D-transposition of the great arteries is a form of congenital heart disease that must be corrected shortly after birth for survival. Read on for information about the characteristics of the defect at birth and the treatment and follow-up care that is necessary into adulthood.

D-Transposition of the Great Arteries in Infancy

In transposition of the great arteries, the aorta and pulmonary artery are switched. Normally, the aorta carries blood from the heart’s lower left chamber (left ventricle) to the body, and the pulmonary artery carries blood from the heart’s lower right chamber (right ventricle) to the lungs.

But in the transposition of these two great arteries, the aorta emerges from the right ventricle, sending oxygen-poor blood that has just returned from the body back out to the body without its usual course through the lungs to pick up oxygen. And the pulmonary artery emerges from the left ventricle and sends oxygen-rich blood that has just returned to the heart from the lungs back to the lungs.

Because the blood carried by the aorta to the body does not first go to the lungs to pick up oxygen, it continues to be poorly oxygenated. As a result, the newborn with this heart defect will have intense bluish skin discoloration.

According to the American Heart Association, of the thousands of babies born each year with a cardiovascular defect, 10 to 11 percent have transposition of the great arteries. 

Progression and Possible Complications 

Life cannot be sustained unless openings between the left and the right sides of the heart allow blood to mix so that oxygen in the blood going to the body is increased.

Before birth, there are normally two openings between the heart’s left and right sides – the atrial septal defect (hole between the heart’s two upper chambers) and the ductus arteriosus (a vessel connecting the pulmonary artery and the aorta). These openings typically close soon after birth. When they close, the baby with transposition of the great arteries lacks oxygen and becomes quite blue unless steps are taken to increase blood mixing. Ultimately, without surgical correction, a child with this defect suffers from lack of oxygen and heart failure and does not live long. 

Treatment 

As the openings between the heart’s left and right sides narrow, the supply of oxygen delivered to the child’s body decreases. The first steps in treating the defect aim to stabilize the baby’s condition. These steps are designed to keep blood flowing through the openings:

• A medication called prostaglandin E1 (PGE) is given to keep the ductus arteriosus open.
• A balloon-tipped catheter (a long, thin tube) is guided through the child’s arteries to the natural hole between the left and right atria (the foramen ovale). Once positioned properly, the balloon is inflated to “tear” and enlarge the opening between the upper chambers of the heart. This enlargement promotes more mixing of blood between the two sides of the heart, thus increasing the amount of oxygen in the blood going out to the body. 

These steps help increase the level of oxygen in the blood going out the body, but it never reaches normal levels. After the baby’s condition is stabilized, surgical repair is performed within one to two weeks of age. In this open-heart procedure, a surgeon switches the two great vessels to their normal positions so that the aorta emerges from the left ventricle and the pulmonary artery from the right ventricle. The coronary arteries have to be switched as well so that they are connected to the aorta after surgery. In addition, the openings between the left and right sides of the heart are closed, and the patent ductus arteriosus is tied off and closed.

Follow Up Care Into Adulthood

Later, narrowing at the arterial connections or within the branch pulmonary arteries may develop. Treatment – either with a thin tube with a balloon on the end (balloon catheter) and insertion of a metal, mesh cage called a stent or with surgery – may be needed to widen them. Patients are also usually watched for the rest of their lives to monitor for narrowing of the coronary arteries.

If You Had the Mustard or Senning Procedure

Over time, it became clear that patients who had undergone an earlier corrective procedure (the Mustard or Senning procedure, which re-directed the flow of blood rather than “switching” the vessels) developed problems later in life – despite an initial belief that the surgery had “cured” them. Even today, it is not uncommon for patients who underwent the Mustard or Senning procedure to see a specialized cardiologist for the first time 20 years or more after the surgery.

Most of the problems related to the Mustard or Senning procedure result because the anatomic right ventricle of the heart was never meant to pump blood to the whole body. Patients who have undergone the procedure often develop signs of heart failure or reduced function of the heart’s right pumping chamber. Reduced function, as well as leakiness of the valve between the heart’s upper and lower right chambers, often cause the right upper chamber (the atrium) to become enlarged.

Enlargement of the ventricle or the numerous suture lines in the atria can lead to a variety of electrical rhythm problems, such as the heart intermittently beating much too fast or much too slowly, or a combination of both. Patients whose hearts develop electrical problems often require pacemakers and sometimes electrical defibrillators. The risk of sudden cardiac death in patients who have undergone the Mustard or Senning procedure is about 100 times that of the general population.

In addition to these problems, the baffle used by the surgeons in the Mustard or Senning procedure to redirect blood flow frequently develops narrowing or leaks, resulting in further problems. Sometimes pacemaker wires must be inserted through these reconstructed areas.

If you underwent the Mustard or the Senning procedure in the past, you need follow-up by a cardiologist who specializes in the treatment of adults with congenital heart defects. You may require special medicines to treat heart rhythm problems as well as medicines to control signs and symptoms of heart failure. If your heart function deteriorates despite medical treatment, then heart transplantation may need to be considered.

It is very difficult to predict outcomes. Therefore, it is critical that your cardiologist tailor your follow-up care to address your individual needs. The right treatment for you may not be the right treatment for another patient.

Except when a heart transplant is needed, repeat open-heart surgery is usually not required, unless interventional catheterization procedures are not possible. Exceptions may include severe narrowing of the baffle that obstructs blood flow from the body or lungs, or leaks within the baffle that cannot be closed using cardiac catheterization procedures.

What is essential for the care of conditions resulting from the Mustard or the Senning procedure is a combination of cardiac catheterization and assessment of the heart’s electrical circuits. This requires the skills and expertise of a heart surgeon, an interventional cardiologist who performs catheterization procedures, a heart rhythm specialist (electrophysiologist) and a cardiologist who specializes in the treatment of adults with congenital heart defects.

In preparation for treatment, you may undergo an MRI (magnetic resonance imaging) or CAT (computerized axial tomography) scan of the heart, as well as an echocardiogram. You will also be assessed by a cardiologist who is a specialist in treating heart rhythm abnormalities to determine whether a pacemaker or other specialized electrical therapy is required as part of the cardiac catheterization procedure.

You will most likely be sedated during the catheterization procedure, and you should expect to stay overnight in the hospital. During the procedure, a thin, flexible tube (catheter) is inserted into a blood vessel in the groin and/or a blood vessel in the neck. Using these catheters, the physician can assess the pressure inside the heart and take pictures to evaluate any leaks or narrowing of the baffle. A special ultrasound may be performed by inserting an ultrasound tube into the throat and esophagus. This helps the physician identify leaks in the baffle.

The physician may be able to close baffle leaks using devices delivered via the catheter. He or she can treat the narrowing of the baffle through insertion (via the catheter) of a balloon, which when inflated, stretches the narrowing. More commonly, a metal mesh tube called a stent is implanted to expand the narrowing and prop it open.

If a pacemaker is needed, it is usually inserted during the catheterization procedure by an electrophysiologist (a physician specializing in heart rhythm abnormalities). While you may not need to undergo more than one procedure, it may last several hours.

Even after a successful catheter procedure and pacemaker implantation (if needed), you will require lifelong follow-up with a specialized cardiologist, as problems can continue to occur. 

Lifestyle Considerations

Consult your cardiologist about the kind and level of activity that is appropriate for you, given your condition. Also, check with him or her before trying new activities.