What is Transposition of the Great Arteries (TGA)?

In Transposition of the Great Arteries (TGA), the aorta and pulmonary artery are transposed, or switched. This means the aorta leaves the right ventricle (instead of the left side of the heart, as in a normal heart) and the pulmonary artery leaves the left ventricle (instead of the right ventricle). With this arrangement, blood is returned to the body without receiving oxygen from the lungs, and oxygen-rich blood continues to circle from the left side of the heart back to the lungs. This results in the lack of adequate oxygen to the vital organs of the body, including the heart muscle. Blood is moving in two separate circuits without adequate communication, unless a large atrial septal defect (ASD) or ventricular septal defects (VSD) is present.

Effects and Symptoms

There is moderate to severe cyanosis, or blue-tinged skin, nail beds and lips at birth.

Diagnosis

TGA can be detected during a fetal echocardiogram, or an ultrasound of the fetal heart during pregnancy. If undetected before birth, newborns will appear cyanotic (blue) and have low oxygen levels in the blood. A murmur may or may not be present on physical examination. An ECG can show nonspecific changes and an echocardiogram will confirm the diagnosis.

Management and Treatment

TGA when detected during pregnancy requires advanced planning before delivery, particularly when there is a suspicion that the communication between the two circuits will be inadequate i.e. when there is no VSD and if there is a suspicion that the ASD will be too small. Parents are advised to deliver in a center with expertise in handling cardiac surgical cases. 

Prostaglandin E (PGE) can be started to keep the ductus arteriosus open to provide communication between the two circuits. Oxygen is provided at times to lower lung pressures and increase blood flow to the lungs and improve oxygen supply to the body. 

A procedure called a balloon septostomy is done through cardiac catheterization ideally within the first few days of life to enlarge the ASD and improve oxygen supply to the body.

Surgery

Surgical options are determined based on individual cardiac anatomy. The great arteries (aorta and pulmonary artery) are moved to their proper position and coronary arteries (vessels that supply blood to the heart muscle) are moved and attached to the new aortic root to receive oxygen-rich blood. ASDs and VSDs are closed with stitches or a patch and the patent ductus arteriosus (PDA) is tied off or cut.