Heart Transplant Human Leukocyte Antigen Matching in the Modern Era.

BACKGROUND: Although numerous reports have studied the consequences of human leukocyte antigen (HLA) mismatching in renal transplantation, there are limited and outdated data analyzing this association in thoracic organ transplantation. Therefore, our study reviewed the impact of HLA mismatching at both the total and the loci levels in the modern-era heart-transplant procedure on survival and chronic rejection outcomes. METHODS: We performed a retrospective analysis of adult patients after heart transplant by using the United Network for Organ Sharing database from January 2005-July 2021. Total HLA and HLA-A, HLA-B and HLA-DR mismatches were analyzed. Survival and cardiac allograft vasculopathy were the outcomes of interest during a 10-year follow-up period using Kaplan-Meier curves, log-rank tests and multivariable regression models. RESULTS: A total of 33,060 patients were included in this study. Recipients with a high degree of HLA mismatching had increased incidences of acute organ rejection. There were no significant differences in mortality rates among any of the total or loci level groups. Similarly, there were no significant differences between total HLA mismatch groups in time to first cardiac allograft vasculopathy, though mismatching at the HLA-DR locus was associated with an increased risk of cardiac allograft vasculopathy. CONCLUSION: Our analysis suggests that HLA mismatch is not a significant predictor of survival in the modern era. Overall, the clinical implications of this study provide reassuring data for the continued use of non-HLA-matched donors in an effort to increase the donor pool. If HLA matching is to be considered for heart transplant donor-recipient selection, matching at the HLA-DR locus should take priority due to its association with cardiac allograft vasculopathy.