Testing & Diagnosis for Transposition of the Great Arteries (TGA) in Children

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At Boston Children's Hospital, we understand that the first step in treating your child is forming an accurate, complete and timely diagnosis.

The exam

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 (and/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.

Note: If your child’s TGA was detected prenatally through ultrasound, upon birth he’ll be immediately admitted for stabilization and surgery.

The tests

For most patients, a echocardiogram and chest x-ray are all that’s needed to form a diagnosis. But in some circumstances, some or all of the following tests may be used to confirm a diagnosis of TGA and its related defects, and to provide detailed information on the exact shape of a patient’s heart:

  • echocardiogram (cardiac ultrasound): An echocardiogram evaluates the structure and function of your 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 your pregnancy, a routine prenatal ultrasound or other signs raise your obstetrician’s 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 your child’s 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: 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): 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.

TGA glossary

aorta
one of the heart’s two great arteries. In a normal heart, the aorta arises from the left ventricle and carries oxygen-rich blood out to the body.

atrial septal defect (ASD)
a congenital (present at birth) heart defect in which there is an opening in the tissue wall (septum) that divides the two upper chambers of the heart (right and left atria). This defect occurs occasionally with TGA and is actually helpful; it can be easily corrected at the time of surgical correction.

cardiac catheterization (cardiac cath)
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 catheterization can also be an interventional procedure. In TGA, a catheterization procedure called balloon atrial septostomy may be performed to improve the mixing of oxygen-rich (red) blood and oxygen-poor (blue) blood between the right and left atria. 

cardiac/cardio  pertaining to the heart 

cardiac magnetic resonance imaging (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. 


cardiac surgery
surgical procedure performed on the heart or one of the blood vessels connected to the heart

cardiac surgeon
doctor who performs surgery on the heart. A pediatric cardiac surgeon performs surgery on the hearts of infants and children.

cardiologist
doctor who diagnoses and treats heart problems non-surgically. A pediatric cardiologist treats infants, children and some adults with heart problems. 

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

cyanosis (cyanotic)
blue color of skin, lips and nailbeds caused by a reduction in the amount of oxygen-rich (red) blood circulating in baby’s bloodstream


congenital heart defect
heart defect present at birth. The heart usually starts to form in the first eight weeks of fetal development. It’s thought that most congenital heart defects develop during this period. 

diagnosis  medical determination of illness or disease based on history, physical examinations and advanced technology diagnostic testing tools

ductus arteriosis, patent ductus arteriosus
a blood vessel that connects the aorta to the pulmonary artery. Before birth, this vessel helps blood flow in the fetus. It usually closes shortly after a baby’s birth. Because an open (patent) ductus can help increase the oxygen level in the blood in a patient with TGA, a medication to keep this vessel from closing (prostaglandin E1) is often given until the great vessels can be repaired surgically.

echocardiogram (echo, cardiac ultrasound)
evaluates the structure and function of your child’s heart using electronically recorded sound waves that produce a moving picture of the heart and heart valves. Can be used to understand flow in the different chambers and to estimate pressures. No discomfort is involved. It takes 30-60 minutes.

electrocardiogram (ECG or EKG)  evaluates the electrical activity of your child’s 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.

IV  intravenous, into the vein; one method of delivering medication 

neonatologist
doctor who specializes in illnesses affecting newborns, both premature and full-term

pulmonary artery
one of the heart’s two great arteries, which normally arises from the right ventricle and carries oxygen-poor blood to the lungs, where it receives oxygen

sporadic
occurring by chance, occasionally, not inherited 

signs and symptoms
the presenting reasons why a child needs medical attention. Characteristics such as onset, quality, triggers and severity help diagnosticians to determine a disease, or to decide which testing is needed to determine the disease. 

ventricular septal defect (VSD)
a congenital (present at birth) heart defect in which there is an opening in the tissue wall (septum) that divides the two lower chambers of the heart (right and left ventricles). This occurs in about 20% of patients with TGA. If large enough, a VSD will need to be surgically closed at the time of surgical correction of the TGA. 

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