Every cell in the body requires oxygen to function and survive. Any medical condition that reduces the amount of oxygen available for use by the cells can cause serious problems. D-Transposition of the Great Vessels is a congenital heart defect associated with reduced oxygen levels and impaired body function. This condition is more commonly referred to as D-Transposition of the Great Arteries (TGA). This defect occurs when the two main arteries leaving the heart—the pulmonary artery and the aorta—are reversed or transposed.
In a heart that is structurally normal, the aorta is attached to the left ventricle, and the pulmonary artery is attached to the right ventricle. When blood returns from the body, it flows through the right atria and ventricle, through the pulmonary artery and on to the lungs where it picks up oxygen. The oxygenated blood then travels through the left atria and left ventricle and is sent through the aorta to nourish and energize the body. The circulation of blood though a healthy heart can be thought of as a continuous, connected loop.
In TGA, the normal flow of blood is disrupted. Blood travels to the lungs where it receives oxygen. It then returns to the heart and travels directly back to the lungs instead of going to the body. Likewise, blood that returns from the body circulates through the heart. It then returns to the body without being oxygenated in the lungs. Because the arteries are reversed, the blood flow is stuck in two separate loops and the body is deprived of the oxygen it needs to function.
Some newborns with TGA have a small hole between the right and left atria. This hole allows the mixing of oxygen-rich and oxygen-poor blood. This means that at least some oxygenated blood travels to the body. Physicians can perform a balloon atrial septostomy, a procedure designed to increase the size of this opening, but it is not a permanent solution.
While the cause of TGA remains unknown, it is linked to mothers who contract rubella or other viral illnesses during pregnancy and mothers over the age of 40. Other conditions that increase the risk of TGA are diabetes, poor nutrition and drinking alcohol during pregnancy. It also occurs in children with Down syndrome.
The consequences of oxygen deprivation are noticeable shortly after birth. A baby’s skin color will be blue (cyanotic), especially in areas farthest from the heart. Other symptoms include:
Physicians have several ways to make a TGA diagnosis. It can be diagnosed prenatally after the 18th week of pregnancy through a fetal echocardiogram. This informative procedure, similar to a traditional prenatal ultrasound, allows physicians to view your baby’s heart. Fetal echocardiograms are not routinely offered unless there is a family history of congenital heart defects or some reason to suspect such a test is necessary.
After a child is born, one clue is bluish skin due to the lack of oxygen. Many states, including Indiana, conduct newborn oxygen-level screening before an infant leaves the hospital. The results of these screenings alert healthcare providers to the need for further testing.
A heart murmur or any of the symptoms listed above may also prompt further investigation. Chest x-rays, echocardiograms, or electrocardiograms or cardiac catheterizations may be used to make a diagnosis.
Most babies with TGA undergo surgical repair of the heart shortly after birth. This open-heart procedure returns the pulmonary artery and the aorta to their normal position. Surgery has a high success rate, and the health of the baby improves quickly afterwards. Without surgery, life expectancy may be quite limited.
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Researchers at Indiana University School of Medicine recently studied resting pulmonary function and its effect on exercise after repair of D-Transposition of the Great Vessels. For more information about how Riley at IU Health is involved in research for congenital heart defects, visit the Herman B Wells Center for Pediatric Research.
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