Is the Increased Utilization of Impella 5.5 Instead of Intra-Aortic Balloon Pump for Bridging Heart Transplant Patients Justified? An Analysis of the UNOS Database

A. Tsiouris¹, G. A. Hernandez², S. T. Lirette², A. Coimbatore Jeyakumar², L. Papadimitriou^2
1University of Mississippi Medical Center, Ridgeland, Mississippi ²University of Mississippi Medical Center, Jackson, Mississippi

Purpose: The aim of your study is to determine if Impella 5.5 devices are now utilized more liberally for status 2 heart transplant candidates and whether this confers any benefit to post heart transplant outcomes compared to patients bridged with Intra-Aortic-Balloon-Pump(IABP). Previously published reports had also included Impella 5.0 and CP.

Methods: We evaluated the UNOS database and analyzed status 2 patients who underwent heart transplantation after being bridged with an Impella 5.5 or IABP from October 2019(time of Impella 5.5 FDA approval)until March 2024. Given that early Impella 5.5 vs IABP results have already been published, we reported outcomes from a subgroup analysis of status 2 patients who were bridged with either IABP or Impella 5.5 from January 2022 until March 2024. A total of 2237 patients were identified of which 1463 had an IABP and 774 an Impella 5.5. Univariate comparisons were made via t-tests for continuous variables and chi-squared tests for categorical variables. Kaplan-Meier methods and log-rank tests were used for survival comparisons. Post transplant complications were modeled with logistic regression. Due to its right-skewed nature, patient length of stay was modeled using generalized linear models with gamma family and identity link functions. All analyses were completed with Stata-v18.5.

Results: From October 2019 until December 2021, 91% (1612/1774) were bridged with an IABP and 9% (162/1774) with an Impella 5.5. After January 2022, the rate of Impella implants for supporting status 2 candidates significantly increased to 35% (774/2237) (p < 0.001). Subgroup analysis of the latter cohort (Jan 2022-March 2024) showed that the average age was 54.7 years in the IABP group with 74% males recipients, whereas in the Impella 5.5 group the average age was 53.7 (p=0.071) and 82% were males (p < 0.001). Preoperative characteristics were analogous between the two groups (p=NS) (table 1). More Impella patients were on inotropic support at the time of transplant (63% vs 58%,p=0.013) and were more likely to have undergone previous cardiac surgery (25% vs 20%,p=0.04). Survival at 30 days, 180, 360 days and two years for the IABP patients was 98%, 93%, 92% and 86% respectively and for the Impella group, 98%, 93%, 91%, 84% respectively (graph 1). The rates of primary graft dysfunction, acute and chronic rejection were similar between the two groups (p=0.187). The Impella patients had a shorter length of hospital stay (20.4 days vs 22.5 days, p=0.05), but had a significantly higher rate of stroke (5% vs 3%,p=0.016).

Conclusion: Despite the more recent liberal utilization of Impella 5.5 for bridging heart transplant candidates, overall outcomes appear to be similar when compared to patients bridged with IABP.Although there are certainly transplant candidates that benefit from Impella 5.5 unloading, in addition to the reduction of post-transplant length of hospital stay as demonstrated in our study, current results do not justify its widespread usage for all Status 2 patients, given the higher cost of the device. Outcomes from more detailed institutional, multi-institutional databases and prospective studies are needed to ascertain other theoretical Impella benefits that are not reported in the UNOS database.

Identify the source of the funding for this research project: None