Decreased survival of simultaneous heart-kidney transplant recipients in the new heart allocation era

Abstract

In 2018, the United Network for Organ Sharing (UNOS) modified their heart allocation policy to reduce waitlist mortality. Rates of simultaneous heart-kidney transplant (SHKT) have dramatically increased in recent years, despite increased rates of post-transplant renal failure in the new policy era. This study sought to investigate the impact of the new allocation system on waitlist and post-transplant outcomes of simultaneous heart-kidney transplantation. Adult patients listed for SHKT between 2012 and 2021 were included. Patients were cross-validated across both Thoracic and Kidney UNOS databases to confirm accurate listing and transplant data. Patients were stratified according to listing era. The Fine and Gray model was used to assess waitlist outcomes and post-transplant renal graft function. Kaplan Meier analysis and Cox regression were used to compare post-transplant survival. A total of 2,588 patients were included, of whom 1,406 (54.1%) were listed between 2012 - 2018 (Era 1) and 1,182 (45.9%) between 2019 - 2021(Era 2). Era 2 was associated with increased likelihood of transplant (aSHR: 1.52; p<0.01) and decreased waitlist mortality (aSHR: 0.63; p<0.01). Post-transplant survival at 2 years was decreased in Era 2 (78.8% vs. 86.9%; p<0.01). Undersized hearts (HR: 2.02; p<0.01), use of extracorporeal membrane oxygenation (HR: 2.67; p<0.1), and transplants performed following the policy change (HR: 1.45; p=0.03) were associated with increased mortality. Actuarial survival (combined waitlist and post-transplant) was significantly lower in the modern era (71.6% vs. 62.2%; p=0.02). The allocation policy change has improved waitlist outcomes in patients listed for SHKT, but potentially at the cost of worsened post-transplant outcomes.