*Purpose: Published estimates showing lower post-transplant survival after implementation of the new heart allocation policy may be biased downward due to incomplete follow-up on surviving recipients. A fundamental assumption of the Kaplan-Meier survival estimator is that censoring is statistically independent of survival time, and heavily censored post-policy survival data could lead to a lower Kaplan-Meier estimate than the true population survival rate. We aimed to evaluate this hypothesis by reassessing the impact of the new allocation policy on post-transplant survival with more complete recipient follow-up.

*Methods: Using the Scientific Registry of Transplant Recipients, we used the Kaplan-Meier method to estimate 1-year post-transplant survival for cohorts transplanted pre-policy (November 1, 2016, to October 31, 2017) and post-policy (November 1, 2018, to October 31, 2019) with follow-up through March 2, 2021, stratified by treatment type. We adjusted for changes in recipient population over time with a multivariable Cox proportional hazards model. To demonstrate the bias created by inadequate follow-up, we repeated the analysis while restricting recipient follow-up at various calendar dates.

*Results: Programs transplanted 2594 patients in the pre-policy cohort and 2761 patients in the post-policy cohort. With follow-up through March 2, 2021, unadjusted 1-year post-transplant survival was 90.6% in the pre-policy cohort and 90.8% in the post-policy cohort (aHR = 0.93, P = 0.45). When follow-up was restricted to November 1, 2019, post-policy survival was biased downward (1-year: 82.2%). Patients bridged with extracorporeal membrane oxygenation experienced greater 1-year survival after policy change (69.3% pre-policy vs. 87.2% post-policy).

*Conclusions: With adequate recipient follow-up, there was no significant difference in 1-year post-transplant survival between policy periods. Informative censoring bias should be considered in any cohort study with a similar design that analyzes transplant registry data from the United States.

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