What is Transposition of the Great Arteries?

Transposition of the great arteries is a congenital heart defect requiring immediate treatment. In a case of transposed arteries, the pulmonary artery is connected to the left ventricle, and the aorta to the right ventricle. The result is that blood that should be going to the lungs for oxygenation is sent back to the body through the aorta. Also, oxygen-enriched blood, rather than flowing to the body, is returned to the lungs through the pulmonary valve.

Before the 1960s, a diagnosis of transposition of the great arteries, also known as "blue-baby" syndrome, meant an extremely short life span. Children rarely lived past their first year. However, two main surgical tactics can now be employed to address this condition. Most children with transposition of the great arteries now have excellent expectations for a healthy future.

The first surgery for transposition of the great arteries was an atrial switch, also called the Mustard or Senning procedure. This open-heart surgery creates a tunnel between the atria. An atrial switch allows the blood to redirect into the appropriate ventricle, to be effectively delivered to the body or the lungs.

Since the Senning correction of transposition of the great arteries requires tunneling through the heart, those who have had this repair have a higher incidence of arrhythmia both directly after the surgery and years later. Heart function may also be impaired because the right ventricle, the weaker of the two ventricles, essentially must do the work of the left ventricle and pump blood to the body. Further surgery, pacemaker implantation or medications may be required to address weaker heart function as the patient ages.

Cardiothoracic surgeons observing the later complications of the atrial switch developed a surgery called the arterial switch, which is now the more commonly used correction for transposition of the great arteries. In this surgery, also called the Jatene procedure, the aorta and pulmonary artery are cut and switched back to normal position. The coronary arteries are also redirected to the aorta.

Opinions differ on when to perform the Jatene procedure to correct transposition of the great arteries. Some surgeons prefer to enlarge the natural connection between the atria, the patent ductus, before later conducting the arterial switch. Other surgeons take a more aggressive approach and elect to perform the Jatene procedure shortly after birth.

Advantages to performing the switch early include better heart function almost immediately. While enlarging the patent ductus buys time, it also results in significantly lower heart function. Many surgeons, however, like to give the newborn a chance to grow, because the larger the arteries, the easier the surgery. Consulting one's pediatric cardiothoracic surgeon on success rates and preference is helpful in determining which option is best for one's child.

Unlike other defects, though, transposition of the great arteries requires immediate treatment, so parents may not have a great deal of time to consider their options. Transposition of the great arteries poses no risk to the fetus, who receives oxygen from the mother, so it is frequently undiagnosed before birth. A fetal echocardiogram, a precise sonogram of the fetal heart, is not generally performed unless other heart defects are spotted.

Some sonographers and radiologists are excellent at finding heart defects. Others are not. However, the infant's blue color, difficulty breathing and inability to feed are usually noted within a few hours of birth, so few pediatricians fail to diagnose transposition of the great arteries.

After surgery, a child with transposition of the great arteries must be followed at least yearly by a pediatric cardiologist. In some cases, the transposed arteries do not grow properly and need to be replaced. Since the arterial switch surgery is relatively new, long-term outlook is not well defined. Children with this repaired condition may have some limitations, such as an inability to participate in organized sports. Also, cardiologists recommend that both children and adults with transposition take antibiotics before dental exams and procedures.

In general, however, the outlook for a child with an arterial switch is excellent. Women with an uncomplicated transposition can have children, something that until recently was not possible without considerable risk. Therefore, though there are some minor limitations on activities, which may change as the field of cardiology improves, those with a repaired transposition can be expected to lead a normal and healthy life.