pediatrics
Transposition of the Great Arteries (TGA)
Introduction
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 of the heart (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 depend 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 Congenitally Corrected Transposition of the Great Arteries (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. and front of the pulmonary artery. This anomaly is usually associated with ventricular inversion due to leftward looping of the primitive heart tube, resulting in the condition commonly known as Congenitally Corrected Transposition of the Great Arteries . Because d-TGA is by far the most common form, it is often simply called transposition. d-TGA is discussed in this topic, and Congenitally Corrected Transposition of the Great Arteries is discussed elsewhere. There are also other rare variants of the transposition of the great arteries, but d-TGA and l-TGA are the most common. ) accounts for 5 to 7% of congenital heart anomalies. About 30 to 40% of patients have a Ventricular Septal Defect (VSD) (VSD); up to 25% have left ventricular outflow tract obstruction (either pulmonic valve or subpulmonary stenosis). Unoxygenated blood returning to the right heart enters the AO, causing severe cyanosis. Oxygenated blood returning to the LA enters the pulmonary circulation again. The RV is hypertrophied, and the foramen ovale permits minimal mixing. Atrial pressures are mean pressures. AO=aorta; IVC=inferior vena cava; LA=left atrium; LV=left ventricle; PA=pulmonary artery; PV=pulmonary veins; RA=right atrium; RV=right ventricle; SVC=superior vena cava. 