Abstract Body (Do not enter title and authors here): Background
Venoarterial extracorporeal membrane oxygenation (ECMO) is commonly used as a bridge to heart transplantation in patients with cardiogenic shock. The addition of a percutaneous microaxial left ventricular assist device such as Impella to ECMO (ECPELLA), has been proposed to enhance unloading of the left ventricle and improve systemic perfusion. Despite increasing use, the impact of ECPELLA on post-transplant outcomes remains uncertain.

Methods
We performed a retrospective cohort study using data from the United Network for Organ Sharing (UNOS) registry to evaluate outcomes of adult patients (aged ≥18 years) who underwent orthotopic heart transplantation between 2018 and 2022, while receiving ECMO support at the time of transplant. Patients were stratified based on support modality into ECPELLA (defined by concurrent use of ECMO and Impella) and ECMO alone. The primary outcome was one-year post-transplant survival. Secondary outcomes included 30-day survival and post operative length of hospital stay. Statistical comparisons were conducted using chi-square or Fisher’s exact tests for categorical variables and the Mann–Whitney U test for continuous variables. Survival was analyzed using Kaplan–Meier estimates and the log-rank test.

Results
A total of 197 patients met the inclusion criteria, comprising 41 patients (20.8%) in the ECPELLA group and 156 patients (79.2%) in the ECMO-alone group. Baseline demographics including age, sex, and race, were comparable between the two cohorts. Among ECPELLA recipients, the most commonly used device was the Impella CP, utilized in 25 patients (61%). One-year survival rates were comparable: 87.3% in the ECPELLA cohort versus 86.5% in the ECMO-alone group (HR- 0.90; 95% CI 0.33–2.43; p=0.82). The median hospital length of stay was shorter among ECPELLA recipients (19.0 days [IQR, 15.5–30.5]) compared with the ECMO-alone cohort (22.5 days [IQR, 16.0–34.0]), though this difference was not statistically significant (p=0.31).

Conclusions
In this national registry analysis, the addition of Impella to ECMO support at the time of heart transplantation was not associated with improved survival or early postoperative outcomes. Although ECPELLA may offer theoretical hemodynamic advantages, its use did not confer measurable clinical benefit over ECMO alone in this cohort. Prospective studies are warranted to further clarify the role of combined support in this patient population.