Association between recipient blood type and heart transplantation outcomes in the United States.

BACKGROUND: In heart transplantation (HT), although blood type O organs can go to any blood type, non-O organs may not be allocated to adult O recipients. Therefore, O candidates wait longer than non-O candidates and frequently require bridging with left ventricular assist devices (LVADs). The effects of this discrepancy are rarely investigated in a large registry. The purpose of this study was to assess the association between candidates' blood type and their outcomes after HT listing. METHODS: This is a retrospective cohort study using the United Network for Organ Sharing Registry, including 34,352 candidates listed for a single-organ, primary HT from January 2000 through December 2015. Main outcome measures were waitlist mortality and post-HT mortality, using blood type A as reference. We conducted inverse-probability weighting to adjust for baseline profiles. RESULTS: Among 34,352 candidates (median age 55, interquartile range 46-62; female 24.8%; blood type A: 13,258, AB: 1,572, B: 4,599, O:14,923), 22,714 candidates (A: 71.5%, AB: 82.1%, B: 73.0%, O: 57.5%; p < 0.001) underwent HT during the study period. Among recipients, bridging LVAD rate was highest in O recipients (A: 23.0%, AB: 15.3%, B: 23.4%, O: 32.1%; p < 0.001). After inverse-probability weighting, O patients demonstrated a significantly higher hazard of death after listing (adjusted hazard ratio 1.11, 95% confidence interval [CI] 1.07-1.16) and after HT (adjusted hazard ratio 1.07, 95% CI 1.01-1.13) as compared with A. CONCLUSIONS: There is a survival discrepancy among blood types. Our findings should facilitate more prospective studies to revisit current policies regarding equity in allocation, where possible. (C) 2020 International Society for Heart and Lung Transplantation. All rights reserved.