Relationship Between Change in Heart Transplant Volume and Outcomes: A National Analysis

Introduction: Although volume-outcome relationships in transplantation have been well-defined, the effects of large changes in center volume are less well understood. The purpose of the current study was to examine the impact of changes in center volume on outcomes after heart transplantation. Methods: Retrospective analysis was performed of adult patients undergoing heart transplant between 2000 and 2017 identified in the United Network for Organ Sharing database. Exclusions included annual volume <10. Patients were grouped according to percentage change in center volume from the previous year. Multivariable Cox regression models were adjusted for the significant preoperative variance identified on univariate analyses. Results: Of the 29,851 transplants during the study period, 64% were at centers with stable volume (+/- 25% annual change), whereas 10% were performed at contracting (-25% change or more) and 26% were performed at growing (+25% change or more) centers. Average volume was lower with contracting centers compared with stable or growing programs (21 vs 36, P<.001). Thirty-day mortality was greater in decreasing centers (6% vs 4%, P < .001), with more acute rejection treatments at 1y (27% vs 24% P < .001). The adjusted risk of mortality among contracting centers was 1.25 ([1.07-1.46], P=.004), whereas growing centers had unaffected risk (0.90 [0.79-1.02], P=.103). Causes of death were similar between groups. Conclusions: Rapid growth of transplant center volume has occurred at select centers in the United States without decrement in programmatic outcomes. Decreasing center volume has been associated with poorer outcomes, although the causative nature of this relationship requires further investigation.