Transposition of the great arteries (tga)

[Lizzy Liz]

Transposition of the great arteries (in this case, dextro-transposition) occurs when the aorta arises directly from the right ventricle and the pulmonary artery arises from the left ventricle, resulting in independent, parallel pulmonary and systemic circulations; oxygenated blood cannot reach the body except through openings connecting the right and left sides (eg, patent foramen ovale, ventricular septal defect [VSD]). Symptoms are primarily severe neonatal cyanosis and occasionally heart failure, if there is an associated VSD. Heart sounds and murmurs vary depending on the presence of associated congenital anomalies. Diagnosis is by echocardiography. Definitive treatment is surgical repair.
(See also Overview of Congenital Cardiovascular Anomalies.)
Transposition of the great arteries (TGA) is a broad term that includes both dextro-TGA (d -TGA) and a rarer defect called levo-TGA (l -TGA).

d -TGA: A more common variation in which the aorta is positioned to the right and front of the pulmonary artery, arising from the right ventricle rather than the left.
l -TGA: A less common variation in which the aorta is positioned to the left and front of the pulmonary artery.

Because d -TGA is by far the most common form, it is often simply called transposition. d -TGA is discussed in this topic, and L-TGA is discussed elsewhere in The Manual . There are also other rare variants of the transposition of the great arteries, but d -TGA and l -TGA are the most common.
Dextro-transposition of the great arteries (see figure Dextro-transposition of the great arteries) accounts for 5 to 7% of congenital heart anomalies. About 30 to 40% of patients have a ventricular septal defect; up to 25% have left ventricular outflow tract obstruction (either pulmonic valve or subpulmonary stenosis).