parts.

How does TGA differ from normal hearts?

Normal heart

TGA

  • In normal heart functioning, the blood moves from the body, pass it through the right side of the heart (pulmonary artery), and reaches the lungs for oxygen.
  • Then the oxygen-rich blood comes back from the lungs, passes it through the left side of the heart (aorta), and travels to the rest of the body.
  • While in TGA, the blood comes from the body to the pulmonary artery, but instead of going into the lungs to carry oxygen, it pumps out from the aorta and travels back to the rest of the body.

 

This disease is first described over two centuries ago, and there was no treatment available at the time that increased the death ratio of neonates. While the twentieth century was the era of scientific developments in which surgical atrial septectomy and balloon atrial septostomy were introduced to treat the transposition of great arteries. This scientific revolution increased the survival rate by about 90% of newborns through using palliative therapies, physiological procedures, and anatomic repair.

Types of GTA

 There are two types of transposition of great arteries such as;

  • Complete transposition of the great arteries: It is also known as D-TGA (dextro-transposition of the great arteries) causes a shortage of oxygen in the blood that is required to move out of the heart to the rest of the body. The symptoms of D-TGA are usually felt and observed during pregnancy, immediately after birth, or within a few weeks of birth. It requires immediate treatment, otherwise leading to serious complications such as death.
  • Congenitally corrected transposition: Whereas, this type of TGA is named as L-TGA (Levo-transposition of the great arteries). This is a less common type of heart anomaly, in which symptoms may not be noticed right away and its treatment will depend upon the extent of the heart defect.

Signs and Symptoms of TGA

Following are the signs and symptoms of TGA that are most commonly observed in newborn babies;

  • Blue or purple tint to lips, skin, and nails (cyanosis)
  • Rapid breathing
  • Difficulty feeding
  • Poor appetite
  • Poor weight gain

Causes of TGA

The causes of the transposition of great arteries are usually unknown. Some of the doctors claimed that it may be caused by a combination of genetics and environmental problems. The heart is developed in the first 8 weeks of fetal development and TGA occurs when the aorta and pulmonary artery are attached to the wrong chamber of the heart.   Most of the time, it didn’t detect in the initial stages but if you notice the blue coloring on the skin, you should immediately rush to the hospital to diagnose the problem well before time.

Diagnosis of TGA

 TGA can be diagnosed before birth while having a fetal ultrasound. If it is not done during pregnancy, then it can be diagnosed within a few hours or days of baby birth. Moreover, Pediatricians recommended the following test and diagnostic procedures to perform immediately, otherwise, it can cause life-threatening situations for neonates;

  • Echocardiogram: It is a procedure in which sound waves create an image of the heart to diagnose TGA.
  • An electrocardiogram (ECG) produces an electrical rhythm of the heartbeat to monitor the smooth functioning of the heart.
  • Chest X-ray can also help to diagnose the existence of TGA in a newborn baby. 
  • Pulse Oximetry is a noninvasive procedure to examine the sufficiency of oxygen content in the blood.
  • Cardiac Catheterization is a procedure in which a thin tube is inserted into the heart of the newborn through the veins and/or artery of his legs or belly button.
  • Cardiac MRI produces a three-dimensional image that shows the heart’s anomalies or abnormalities.

Treatment of TGA:

The doctor strives to maintain, enlarge or create openings to allow oxygen-rich blood to move it to other body parts. For this, the following treatment options can be used;

Temporary Treatments

  • Medication: The doctor will immediately give a prostaglandin medicine through an IV to keep the blood vessel open and allow the mixing of two blood circulations.
  • Balloon Catheter: Moreover, the doctor can create the opening between the right and left atrium of the heart to allow blood to mix.
  • Permanent Treatment: To improve the life survival of the newborn, the doctor will perform heart surgery to fix the great arteries into their correct positions. It includes the following methods;
  • Arterial Switch Operation: It is a heart surgery in which both great arteries are switched to their usual positions to restore the normal blood flow through the heart to the lungs and then move back through the heart to the rest of the body. This is one of the most common procedures that doctors usually preferred to perform in the first month of life.
  • Atrial Switch Operation:This is the less adopted procedure in which a tunnel is created between the top chambers (atria) of the heart to move out the oxygen-poor blood from the right atrium to the left ventricle and out the pulmonary artery to the lungs. And similar procedure will be repeated when the oxygen-rich blood comes back from the lungs to pass it through the heart to the rest of the body.

Potential Complications of TGA

TGA can cause potential health complications in the near future such as;

  • Hypoxia (lack of oxygen to tissues)
  • Heart valve problems
  • Irregular heart rhythms
  • Difficulty in heart pumping
  • Heart failure

Risk Factors:

Various factors can increase the risk of TGA in newborn babies;

  • Viral illness in mother during pregnancy
  • Smoking or drug abuse during pregnancy
  • Diabetic mother during pregnancy

Prevention for TGA:

If you have a family history of congenital heart problems, you must approach a cardiologist before planning your next pregnancy.  Moreover, you must take a healthy diet, avoid taking drugs, stop smoking and keep a strong check on diabetes. The risk of TGA can be reduced by taking immunization against viral diseases.

References:

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