Percutaneous Microaxial Flow Pump in Cardiogenic Shock Complicating Acute Myocardial Infarction: A Meta-Analysis of Randomized Controlled Trials

Cardiogenic shock (CS) is a sudden low-cardiac-output state resulting in life-threatening hypoperfusion, complicating 3–13% of acute myocardial infarctions (AMI).1 Despite urgent revascularization and advanced acute mechanical circulatory support (aMCS) devices (extracorporeal life support [ECLS], microaxial flow pump [mFP]), AMI-CS mortality remains unacceptably high approaching 45–60% at 1 year. While the latest guidelines for AMI management1 suggest that aMCS (whatever the device used) may be considered for selected AMI-CS patients, caution is advised due to potential adverse events (bleeding, kidney failure), resulting in a class IIb recommendation pending further randomized data. Currently, four randomized controlled trials (RCTs) in AMI-CS (including ECLS-SHOCK, the largest trial carried out to date in ECLS (n = 420)2) failed to demonstrate any survival benefits of ECLS over optimal medical therapy. Conversely, the DanGer-Shock trial3 presents a significant breakthrough, providing evidence to support the use of mFP for narrowly selected AMI-CS patients with ST-segment elevation (STEMI) and without prolonged cardiac arrest (CA), demonstrating a 13% mortality reduction after 180 days. However, uncertainties persist, particularly concerning non-STEMI or non-AMI-CS populations and patients with CA. The neutral outcomes observed in both per-protocol and as-treated analyses in recent studies emphasize the critical need to pursuit research effort.2,3 Methods Nevertheless, the few studies conducted on this topic are subject to bias due to the small number of patients and their narrow subselection. Therefore, we felt the need to perform a meta-analysis of existing RCTs to reassess the efficacy and safety of mFP use in AMI-CS compared with standard therapy. Notably, we considered it acceptable to categorize patients treated with intra-aortic balloon pump (IABP) as receiving “standard therapy,” especially given the IABP-SHOCK II results (NCT00491036), demonstrating the neutral impact of IABP on mortality in AMI-CS, leading to a class III recommendation for AMI-CS.1 The study was registered with PROSPERO (CRD42024596181) and performed in line with the PRISMA Guidelines. Heterogeneity, assessed by Higging’s I²-index, deemed acceptable at I² < 50%, leading to a fixed-effects model. Analyses were two-tailed, with statistical significance at p < 0.05, and were performed using R (v4-3-2). A sensitivity analysis was performed to account for the different models of mFP (Impella CP and 2.5). Institutional review committee approval was not required since this is a meta-analysis of published data. Results and Discussion After fulfilling our inclusion criteria, only three RCTs could be included in our study (see Supplementary Tables 1 and 2, Supplemental Digital Content, https://links.lww.com/ASAIO/B415). Preceding DanGer-Shock,3 the IMPRESS4 and ISAR-SHOCK5 trials examined the outcomes of routine mFP use in STEMI-related CS, with almost all patients having had a prior CA. As previously discussed, DanGer-Shock compared mFP with medical treatment, while the IMPRESS and ISAR-SHOCK trials compared mFP with IABP devices. DanGer-Shock and ISAR-SHOCK specified exclusion of patients with prolonged CA or severe right ventricular failure, whereas patients in IMPRESS were only qualified based on mechanical ventilation before randomization, and 92% of patients had experienced prerandomization CA. The main exclusion criteria in both trials were severe arterial disease impeding the placement of IABP/mFP, known severe aortic valvular disease, and serious comorbidities with life expectancy under 1 year. Overall, 429 patients were randomized to either mFP use (n = 216) or standard care alone (n = 213). Figure 1 shows that the difference in 30 day mortality did not reach statistical significance (40.7% vs. 46.9%, odds ratio [OR]: 0.78 [0.53–1.14]). However, patients in the mFP group exhibited a lower mortality rate at 6 months (46.3% vs. 57.5%, OR: 0.64 [0.43–0.95]). No significant difference was observed in the need for escalation to additional aMCS therapy. Importantly, mFP support was associated with higher rates of renal replacement therapy (40.9% vs. 27.0%, OR: 1.87 [1.23–2.84]) and major bleeding (21.8% vs. 10.8% OR: 2.28 [1.32–3.94]), without difference for strokes.Figure 1.: Meta-analysis of main mortality and safety outcomes with microaxial flow pump use in acute myocardial infarction complicated by cardiogenic shock. aMCS, acute mechanical circulatory support; CI, confidence interval; mFP, microaxial flow pump; OR, odds ratio.Finally, we must acknowledge several limitations, primarily concerning discrepancies in inclusion criteria. Indeed, out-of-hospital CA with a persistent Glasgow Scale score under 8 after return of spontaneous circulation was considered an exclusion criterion in DanGer-Shock (although CA occurring in ambulance or after arrival at the hospital was not), hindering the ability to draw clear conclusions for this subpopulation. Furthermore, no conclusion can be drawn for patients with non-STEMI nor other types of nonischemic cardiomyopathy, because no specific RCT exist to date. Following the discontinuation of the RECOVER-IV trial (NCT05506449), only the ULYSS trial (NCT05366452) is currently underway to attempt to confirm the DanGer-Shock results and potentially extend its findings to the non-STEMI CS population. Conclusion In conclusion, our meta-analysis indicates that the use of mFP in STEMI-related CS is associated with reduced all-cause 6 month mortality, albeit with increased adverse events such as renal replacement therapy or major bleedings. Further trials are warranted to provide better stratification of the mFP benefit–risk balance to select the best candidates who will derive the greatest benefit regarding myocardial recovery while minimizing adverse events.