Impact of predicted heart mass-based size matching on survival after heart transplantation in Korea: Analysis of the Korean Organ Transplant Registry

Background: Previous studies regarding donor–recipient size and sex matching in heart transplantation (HTx) mainly included Caucasians with only a small portion of Asians. Even predicted heart mass (PHM) has not yet been elucidated in Asians. We evaluated the association between donor–recipient sex and size matching, including mismatching by PHM, and post-heart transplant survival in Korea. Methods: We enrolled 660 adult HTx recipients between January 2014 and December 2020 using the Korean Organ Transplant Registry data. Recipients were categorized based on donor–recipient PHM, body weight, and sex matching. The primary outcome was 1-year mortality and retransplantation after HTx and survival analyses were performed using Kaplan–Meier method and Cox proportional hazard models. Results: Among 660 patients, 74 (11.2%), 404 (61.2%), and 182 (27.6%) received undersized (<−15%), matched (−15% to 20%), and oversized (>20%) hearts by PHM, respectively. Size mismatching by PHM was present in a large number of sex-mismatched patients with 85.1% of male donor–female recipients being classified as oversized by PHM and 62.2% of female donor–male recipients being classified as undersized by PHM. Recipients of undersized or oversized hearts by PHM showed an increased 1-year mortality compared with recipients of matched-size hearts (14.8% versus 9.7%; log-rank p = 0.038). The increased mortality persisted after adjusting for other factors affecting mortality (hazard ratio = 1.60, 95% confidence interval: 1.01-2.56). These associations were not shown in obese recipients (body mass index ≥25 kg/m²). Heart size mismatching by body weight (log-rank p = 0.332) or sex mismatching (all, log-rank p > 0.05) did not predict 1-year mortality after HTx. Conclusion: Heart size matching by PHM, not by body weight or sex, was associated with increased 1-year mortality after HTx in Korea.