Diagnosis

Although it's possible your baby's transposition of the great arteries may be diagnosed before birth, it can be difficult to diagnose. Prenatal tests for transposition of the great arteries aren't usually done unless your doctor suspects your baby may have congenital heart disease.

After your baby is born, his or her doctor will immediately suspect a heart defect such as transposition of the great arteries if your baby has blue-tinged skin (cyanosis) or if your baby is having trouble breathing.

Sometimes, the bluish skin color isn't as noticeable if your baby has another heart defect, such as a hole in the wall separating the left and right chambers of the heart (septum), that's allowing some oxygen-rich blood to travel through the body. If the hole is in the upper chambers of the heart, it's called an atrial septal defect. In the lower chambers of the heart, the defect is called a ventricular septal defect.

It's also possible your baby could have a patent ductus arteriosus — an opening between the heart's two major blood vessels, the aorta and the pulmonary artery — that allows oxygen-rich and oxygen-poor blood to mix.

As your baby becomes more active, the heart defects won't allow enough blood through and eventually the cyanosis will become obvious.

Your baby's doctor may also suspect a heart defect if he or she hears a heart murmur — an abnormal whooshing sound caused by turbulent blood flow.

A physical exam alone isn't enough to accurately diagnose transposition of the great arteries. One or more of the following tests are necessary for an accurate diagnosis:

• Echocardiogram. An echocardiogram is an ultrasound of the heart — it uses sound waves that bounce off your baby's heart and produce moving images that can be viewed on a video screen. Doctors use this test to diagnose transposition of the great arteries by looking at the position of the aorta and the pulmonary artery.

  Echocardiograms can also identify associated heart defects, such as a ventricular septal defect, atrial septal defect or patent ductus arteriosus.

• Cardiac catheterization. This procedure is typically done only when other tests, such as an echocardiogram, don't show enough information to make a diagnosis.

  During a cardiac catheterization, the doctor inserts a thin flexible tube (catheter) into an artery or vein in your baby's groin and directs it up to his or her heart. A dye is injected through the catheter to make your baby's heart structures visible on X-ray pictures. The catheter also measures pressure in the chambers of your baby's heart and in the blood vessels and can measure the amount of oxygen in the blood.

  Cardiac catheterization may be done urgently to perform a temporary treatment for transposition of the great arteries (balloon atrial septostomy).

• Chest X-ray. Although a chest X-ray doesn't provide a definitive diagnosis of transposition of the great arteries, it does allow the doctor to see your baby's heart size and the position of the aorta and pulmonary artery.
• Electrocardiogram. An electrocardiogram records the electrical activity in the heart each time it contracts. During this procedure, patches with wires (electrodes) are placed on your baby's chest, wrists and ankles. The electrodes measure electrical activity, which is recorded on paper.