Is ABO group incompatibility really the reason of accelerated failure of cryopreserved allografts in very young patients? – Echography assessment of the European Homograft Bank (EHB) cryopreserved allografts used for reconstruction of the right ventricular outflow tract*

Right ventricular outflow tract reconstruction (RVOTR) with cryopreserved allograft for Ross operation and other congenital or acquired cardiac malformation has become a routine and currently, the procedure of choice for children and young patients. A tendency of accelerated degeneration in the youngest recipients has been reported. Some authors advocate the ABO group incompatibility as the main reason for such failure. This retrospective monocentric study presents the long-term outcome of the European Homograft Bank (EHB) cryopreserved allografts, used for RVOTR in Ross operation (group one) and other congenital heart malformation-s (group two). The evaluation of the allograft performance was done by means of echography, considering the allografts with the transvalvular gradient of ≥40 mm Hg and/or regurgitation of ≥3+ as failed. Fifty-one patients of group one and 123 of group two were analysed after completed follow-up information. About 25.5% of patients of group one and 30.8% of group two had a compatible, whereas 74.5% of group one and 68.92 of group two an incompatible ABO group with the donor. The mean follow up was 45.77 and 68.88 months, respectively. In second group 22.76% received the aortic, while 77.24% pulmonary allograft. Only three cases of group one (5.88%) failed: one with a compatible (7.69%) and two with an incompatible ABO group (5.26%) (p = 0.1), whereas 39 patients (29.4%) of group two failed between 20.1 and 120.2 months (29.73% with and 29.07% without ABO compatibility, p = 0.03). Contrary, the age showed more importance in the allograft failure: out of 41 failed allografts, 24 (58.54%) were implanted in patients of 0–5 years (9 or 37.5% with compatible and 15 or 62.5% with incompatible ABO group). Generally, analysing both groups together, there was no influence of ABO mismatching on the allograft failure (p = 0.79). Contrary, there was a significant difference in survival between Ross and non-Ross group (p = 0.00082).