The Impact of the New UNOS Allocation System on Heart Kidney Recipients

Abstract

Purpose In October 2018, the United Network for Organ Sharing (UNOS) updated the allocation system for adult heart transplants (HT). While data suggests equivalent outcomes among HT recipients before and after this change, its effect on heart kidney transplants (HKT) has not been investigated. Methods A retrospective analysis of adults in the UNOS database undergoing HT and HKT from 2015 - 2021 was performed. The population was divided into a before and after allocation change group. Univariate t-test and chi-square tests were used to compare the cohorts. Our primary outcome was the effect of this change on patient survival. We also examined the use of mechanical support prior to transplantation (Tx). Results 17,684 patients were included; 9,805 transplanted before the change and 7,879 after. Mean wait time for HT decreased from 255 to 187 days following change in allocation system (p < 0.001). HT patients in the prior system were more likely to have a left ventricular assist device (LVAD) before Tx than HT patients in the new system (51.3% v 35.7%, p < 0.001). Use of intra-aortic balloon pump (IABP) and extracorporeal membrane oxygenator (ECMO) was higher in the group transplanted after the allocation change (IABP: 26.8% v 7.4%, p < 0.001 and ECMO: 4.9% v 0.8%, p < 0.001). The proportion of HKT increased following the change (8.5% vs 5.6%). Pre-management of HKT mirrored that seen in HT with more HKT recipients on LVAD support before than after the change (41.7% v 29.9%, p < 0.001). Utilization of IABP and ECMO was also higher in the group transplanted after the allocation change (IABP: 26.2% v 9.8%, p < 0.001 and ECMO: 5.8% v 1.3%, p < 0.001). Under the new system, survival was lower among HKT recipients compared to only HT recipients (mean 382 days vs 446 days); meanwhile there was no difference in survival between HKT and HT alone in the old system. Conclusion Following the change in the allocation system, a higher proportion of patients receiving HT and HKT were on ECMO and IABP support pre-Tx, while less patients were on LVAD support pre-Tx. We observed a decrease in survival among HKT recipients after the change. This may be due to higher acuity of the HKT group under the new system, or may demonstrate an impact of temporary mechanical support on survival. More detailed analysis is needed to determine factors that are influencing survival in this cohort. In October 2018, the United Network for Organ Sharing (UNOS) updated the allocation system for adult heart transplants (HT). While data suggests equivalent outcomes among HT recipients before and after this change, its effect on heart kidney transplants (HKT) has not been investigated. A retrospective analysis of adults in the UNOS database undergoing HT and HKT from 2015 - 2021 was performed. The population was divided into a before and after allocation change group. Univariate t-test and chi-square tests were used to compare the cohorts. Our primary outcome was the effect of this change on patient survival. We also examined the use of mechanical support prior to transplantation (Tx). 17,684 patients were included; 9,805 transplanted before the change and 7,879 after. Mean wait time for HT decreased from 255 to 187 days following change in allocation system (p < 0.001). HT patients in the prior system were more likely to have a left ventricular assist device (LVAD) before Tx than HT patients in the new system (51.3% v 35.7%, p < 0.001). Use of intra-aortic balloon pump (IABP) and extracorporeal membrane oxygenator (ECMO) was higher in the group transplanted after the allocation change (IABP: 26.8% v 7.4%, p < 0.001 and ECMO: 4.9% v 0.8%, p < 0.001). The proportion of HKT increased following the change (8.5% vs 5.6%). Pre-management of HKT mirrored that seen in HT with more HKT recipients on LVAD support before than after the change (41.7% v 29.9%, p < 0.001). Utilization of IABP and ECMO was also higher in the group transplanted after the allocation change (IABP: 26.2% v 9.8%, p < 0.001 and ECMO: 5.8% v 1.3%, p < 0.001). Under the new system, survival was lower among HKT recipients compared to only HT recipients (mean 382 days vs 446 days); meanwhile there was no difference in survival between HKT and HT alone in the old system. Following the change in the allocation system, a higher proportion of patients receiving HT and HKT were on ECMO and IABP support pre-Tx, while less patients were on LVAD support pre-Tx. We observed a decrease in survival among HKT recipients after the change. This may be due to higher acuity of the HKT group under the new system, or may demonstrate an impact of temporary mechanical support on survival. More detailed analysis is needed to determine factors that are influencing survival in this cohort.