Comment
The initial diagnosis was given as “false Taussig Bing” malformation
on fetal echo examination as a shorthand; we had been aware that the
term is often confusing 2. The pattern of blood
streaming on ventriculography also deceived us. We should have been
super-cautious about the intracardiac morphology. Retrospectively, the
3-dimensional CT had been informative enough to recognize the variation
of DORV. [Figure 2] At the preoperative stage, right aortic arch
gathered more attention of the surgeons; whether any technical pitfalls
were hidden. The arterial switch is relatively rare in such a
circumstance 3. Fortunately, it did not turn out to be
an issue.
Having admitted that the preoperative diagnosis could have been more
precise, what would have been the alternative strategy? Initial banding
of the pulmonary trunk would have been less invasive and provided broad
strategical choices in the future. An immediate downside of the
palliation would be considerable arterial desaturation persisting
because of transposition physiology.
This streaming issue would be much less when banding is carried out
concomitantly with the arterial switch maneuver. Oxygenated blood would
mainly flow to the neo-aorta, providing a pinker circulation. When the
patient became older beyond early infancy, intraventricular rerouting
could be less demanding. A RV incision is dispensable at the neonatal
stage.
The Réparation à l’Etage Ventriculaire (REV) procedure is an
alternative, rerouting the LV to both semilunar valves4. The outlet septum was missing; therefore, nothing
to resect. VSD enlargement is anatomically limited; better not to
penetrate the ventriculo-infundibular fold. A downside of the REV
procedure would be pulmonary regurgitation in the longer terms.
Pulmonary valve replacement will not be straightforward because of the
geometry around.
An intraventricular tunnel becomes long and tortuous in DORV with a
non-committed VSD 5,6 when biventricularly repaired.
Even for the REV procedure, the baffle design is compromised because of
the presence of the tricuspid valve and its tension apparatus. As
described by Belli et al. 7, the intraventricular
tunnel becomes straighter and shorter by switching the great arteries.
Still, the tricuspid valve interferes in accommodating a baffle. The
septal leaflet would most likely adheres to the baffle, eventually
causing tricuspid regurgitation. Thus, the Fontan type procedure remains
as a definitive correction of the cyanotic circulation. Using the
ventricles as a solitary chamber, the ventricular outlet is not
compromised with a baffle. The tricuspid valve remains intact. Downside
of this strategy is, of course, the unique circulation itself. It causes
certain impediments in the longer terms. Heart failure and
Fontan-associated liver disease are among current topics of concern.
Biventricular physiology, if achievable, is preferred in this respect.
It is uncommon to repair of DORV of a non-committed VSD type during a
neonatal period. We have come across only one case reported in
literature 8. Although the doubly-committed VSD type
has a morphological spectrum 1, the combination of
DORV with a non-committed VSD type and lack of the outlet septum has not
been described in a clinical series to the best of our knowledge.
Sequelae could grow in due course. Obstruction across the LV outflow
tract and tricuspid regurgitation would be related to the
intraventricular baffle. Neonatal ventricular incision could
consequently cause ventricular dysfunction or ventricular arrhythmia.
Function of the semilunar valves might deteriorate eventually, despite
the baffle was meticulously fixed there.
After all, what could we have done better? No definitive answer. As far
as the results in the immediate postoperative term is concerned, our
neonatal repair was not unreasonable. Should we take a similar approach
in an identical case? Yes, although a rare form of DORV is to be
preoperatively recognized next time.