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Congenitally corrected transposition of the great arteries (ccTGA) is a rare defect representing approximately 0.5% of all congenital heart disease. ccTGA is characterised by the combination of atrioventricular (AV) discordance and ventriculo-arterial (VA) discordance. Various terms have been used to describe this anatomy: congenitally or physiologically corrected transposition of the great arteries, L-transposition, double discordance and ventricular inversion being the most frequently used. The term ‘congenitally corrected transposition’ is used to differentiate this condition from ‘complete transposition’ (d-TGA) in which there is VA discordance but AV concordance.
There is usually normal drainage of the systemic and pulmonary veins to the right and left atriums respectively. The right atrium connects via the mitral valve to the morphologic left ventricle which supplies the pulmonary artery. The left atrium connects via the tricuspid valve to the morphologic right ventricle which supplies the aorta via a sub-aortic infundibulum. The ventricles are most commonly side by side: in patients with situs solitus the morphologic left ventricle is rightward and the morphologic right ventricle is leftward.
The anatomy is described as congenitally ‘corrected’ because the flow of blood is normal with the deoxygenated systemic venous blood being pumped to the lungs and the well oxygenated pulmonary venous blood being pumped to the body. Nevertheless, the two wrongs of AV and VA discordance do not make a right, as the morphologic left ventricle (LV) and mitral valve supply the pulmonary circulation and the morphologic right ventricle (RV) and tricuspid valve supply the systemic circulation.
The most common anatomical arrangement is situs solitus with L-looping of the ventricles and the aorta anterior and leftward of the pulmonary artery (S,L,L), found in 19/22 of our cases in Auckland (unpublished data). The aorta was anterior and rightward (S,L,D) in two of 21 cases of ccTGA with situs solitus. In patients …