Transposition of the great arteries (TGA) is a heart condition that is present at birth, and often is called a congenital heart defect. TGA occurs when the two main arteries going out of the heart—the pulmonary artery and the aorta—are switched in position, or “transposed”.

Normally, blood returning to the heart from the body is pumped from the right side of the heart through the pulmonary artery to the lungs. There, it receives oxygen and returns to the left side of the heart. Then, the oxygen-rich blood is pumped from the left side of the heart through the aorta to the body. In TGA, blood returning from the body bypasses the lungs and is pumped back out to the body. This occurs because the main connections are reversed. The pulmonary artery, which normally carries oxygen-poor blood from the right side of the heart to the lungs, now arises from the left side and carries oxygen-rich blood returning from the lungs back to the lungs. The aorta, which normally carries blood from the left side of the heart to the body, now arises from the right side and carries oxygen-poor blood back out to the body. The result of transposition of these two vessels is that too little oxygen is in the blood that is pumped from the heart to the rest of the body.

TGA might also be referred to as transposition of the great vessels (TGV), but TGA is the more common term.

To learn more about transposition of the great arteries click on one of the following links or scroll down the page.

What We Know About Transposition of the Great Arteries

• How often does transposition of the great arteries occur?
• What problems do children with transposition of the great arteries have?

What We Still Do Not Know About Transposition of the Great Arteries

• What causes transposition of the great arteries?
• Can transposition of the great arteries be prevented?

Resources for Families and Individuals Affected by Transposition of the Great Arteries

How often does transposition of the great arteries occur?
CDC estimates that each year about 1,901babies in the United States are born with TGA (1). In other words, about 5 out of every 10,000 babies born in the United States each year is born with TGA.

What problems do children with transposition of the great arteries have?
Because the main arteries are switched, there are two separate blood circulations instead of a single connected one. Thus, blood with oxygen from the lungs does not get to the rest of the body. This means that TGA is a cyanotic (lacking oxygen) heart defect that leads to a bluish-purple coloring of the skin and shortness of breath.

Symptoms appear at birth or very soon afterwards. How bad the symptoms are depends on whether there is a way for the two separate blood circuits to mix, allowing some oxygen-rich blood to get out to the body. This mixing can occur through other defects, such as a hole between the bottom chambers of the heart (a ventricular septal defect), or through a shunt that normally is present at birth. Symptoms also can depend on whether other defects are present as well. Common symptoms of TGA include:

• Blueness of the skin
• Shortness of breath
• Poor feeding

Surgery might be needed shortly after birth. In most hospitals, a type of surgery called an arterial switch procedure can be used to permanently correct the problem within the first week of life.

Without corrective surgery, severe cases of TGA can be fatal during the first 6 months of life. Babies who have surgery to correct TGA sometimes have the following associated conditions later in life:

• Leaky heart valves
• Problems with the arteries that supply the heart muscle with blood (coronary arteries)
• Abnormal heart rhythm (arrhythmias)
• A decline in function of the heart muscle or heart valves
• Heart failure
• Damage to the lungs and difficulty breathing

Babies with TGA will require lifelong follow-up with a cardiologist. Even so, with proper treatment, most babies with TGA grow up to lead healthy, productive lives.

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What causes transposition of the great arteries?
The cause of TGA is unknown at this time. Scientific researchers have found that some diseases and behaviors might be associated with a higher risk for TGA. These include:

• The mother having a viral illness during pregnancy
• The mother having poor nutrition during pregnancy
• The mother using an excessive amount of alcohol during pregnancy
• The mother being older than 40 years of age
• The mother having diabetes during pregnancy
• The baby having Down syndrome

CDC works with many researchers to study risk factors that can increase the chance of having a baby with TGA, as well as outcomes of babies with the defect. Following are examples of what this research has found:

• TGA seems to be occur more often among White babies than non-White babies, although more research is needed (2).
• No strong link exists between caffeine use by a mother during pregnancy and the risk for TGA (3).
• There are signs that the rate of TGA is decreasing over time (2).
  

Can transposition of the great arteries be prevented?
There is no known way to prevent this defect, but some of the problems experienced later in life by babies born with TGA can be prevented or lessened if the defect is found early.

Even so, mothers can take steps before and during pregnancy to have a healthy pregnancy. Steps include taking a daily multivitamin with folic acid (400 micrograms), not smoking, and not drinking alcohol during pregnancy.

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American Heart Association

Mayo Clinic

Medline

References

1. Canfield MA, Honein MA, Yuskiv N, Xing J, Mai CT, Collins JS, et al. National Estimates and Race/Ethnic-Specific Variation of Selected Birth Defects in the United States, 1999-2001. Birth Defects Res Part A Clin Mol Teratol. 2006;76(11); 747-56.
2. Lorenzo DB, Correa A, Erickson JD. Racial and temporal variations in the prevalence of heart defects. Pediatrics. 2001;107(3): 1-8
3. Browne ML, Bell EM, Druschel CM, et al. Maternal caffeine consumption and risk of cardiovascular malformation. Birth Defects Res A Clin Mol Teratol. 2007;79: 533-43.
   

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Date: March 11, 2009
Content source: National Center on Birth Defects and Developmental Disabilities