Transposition of the great arteries is a congenital (present at birth) heart defect. Due to abnormal development of the fetal heart during the first eight weeks of pregnancy, the large vessels that take blood away from the heart to the lungs, or to the body, are improperly connected.
Normally, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped through the aorta out to the body.
In transposition of the great arteries, the aorta is connected to the right ventricle, and the pulmonary artery is connected to the left ventricle—the exact opposite of a normal heart's anatomy.
Two separate circuits are formed—one that circulates oxygen-poor (blue) blood from the body back to the body, and another that recirculates oxygen-rich (red) blood from the lungs back to the lungs.
Other heart defects are often associated with TGA, and they actually may be necessary in order for an infant with transposition of the great arteries to live. An opening in the atrial or ventricular septum will allow blood from one side to mix with blood from another, creating "purple" blood with an oxygen level somewhere in-between that of the oxygen-poor (blue) and the oxygen-rich (red) blood. Patent ductus arteriosus (another type of congenital heart defect) will also allow mixing of oxygen-poor (blue) and oxygen-rich (red) blood through the connection between the aorta and pulmonary artery. The "purple" blood that results from this mixing is beneficial, providing at least smaller amounts of oxygen to the body, if not a normal amount of oxygen.
Because of the low amount of oxygen provided to the body, TGA is a heart problem that is labeled "blue-baby syndrome."
Transposition of the great arteries is the second most common congenital heart defect that causes problems in early infancy. TGA occurs in 5 to 7 percent of all congenital heart defects. Sixty to 70 percent of the infants born with the defect are boys.
The heart is forming during the first eight weeks of fetal development. The problem occurs in the middle of these weeks, allowing the aorta and pulmonary artery to be attached to the incorrect chamber.
Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families. Most of the time this heart defect occurs sporadically (by chance), with no clear reason for its development.
Babies with TGA have two separate circuits—one that circulates oxygen-poor (blue) blood from the body back to the body, and another that recirculates oxygen-rich (red) blood from the lungs back to the lungs. Without an additional heart defect that allows mixing of oxygen-poor (blue) and oxygen-rich (red) blood, such as an atrial or ventricular septal defect, infants with TGA will have oxygen-poor (blue) blood circulating through the body—a situation that is fatal. Even with an additional defect present that allows mixing, babies with transposition of the great arteries will not have enough oxygen in the bloodstream to meet the body's demands.
Even when a good bit of mixing of oxygen-poor (blue) and oxygen-rich (red) blood can occur, other problems are present. The left ventricle, which in TGA is connected to the pulmonary artery, is the stronger of the two ventricles since it normally has to generate a lot of force to pump blood to the body. The right ventricle, connected to the aorta in TGA, is the weaker of the two ventricles. Because the right ventricle is weaker, it may not be able to pump blood efficiently to the body, and it will enlarge under the strain of the job. The left ventricle may pump blood into the lungs more vigorously than needed, leading to strain in the blood vessels in the lungs.
The obvious indication of TGA is a newborn who becomes cyanotic (blue) in the transitional first day of life when the maternal source of oxygen (from the placenta) is removed. Cyanosis is noted in the first hours of life in about half of the infants with TGA, and within the first days of life in 90 percent of them. The degree of cyanosis is related to the presence of other defects that allow blood to mix, including a patent ductus arteriosus—a fetal connection between the aorta and the pulmonary artery present in the newborn, which usually closes in the first few days after birth.
The following are the other most common symptoms of TGA. However, each child may experience symptoms differently. Symptoms may include:
The symptoms of TGA may resemble other medical conditions or heart problems. Always consult your child's physician for a diagnosis.
A pediatric cardiologist and/or a neonatologist may be involved in your child's care. A pediatric cardiologist specializes in the diagnosis and medical management of congenital heart defects, as well as heart problems that may develop later in childhood. A neonatologist specializes in illnesses affecting newborns, both premature and full-term.
Cyanosis is the major indication that there is a problem with your newborn. Your child's physician may have also heard a heart murmur during a physical examination. A heart murmur is simply a noise caused by the turbulence of blood flowing through the openings that allow the blood to mix.
Diagnostic testing for congenital heart disease varies by the child's age, clinical condition, and institutional preferences. Some tests that may be recommended include the following:
Specific treatment for transposition of the great arteries will be determined by your child's physician based on:
Your child will most likely be admitted to the intensive care unit (ICU) or special care nursery once symptoms are noted. Initially, your child may be placed on oxygen, and possibly even on a ventilator, to assist his or her breathing. Intravenous (IV) medications may be given to help the heart and lungs function more efficiently.
Other important aspects of initial treatment include the following:
Within the first 1 to 2 weeks of age, transposition of the great arteries is surgically repaired. The procedure that accomplishes this is called a "switch," which roughly describes the surgical process.
The operation is performed under general anesthesia, and involves the following:
After surgery, infants will return to the intensive care unit (ICU) for a few days to be closely monitored during recovery.
While your child is in the ICU, special equipment will be used to help him or her recover, and may include the following:
Your child may need other equipment not mentioned here to provide support while in the ICU, or afterwards. The hospital staff will explain all of the necessary equipment to you.
Your child will be kept as comfortable as possible with several different medications; some of which relieve pain, and some of which relieve anxiety. The staff will also be asking for your input as to how best to soothe and comfort your child.
After discharge from the ICU, your child will recuperate on another hospital unit for a few days before going home. You will learn how to care for your child at home before your child is discharged. Your child may need to take medications for a while, and these will be explained to you. The staff will give you written instructions regarding medications, activity limitations, and follow-up appointments before your child is discharged.
Infants who spent a lot of time on a ventilator, or who were fairly ill while in the ICU, may have trouble feeding initially. These babies may have an oral aversion; they might equate something placed in the mouth, such as a pacifier or bottle, with a less pleasant sensation such as being on the ventilator. Some infants are just tired, and need to build their strength up before they will be able to learn to bottle feed. Strategies used to help infants with nutrition include the following:
Pain medications, such as acetaminophen or ibuprofen, may be recommended to keep your child comfortable at home. Your child's physician will discuss pain control before your child is discharged from the hospital.
If any special treatments are to be given at home, the nursing staff will ensure that you are able to provide them, or a home health agency may assist you.
You may receive additional instructions from your child's physicians and the hospital staff.
Many infants who undergo TGA surgical repair will grow and develop normally. However, after TGA repair, your infant will need to be followed periodically by a pediatric cardiologist who will make assessments to check for any heart-related problems, which can include the following:
Prior to the early 1990s, TGA was generally treated surgically with a Mustard procedure or a Senning procedure. These procedures created a tunnel, or baffle, in the atria to correct blood flow. In the late 1980s, the arterial switch procedure was introduced. This procedure "switches" the aorta and pulmonary artery to the proper locations. However, the arterial switch procedure may not be indicated in certain situations.
For individuals whose TGA was repaired using a Mustard or Senning procedure, complications such as heart failure and dysrhythmias may develop in the second or third decade of life. There is also a risk for sudden death. Thus, these individuals should receive regular follow-up care at a center offering pediatric or adult congenital cardiac care throughout the individual's lifespan.
Consult your child's physician regarding the specific outlook for your child.
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