ECMO for Shock in Acute MI Won't Help, May Harm: ECLS-SHOCK

Patients with acute myocardial infarction (MI) and shock are often put on extracorporeal membrane oxygenation (ECMO) support before heading to the catheterization laboratory. But the practice, done routinely, doesn't have much backing from randomized trials. Now it's being challenged by one of the largest such studies to explore the issue.

In a new multicenter trial, there was no survival advantage at 30 days to early use of ECMO in such patients with cardiogenic shock compared to a usual-care medical approach. ECMO-managed patients, moreover, had sharply increased risks for moderate and severe bleeding and vascular complications.

A Challenge to Common Practice

The results undercut guidelines that promote mechanical circulatory support in MI-related cardiogenic shock primarily based on observational data, and they argue against what's become common practice, said Holger Thiele, MD, Heart Center Leipzig, University of Leipzig, Germany.

Such use of ECMO could well offer some type of advantage in MI-related shock, but the data so far don't show it, Thiele said at a press conference on the new study, called ECLS-SHOCK, at the European Society of Cardiology (ESC) 2023 Congress in Amsterdam, the Netherlands. He formally presented the trial at the Congress on August 26 and is lead author on its simultaneous publication in the New England Journal of Medicine.

Almost half of the trial's patients died, whether or not they had been put on ECMO. All-cause mortality at 30 days, the primary endpoint, was about the same, at 47.8% and 49.0% for the ECMO and usual-care groups, respectively.

Meanwhile, Thiele reported, risks for moderate or severe bleeding more than doubled and serious peripheral vascular complications almost tripled with addition of ECMO support.

The findings, he noted, are consistent with a new meta-analysis of trials testing ECMO in MI-related shock that also showed increases in bleeding with survival gains using the devices. Thiele is senior author on that report, published August 26 in The Lancet to coincide with his ECLS-SHOCK presentation.

Would Any Subgroups Benefit?

Importantly, he told theheart.org | Medscape Cardiology, ECMO's failure to improve 30-day survival in the trial probably applies across the spectrum of patients with MI-related shock. Subgroup analyses in both ECLS-SHOCK and the meta-analysis didn't identify any groups that benefit, Thiele observed.

For example, there were no significant differences for the primary outcome by age, sex, whether the MI was ST-segment elevation MI or non–ST-segment elevation MI or anterior or nonanterior, or whether the patient had diabetes.

If there is a subgroup in MI-related shock that is likely to benefit from the intervention with lower mortality, he said, "it's less than 1%, if you ask me."

An accompanying editorial essentially agreed, arguing that ECLS-SHOCK contests the intervention's broad application in MI-related shock without shedding light on any selective benefits.

"Will the results of the ECLS-SHOCK trial change current clinical practice? If the goal of [ECMO] is to improve 30-day mortality, these data should steer interventional and critical care cardiologists away from its early routine implementation for all or even most patients with myocardial infarction and cardiogenic shock," the editorialists say.

"There will be some patients in this population for whom [ECMO] is necessary and lifesaving, but the results of the ECLS-SHOCK trial do not tell us which ones," write Jane A. Leopold, MD, Brigham and Women’s Hospital, Boston, Massachusetts, and Darren B. Taichman, MD, PhD, Penn Presbyterian Medical Center, Philadelphia, Pennsylvania.

"For now, the best course may be to reserve the early initiation of [ECMO] for those patients with infarct-related cardiogenic shock in whom the likely benefits more clearly outweigh the potential harms. We need further studies to tell us who they are," write Leopold and Taichman, who are deputy editors with the New England Journal of Medicine.

ECLS-SHOCK randomly assigned 420 patients with acute MI complicated by shock and slated for coronary revascularization to receive standard care with or without early ECMO at 44 centers in Germany and Slovenia. Their median age was 63 years, and about 81% were men.

The relative risk (RR) for death from any cause, ECMO vs usual care, was flatly nonsignificant at 0.98 (95% CI, 0.80 - 1.19; P = .81).

ECMO came at the cost of significantly more cases of the primary safety endpoint, moderate or severe bleeding by Bleeding Academic Research Consortium criteria. That endpoint was met by 23.4% of ECMO patients and 9.6% of the control group, for an RR of 2.44 (95% CI, 1.50 - 3.95).

Rates of stroke or systemic embolization were nonsignificantly different at 3.8% and 2.9%, respectively (RR, 1.33; 95% CI, 0.47 - 3.76).

Speaking with theheart.org | Medscape Cardiology, Sripal Bangalore, MD, MHA, pointed out that only 5.8% of the ECMO group but about 32% of those managed with usual care received some form of left ventricular (LV) unloading therapy.

Such measures can include atrial septostomy or the addition of an intra-aortic balloon pump or percutaneous LV-assist pump.

Given that ECMO increases afterload, "which is physiologically detrimental in patients with an ongoing MI, one is left to wonder if the results would have been different with greater use of LV unloading," said Bangalore, of Langone Health and NYU School of Medicine, New York City, who isn't associated with ECLS-SHOCK.

Also, he pointed out, about 78% of the trial's patients had experienced some degree of cardiopulmonary resuscitation despite exclusion of anyone who had undergone it for more than 45 minutes. That may make the study more generalizable but also harder to show a benefit from ECMO. "The overall prognosis of that subset of patients despite heroic efforts is bleak at best."

Thiele had no disclosures; statements for the other authors can be found at nejm.org. Bangalore has previously disclosed financial relationships with Abbott Vascular, Amgen, Biotronik, Inari, Pfizer, Reata, and Truvic. Leopold reports grants from Astellas and personal fees from United Therapeutics, Abbott Vascular, and North America Thrombosis Forum. Leopold and Taichman both report employment by the New England Journal of Medicine.

European Society of Cardiology (ESC) 2023 Congress. Hot Line 3. Presented August 26.

ECLS-SHOCK: N Engl J Med. Published online August 26, 2023. Abstract, Editorial

Meta-analysis: Lancet. Published online August 26, 2023. Abstract

Follow Steve Stiles at @SteveStiles2. For more from theheart.org | Medscape Cardiology, follow us on X (formerly known as Twitter) and Facebook.

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