Differences in Heart Transplant Volume Growth and Outcomes among Low and High Volume Centers

Abstract

Heart transplant volume in the United States (US) has increased significantly over the past five years. It is unclear if the volume growth is distributed equally amongst large and small volume centers. We examined heart transplant volumes for centers that consistently performed heart transplants between 2008 and 2017 (n=130). Summary statistics for 130 transplant centers over the 5-year period of 2008 to 2012 was used to calculate the number of transplants per each center per calendar year. We then examined the change in volume over the next 5 years (2013-2017). We conducted a multivariable Cox regression model to examine overall survival post-transplant comparing larger volume centers to smaller volume centers. The average number of heart transplants performed in the US per center was 18.2 (range 9.6-21.6; Q1-Q3). By selecting a conservative cutoff of 20 or more transplants yearly per center, we identified 39 high volume centers and 91 small volume centers. From 2008-2012, high volume centers performed 6929 transplants whereas small volume centers performed 4904 transplants. From 2013-2017, high volume centers performed 8067 heart transplants, representing a 16.4% increase, whereas small volume centers performed 7053, a 43.8% increase. In multivariable Cox models, post-transplant survival among larger volume centers was slightly but significantly better (hazard ratio 0.93; p 0.012) compared to small volume centers. Small volume centers increased their transplant volume significantly in the past 5 years compared to high volume centers. Despite a significant increase in transplant volume over the past five years by smaller volume centers, larger volume centers demonstrate better recipient survival when compared to small volume centers over the past decade. With the new UNOS heart allocation policy, further investigation is warranted into the distribution and utilization of donor organs by large and small volume centers.