Page 139 - Read Online

Page 8 of 43 Rao. Vessel Plus 2022;6:26 https://dx.doi.org/10.20517/2574-1209.2021.93

commonly, the aortic valve is situated to the right of the pulmonary valve, which is termed d-TGA. As a
result, the systemic venous blood from the superior and inferior vena cavae empties into the RA and is then
transported to the RV and from there into the aorta, while the pulmonary venous blood empties into the LA
and from there transported to the LV and then ejected into the PA. Hence, the TGA patient’s circulatory
pattern is parallel in place of the normal circulation which is in-series. This state of circulatory abnormality
results in not conveying the pulmonary venous blood return to the body and not delivering the systemic
venous return to the lungs. Given this type of circulatory anomaly, the neonates have no chance to survive
unless there is mixing between both circulations through persistent fetal pathways, for instance, patent
foramen ovale (PFO) and PDA, or an ASD or VSD [3,4,12-14] .

Because of differences in presentations and the types of management required, we have arbitrarily classified
TGA into [12,13] : (1) Group I, TGA with intact ventricular septum; (2) Group II, TGA with VSD; and (3)
Group III, TGA with VSD and PS.

Group I, TGA with intact ventricular septum
Echocardiograms are valuable in the diagnosis of TGA and in the evaluation of co-existing cardiac defects.
Since the anatomy of the atria and ventricles is normal, as well as those of the semilunar (aortic and
pulmonary) valves, the identification of transposition may be a bit tricky by echocardiogram, mostly for the
novice. An incidental sign is a slightly posterior passage of the artery arising from the LV in a parasternal
long-axis projection [Figure 11A], signifying that this artery is likely to be the PA, is useful. Such an
appearance is in contrast to an anteriorly traversing proximal aorta [Figure 11B] in normal neonates. When
the blood vessel coming off of the LV is followed, and its division into branch PAs is shown [Figure 12], that
artery is recognized as PA with consequent confirmation of the finding of transposition. Additional signs
that are useful and indicative of transposition are a parallel positioning of the aorta and PA in an
echocardiographic long-axis projection [Figures 11A and 13A] and a concurrent on-end imagining of both
the aortic and pulmonary valves on a parasternal short-axis projection [Figure 13B].

The inter-atrial septum must be assessed in the subcostal projections by 2D [Figure 14A] and color flow
Doppler [Figure 14B and C]. The atrial defect is typically a PFO and rarely, a true ASD may be seen. An
atrial defect that is 5 mm or more in diameter is commonly deemed sufficient for the provision of adequate
admixture of blood across the atrial septum and for the avoidance of balloon atrial septostomy.

PDA may also be seen and the shunting via the ductus by pulsed, CW, and color [Figures 15 and 16]
Doppler should be ascertained.

Group II. TGA with VSD
Group II TGA babies characteristically manifest signs and symptoms indicative of congestive heart failure
and their presentation is much later than the babies with intact ventricular septum. Echocardiographic
studies are useful in diagnosing TGA [Figures 11-13] and in identifying size and shunt across the VSD
[Figure 17].

Group II. TGA with VSD and PS
The timing of presentation of babies with transposition associated with VSD and PS (Group III) varies,
largely based on the degree of inter-circulatory blood admixture and the degree of PS. Echocardiographic
studies are helpful in the visualization of VSD and PS [Figure 18]. Shunts across the ventricular defect by
color Doppler imaging [Figures 18A and B] and extent of narrowing of the pulmonary outflow tract by
pulsed, CW, and color [Figure 18] Doppler must be assessed and such an evaluation is useful in evaluating
the physiologic status of the infant.