Discussion
Artificial valve implantation in small children with a single-ventricle
is associated with an increased risk of mortality [4]. The rigid
frame of the artificial valve disturbs the motion of the ventricle and
prevents the growth of the AVV annulus. In the small ventricle space,
the leaflet motion can be hindered by the ventricular structure, such as
chordae, and in the small atrial space, the bloodstream through the
valve leaflet is also obstructed. Considering the growth of children, it
might be preferable to select a larger size valve for implantation to
secure an adequate valve orifice area. However, this strategy could
result in valve dysfunction caused by bloodstream obstruction and a
stuck leaflet. In addition to these drawbacks, implanting a large
artificial valve could result in restriction of ventricle motion due to
the rigid frame of the valve followed by ventricle dysfunction.
Ventricle dysfunction may cause congestion of blood stream, which result
in artificial valve leaflet stuck as well. Implantation of a larger size
artificial valve in smaller children is a major risk factor for
mortality [4] for these reasons.
We also encountered much technical difficulty in removing the old valve
and implanting the new one because the direction of the cardiac apex
could not be changed to enable a good surgical field due to severe
adhesion caused by repeat heart surgery and after the multiple insertion
of an artificial valve, a thickening of the AVV annulus can often be
observed, which results in difficult insertion of a new valve on the
annulus.
In our case, a severe thickening of the AVV annulus and small LA space
were noted; thus, a smaller size valve with a diameter of 19 mm was
selected and implanted in the supra AVV annulus position. We were
concerned that the structure in the ventricle could hinder the opening
of the artificial valve leaflet. To reduce the chance of valve leaflet
dysfunction, the bottom of the mechanical valve was raised with an
e-PTFE graft. The LA wall was augmented with an e-PTFE patch because the
artificial valve was projected into the LA space. Various technical
modifications in mechanical valve implantation are necessary for the
case who had received repeated valve procedure.
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