Impact of Various Sizing Metrics on Female Donor to Male Recipient Heart Transplant Outcomes

Abstract

Background: This study evaluated the impact of various sizing metrics on outcomes of female donor to male recipient orthotopic heart transplantation (OHT). Methods: We queried the United Network of Organ Sharing database to analyze all isolated, primary adult OHTs from 1/12010-3/20/2020. Patients were stratified by donor-recipient sex pairing. Logistic regression was used to investigate risk-adjusted effects of current size matching criteria (weight ratio, body mass index (BMI) ratio, predicted heart mass (pHM) ratio) on one-year post-transplant mortality. Kaplan-Meier analysis was used to compare posttransplant survival among cohorts. Results: A total of 22,450 patients were analyzed, of which 3,019 (13.4%) underwent female-to-male transplantation. Of sex-matched pairs, female-to-male donation had the lowest proportion of undersized hearts using weight and BMI ratio metrics (10.5% and 5.2%) but had the highest proportion of undersizing using pHM metrics (48.1%) (all P<0.001). Female-to-male recipients had the lowest rate of unadjusted one-year survival (90.0%, P = 0.0169), and increased hazards of mortality after risk adjustment (OR 1.17, 95% CI 1.01-1.36, P=0.034)). Undersizing using pHM (donor-recipient ratio < 0.85) was the only metric found to be associated in increased mortality after risk adjustment (OR 1.32, 95% CI 1.02 to 1.71, P=0.035). Conclusions: Female-to-male heart transplantation has the worst survival of all sex-matching combinations. Although female donors in this cohort are appropriately sized using traditional metrics, half are under-sized using pHM. This, combined with its strong association with mortality, underscores the importance of routine pHM assessment when evaluating female donors for male recipients.