ABO Incompatible Heart Transplantation in Young Children: Less Rejection and Infection

Abstract

Purpose Transplantation (Tx) of young children with ABO incompatible (ABOi) hearts has evolved from an experimental approach to a routine procedure in many centers. Prior studies have shown equal survival after ABOi and ABO compatible (ABOc)-Tx, but also revealed altered B-cell response and less HLA sensitization following ABOi-Tx with yet unknown clinical impact. Using a large registry cohort, we investigated outcomes of ABOi recipients in comparison to all and directly matched ABOc recipients. Methods Data from the Pediatric Heart Transplant Society was analyzed comparing children < 2 years of age undergoing ABOi or ABOc-Tx as identified by donor and recipient blood groups between 1999 and 2017. Given significantly different demographics, each ABOi recipient was directly matched to 2 ABOc recipients by age ± 1 month, diagnosis, and use of mechanical circulatory support. Results ABOi-Tx was performed in 337 (16%) of children < 2 years. These recipients were younger, had lower BSA, were transplanted more recently, and had a higher proportion of mechanical circulatory support than ABOc recipients. After matching, only expected differences in blood group persisted with more O in the ABOi and AB in the ABOc group. Post-Tx graft survival, coronary allograft graft vasculopathy (CAV), and malignancy were similar between groups. ABOi recipients had significantly longer time to first rejection (p=0.03), hemodynamically compromising rejection (p=0.01) and first severe infection (p=0.005). These outcome differences remained when comparing ABOi-Tx to all 1801 ABOc-Tx <2 years despite lower acuity profile of the latter. Conclusion In this large cohort of young children receiving ABOi-Tx in a clinical routine setting rates of graft survival, CAV and malignancy were equivalent to matched ABOc recipients. ABOi-Tx was associated with longer time to rejection, suggesting better graft acceptance associated with acquired blood group tolerance. ABOi-Tx was also associated with longer time to severe infection, potentially secondary to less rejection treatment. The benefits of ABOi-Tx seen in the matched cohort analysis persisted when analyzed against all ABOc-Tx children. Transplantation (Tx) of young children with ABO incompatible (ABOi) hearts has evolved from an experimental approach to a routine procedure in many centers. Prior studies have shown equal survival after ABOi and ABO compatible (ABOc)-Tx, but also revealed altered B-cell response and less HLA sensitization following ABOi-Tx with yet unknown clinical impact. Using a large registry cohort, we investigated outcomes of ABOi recipients in comparison to all and directly matched ABOc recipients. Data from the Pediatric Heart Transplant Society was analyzed comparing children < 2 years of age undergoing ABOi or ABOc-Tx as identified by donor and recipient blood groups between 1999 and 2017. Given significantly different demographics, each ABOi recipient was directly matched to 2 ABOc recipients by age ± 1 month, diagnosis, and use of mechanical circulatory support. ABOi-Tx was performed in 337 (16%) of children < 2 years. These recipients were younger, had lower BSA, were transplanted more recently, and had a higher proportion of mechanical circulatory support than ABOc recipients. After matching, only expected differences in blood group persisted with more O in the ABOi and AB in the ABOc group. Post-Tx graft survival, coronary allograft graft vasculopathy (CAV), and malignancy were similar between groups. ABOi recipients had significantly longer time to first rejection (p=0.03), hemodynamically compromising rejection (p=0.01) and first severe infection (p=0.005). These outcome differences remained when comparing ABOi-Tx to all 1801 ABOc-Tx <2 years despite lower acuity profile of the latter. In this large cohort of young children receiving ABOi-Tx in a clinical routine setting rates of graft survival, CAV and malignancy were equivalent to matched ABOc recipients. ABOi-Tx was associated with longer time to rejection, suggesting better graft acceptance associated with acquired blood group tolerance. ABOi-Tx was also associated with longer time to severe infection, potentially secondary to less rejection treatment. The benefits of ABOi-Tx seen in the matched cohort analysis persisted when analyzed against all ABOc-Tx children.