Abstract 14444: Sex-Mismatch in Heart Transplantation Confers No Additional Risk of Postoperative Outcomes Established via Two One-Sided Equivalence Testing on a Propensity-Matched Cohort

Introduction: Donor-recipient sex-mismatch in heart transplantation (HTx) has decreased since the 1990s, possibly due to conflicting findings regarding its risk. Size mismatch is known to confer risk.

Hypothesis: Previously observed differences in outcomes between the arms of sex-matched and sex-mismatched patients were due to underlying size mismatch. Sex-mismatch confers no postoperative risks beyond that due to risk beyond those due to size mismatch.

Methods: Patients from the UNOS database between October 1, 1987 and December 31, 2022 were analyzed; under 18 years old, multiorgan transplants, and retransplants were excluded. Cohorts were separated into male and female recipients. Propensity score matching on age, transplant year, waitlist status, donor/recipient PHM ratio, preoperative diagnosis, creatinine clearance, total bilirubin, and mechanical circulatory support was performed. Two One-Sided Testing (TOST) was performed to assess between-arm equivalence in postoperative outcomes. Survival differences were measured by the between-arm ratio of Restricted Mean Survival Time (RMST) and binary outcome differences by the Odds Ratio (OR). We set the equivalence bounds per Wellek’s strict a priori bounds of (0.66, 1.50) for OR and (0.95, 1.05) for the between-arm RMST ratio.

Results: In the non-propensity matched cohort, there were significant differences in survival at temporal endpoints up to five years for male recipients (p<0.001) but no significant differences in the female recipients at temporal endpoints up to five years (p=0.3). In the propensity matched cohort, we found significant equivalence between arms in both male and female recipients for all outcomes (Table 1).

Conclusions: Sex-mismatch in HTx confers no additional risk to postoperative outcomes beyond those present due to size mismatch. Increasing the acceptance of sex-mismatched donors could potentially expand the donor pool and increase female donor utilization.