The Impact of Ex Situ Heart Perfusion in Pediatric Transplantation: An Analysis of the UNOS Registry

Abstract

Purpose Ex situ heart perfusion (ESHP) has increased the number of heart donors in adult heart transplant (HTx). However, this benefit has not been seen in paediatrics due to lack of appropriate devices. While the development of these devices is in the early stages for paediatrics, it is important to determine what the potential impact of this technology could be in paediatric heart donation. Methods The UNOS data was queried between 2000-2019 to identify donor hearts offered that were refused due to distance between donor and recipient centers. Utilizing the average calculated ischemic time (3.6 hours) and distance between donor and recipient sites, the average travel speed was determined [87.6 nm/h (CI 84.7-90.5)]. From this information and presuming that EHSP could extend the total out-of-body time by an additional 6.4 hours (total 10 hours), we calculated the number of donor hearts that could be utilized through increasing the transportation distance. Results There were 31,434 donor offers to paediatric programs for 10,807 donor hearts of which 25.2% (n=2,726) hearts were accepted for HTx. Six percent (n=1,893) of the offers were refused due to donor distance representing 776 hearts, with 680 of these hearts never used. The median number of offers per donor refused for distance was 24 (IQR 62) compared to 2 (IQR 3) for hearts accepted. For hearts never used due to distance, the median distance to the final refused offer was 1,336.7 nm (IQR 674.4). These donors were on average 23±17 yrs, weighed 56.5±32.8 Kg with an EF of 61.2%±10.1% and majority blood type being O (43.9%). Using the above assumptions, the distance the travel could be increased with EHSP was 560.64nm (CI 542.08-579.2). This increase in distance would have allowed 94.1%-95.3% (n=640-648) of the hearts turned down and not used solely due to distance to be accepted if there was an appropriate recipient. Conclusion Through addressing transportation distance and the impact of ischemic time, ESHP has the potential to increase the number of available paediatric donors by close to 25%. While no device exist in paediatrics this analysis lends support to the importance of developing technology for paediatrics.