Comparative effectiveness of impella and IABP as ventricular unloading strategies in patients with cardiogenic shock undergoing ECMO: a systematic review and meta analysis

Background

In cardiogenic shock, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) rapidly restores systemic perfusion but increases LV afterload, often requiring unloading strategies. LV unloading is often achieved using either an intra-aortic balloon pump (IABP) or an Impella device. Although observational studies suggest lower mortality with unloading compared with VA-ECMO alone, both unloading strategies are associated with significant complications. Therefore, a direct comparative synthesis of Impella and VA-ECMO versus IABP and VA-ECMO is needed to inform patient selection and optimal unloading strategy.

Purpose

To compare the safety and efficacy of Impella versus IABP as ventricular unloading strategies in patients with cardiogenic shock undergoing ECMO therapy.

Methods

We performed a systematic review and meta-analysis of comparative studies in adults with cardiogenic shock supported with VA-ECMO who received LV unloading with either Impella or IABP. Data sources included PubMed, Embase, ScienceDirect, Cochrane Central and grey literature. The primary outcome was all-cause mortality. Secondary outcomes included acute kidney injury; major bleeding; stroke and limb ischemia. Meta-analysis was performed using R version 4.5.2 with a random-effects model (Mantel-Haenszel method, Hartung-Knapp adjustment). Statistical heterogeneity was assessed using I².

Results

A total of 11 retrospective cohort studies were included, encompassing a total of 51783 patients, of whom, 5183 received Impella+ECMO, and 46380 received IABP+ECMO. In the primary random-effects meta-analysis, there was no statistically significant difference in all-cause mortality between the two strategies (RR 0.92, 95% CI 0.81-1.05, p=0.185), although considerable heterogeneity was observed (I²=87.6%). Sensitivity analyses confirmed the robustness of findings, with no individual study exerting a disproportionate influence on all-cause mortality.

In the analysis of secondary outcomes, the Impella+ECMO group was associated with a significantly increased risk of acute kidney injury (RR 1.23, 95% CI 1.11-1.36, p=0.007, 5 studies, 16342 patients). There were no statistically significant differences observed between the groups regarding major bleeding (RR 1.34, 95% CI 0.88-2.03, p=0.142, 7 studies, 19884 patients), stroke (RR 1.28, 95% CI 0.84-1.96, p=0.194, 6 studies, 163408 patients), or limb ischemia (RR 1.52, 95% CI 0.37-6.27, 3 studies, 1884 patients ), although point estimates consistently trended toward higher complication rates with Impella+ECMO.

Conclusions

Impella-based LV unloading during ECMO was not associated with an improvement in survival when compared with IABP and was associated with a significantly higher risk of acute kidney injury. IABP + VA-ECMO appears to provide comparable mortality with a more favorable risk profile; however, further research is needed to define whether selected subgroups may benefit from Impella-based unloading.For image description, please refer to the figure legend and surrounding text.For image description, please refer to the figure legend and surrounding text.