Abiomed’s Impella pump is being used across America to support patients with acute myocardial infarction with cardiogenic shock (AMICS) – but do we know it’s safe and effective?
The FDA teamed up with Boston-based researchers to tackle this question in response to previous studies suggesting that Impella is associated with worse outcomes.
- However, their results led to even more questions and prompted new debates about how we can properly assess devices used to treat sudden, life-threatening complications.
Using data from 23,478 Medicare patients with AMICS who underwent PCI, they found that, on the same day as the PCI procedures:
- 17.3% were supported with the Impella percutaneous microaxial LVAD
- 29.7% were supported with an intra-aortic balloon pump (IABP)
- 53% didn’t receive support from a mechanical circulatory device
The Impella patients were younger, more likely to be male, and more likely to have severe cases or CVD histories.
To overcome challenges associated with observational studies, the researchers used a range of advanced statistical techniques, finding that Impella patients had higher 30-day mortality rates based on:
- Inverse probability analysis (risk difference: 14.9%, 95% CI, 12.9%-17.0%)
- Grace period analysis w/ support within 48 hours of PCI (risk difference: 18.4%; 95% CI, 12.1%-24.7%)
- Instrumental variable analysis (risk difference: 13.5%; 95% CI 3.9%-23.2%)
However, when they compared hospitals with different levels of Impella adoption, they found such wide variations that they concluded that these outcomes were influenced by confounding factors (Impella patients are often sicker, usage/results vary by institution, and Medicare severity data is lacking). That also prompted the researchers to believe that observational data might not ever allow accurate comparisons.
The Takeaway
The study and editorial authors (and folks on CardioTwitter) all seemed to agree that this largely proves that physicians are more likely to use the Impella pump with more severe AMICS patients, and that it will take a RCT to know for sure how the Impella pump compares to alternatives.
The good news is two Impella RCTs are on the way, but the bad news is the Impella pump has been in use for years without RCT confirmation of its safety, efficacy, or most appropriate patients. The risk of patient recruitment bias with cardiogenic shock also has some doubting whether these future RCTs can be trusted when they do come out.
