Discussion:
In this present case series, late reoperation of the RVOT for PH failure
after PH implantation for RVOT reconstruction is of 3.9% (4 patients),
while late PH failure occurred in 12 patients (11.2%). PH implantation
for reconstruction of the RVOT was first reported in 1966 by Fulleret al [11] in a 9 year-old girl presenting pulmonary atresia
with VSD. Since then, PH gradually became the conduit of choice for RVOT
[2,12], considered as the preferred substitute by many surgeons.
However, durability of the PH implanted for RVOT reconstruction has been
described in studies of children and young adults, and young age of PH
implantation is known to be a determinant of the PH longevity [6].
In our study, mean age of PH implantation was higher with a mean age of
26.29 ± 13.62 years old and provided implantation of a quiet homogeneous
range of PH sizes (23.06 ± 6.85 mm). Therefore, the confounding factor
related to the small size of the PH implanted during childhood and the
mismatch induced by the patients growth did not affect the results of
our study. In a similar way, the need of an extra-anatomic PH
implantation in children described by Wells et al [13] as a
risk factor of PH has been avoided by routine anatomic PH implantation
in this study population.
Patients who were implanted with PH in this study presented a large
spectrum of congenital heart diseases, such as TOF, pulmonary atresia,
truncus arteriosus or TGA. Therefore, results could be more
representative of the PH performance in a wide range of RVOT
reconstruction of different GUCH involving the RVOT. To our knowledge,
most of the studies reporting the PH durability in GUCH are performed
only with TOF patients [14].
Immunological mechanisms have been previously described as risk factors
for accelerated PH failure by Baskett et al [5] in a study of
children who were implanted with PH. ABO blood group and human
antigen-DR were significantly identified as prognosis factors of early
dysfunction of the PH. Da Costa et al [12] compared
decellularized PH to standard PH implanted in children less than 12
years old and found a lower incidence of structural valve disorder in
favor of the decellularized conduit. Decellularization of the PH may
reduce the antigenicity of the implanted tissue. Dekens et al[15] also reported that matching ABO compatibility may improve the
PH durability in PH more than 22 mm of diameter, but median age of
implanted recipients was 15 years old and this conclusion was obtained
in a sub-group univariate analysis. In our study, Rhesus and ABO blood
group compatibility matching between the recipient and the donor was
obtained in only 28.0% and was not identified as a risk factor of late
re-operation for PH failure in univariate analysis (p=0.167), of adults
implanted with large sizes of PH. This result supports the fact that a
young age of implantation may be a confounding factor, and that
immunological mechanisms of PH deterioration are maybe less important in
adults than in children implanted.
Re-operation rate of PH is low in our study (7.8% of the patients
implanted with PH, 3.9% for secondary PH failure) and is quiet similar
to other studies [14]. However, the rate of PH failure during
follow-up is higher than the re-operation rate because of non clinical
or functional evidence of such PH dysfunction. This result emphasizes
that current evaluation by echocardiography and magnetic resonance
imaging of the PH performances has to be more effective and reliable
with regard to the clinical status.
Concomitant tricuspid valve surgery was also identified as a risk factor
of late re-operation of PH (p=0.037) univariate analysis, but not in
multivariate analysis (p=0.504). Indication of tricuspid surgery was
mostly moderate to severe tricuspid regurgitation and a great majority
of the tricuspid surgery consisted in tricuspid annuloplasty with a
prosthesis ring. Shaher et al [16] suggested that initial PR
induced right ventricle dilatation and tricuspid regurgitation,
resulting in deterioration of the right ventricle function. Meijeret al [17] supposed that the dilatation of the right
ventricle may cause homograft PR, and suggested that reconstruction of
the ventricular outflow tract should be associated to the PH
implantation to restore a normal volume of the right ventricle.
Two of the 8 patients who were re-operated for PH had implantation of
transcatheter bioprosthetic valve Sapien XT (Edwards Lifesciences,
Irvine, CA, USA) in the pulmonary position. Since the first
transcatheter pulmonary valve implantation reported by Bonhoefferet al [18], this innovative technique has gradually expanded
and became a good alternative to pulmonary valve replacement, with
similar short and mid-term results [19]. However, long-term
performance of surgical pulmonary valve replacement with bioprothesis is
well known [5]. Bell et al [20] found that pulmonary
valve replacement with a bioprosthetic valve was more than 8 times at
risk of re-operation (Hazard Ratio = 8.34) compared to PH implantation
for RVOT reconstruction. These different results may suggest that the
conduit of choice for RVOT reconstruction is a PH in the setting of GUCH
involving the RVOT, but long-term analysis of transcatheter procedures
and improvement of the endovascular technology may change clinical
practice.