Multivariable Cox Regression for Mortality
Cox Frailty modeling was conducted to investigate associations between center acceptance rates and ECD risk factors on overall mortality. In a multivariable model, higher tier centers with greater donor acceptance rates were not found to have significant impacts on mortality (mid-tier HR 0.91; 95% CI 0.8-1.1; p=0.30 and high-tier HR 0.9; 95% CI 0.79-1.1; p=0.24) (Supplemental Table 5 ). With the exception of donor age >40 years, all ECD risk factors were not associated with hazards for mortality in univariate analysis (all, p>0.05), and were not included in the multivariable model. Recipients of donor hearts older than 40 years had a 33% (HR 1.33, 95% CI 1.22-1.46, p<0.001) increased hazard for posttransplant mortality. Other risk factors for posttransplant mortality included recipient creatinine >1.5 mg/dL (HR 1.23; 95% CI 1.1-1.4; p<0.001), graft ischemic time >180 minutes (HR 1.2; 95% CI 1.1, 1.3; p=0.001), and pre-OHT extracorporeal membrane oxygenator support (HR 2.3; 95% CI 1.6, 3.1, p<0.001).
In a univariate analysis, donor acceptance tier was not associated with mortality across most ECD risk factors (over 50 offers, over 500 miles from the transplant center, and HCV, HBV or HIV positive) (all, p>0.05) (Supplemental Table 6 ). In donors with LVEF <60%, high-tier was associated with decreased hazards for mortality (HR 0.79; 95% CI 0.63-0.00, p=0.039).