A Paired Kidney Analysis of Simultaneous Heart-Kidney Transplantation and Kidney Transplantation After Heart Transplantation.

Objective: To assess the outcomes of a pair of kidneys from a single donor used for simultaneous heart-kidney transplantation (SHKT) or kidney after heart transplantation (KAH).

Background: An Increase in kidney dysfunction among heart transplant candidates has led to an increased need for SHKT and KAH. The risk of early kidney graft loss and mortality is higher in SHKT compared with kidney-alone recipients.

Methods: Among adult kidney transplant recipients from Oct 2014 to Oct 2022, outcomes were compared between paired kidney-alone vs SHKT and kidney-alone vs KAH. Paired kidney models were used to mitigate differences among donor risk factors. Differential graft years were calculated using restricted mean survival analysis.

Results: A total of 1220 pairs of kidney-alone and SHKT recipients and 441 pairs of kidney-alone and KAH recipients were identified. Among the paired donor kidneys, graft survival was significantly lower in SHKT recipients compared with kidney-alone recipients at 1-year post-transplant (96.1% vs 89.3%; P < 0.001) and at 3-year post-transplant (83.9% vs 78.8%; P < 0.001). This resulted in lower mean graft years [SHKT (3.98 years, standard error = 0.06) vs kidney-alone (4.55 years, standard error = 0.04); P < 0.001] and an additional loss of 57 kidney graft years per 100 transplants (P < 0.01) during the study period. There was no difference in graft survival of paired kidneys in kidney-alone vs KAH recipients with additional loss of 17 kidney graft years per 100 transplants (P = 0.20).

Conclusions: Optimal recipient selection for kidney after heart transplant under the new safety-net policy may help mitigate the significant risk of kidney graft failure among SHKT recipients.