Background: The clinical differences between intra-aortic balloon pumping (IABP) and a microaxial flow pump (Impella) for left ventricular (LV) unloading in patients with fulminant myocarditis (FM) supported with venoarterial extracorporeal membrane oxygenation (VA-ECMO) remain unclear.

Methods and Results: In this single-center, retrospective cohort study, we analyzed 27 consecutive patients with lymphocytic FM who received VA-ECMO support. Patients were stratified by the LV unloading device that was used: IABP (n=15); or Impella (n=12). The primary endpoint was a composite of all-cause mortality or implantation of an extracorporeal ventricular assist device (exVAD) within 30 days of VA-ECMO initiation. Temporal changes in laboratory and hemodynamic parameters during the first 7 days of support were also assessed. Baseline characteristics, including LV ejection fraction (IABP 16% vs. Impella 18%; P=0.814) and QRS duration (139 vs. 105 ms; P=0.805), were comparable between groups. Nine patients met the primary endpoint (mortality [n=7]; exVAD implantation [n=2]). Kaplan-Meier analysis revealed a significantly lower incidence of the primary endpoint in the Impella group (log-rank P=0.018). The Impella group also showed a significantly greater improvement in cardiac power output (group×time interaction, P=0.040). Hemolysis, elevated total bilirubin, and increased serum creatinine were more pronounced in the Impella group.

Conclusions: In patients with FM requiring VA-ECMO, LV unloading with Impella was associated with improved short-term clinical outcomes compared with IABP.