*Purpose: Analysis of combined heart-kidney transplants (HKTx) reveals equivalent or improved patient survival and reduced allograft rejection rates as compared to single-organ transplants. The rate of HKTx is growing rapidly compared with heart transplants alone. We seek to provide an updated comprehensive analysis of risk factors and outcomes in the HKTx cohort, which may help guide future selection processes and therapeutic interventions.

*Methods: HKTx patients from 2010 until 2017 were identified from the United Network for Organ Sharing (UNOS) database. Univariate Cox proportional hazard models were used to determine risk factors for patient overall survival. Cut point analysis was then performed using the %findcut macro to determine the optimal dichotomization of continuous risk factors for Cox regression analysis. Hazard ratios (HR) and their 95% confidence intervals (CI) as well as the log rank p-value are presented for overall survival and rejection-free survival. Survival estimates were calculated using the Kaplan-Meier method. All hypotheses were two-sided with p<0.05 considered statistically significant. Analyses were performed in SAS v9.4 (SAS Institute; Cary, NC).

*Results: One, 5, and 10 year overall survival estimates for the entire 1148 patient cohort were 86.9%, 76.7%, and 59.7%, respectively. One, 5, and 10 year rejection-free survival estimates for the entire cohort were 83.9%, 71.8%, and 54%, respectively. Of the 1148 patients, 69% experienced no rejection in either organ, 1.7% experienced only heart rejection, 3.3% experienced only kidney rejection, and 26% had dual organ rejection. Donor age was found to be significantly associated with survival (HR = 1.02, CI = 1.01-1.02, p=0.001). No other variables analyzed for both donor and recipient were found to be significantly associated with survival, including gender, blood type, dialysis at time of transplant, and kidney cold ischemic time or heart ischemic time. For recipient-specific findings, negative variables included previous number of transplants, left ventricular ejection fraction, and intra-aortic balloon pump at transplant. Donor age was dichotomized at 41 years old based on cut point optimization analysis. Overall survival was significantly higher in patients with donors age <41 with median survival estimates of 149.3 months compared to 116.3 months (log-rank p=0.001). Rejection-free survival was significantly higher in patients with donors age <41 with median survival estimates of 141.4 months compared to 99.3 months (log-rank p=<.001).

*Conclusions: Overall survival and rejection-free graft outcomes at 1, 5, and 10 years continue to support combined HKTx in patients with dual end-organ failure. Of the many variables analyzed, only younger donor age was found to be significantly associated with improved survival.

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