Comparative Effectiveness of Percutaneous Microaxial Left Ventricular Assist Device vs Intra-Aortic Balloon Pump or No Mechanical Circulatory Support in Patients With Cardiogenic Shock

Abstract

ImportanceRecent studies have produced inconsistent findings regarding the outcomes of the percutaneous microaxial left ventricular assist device (LVAD) during acute myocardial infarction with cardiogenic shock (AMICS).ObjectiveTo compare the percutaneous microaxial LVAD vs alternative treatments among patients presenting with AMICS using observational analyses of administrative data.Design, Setting, and ParticipantsThis comparative effectiveness research study used Medicare fee-for-service claims of patients admitted with AMICS undergoing percutaneous coronary intervention from October 1, 2015, through December 31, 2019. Treatment strategies were compared using (1) inverse probability of treatment weighting to estimate the effect of different baseline treatments in the overall population; (2) instrumental variable analysis to determine the effectiveness of the percutaneous microaxial LVAD among patients whose treatment was influenced by cross-sectional institutional practice patterns; (3) an instrumented difference-in-differences analysis to determine the effectiveness of treatment among patients whose treatment was influenced by longitudinal changes in institutional practice patterns; and (4) a grace period approach to determine the effectiveness of initiating the percutaneous microaxial LVAD within 2 days of percutaneous coronary intervention. Analysis took place between March 2021 and December 2022.InterventionsPercutaneous microaxial LVAD vs alternative treatments (including medical therapy and intra-aortic balloon pump).Main Outcomes and MeasuresThirty-day all-cause mortality and readmissions.ResultsOf 23 478 patients, 14 264 (60.8%) were male and the mean (SD) age was 73.9 (9.8) years. In the inverse probability of treatment weighting analysis and grace period approaches, treatment with percutaneous microaxial LVAD was associated with a higher risk-adjusted 30-day mortality (risk difference, 14.9%; 95% CI, 12.9%-17.0%). However, patients receiving the percutaneous microaxial LVAD had a higher frequency of factors associated with severe illness, suggesting possible confounding by measures of illness severity not available in the data. In the instrumental variable analysis, 30-day mortality was also higher with percutaneous microaxial LVAD, but patient and hospital characteristics differed across levels of the instrumental variable, suggesting possible confounding by unmeasured variables (risk difference, 13.5%; 95% CI, 3.9%-23.2%). In the instrumented difference-in-differences analysis, the association between the percutaneous microaxial LVAD and mortality was imprecise, and differences in trends in characteristics between hospitals with different percutaneous microaxial LVAD use suggested potential assumption violations.ConclusionsIn observational analyses comparing the percutaneous microaxial LVAD to alternative treatments among patients with AMICS, the percutaneous microaxial LVAD was associated with worse outcomes in some analyses, while in other analyses, the association was too imprecise to draw meaningful conclusions. However, the distribution of patient and institutional characteristics between treatment groups or groups defined by institutional differences in treatment use, including changes in use over time, combined with clinical knowledge of illness severity factors not captured in the data, suggested violations of key assumptions that are needed for valid causal inference with different observational analyses. Randomized clinical trials of mechanical support devices will allow valid comparisons across candidate treatment strategies and help resolve ongoing controversies.

Impella and venoarterial extracorporeal membrane oxygenation in cardiogenic shock complicating acute myocardial infarction

“…For instance due to physicians' preferences and device availability, but also depending on cardiogenic shock severity (according to the SCAI classification), risk modifiers, and cardiogenic shock phenotype. 8,[19][20][21] Nevertheless, the Impella and VA-ECMO patients in our study were quite comparable with regard to comorbidities and cardiogenic shock aetiology, though Impella patients were older and presented less frequently after an OHCA. In contrast to previous literature, [21][22][23] in-hospital mortality rates in our cohort were comparable when OHCA patients were excluded from the analysis (Figure 3).…”

“…17 Like our study, higher in-hospital mortality in VA-ECMO patients compared to Impella patients has been reported previously. [16][17][18] However, as underscored by the recent publication of Almarzooq et al, 19 the differences in clinical outcomes between Impella and VA-ECMO in this observational data analysis must be interpreted in the setting of possible unmeasured and unadjusted confounders in patient and institutional characteristics. For instance due to physicians' preferences and device availability, but also depending on cardiogenic shock severity (according to the SCAI classification), risk modifiers, and cardiogenic shock phenotype.…”

Treatment of Acute Myocardial Infarction and Cardiogenic Shock: Outcomes of the RECOVER III Postapproval Study by Society of Cardiovascular Angiography and Interventions Shock Stage

“…A recent Medicare claims database analysis comparing percutaneous left ventricular assist device versus other treatments (medical therapy or IABP) for AMICS found that patients using percutaneous left ventricular assist devices had the highest 30‐day mortality; however, the population using left ventricular assist devices had more factors suggesting severe illness. 11 Furthermore, Almarzooq et al noted that potentially confounding differences in patient and provider factors between treatment groups render any causal inference as to the association between treatment and outcome invalid, pointing to the necessity for randomized controlled trials in this setting to perform a legitimate and conclusive comparison of these therapies. 11 …”

“… 11 Furthermore, Almarzooq et al noted that potentially confounding differences in patient and provider factors between treatment groups render any causal inference as to the association between treatment and outcome invalid, pointing to the necessity for randomized controlled trials in this setting to perform a legitimate and conclusive comparison of these therapies. 11 …”

Contemporary use of temporary mechanical circulatory support in infarct‐related cardiogenic shock: Time to stop and reflect?

“…The study is thus unsuited to assess benefit of the devices in terms of outcome, and the authors should be commended for refraining from flawed attempts to compare survival and complication rates across groups treated with or without MCS. 4 The strength and importance of this paper is the size and insight to the hospital course of AMICS treated with MCS in Europe. Crude mortality rates were seven-fold that of acute myocardial infarction without shock and providing insight in what can be considered as standard of care in AMICS.…”