This case illustrates transposition of the great arteries (D-TGA) with VSD and a small PDA.
Segmental Approach to Imaging of Congenital Heart Disease (set forth by Van Praagh et al) implies:
- Step I: Viscero-atrial situs. It is either solitus (S), inversus (I) or ambiguous (A).
- Step II: Position of the ventricular loop; either D-loop (with the morphological right ventricle is to the right of the left ventricle) or L-loop with the morphological right ventricle is to the left of the left ventricle.
- Step III: Position of the great vessels: conus anomalies are either D-TGA, L-TGA or D-malposition with double outlet right ventricle (DORV). Atrio-ventricular and ventriculo-arterial concordance or disconcordance are then evaluated.
- Other associated anomlaies of the cardiac chambers, septa, outflow tracts, PDA or aortic coarctaction & venous drainage are searched for.
According to this segmental approach, this case may is classified as (S,D, D-TGA), referring to the Situs solitus, D-venricular loop and D-transposition of the great arteries.
Normally, the pulmonary valve is anterior and to the left of the aortic valve. The pulmonary artery arises from the right ventricle and the aortic valve arises from the left ventricle. The aortic valve is postioned posteriorly and to the right to the pulmonary valve.
Transposition of the great arteries (TGA) implies that the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. Two types of transposition are: D-transposition and L-transposition.
In D-transposition, normal atrial and ventricular positions is maintained. The anomaly is at the conus level: the aorta is positioned anteriorly and to the right to the pulmonary artery and arises from the right ventricle with a subaortic conus, and the left-sided pulmonary artery is posteriorly positioned and arises from the left ventricle with mitropulmonary fibrous continuity.
In L-transposition, also termed "physiologically corrected TGA", ventricular inversion or double discordance (atrio-ventricular and ventriculo-arterial disconcordance) , despite an abnormal conal anatomy and abnormal positioning of the great vessels, the circulation is “corrected” because the ventricular position is also inverted (L- ventricular loop). Accordingly, the right ventricle located to the left of the left ventricle in a left-sided position is connected to the left atrium and the anteriorly positioned left-sided aorta with subaortic conus, whereas the left ventricle in a right-sided position is connected to the right atrium and the right-sided pulmonary artery with mitro-pulmonary fibrous continuity.