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.