The Effect of Center Transplant Rate and the Use of Temporary Mechanical Circulatory Support on Heart Transplant Outcomes

Abstract

<h3>Purpose</h3> The use of temporary mechanical circulatory support (tMCS) to bridge candidates to heart transplantation has increased. The intra-aortic balloon pump (IABP) is considered a less invasive form of mechanical support. We hypothesize that tMCS utilization varies by center transplant rate with an effect on waitlist and transplant outcomes. <h3>Methods</h3> The Scientific Registry for Transplant Recipients was queried from October 2017 to June 2021. Transplant candidates age 18 or older listed for heart-only transplant were included. Annual transplant rate was calculated as the number of heart transplants performed per 100 person waiting years. Transplant centers were divided into tertiles by average transplant rate over the study period (tertile 1-3 low to high). Candidates with tMCS were identified via the presence of veno-arterial extracorporeal membrane oxygenation and a review of devices during listing, including a manual search using the following terms: "impella", "centrimag", "macquet" "tandem", and "protek duo". Candidates with intra-aortic balloon pumps (IABP) were identified as a separate group. A competing outcomes analysis was used for waitlist outcomes. A Cox proportion hazards analysis was used for post-transplant outcomes. <h3>Results</h3> We identified 15,152 transplant candidates, of whom 64.9% were ultimately transplanted. All candidates in tertile 3 had lower waitlist mortality when compared to tertile 1 (SHR 0.56, p<0.0001). The waitlist mortality risk was lower in tertile 3 compared to tertile 1 both in those listed with tMCS (SHR 0.62, p=0.006) and those listed with IABP (SHR 0.49, p=0.04). Post-transplant, all recipients at tertile 3 centers had lower one-year mortality compared to tertile 1 centers (HR 0.79, p=0.006). This mortality difference was not seen in those transplanted with tMCS when comparing tertile 3 to tertile 1 (HR 0.92, p=0.679). The one-mortality post-transplant mortality when compared tertile 3 to tertile 1 was significant in those transplanted with IABP (HR 0.68, p=0.040) <h3>Conclusion</h3> Transplant centers with a high transplant rate have lower waitlist mortality, which also applied to those with tMCS and IABP. Although one-year post-transplant are superior in centers with a higher transplant rates for all transplant recipients and those with IABP, this mortality difference was not seen in those transplanted with tMCS.