Impella Pump for MI With Cardiogenic Shock Again Fares Poorly vs IABP in Study

Marilynn Larkin

July 26, 2022

Another observational study has questioned whether Impella ventricular assist pumps (Abiomed) should be used in patients with acute myocardial infarction (MI) complicated by cardiogenic shock (CS), at least compared with an intra-aortic balloon pump (IABP), the most common alternative.

Management with an Impella device, compared with IABP support, was associated with excess risks of bleeding complications, renal injury, and death, both short-term and at 1 year, in a new analysis of American claims data from such patients undergoing supported percutaneous coronary intervention (PCI).

Total healthcare costs during hospitalization were also significantly higher with Impella, which the literature often describes as an intravascular microaxial left ventricular assist device (LVAD).

Clinical outcomes in the analysis are largely consistent with previous observational studies and other data that have indicated similar relative harms from Impella during the hospitalization of patients with acute MI and CS. But the current analysis adds by suggesting such outcomes extend out to 1 year.

Although such results could conceivably vary across some patient subgroups, "currently, there are not enough data to definitively say if there is a specific patient phenotype that would benefit more from a specific device," said P. Elliott Miller, MD, MHS, Yale School of Medicine, New Haven, Connecticut, who is lead author on the analysis published online July 18 in JAMA Internal Medicine.

The current findings, he told | Medscape Cardiology, "are consistent with several other observational studies, and should be strongly considered when guideline writers are making recommendations." But a randomized trial is needed to clarify these issues, he added, noting that the report concludes that "there is an urgent need for properly powered randomized clinical trials to better inform clinical decisions in this critically ill patient population."

In Hospital, 30 Days, and 1 Year

The group looked at claims data for 3077 patients, about 28% of whom were female, who underwent PCI for acute MI with CS from 2015 to 2020. They assembled 817 propensity-matched pairs of patients who received PCI with mechanical circulatory support (MCS) using an Impella device or IABP.

The odds ratios (OR) or hazard ratios (HR) for mortality for those receiving Impella, compared with IABP, were:

  • OR, 1.63 (95% CI, 1.32 - 2.02) in hospital

  • OR, 1.71 (95% CI, 1.37 - 2.13) at 30 days

  • HR, 1.44 (95% CI, 1.21 - 1.71) at 1 year

Other 30-day outcomes for Impella vs IABP included:

  • OR, 1.35 (95% CI, 1.04 - 1.76) for bleeding

  • OR, 1.88 (95% CI, 1.30 - 2.73) for renal replacement therapy

  • +$51,680 for mean total healthcare costs

Corresponding outcomes at 1 year for Impella vs IABP were:

  • HR, 1.36 (95% CI, 1.05 - 1.75) for bleeding

  • HR, 1.95 (95% CI, 1.35 - 2.83) for renal replacement therapy

  • +$46,609 for mean total healthcare costs

The findings were similar in various sensitivity analyses, including one that involved the entire 3077-patient cohort from which the propensity-matched pairs were taken, adjusted for the propensity-matching criteria, the group reports.

"This is a retrospective observational study with a very significant chance of indication bias," Riyaz Bashir, MD, Temple University, and director of vascular and endovascular medicine at Temple University Hospital, Philadelphia, said for | Medscape Cardiology. "The study is very good, but hypothesis-generating, and should not change guidelines."

Bashir, not connected to the analysis, agreed on the need for large randomized controlled trials to determine the better MCS strategy. He said the microaxial LVAD would likely be preferable to IABP for the subgroup of acute MI patients with CS who "are so sick that the additional 0.5 liters of cardiac output augmentation given by an IABP isn't enough. You want to be able to get through the case and finish treating the patient. And that would be the time when the LVAD should be the first device implanted."

An accompanying editorial highlights the need for reforms in the US Food and Drug Administration approval and postmarket surveillance processes for invasive devices used in the treatment of acute MI with CS, as well as more robust surveillance. But it also advocates for a halt to this use of the microaxial LVAD in clinical practice.

"Until such reforms are implemented, and given the preponderance of existing evidence, use of the intravascular microaxial LVAD in individuals presenting with myocardial infarction with cardiogenic shock should be restricted to patients enrolled in [a randomized controlled trial]," write the authors of the editorial, led by Gene Hu, MD, Anand R. Habib, MD, MPhil, and Rita F. Redberg, MD, MSc, all from the University of California, San Francisco. Hu is an editorial fellow and Redberg the editor of JAMA Internal Medicine.

But Timothy Henry, MD, commenting on the study for | Medscape Cardiology, pointed out the position taken by last year's American Heart Association (AHA) scientific statement on the invasive management of acute MI complicated by CS, for which he was lead author.

The statement acknowledges studies in the literature that uphold Impella-supported PCI for MI with CS, as well as those suggesting harm, and states that such research should "inform the management" of such patients. Meanwhile, it continues, "there is cause for caution, with observational data illustrating heterogeneity in safety and outcomes of MCS use in the context of steadily growing use."

As such, Henry said, it's important to tailor MCS use and device selection for individual patients with acute MI complicated by CS. Such individualized care, the scientific statement states, considers "the underlying mechanisms of shock, anticipated benefits and risks of MCS, and ideal timing for device insertion."

Similar positions were taken by an AHA policy statement, also published in 2021, that counted Henry among its authors. Impella, IABP, and other MCS devices should be available for the management of patients with acute MI and CS at experienced centers, it states. "However, it should be noted that robust data from adequately powered randomized trials evaluating the risks and benefits of mechanical circulatory support are lacking."

Therefore, says the statement, with lead author Alice K. Jacobs, MD, Boston University and Boston Medical Center, Massachusetts, an individualized approach to care with consideration of early mechanical support before PCI for patients with refractory hemodynamic instability despite aggressive medical therapy is recommended." For those who present with or develop CS in the hospital, it states, "treatment with advanced mechanical circulatory support devices should be initiated early."

Miller reported no conflicts; disclosures for the other authors are in the report. Henry had no disclosures in the AHA scientific statement. Bashir is on record as having no relevant disclosures.

JAMA Intern Med. Published online July 18, 2022. Abstract, Editorial

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