Dextro transposition of the great arteries (D TGA) is a congenital cyanotic heart defect in which the pulmonary artery and the aorta are transposed. Another type of TGA is levo transposition of the great arteries (L TGA), in which the aorta is to the left of the pulmonary artery. In this article, you’ll learn about D TGA as it is the most common form, and also the most serious. To fully understand the implications of this condition, it’s helpful to review normal cardiopulmonary circulation.

Review of cardiopulmonary circulation

In normal physiology, blood flows from the system into the inferior vena cava and superior vena cava. From there it enters the right atrium, flows through the tricuspid valve and into the right ventricle. It is then pumped through the pulmonary valve and into the pulmonary artery. The pulmonary artery leads into the pulmonary vasculature where oxygen exchange occurs. The blood then leaves the lungs and returns to the heart through the pulmonary veins. It enters at the left atrium, flows through the mitral valve and into the left ventricle. From there it is pumped out through the aortic valve into the aorta and into systemic circulation.

Blood flow through heart

Pathophysiology of D TGA

In D TGA, the pulmonary artery and aorta are transposed, meaning they’ve switched places. In short, there is no communication between pulmonary and systemic circulation. In normal anatomy, the pulmonary artery comes off the right ventricle and takes deoxygenated blood to the lungs where it can participate in gas exchange. In D TGA anatomy, the pulmonary artery comes off the left ventricle. The result is that oxygenated blood coming in from the pulmonary veins goes to the left atrium, then to the left ventricle. Instead of going out through the aorta and into the system, the blood goes back into the lungs via the pulmonary artery. So, this oxygenated blood never gets sent out into the system.

As for the aorta, in normal anatomy, the aorta exits from the left ventricle. Oxygenated blood flows through the aorta to be sent into systemic circulation. In D TGA anatomy, the aorta exits from the right ventricle, which is full of deoxygenated blood. The result is that deoxygenated blood is sent out through the aorta into systemic circulation. Without some kind of underlying compensation, D TGA is incompatible with life.

Normal AnatomyD TGA AnatomyD TGA Pathophysiology
Pulmonary artery comes off the right ventriclePulmonary artery comes off the left ventricleOxygenated blood coming in from the pulmonary veins goes to the left atrium, then to the left ventricle, and then back into the lungs via the pulmonary artery.

This oxygenated blood does not go into systemic circulation!
Aorta exits from the left ventricleAorta exits from the right ventricleDeoxygenated blood returns from the system, goes from the right atrium to the right ventricle and into the aorta where it is sent into systemic circulation.
Note this blood is sent into systemic circulation without participating in gas exchange or picking up oxygen in the lungs. 

Compensation for D TGA

Dextro transposition of the great arteries is one condition in which you want the child to have other congenital heart defects such as a patent foramen ovale, patent ductus arteriosis and/or ventricular septal defect. These defects (especially a VSD) will force oxygenated blood from the left ventricle into the right ventricle so that it can go out through the misplaced aorta and into systemic circulation. However, these defects can resolve on their own, so once these openings start to close, the child will begin to show signs of compromise, such as cyanosis. If no compensatory defects are present, cyanosis typically begins to show soon after birth.

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Signs and symptoms of D TGA

  • Weak pulses
  • Poor appetite
  • Failure to thrive or slow weight gain
  • Tachypnea
  • Labored breathing
  • Tachycardia
  • Cyanotic skin signs

How is D TGA diagnosed?

Dextro transposition of the great arteries may be diagnosed prior to birth with a prenatal ultrasound, though detection at this time is difficult. After the baby is born, diagnostic tests include echocardiogram, cardiac catheterization and chest X-ray. If a child can be diagnosed prenatally, outcomes are generally better as plans can be made for the birth to take place at a specialty center with a NICU and pediatric cardiologists available.

Treatment for D TGA

The only treatment for D TGA is surgery to switch the positions of the arteries. Prior to surgery, treatments include: 

  • Prostaglandin to maintain a patent ductus arteriosus, which is administered as a continuous infusion. Note that apnea can occur as an adverse effect of this medication, so the infant may need to be intubated.
  • Fluids to correct hypotension resulting from prostaglandin infusion (prostaglandin causes vasodilation).
  • Supplemental oxygen.


Another procedure that may be conducted to stabilize the patient prior to surgery is a balloon atrial septostomy (BAS). In this procedure, a catheter is advanced through the umbilical or femoral vein, inserted into the heart and a balloon is deployed across the atrial septum to create an opening between the right and left atrium. This allows oxygen-rich blood from the left side of the heart to enter the right side of the heart and, ultimately, systemic circulation. Children who undergo this procedure will still require full surgical repair of the transposed arteries.

Risk factors for D TGA

Factors which put a baby at higher risk for developing D TGA include: 

  • Family history of congenital heart defects
  • Alcohol use during pregnancy
  • Use of certain medications during pregnancy, specifically antiseizure medications
  • Smoking during pregnancy
  • Poorly controlled diabetes during pregnancy
  • Viral infections during pregnancy (including rubella)

To help prevent D TGA, important prenatal teaching includes things like getting the rubella vaccine, avoiding smoking and alcohol, controlling blood glucose levels, and discussing all medications with the OB/GYN.


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References:

Cedars, A. M. (2024, January 11). Transposition of the Great Arteries (TGA). Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/transposition-of-the-great-arteries-tga

Cleveland Clinic. (2022, June 26). Transposition of the Great Arteries: Symptoms and Causes. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/23387-transposition-of-the-great-arteries

Fulton, D. R. (2023). D-transposition of the great arteries (D-TGA): Management and outcome – UpToDate. UpToDate. https://www.uptodate.com/contents/d-transposition-of-the-great-arteries-d-tga-management-and-outcome?search=transposition%20of%20the%20great%20arteries&source=search_result&selectedTitle=2~65&usage_type=default&display_rank=2

Lynch, T. A., & Abel, D. E. (2015). Teratogens and Congenital Heart Disease. Journal of Diagnostic Medical Sonography, 31(5), 301–305. https://doi.org/10.1177/8756479315598524

Mayo Clinic. (2023, April 4). Transposition of the great arteries – Symptoms and causes. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/transposition-of-the-great-arteries/symptoms-causes/syc-20350589

MedlinePlus. (2021, October 10). Transposition of the great arteries: MedlinePlus Medical Encyclopedia. MedlinePlus. https://medlineplus.gov/ency/article/001568.htm