Small Fraction of STEMI Patients With Shock Meet DanGer Criteria

Just one in three North American patients admitted to the cardiac intensive care unit (CICU) for STEMI complicated by cardiogenic shock (STEMI-CS) would meet the high bar set for entry into the DanGer Shock trial, according to a report from the Critical Care Cardiology Trials Network (CCCTN) Registry. What’s more, these STEMI-specific cases make up just 5% of the overall cardiogenic shock population.

The data, published online Wednesday in the Journal of the American College of Cardiology, confirm the caveat raised by many in the wake of DanGer Shock’s long-awaited results: that the survival benefit seen with Impella (Abiomed) in the trial cannot be extrapolated to other patient populations.

DanGer Shock principal investigator Jacob Eifer Møller, MD, PhD, DMSc (Copenhagen University Hospital Rigshospitalet, Denmark), when presenting the data this spring, stressed that their positive finding for microaxial flow pump (mAFP) support did not apply to patients with out-of-hospital cardiac arrest (OHCA), non-ST-segment elevation MI, and nonischemic cardiogenic shock. The study’s entry criteria also included specific cutoffs for timing of presentation, lactate levels, and left ventricular ejection fraction.

Connor G. O’Brien, MD (University of California San Francisco), who led the analysis of the CCCTN data, told TCTMD that this cautious perspective was appropriate. “The investigators, I would say, have been very, very responsible and great about moderating excitement about results that are first in class and high quality, but also limited in scope,” he said.

O’Brien pointed out that their observational study provides a useful snapshot of what sorts of shock occur—many cardiologists and physicians in the community, unless they’re practicing at large centers, “don't see a high volume of shock across its spectrum,” he said.

Awareness of shock’s scope, said O’Brien, “helps people to keep in mind how to reach out for help and make sure that they're getting the support they need to care for these patients rather than dropping an Impella on them.” He added that this knowledge also helps clinicians understand when it makes sense to escalate support beyond an Impella CP to a more powerful Impella or other method, like extracorporeal membrane oxygenation.

We’re not trying to do high-risk interventional procedures in patients who are not sick enough to warrant that device. Srihari Naidu

Srihari Naidu, MD (Westchester Medical Center, Valhalla, NY), president-elect of the Society for Cardiovascular Angiography & Interventions (SCAI), isn’t dissuaded by the fact that only one in twenty of the cardiogenic shock cases identified in the registry are STEMI-related. “That is the patient population that we're most interested in for this device, because this device is anti-ischemic and also facilitates PCI. . . . So really the denominator is that 5% of those [cardiogenic shock] patients,” he explained.

Naidu said, too, that the CCCTN data support the utility of SCAI’s classification system for cardiogenic shock: essentially the DanGer criteria mirror the SCAI SHOCK categories C, D, and E, where patients would be expected to benefit from advanced therapies. “We’re not trying to do high-risk interventional procedures in patients who are not sick enough to warrant that device,” he commented, adding that by excluding the less-severe cases, DanGer Shock “did hit the target” by enrolling the right population.

Møller, in an email to TCTMD, said that the one in three ratio for STEMI-CS in North America “is spot on” with what they’ve found in European data. He reiterated the need for clinicians to carefully interpret DanGer Shock’s results by keeping its population in mind, saying, “This is the message I have to tried to get out from the very beginning.”

CCCTN Registry

O’Brien et al analyzed data from the CCCTN Registry for 20,519 CICU admissions that took place in the US and Canada between 2019 and 2023. To count as an admission for cardiogenic shock, the following criteria had to be met:

• Systolic BP < 90 mm Hg for ≥ 30 minutes, or vasopressors or inotropes to maintain systolic BP ≥ 90 mm Hg
• Evidence of end-organ hypoperfusion, with a cardiogenic cause

There were 4,842 cases of cardiogenic shock, of which 757 (16%) were in the context of STEMI. DanGer Shock also included specific enrollment criteria for timing, so the researchers further winnowed down the STEMI-CS group to the 623 patients within 24 hours of shock onset. Among them, 430 presented with lactate ≥ 2.5 mmol/L; within this group, 371 met the DanGer Shock criteria of LVEF < 50%.

In the end, 245 (32%) of the STEMI-CS patients—amounting to 5% of the overall cardiogenic shock population—in the CCCTN Registry would have qualified for enrollment in the trial.

The investigators, I would say, have been very, very responsible and great about moderating excitement about results that are first in class and high quality, but also limited in scope. Connor G. O’Brien

“DanGer Shock provides high-quality evidence that mAFP support improves survival in selected patients with STEMI-CS in the early phases of shock. The narrow scope of eligibility for the trial is important for the interpretation and clinical application,” the researchers write, adding, “Successful utilization of mAFP will be contingent upon appropriate patient selection with counterbalancing of risks. Such success may depend on early implementation of support before development of irreversible end-organ dysfunction.

Reassuringly, the percentage of STEMI-related cardiogenic shock cases in the CCCTN Registry that met DanGer Shock’s criteria was quite similar to the percentage of screened patients who ultimately enrolled in the trial, Naidu pointed out.

He also noted that this segment of the whole is larger than what has been seen in earlier trials that have been used to justify clinical decision-making—COURAGE and ISCHEMIA, for example, each enrolled around one in 10 screened patients.

Møller said that even though DanGer Shock applies to the patient profile they studied, it may still be possible to demonstrate that mAFP can aid other groups. Citing a meta-analysis recently published in the Lancet, he said that there’s evidence suggesting selected OHCA patients might benefit. “But to test this will likely require much larger sample sizes, and the risk of complications will be the same,” said Møller.

The upcoming TCT 2024 meeting, he added, will feature fresh analyses of the DanGer data.

O’Brien said it’s important to continue building the evidence base, so that clinicians can benefit from having a strong grasp of the field’s nuances. In an acute setting like the cath lab, “it’s hard to intervene, decide on the right support, and be critical of that data all at the same time,” he said.

While the STEMI-CS patients who meet the DanGer Shock profile are likely to benefit from Impella CP, other shock patients may present with congestive physiology or progression of chronic disease that would require a different strategy. “We need to continue to design trials and think about how to create evidence to figure out what the right thing to do for those patients is, because it's going to be a very different group [with] more heterogeneous results. It’s going to be a very hard thing to study,” O’Brien said.