Transposition of the Great Arteries (TGA) | Symptoms and Diagnosis

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What causes transposition of the greater arteries?

Transposition of the greater arteries (TGA) is a congenital heart defect, which means children are born with it.

The heart forms during the first eight weeks of fetal development. The problems associated with TGA occur in the middle of these weeks, when the aorta and the pulmonary artery each attach to the incorrect heart chamber. It isn’t clear what causes congenital heart malformations, including TGA, although in most cases it appears that some combination of genetics and environment is involved.

Very few risk factors have been identified, but it appears that the risk of TGA is increased in mothers with type 1 diabetes mellitus (formerly known as "insulin-dependent" or "juvenile") and possibly with the ingestion of certain drugs, such as benzodiazepines.

What are the signs and symptoms of TGA?

Cyanosis (blue coloration of the skin) is the most common symptom of TGA.

What kind of examination will diagnose TGA?

If your newborn baby was born with a bluish tint to his skin, or if your young child is experiencing certain symptoms, your pediatrician will immediately refer you to a pediatric cardiologist (or neonatologist), who will perform a physical exam. Your child’s doctor will listen to your baby’s heart and lungs, measure the oxygen level in his blood (non-invasively) and make other observations that help to determine the diagnosis.

Your child’s cardiologist will also investigate whether he has a heart murmur — a noise heard through the stethoscope that’s caused by the turbulence of blood flow. If there’s a murmur (there isn’t always with TGA), the location in the chest where the murmur is best heard, as well as the sound and character of the murmur itself, will give the cardiologist an initial idea of the kind of heart problem your baby may have.

How do you diagnose TGA?

For most patients, an echocardiogram and chest x-ray is all that’s needed to form a diagnosis. But in certain circumstances, certain tests may be necessary.

Echocardiogram (cardiac ultrasound)

An echocardiogram evaluates the structure and function of a child’s heart, using electronically recorded sound waves that produce a moving picture of the heart and heart valves. No discomfort is involved. It takes 30-60 minutes.

If, during pregnancy, a routine prenatal ultrasound or other signs raise suspicion of a congenital heart defect in the fetus, a cardiac ultrasound (described in the paragraph above) of the baby in utero will usually be the next step. The cardiac ultrasound — focusing exclusively on the baby’s heart — can usually detect a congenital heart defect.

Chest x-ray 

A conventional chest x-ray will evaluate the size and spatial relationships of the heart within the child’s chest. It takes a few moments. There's no pain or discomfort.

Electrocardiogram (EKG)

An EKG is used to evaluate the electrical activity of the heart. An EKG is usually the initial test for evaluating the causes of symptoms and detecting heart abnormalities, including TGA. It’s performed by placing electrodes on the arms, legs and chest to record the electrical activity. The test takes five minutes or less and involves no pain or discomfort.

Cardiac catheterization

Cardiac catheterization provides detailed visual information and measurements about the structures and pressures inside the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, as well as the pulmonary artery and aorta.

Cardiac magnetic resonance imaging (MRI) 

MRI provides a picture of the heart and blood vessels, but without using x-rays. MRI is rarely used in babies with TGA but may be helpful in follow-up to TGA surgery to detect complications.

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