247.7: Trends and Risk Factors for Mortality While Awaiting Heart Transplantation: A UNOS Registry Analysis

Abstract

Background: Orthotopic heart transplantation (OHT) remains the gold standard treatment of end-stage heart failure. In order to address organ scarcity, allocation systems aim to decrease waitlist mortality while maintaining acceptable post-transplant outcomes. The purpose of this study was to examine the characteristics of patients who suffered mortality on the waitlist versus those who underwent transplantation, as well as the impact of recent changes in the United States heart allocation policies on these outcomes. Methods: The United Network for Organ Sharing database was queried, and adult, isolated OHT candidates listed for transplant within the United States from 11/5/2015 to 9/30/2021 were analyzed. Baseline characteristics among candidates that either were transplanted, or had been removed from the waitlist due to death clinical deterioration were compared. Comparisons were also made between heart allocation policy (pre or post-10/18/2018) time eras. Multivariable competing risk regression was conducted to identify risk-adjusted predictors of transplantation from the waitlist. Additionally, predictors of the outcome of death or de-listing from the waitlist due to clinical decline were also modeled. Results: During the study period, a total of 13,575 recipients were transplanted (6,926 under the old policy and 6,649 under the new). A total of 1,875 candidates died or were de-listed (1,235 listed under the old policy and 640 listed under the new). In a comparison of baseline characteristics at time of listing, candidates that were transplanted differed significantly to those who were de-listed due to death or clinical decline with respect to age, heart failure etiology, mechanical circulatory support bridging, and baseline comorbidity (Table). In a multivariable model, waitlisting under the new allocation policy was associated with reduced hazards for death or de-listing (HR 0.57, 95% CI 0.51-0.63; P<0.001), and increased hazards for undergoing transplantation (HR 1.36; 95% CI 1.31-1.41; P<0.001). The two largest predictors of transplantation were bridging with an intra-aortic balloon pump (HR 2.13, 95% CI 1.97-2.31; P<0.001) and AB blood type (HR 1.43, 95% CI 1.30-1.57; P<0.001). The strongest predictors of death or de-listing were diagnosis of hypertrophic cardiomyopathy (HR 3.77, 95% CI 2.69-5.29; P<0.001) or biventricular hemodynamic support in the form of either extracorporeal membrane oxygenation (HR 2.59, 95% CI 1.96-3.42; P<0.001), total artificial heart (HR 2.36, 95% CI 1.28-4.35; P=0.006), or combined right and left ventricular assist device support (HR 2.45, 95% CI 1.71-3.50; P<0.001). Conclusions: Since the United States 2018 heart allocation policy change, waitlisted candidates are more likely to be transplanted and less likely be de-listed due to death or clinical decline. Need for biventricular mechanical circulatory support at time of waitlisting are associated with higher risk of death or falling too ill for transplantation.