A novel method for abo-incompatible heart transplantation

Background Since 1996, ABO- incompatible heart transplants have been undertaken by carrying out a whole body plasma exchange to remove isohaemagglutinins using the cardiopulmonary bypass circuit at the time of transplantation. However, this requires large volumes of donated blood and blood products, causes haemodynamic instability during the exchange transfusion and limits the practical usage to small children. We sought to determine the efficacy of anti-A/B immunoadsorption within the cardiopulmonary bypass circuit on removal of isohaemagglutinins in an ex vivo setting, prior to its use clinically. Methods An anti-A/B immunoadsorption column was placed into a CPB circuit mimicking a typical ABO-incompatible transplant patient, which had been primed with group O whole human blood. Samples were taken for determination of isohaemagglutinin titres following each plasma volume pass through the anti-A/B immunoadsorption column. Results There was a linear decrease of at least one dilution seen in both anti-A and -B IgG and IgM antibodies with each plasma volume pass through the column. This predictable removal allowed the formulation of selection criteria for ABO-incompatible heart transplantation given the reciprocal of titre and patient weight. This degree of predictability allowed us to use it successfully in the clinical setting, reducing antibodies to an undetectable level during an ABO-incompatible heart transplant. Conclusions The incorporation of an anti-A/B immunoadsorption column into the extracorporeal circuit reduces the allogeneic blood product requirement for ABO-incompatible heart transplantation whilst providing efficacious removal of anti-A and anti-B isohaemagglutinins. Furthermore, this can be undertaken within the time period of cardiopulmonary bypass before graft reperfusion and expands the potential recipient pool to larger patients with higher isohaemagglutinin titres.