Impella Pump Improves Survival in STEMI-Related Cardiogenic Shock

ATLANTA — Routine use of the Impella CP microaxial flow pump significantly improved survival in patients with infarct-related cardiogenic shock, the randomized DanGer Shock trial showed.

In more than 350 patients receiving standard treatment for ST-segment elevation myocardial infarction (STEMI)-related cardiogenic shock, the risk for death over 6 months was reduced by an absolute 13% with the device versus standard care alone, which usually means immediate revascularization of culprit lesions (45.8% vs 58.5%; HR 0.74, 95% CI 0.55-0.99, P=0.04), reported Jacob Møller, DMSc, of Odense University Hospital in Denmark.

Eight patients needed to receive the microaxial flow pump to save one life, according to results presented during a late-breaking presentation here at the American College of Cardiology (ACC) annual meeting and published in the New England Journal of Medicine.

When people experience STEMI — a so-called big heart attack — cardiogenic shock occurs in about 10% of cases, Møller said. And as shown, the mortality rate in these individuals reaches about 50%.

“This is the first time in a very long time that we have a positive study for managing cardiogenic shock,” he said. “I think this will be a routine device that will be used in these desperately ill patients.”

While saving lives, use of the pump did not come without a cost in adverse events, Møller told MedPage Today. Among the more serious challenges was an increase in patients who required renal-replacement therapy — usually temporary dialysis.

Overall, 41.9% of patients in the Impella CP group required renal-replacement therapy, as compared with 26.7% of patients in the group receiving standard care alone (relative risk [RR] 1.98, 95% CI 1.27-3.09).

“The microaxial pump causes a lot of stress on red blood cells, which in turn can cause kidney damage,” Møller said. Of the 75 patients receiving the microaxial flow pump who required renal support, all but three recovered renal function.

For the overall composite safety endpoint, 24% of patients in the Impella CP group and 6.2% of those in the standard-care group experienced an event (RR 4.74, 95% CI 2.36-9.55).

“This is a groundbreaking trial because the last trial to show a positive effect in cardiogenic shock was in 1999,” Robert Roswell, MD, of Northwell Health/Zucker School of Medicine at Hofstra University in Hempstead, New York, said at an ACC press conference. “So it is 25 years later that we actually have an intervention that can reduce mortality. This was also a difficult trial that took 10-12 years to recruit patients.”

“This study signals that it is important to first stabilize the patients hemodynamically before opening those blocked vessels,” said Roswell, who was not involved in the research. “A lot of practice will be changing because of this trial. We do see a lot of complications in the intensive care units related to hemolysis and limb ischemia with the devices, and we wonder if these risks are worth it. We now see that they are, because we are saving lives.”

In response to questions, Møller said that device failures reported with various Impella devices were not seen in the trial. “We only had about 300 patients in our study, so it is possible that these problems might be seen in much larger trials,” he cautioned.

In an editorial accompanying the study publication, Sunil Rao, MD, of NYU Grossman School of Medicine/New York University Langone Health in New York City, said that while the intervention reduced mortality, unresolved issues remain “given the rapidly evolving nature of mechanical circulatory support use.”

“These include the timing of microaxial-flow-pump placement (before primary percutaneous coronary intervention or after opening the infarct-related artery), the incorporation of shock protocols or a ‘shock team’ as a standardized approach, and the combined use of the microaxial flow pump with other mechanical circulatory support,” said Rao. “Some of these issues are being addressed in ongoing randomized trials, such as RECOVER IV.”

“Until these data become available, the DanGer Shock trial is evidence of progress in the treatment of patients with [acute myocardial infarction with cardiogenic shock] whose peripheral vessels are able to accommodate the microaxial flow pump in the context of safe vascular access and closure and standardized weaning and removal protocols,” Rao added.

DanGer Shock enrolled patients with infarct-related cardiogenic shock at 14 centers in Denmark, Germany, and the United Kingdom from 2013 to 2023, though most were randomized after 2019; the analysis included 355 patients.

Participants were randomized before, during, or up to 12 hours after receiving treatment in the cardiac catheterization laboratory, depending on when cardiogenic shock was diagnosed. Those who suffered out-of-hospital cardiac arrest with coma and increased risk of brain damage were excluded from the trial, as were those with overt right ventricular failure.

As per the trial protocol, patients underwent a revascularization procedure and received pressor support if indicated. In the patients assigned to receive the microaxial flow pump, the device was to be placed immediately after randomization and run at the highest possible performance level for at least 48 hours unless complications occurred. In the event of hemodynamic instability, treatment could be escalated to additional mechanical circulatory support after randomization in either group.

In the pump group, treatment could be escalated to the placement of an Impella 5.0 Impella RP device or extracorporeal life support. In the standard-care group, extracorporeal life support was recommended, although placement of an Impella 5.0 device was allowed. Any use of an Impella CP device for hemodynamic instability in the standard-care group was considered to be a protocol violation.

The primary endpoint was death from any cause through 180 days. Møller also reported a reduction in a composite cardiac endpoint for patients who received the Impella CP pump (HR 0.72, 95% CI 0.55-0.95), an endpoint that included additional mechanical heart support, heart transplant, or death. A numerical difference in the number of days out of hospital also favored the pump group but was not significant.

The composite safety endpoint included failure of the microaxial flow pump and cases of severe bleeding, limb ischemia, hemolysis, or worsening of aortic regurgitation. The Impella CP group had higher rates of moderate or severe bleeding (21.8% vs 11.9% in the standard-care alone group), limb ischemia (5.6% vs 1.1%), and sepsis with positive blood culture (11.7% vs 4.5%).

Some noted limitations included the strict enrollment criteria, that the trial was not blinded, the small number of centers included, and that race or ethnicity data were not collected.

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