SAS/SQL and Stata programs for UNOS-STAR: heart flush study (UW, Celsior, HTK)

Background
Heart flush solutions (HFS) are pivotal in the heart procurement for transplant. The three most popular are University of Wisconsin (UW), Celsior, and histidine-tryptophan-ketoglutarate (HTK). Previous studies suggested UW might be the best choice, but some still disagreed. We would like to analyze the national UNOS (United Network of Organ Sharing) database, to test the hypothesis if UW could provide the best outcomes.
Methods
In the UNOS-STAR (Standard Transplant Analysis and Research) database, we selected the adult heart donors-recipients from 2015 to October 2021, excluding pediatric cases, machine perfusion, or multi-organ transplants. Firstly, intracellular (IC) solution (UW), and extracellular (EX) solution (Celsior or HTK) had a crude comparison for their outcomes: length of stay (LOS), graft failure, patient death, and 1-year rejection. Secondly, adjusted for ischemic time, they were compared by multiple regressions models. Thirdly, crude comparisons were made in three sub-groups (ischemia over 3 hours, ischemia over 4 hours, and donors over 50 years of age), and in the pre-defined high-risk sub-group (ischemia over 4 hours or donor over 50 years of age). SAS/SQL and Stata codes were shared online.
Results
There were 15,338 eligible cases: 9,104 (59.4%) intracellular (UW) and 6,234 (40.6%) extracellular (HTK or Celsior). Their ratios fluctuated around 60%: 40% from 2015 to 2021. UW had less favorable donor baseline such as longer ischemia time. Compared to HTK or Celsior, UW had shorter LOS (median 16 vs 17 days, p=0.0001 ) and less 1-year rejection (17.3% vs 22.2%, p=0.0001). When adjusted for ischemic time, UW had less 1-year rejection (17.3% vs 22.2% , p=0.0001). When ischemia was over 3 hours, UW had shorter LOS (median 16 vs 17 days , p=0.0001), less Kaplan-Meier graft failure (log-rank test p=0.0274; 16.7% vs 18.0% at 3 years), and less Kaplan-Meier patient death (log-rank test p=0.0523; 16.5% vs 17.2% at 3 years). With ischemia over 4 hours, donors age over 50 years, or in the high-risk sub-group (ischemia over 4 hours, or donors age over 50 years) , UW had shorter LOS (median 17 vs 18 days, p=0.0013).
Conclusion
For the heart procurement for transplant, UW showed superiority to HTK or Celsior in the outcomes of LOS, graft failure, patient death, and 1-year rejection, when ischemia was over 3 hours. UW still had shorter LOS, when ischemia was over 4 hours, or donors age was over 50 years. The UNOS-STAR data supported UW to be the flush solution of choice for heart procurement.