Presentation
Cyanosis since birth.
Patient Data
Frontal CT scout
- mild cardiomegaly with narrow superior mediastinum and characteristic egg-on-side appearance
- mild increase in pulmonary vascularity
Heart
- Situs solitus with the cardiac apex to the left. Normal tracheobronchial tree with right epiarterial and left hyparterial bronchi
- D-ventricular loop is noted with the morphological right ventricle (coarse trabeculation with apical moderator band) is seen to the right of the left ventricle
- atrio-ventricular concordance and ventriculoatrial discordance. The pulmonary artery arises from the left ventricle and the aorta from the right ventricle
- cardiomegaly is noted
- large VSD is noted
Aorta
- the ascending aorta is seen anterior to the main pulmonary artery
- the coronaries have normal course and origin
- right-sided bovine aortic arch with the brachiocephalic and Lt CCA arteries having a common origin
- the descending aorta is seen running in the left para-vertebral course
- a small curved PDA arises just distal to the Lt SCA
- no evidence of thoracic or abdominal aortic coarctation
Pulmonary arteries & veins
- confluent and average sized main pulmonary artery as well as the right and left pulmonary arteries
- Normal pulmonary veins. No evident anomalous pulmonary venous drainage
Venae cava & innominate veins
- normal course of the innominate veins, SVC and the visualized segment of the IVC
Case Discussion
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 anomalies of the cardiac chambers, septa, outflow tracts, PDA or aortic coarctation & 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 positioned 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 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.
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