Prospective randomized trial of azathioprine in cryopreserved valved allografts in children.

Background: The purpose of this study was to prospectively assess the effects of azathioprine on the humoral immune response to HLA alloantigens and allograft function in children receiving cryopreserved valved allografts.

Methods: We randomized 13 children to receive azathioprine or not to receive azathioprine (controls) after receiving a cryopreserved valved allograft. Azathioprine patients received intraoperatively 4 mg/kg of azathioprine and 2.0 +/- 0.5 mg/kg once daily for 3 months after operation. Panel reactive antibodies against HLA class I and class II alloantigens were measured before, 1 month, and 3 months after operation.

Results: Panel reactive antibodies were not significantly different between the azathioprine and control groups before (0.0% +/- 0% versus 1.6% +/- 1%), 1 month (59% +/- 17% versus 71% +/- 12%), or 3 months (84% +/- 15% versus 96% +/- 1.3%) after operation. There were no differences in degree of allograft valve stenosis between azathioprine (31.5 +/- 26 mm Hg, 13.4 +/- 7 months postoperatively) and control groups (25.4 +/- 11 mm Hg, 17.2 +/- 10 months postoperatively) or allograft valve insufficiency.

Conclusions: Azathioprine does not significantly decrease the immune response to HLA alloantigens or affect the function of cryopreserved valved allografts used in children to repair congenital heart defects.