Percutaneous Microaxial LVAD Linked to Worse Outcomes in Some Analyses in AMICS Patients

Percutaneous microaxial left ventricular assist devices (LVAD) are associated with worse outcomes compared with other treatments in patients with acute myocardial infarction with cardiogenic shock (AMICS) in some analyses, and the association is imprecise in other analyses, investigators reported in JAMA Cardiology.

The researchers evaluated multiple approaches to assess the potential effect of the percutaneous microaxial LVAD compared with alternative treatments, including intra-aortic balloon pump (IABP) or no mechanical circulatory support (MCS) device, with use of an observational administrative database of Medicare fee-for-service beneficiaries receiving percutaneous coronary intervention (PCI) for AMICS.

The participants were hospitalized with AMICS and received PCI from October 1, 2015, to December 31, 2019. Outcomes included all-cause mortality and the composite of all-cause mortality or readmission at 30 days post-PCI.

The analysis included 23,478 patients (60.8% men), with a mean (SD) age of 73.9 (9.8) years.

Baseline severity markers such as intubation, treatment with vasopressors, and use of right-sided heart catheterization were more common in patients treated with the percutaneous microaxial LVAD. These differences and the absence of information on other known markers of illness severity suggested considerable potential for residual unmeasured confounding, according to the researchers.

After weighting, the 30-day mortality risk post-PCI was increased among patients who initially received a percutaneous microaxial LVAD vs those who did not (53.8% [95% CI, 52.0%-55.7%] vs 38.9% [95% CI, 38.1%-39.7%], respectively), as was the risk of all-cause mortality or readmission at 30 days (58.8% [95% CI, 57.1%-60.6%] vs 45.6% [95% CI, 44.8%-46.4%], respectively).

The adjusted risk of mortality or readmission at 30 days post-PCI was greater with the initial treatment with percutaneous microaxial LVAD vs the other treatments:

• 57.8% (95% CI, 56.1%-59.5%) for percutaneous microaxial LVAD
• 47.8% (95% CI, 46.4%-49.1%) for IABP
• 43.9% (95% CI, 42.9%-44.9%) with no MCS

For the instrumental variable analysis, an increased 30-day mortality risk was observed with percutaneous microaxial LVAD compared with no percutaneous microaxial LVAD (difference, 13.5% [95% CI, 3.9%-23.2%]). The difference for the composite outcome of 30-day mortality or readmission of percutaneous microaxial LVAD vs no percutaneous microaxial LVAD was 9.1% (95% CI, −0.9% to 19.1%).

Significant variation in longitudinal trends was found for hospitals for percutaneous microaxial LVAD use and baseline characteristics among the groups, indicating potential violation of the assumption of no unmeasured differences in time-varying confounding among difference-indifferences design (DiD)–defined groups.

The risk difference for percutaneous microaxial LVAD compared with no percutaneous microaxial LVAD regarding 30-day mortality was -4.7% (95% CI, -15.9% to 39.9%) with use of moderately increasing vs decreasing percutaneous microaxial LVAD use hospitals as the DiD and 9.7% (95% CI, -15.9% to 39.9%) when using rapidly increasing vs moderately increasing percutaneous microaxial LVAD use hospitals as the DiD. Wide CIs were observed for estimated DiD treatment effects.

The researchers noted that their analysis focused on causal questions that can be answered in observational studies. Also, data were unavailable regarding changes in hemodynamic measurements, markers of tissue perfusion, and response to treatment, and the population included only patients enrolled in Medicare fee-for-service.

“Our findings suggest that commonly used observational datasets cannot support a causal interpretation of the estimates produced by different analyses used for the evaluation of percutaneous mechanical support devices in cardiogenic shock,” wrote the investigators. “Randomized clinical trials will allow valid comparisons across candidate treatment strategies and help resolve ongoing controversies.”

Disclosure: Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.