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Percutaneous Microaxial LVAD for Patients With Cardiogenic Shock
Quick Takes
- 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.
- These findings suggest that commonly used observational data sets cannot support a causal interpretation of the estimates produced by different analyses used in the evaluation of percutaneous MCS devices in cardiogenic shock.
- Randomized clinical trials are indicated for valid comparisons across candidate treatment strategies and help resolve ongoing controversies.
Study Questions:
What is the potential effect of the percutaneous microaxial left ventricular assist device (LVAD) versus alternative treatments, including intra-aortic balloon pump (IABP) or no mechanical circulatory support (MCS) device?
Methods:
The investigators conducted a comparative effectiveness research study using Medicare fee-for-service claims of patients admitted with acute myocardial infarction with cardiogenic shock (AMICS) undergoing percutaneous coronary intervention (PCI) 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 PCI. Analysis took place between March 2021 and December 2022. Percutaneous microaxial LVAD versus alternative treatments (including medical therapy and IABP) were compared. The main outcome measures were 30-day all-cause mortality and readmissions.
Results:
Of 23,478 patients, 14,264 (60.8%) were male and the mean (standard deviation) 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% confidence interval [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.
Conclusions:
The authors report that in 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.
Perspective:
This study used different approaches in an attempt to answer a set of questions regarding the effect of percutaneous microaxial left ventricular assist MCS devices with 30-day outcomes of mortality and rehospitalization. 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. These findings suggest that commonly used observational data sets cannot support a causal interpretation of the estimates produced by different analyses used in the evaluation of percutaneous MCS devices in cardiogenic shock. Randomized clinical trials are indicated for valid comparisons and generate high-quality evidence across candidate MCS treatment strategies to help resolve ongoing controversies.
Clinical Topics: Acute Coronary Syndromes, Cardiac Surgery, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Aortic Surgery, Cardiac Surgery and Heart Failure, Acute Heart Failure, Mechanical Circulatory Support, Interventions and ACS
Keywords: Acute Coronary Syndrome, Critical Care, Heart-Assist Devices, Heart Failure, Intra-Aortic Balloon Pumping, Myocardial Infarction, Myocardial Ischemia, Outcome Assessment, Health Care, Patient Readmission, Percutaneous Coronary Intervention, Shock, Cardiogenic
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