Sex-Based Disparities in Waitlist and Posttransplant Outcomes Under the Previous and Revised United States Heart Allocation Systems

Background: In October 2018, the heart transplant (HT) allocation system in the United States was revised to address limitations of the prior model. Changes included more granular patient population stratifications and expansion of geographic boundaries. While the revised allocation system has improved transplant access for critically ill patients, limited data exist regarding its impact on sex-based disparities in waitlist and posttransplant outcomes. Objective: To evaluate the impact of the revised HT allocation system on sex-based differences on waitlist and posttransplant outcomes. Methods: We conducted a retrospective study of adult patients listed for HT in the Organ Procurement and Transplantation Network database between January 1, 2014 and December 31, 2021. Patients were stratified by sex and allocation system era. Waitlist outcomes were analyzed using competing risks methodology. Posttransplant outcomes were analyzed using Kaplan–Meier and Cox proportional hazards models. Results: Of 26,876 patients, 16,053 (59.7%) were listed under the previous system and 10,823 (40.3%) under the current system. A total of 4,216 (26.2%) were women in the previous system and 2,882 (26.6%) were women in the current system. In both allocation systems, women had a significantly higher cumulative incidence of transplantation at 1 year compared with men (old: 60.4% versus 54.1%; new: 72.4% versus 66.6%, p < 0.001). Among 18,725 transplant recipients, adjusted 1-year posttransplant survival was significantly lower for women compared with men in both systems (old: 91.2% versus 93.3%, p < 0.001; new: 89.7% versus 91.4%, p = 0.036). Female sex remained an independent predictor of lower adjusted survival despite increased access to transplantation. Conclusion: The updated allocation system has improved transplant access for women without increasing waitlist mortality. However, women continue to experience worse adjusted posttransplant survival compared with men. These disparities likely reflect a combination of immunological, clinical, and system sex-based factors. Ongoing investigation is needed to address sex-based inequities in transplant outcomes.