Transposition of the great arteries (TGA) occurs when the positions of the pulmonary artery and the aorta are reversed. The aorta is connected to the right ventricle, so most of the blood returning to the heart from the body is pumped back out without first going to the lungs. The pulmonary artery is connected to the left ventricle, so most of the blood returning from the lungs goes back to the lungs again. Therefore the red, oxygen-rich blood remains red and the oxygen-poor blue blood remains blue.
Heart with Transposition of the Great Arteries
Infants born with transposition survive only if they have one or more connections that let oxygen-rich blood reach the body. One such connection may be a hole between the two atria, called atrial septal defect, or between the two ventricles, called ventricular septal defect (VSD). Another may be a vessel connecting the pulmonary artery with the aorta, called patent ductus arteriosus.
Most babies with transposition of the great arteries are extremely blue (cyanotic) soon after birth because these connections are inadequate.
The primary symptom and finding on physical examination of infants with TGA is cyanosis. This is noted in the newborn period. There are circumstances where this may not be noticed immediately, but it will be present eventually.
Definitive treatment for TGA always involves open-heart surgery, though some treatment measures may be undertaken soon after birth. To improve the body's oxygen supply, the ductus arteriosus may be kept open with a medicine called prostaglandin. Also, a special procedure called balloon atrial septostomy may be used to allow more oxygen-rich blood from the left atrium to mix with the oxygen-poor blood in the right atrium. This procedure is performed either in the catheterization laboratory or at the bedside and involves placing a catheter from the right atrium to the left atrium and blowing up a balloon in the left atrium. The balloon is then pulled across the wall between the two atria to tear a hole in the wall. Treatment with prostaglandin and the balloon atrial septostomy help improve the oxygenation and stabilization of the infant until surgery can be performed. Depending on other associated heart defects, these treatment measures are not always required.
In general, the goal of surgery is to end up with the appropriate ventricle hooked up to the appropriate artery the way a normal heart is supposed to be. In the past, surgical operations known as the Senning and Mustard procedure were performed, but are no longer part of current surgical management in uncomplicated TGA. (However, adults may have had these surgeries in infancy or early childhood when these procedures were still being performed.) The standard surgical operation for TGA at most hospitals is the Jatene procedure or arterial switch operation. This procedure hooks up the aorta to the left ventricle and the pulmonary artery to the right ventricle the way they are supposed to be. There is also a surgical operation known as the Rastelli procedure for patients with TGA, and additional defects consisting of a VSD and pulmonary stenosis.
The risks of open-heart surgery always include bleeding, infection and the need for cardiopulmonary bypass. Special risks of the Jatene procedure include injury to the coronary arteries, the possibility of narrowing of the pulmonary arteries.
After surgery, the long-term outlook varies, depending on the type of surgical operation performed and on associated heart defects. With the arterial switch procedure (Jatene) much of the risk is undertaken initially during reconnection of the coronary arteries. There is also a risk of narrowing of the pulmonary arteries due to the need to switch their location. Because of this, there should be lifelong follow-up. So far, it is expected that lifestyle and lifespan should be quite good. Preventive measures against bacterial endocarditis are probably required for life.