*Purpose: Isolate the impact of organ ischemic time on post-transplant survival using the recent change in heart allocation policy as a natural experiment.

*Methods: We examined heart transplants occurring prior to (11/01/2016 – 10/31/2017) and after the policy change (11/01/2018 – 10/31/2019). The exposure of our interest is the receipt of a graft with extended (>4 hours) cold ischemic time. Using an instrumental variable (IV) model, we isolated the effect of graft ischemic time on one-year post-transplant mortality by addressing bias from unobserved confounders. We also controlled for observed characteristics of donors and transplant recipients.

*Results: There were N = 3418 recipients in the post-policy period compared with N = 3278 recipients in the pre-policy period. Demographic variables (age, diagnosis, comorbidities) were similar in both cohorts. An additional 10% of heart recipients post-policy change received an organ with > 4 hours ischemic time compared to the pre-policy period (15% pre vs. 25% post, F-value = 116). Without addressing unobserved confounders, 1-year post-transplant survival was significantly worse among those who received graft with prolonged ischemic time (adjusted HR: 1.43, in green, P < 0.001). By using the policy period as an instrument to eliminate unobserved confounders, we found no difference in survival between those whose grafts sustained < 4 hours ischemic time and those whose graft had longer ischemic time solely due to the policy change (adjusted HR: 0.689, in blue, P = 0.73).

*Conclusions: For heart transplant recipients who were “randomized” to grafts with > 4 hours of ischemic time by changes in heart allocation policy, we found no effect on survival within the first year of transplantation.

« Back to 2022 American Transplant Congress