Transposition of the great vessels (d-TGA) is a congenital heart defect where the aorta and pulmonary artery are switched or “transposed” resulting in inadequate delivery of oxygen to the vital organs and is one of the congenital heart diseases that results in a so called “blue baby.”
In the normal circulation, the deoxygenated (oxygen-deficient blood) returns to the right side of the heart that pumps blood to the lungs via the pulmonary artery. The oxygenated blood from the lungs is returned to the left side of the heart that pumps the oxygenated blood to the rest of the body. When the aorta and pulmonary artery are switched (transposed), the deoxygenated blood from the body enters the right side of the heart and instead of going to the lungs via the pulmonary artery, goes directly to the back to the rest of the body via the aorta resulting in an extreme lack of oxygen delivery to the vital organs. At the same time, the oxygen rich blood from the lungs that enters the left side of the heart is pumped directly back to the lungs.
D-TGA can often be diagnosed during pregnancy through a fetal echocardiogram.
It’s important to determine the diagnosis of d-TGA as early as possible because babies with this condition can be extremely ill at birth,” said Neill Videlefsky, MD. “Prenatal diagnosis allows us to arrange for the birth to take place at an appropriate delivery center and to arrange for rapid transfer to a cardiac center.”
D-TGA may also be diagnosed on the cyanotic heart disease screening test by pulse oximetry (measures oxygen saturation using a probe on the skin) that is performed on all newborns at around 24 hours of age. Sibley Cardiology’s very own Matthew E. Oster, MD, helped develop the revised guidelines for this simple non-invasive test.
According to Dr. Videlefsky, these babies present soon after birth as so-called “blue babies.” The bluish discoloration of the skin (cyanosis) is due to the lack of oxygen and results in an intense bluish, ashen discoloration of the lips, mouth, fingertips and toes. Due to the “air hunger” resulting from the reduced oxygen supply to the vital organs, the babies develop respiratory distress manifested by rapid breathing and pulling in of the skin between the ribs (intercostal recession). These babies use up all their energy trying to breathe, and as a result have no energy to feed and struggle to gain weight. As part of the stress response, these babies are often sweaty and lethargic.
The diagnosis is confirmed after birth by echocardiogram, which is an ultrasound of the heart that exquisitely defines the structure and function of the heart.
The baby is stabilized by creating mixing between the oxygenated and deoxygenated blood thereby improving oxygen delivery to the tissues. This is accomplished by starting an intravenous medication called prostaglandin that helps to keep the ductus arteriosus open (a vessel that connects the aorta and pulmonary artery in the fetus that usually closes after birth) and also by proceeding urgently to cardiac catheterization in order to perform an atrial balloon septostomy. This is a procedure that enlarges the natural opening (Patent foramen ovale) between the right and left atrium allowing for more effective mixing and improved oxygenation.
The definitive treatment for d-TGA consists of an open-heart surgery known as the arterial switch procedure. In this surgery the surgeon “switches” the aorta and the pulmonary artery back to the normal positions such that the aorta arises from the left ventricle and the pulmonary artery arises from the right ventricle.
This procedure has a greater than 98 percent success rate with few long-term complications.
“The newest advancements in treatment of d-TGA have given people born with this condition a new outlook on life,” Dr. Videlefsky said. “Patients now can expect to have a normal lifespan and excellent quality of life. However, they do require lifelong follow up by a cardiologist with expertise in congenital heart disease, as they need to be monitored for potential complications.”
- Centers for Disease Control and Prevention: Facts about dextro-Transposition of the Great Arteries (d-TGA)
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