Transposition of the great arteries (TGA) is a type of heart defect that your baby is born with (congenital). In this condition, the two arteries that carry blood out of the heart aren't connected as they should be. They are reversed (transposed).

In TGA, the following occur:

• The aorta is connected to the right ventricle. It should normally be connected to the left ventricle.
• The pulmonary artery is connected to the left ventricle when it should normally be connected to the right ventricle.

This means that:

• Oxygen-poor (blue) blood is sent to the body instead of to the lungs.
• Oxygen-rich (red) blood is sent to the lungs instead of going to the body.

This is the opposite of a normal heart.

Babies can't live with this condition unless they get treatment.

TGA may occur on its own. Or your child may also have other heart problems in addition to TGA. These might include blockage of blood flow from the right ventricle to the aorta, or variations in the course of the coronary arteries. Other heart problems, such as a hole in the wall between the upper chambers of the heart (atrial septal defect) or a hole in the wall between the lower chambers of the heart (ventricular septal defect), may allow some oxygen-rich blood to mix with oxygen-poor blood that is sent to your baby's body. Also, some parts of your baby's heart may stay intact to allow oxygen-rich blood to reach your child's body. Normally, these connections would close shortly after birth.

The exact cause is often unknown, but risk factors include:

• Genetic syndromes or chromosomal abnormalities (rarely)
• Maternal diabetes or poorly controlled blood sugar in pregnancy
• Maternal exposure to certain medicines or toxins during early pregnancy
• Family history of congenital heart disease

Many babies with TGA have a bluish or gray color to the skin (cyanosis) in the first hours or days of their lives.

Other symptoms that can occur include:

• Fast breathing
• Trouble breathing
• Fast heart rate
• Poor feeding

The symptoms of TGA may be similar to symptoms of other conditions. Make sure that your child sees their doctor for a diagnosis.

If your child has signs of TGA after birth, a pediatric cardiologist or neonatologist will check your child. A pediatric cardiologist is a doctor with special training in treating heart problems in babies and children. A neonatologist is a doctor with special training in treating problems in newborns. These doctors will be part of your baby's heart care team.

Your child will likely have tests to confirm the diagnosis. The tests your child has depend on your child's age and condition, and the doctor's preferences.

For this test, a probe is placed on your child's finger or toe. It measures the level of oxygen in the blood. If it is below a certain level, this may be a sign of TGA.

A chest X-ray shows the size and shape of the heart and lungs.

This test records the electrical activity of the heart. It also shows abnormal rhythms (arrhythmias or dysrhythmias) and spots heart muscle stress.

An echocardiogram uses sound waves to make a moving picture of the heart and heart valves. This test is used to diagnose TGA.

A cardiac catheterization gives detailed information about the structures inside the heart. In this test, a small, thin, flexible tube called a catheter is put into a blood vessel in your child's groin. Then the doctor guides it to your child's heart. Your child's doctor will inject your child with contrast dye to see the heart more clearly. This test measures your child's pressure and oxygen levels in the four chambers of the heart, the pulmonary artery, and aorta. Your child will get medicine to help them relax and prevent pain (sedation).

This test uses magnets and radio waves to make images of the heart, blood vessels, and surrounding structure.

All children with a TGA will need to have surgery to fix it. Your baby will likely be admitted to the intensive care unit.

At first, your baby may get the following care:

• Supplemental oxygen or a ventilator (a machine that helps do the work of breathing for the baby)
• Different types of medicine given by I.V. This will help your baby's heart and lungs work better.
• A medicine called prostaglandin E1. This is used to keep the ductus arteriosus open. This allows blood to flow through the heart until surgery can be done.

Your child may have a procedure called a balloon atrial septostomy. This may be done during cardiac catheterization or at the bedside using an echocardiogram. This procedure uses a balloon catheter to make or enlarge an atrial septal defect. It allows oxygen-rich blood and oxygen-poor blood to mix and makes it easier for oxygen-rich blood to reach the rest of the body.

Typically, in the first two weeks of life, your baby will need surgery for TGA. This procedure is called an arterial switch. Your child's surgeon will connect the aorta and pulmonary artery to their normal ventricles. The surgeon will also have to move the coronary arteries. The surgeon will also fix any other heart problems, such as a ventricular septal defect, which is a hole in the heart.

Complications of untreated TGA include:

• Heart valve problems
• Heart muscle problems or problems with the arteries that supply blood to the heart muscle
• Abnormal heart rhythm
• Heart failure
• Lung problems
• Death

Your child will stay in the hospital until after surgery. Your child's health care team will tell you how to care for your baby before you leave the hospital. They may also give you information about home health care for your baby, if you need it.

Most children who have surgery for this condition will grow and develop normally. Ask your child's doctor about your child's outlook. Your child will still need to see their doctors for checkups. Your child may need additional surgeries or cardiac catheterizations in the future.

Your child may need to have antibiotics before surgeries or dental procedures. This is to prevent infections. Your child may also need to limit physical activity and stay away from certain sports. Ask your child's cardiologist about what activities are safe for your child.

If your child has trouble breathing or any new symptoms, call their doctor.

In TGA, your child's aorta is connected to the right ventricle, and the pulmonary artery is connected to the left ventricle. This is the reverse of a normal heart.

• A newborn with TGA will usually have gray or bluish skin color in the first days of life.
• All children with a TGA will need to have surgery to fix it.
• Most children who have surgery for this condition will grow and develop normally. Your child will still need checkups and may need more surgery in the future.

Tips to help you get the most from a visit to your child's doctor:

• Know the reason for the visit and what you want to happen.
• Before your visit, write down questions you want answered.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you for your child.
• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
• Ask if your child's condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if your child does not take the medicine or have the test or procedure.
• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your child's doctor after office hours and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.