Age-Dependent Association Between Pre-transplant Blood Transfusion and Outcomes of Pediatric Heart Transplantation

Avoidance of red blood cell (RBC) transfusions in patients awaiting heart transplantation (HTx) has been suggested to minimize the risk of allosensitization. Although recent studies have suggested that an immature immune system in younger HTx recipients may reduce risks associated with RBC transfusion, the role of age in moderating the influence of transfusion on HTx outcomes remains unclear. We used available data from a national transplant registry to explore whether the association between pre-transplant transfusions and outcomes of pediatric HTx varies by patient age. De-identified data were obtained from the United Network for Organ Sharing registry, including first-time recipients of isolated HTx performed at age 0-17 years in 1995-2015. The primary exposure was receiving blood transfusions within 2 weeks prior to HTx. Patient survival after HTx was evaluated using multivariable Cox proportional hazards, where age at transplant was interacted with exposure to pre-transplant transfusion. Age-specific hazard ratios (HRs) of pre-transplant transfusion were plotted across ages at transplant. There were 4883 patients meeting inclusion criteria, of whom 1258 died during follow-up (mean follow-up duration 6 ± 5 years). Patients receiving pre-transplant transfusions were distinguished by younger age, higher prevalence of prior cardiac surgery, greater likelihood of being in the intensive care unit, and greater use of left ventricular assist device bridge to transplant. In multivariable analysis, pre-transplant transfusions were associated with increased mortality hazard among infants < 1 year of age (HR = 1.46; 95% CI 1.23, 1.74; p < 0.001). For each additional year of age, the excess hazard associated with pre-transplant transfusions decreased by 3% (interaction HR = 0.97; 95% CI 0.98, 0.99; p = 0.003). By age 8, the association between pre-transplant transfusions and post-transplant mortality was no longer statistically significant (HR = 1.15; 95% CI 0.99, 1.32; p = 0.060). Pre-transplant transfusions were associated with increased mortality hazard only among younger children (age < 8 years) undergoing HTx. These data support the current practices of transfusion avoidance prior to HTx, particularly in younger patients.