Transposition of Great Arteries
Amar Taksande
Transposition of Great Arteries - Introduction
Transposition of the great arteries (TGA) is the common cyanotic congenital heart lesion that presents in neonates. It is ventriculoarterial discordance, in which the aorta arises from the morphologic right ventricle and the pulmonary artery arises from the morphologic left ventricle. The anatomical classifications of TGA depend on the relationship of the great arteries to each other.
• In dextro-Transposition of the great arteries (d-TGA), the aorta is anterior and to the right of the pulmonary artery. The aorta arises anteriorly from right ventricle carrying desaturated blood to the body and pulmonary artery arises posteriorly from left ventricle carrying oxygenated blood to the lungs. There are two parallel circulations in D-TGA. Unless there is mixing of blood between these two parallel circulations, this condition is incompatible with life. The common anatomic sites for mixing of oxygenated and deoxygenated blood in TGA are atrial septal defect, ventricular septal defect and patent ductus arteriosus.
• In Levo-Transposition of the great arteries (l-TGA), the aorta may be anterior and to the left of the pulmonary artery and the morphologically left and right ventricles with their corresponding atrioventricular valves are also transposed.
The hearts with TGA represent 5-7% of all congenital heart defects, corresponding to an incidence of 20-30/100000 live births.

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