The Impact of the New Heart Allocation System: Is Donor-Recipient Mismatch Still Clinically Important?

PURPOSE: The heart allocation system underwent major changes 1 year ago and the clinical impact is yet to be fully analyzed. We sought to examine clinical characteristics that have been viewed as critical to the donor-recipient matching process before and after the allocation change. METHODS: The United Network for Organ Sharing database was queried from 2006 to 2019 for all adult recipients who underwent heart transplant. Patients were excluded if they were listed for multiple organs, re-transplant, or a diagnosis of congenital heart disease. Six mismatch variables between donor and recipients were used for a logistic regression analysis that included difference for age, height, and weight, sex mismatch, ethnicity mismatch, and distance between procurement and transplant centers. These results were then analyzed for pre- and post- implementation of the allocation system: January, 2006- September, 2018 (Era 1) and October, 2018 - June, 2019 (Era 2). RESULTS: A total of 25,820 patients were identified with 25,209 and 619 patients in Era 1 and Era 2, respectively. Results from the logistic regression analysis are summarized in Table 1. All six mismatch variables significantly impact overall survival and survival in Era 1; however, they lose significance in Era 2. Further analysis comparing mismatch variables in Eras 1 and 2 demonstrate an increased use of ethnicity mismatch (p=0.023), oversized donors by weight (p<0.001), and distance between centers (p<0.001), while there was no difference in age (p=0.065), sex (p=0.550), or height mismatch (p=0.511), respectively. CONCLUSION: Early results from the new heart allocation system demonstrate practice changes most notably with increased use of oversized donors. However, donor-recipient mismatch in other clinically relevant characteristics often used to select donors did not predict poorer outcomes in the early new era whereas they did prior to the change. Further data collection in the new era of heart allocation will show if these conclusions are valid.