Safety of percutaneous microaxial LVAD for cardiogenic shock uncertain vs. other options
Key takeaways:
- In some analyses, percutaneous microaxial LVAD for cardiogenic shock was tied to worse outcomes vs. medical therapy and intra-aortic balloon pump.
- Too many confounding variables affected the analysis.
For patients presenting with acute MI with cardiogenic shock, the safety of percutaneous microaxial left ventricular assist device use vs. other treatments could not be well established using observational Medicare data, findings show.
Although some analyses hinted at greater 30-day mortality risk among those treated using the percutaneous microaxial LVAD (Impella, Abiomed) compared with medical therapy and intra-aortic balloon pump (IABP), the correlation was too imprecise due to varying patient illness, among other confounders, according to data published in JAMA Cardiology.
Image: Adobe Stock
“Recent observational analyses of claims and registry data have raised concerns regarding increases in the risk of death and bleeding associated with percutaneous microaxial LVAD use in patients undergoing PCI. Other observational analyses have suggested improved outcomes with use of percutaneous microaxial LVAD prior to PCI. Critiques of these analyses have highlighted methodological concerns, particularly the potential for confounding by unmeasured variables,” Zaid I. Almarzooq, MBBCh, MPH, clinical fellow in medicine at the Richard A. and Susan F. Smith Center for Outcomes Research in Cardiology at Beth Israel Deaconess Medical Center and the division of cardiology at Brigham and Women’s Hospital, and colleagues wrote. “The primary objective of this study was to explore various approaches to assess the potential effect of the percutaneous microaxial LVAD vs. alternative treatments, including IABP or no mechanical circuitry support device, using an observational administrative database of Medicare fee-for-service beneficiaries undergoing PCI for acute MI with cardiogenic shock.”
For the present analysis, Almarzooq and colleagues considered all Medicare beneficiaries hospitalized with acute MI with cardiogenic shock who underwent PCI from October 2015 to December 2019.
Thirty-day all-cause mortality and readmissions were compared among 23,478 patients who received treatment using a percutaneous microaxial LVAD or alternative treatments including medical therapy and IABP (mean age, 74 years; 61% men). Overall, 17.3% of patients received percutaneous microaxial LVAD on the day of PCI and the remainder did not (35.9% IABP; 64.1% medical therapy).
Percutaneous microaxial LVAD and 30-day mortality
After conducting inverse probability of treatment weighting analysis and grace period analyses, the researchers reported that percutaneous microaxial LVAD treatment was associated with greater adjusted risk for 30-day mortality compared with the alternative treatments (risk difference, 14.9%; 95% CI, 12.9-17). Results were similar after instrumental variable analysis (risk difference, 13.5%; 95% CI, 3.9-23.2); however, Almarzooq and colleagues posited that these results were affected by confounding by measures of illness severity not available in the data, and patient and hospital characteristics that suggested possible confounding by unmeasured variables.
Association ‘too imprecise to draw meaningful conclusions’
After instrumented difference-in-differences analysis, the researchers reported that the association between percutaneous microaxial LVAD and mortality was too imprecise to draw a definitive decision.
“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,” the researchers wrote. “The distribution of patient and institutional characteristics between treatment groups or groups defined by changes in treatment use over time, combined with clinical knowledge of illness severity factors not captured in the data, suggested violations of key assumptions needed for valid causal inference with different observational analyses. Our findings suggest that commonly used observational data sets cannot support a causal interpretation of the estimates produced by different analyses used for the evaluation of percutaneous mechanical support devices in cardiogenic shock. Randomized clinical trials will allow valid comparisons across candidate treatment strategies and help resolve ongoing controversies.”
Collapse