SCAI SHOCK: Update Refines Cardiogenic Shock Classification

First released in 2019, the Society for Cardiovascular Angiography and Interventions (SCAI) cardiogenic shock categories have gotten a rethink, one that adds nuance to aid decision-making and incorporates validation data.

Attendees at the TCT 2021 meeting got a sneak peek at updates to the expert consensus document. Now full details are being published in the newly launched Journal of the Society for Cardiovascular Angiography and Interventions.

Srihari S. Naidu, MD (Westchester Medical Center, Valhalla, NY), who led the latest version and also took part in the original effort, told TCTMD that from the outset there was enthusiasm for the SCAI SHOCK classification system. “Essentially, when we first took a stab at this, I think it really caught like wildfire because there was nothing out there. There was nothing that would allow people to even communicate. And so people were happy with just having a lexicon itself,” he said.

The 2022 iteration offers more granularity, Naidu explained, drawing attention to its main additions:

• A three-axis model illustrating cardiogenic shock evaluation and prognostication. Beyond severity, which sits at the top of the model, there are two other arrows: risk modifiers and phenotype/etiology.
• Revisions to the table listing the various shock categories. The streamlined table now puts “things in context in terms of what is typically seen versus what might be seen,” he said.
• Clarification on cardiac arrest as a risk modifier. To reflect the heterogeneity of cardiac arrest, the document now specifies that neurologic status (awake or comatose), plus the physiological impact of the arrest, should be considered.

One thing that has stayed the same are the shock categories, ranging from A (At Risk) to B (Beginning), C (Classic), D (Deteriorating), and E (Extremis).

Holger Thiele, MD (Heart Center Leipzig, Germany), another co-author of both iterations, pointed out that “the prior version was more based on expert opinion in the situation, and there was really no evidence to support any of the SCAI SHOCK stages.” Since then, several analyses have lent support to the classification but also revealed a lot of heterogeneity with respect to mortality across the shock spectrum, he said. As a remedy, they aimed to be more specific about what constitutes each category.

Essentially, when we first took a stab at this, I think it really caught like wildfire because there was nothing out there. There was nothing that would allow people to even communicate. Srihari S. Naidu

Naidu, too, noted that while ensuing studies showed the SCAI categories “tracked quite well in all different patient groups, there’s quite a variability in terms of the predicted mortality or the predicted survival.

“So it was one part of the picture, but not the full picture,” he continued. “We wanted to get ahead of the curve and realize that, for this to be very impactful and to continue to make inroads into cardiology—and cardiac shock, in general, regardless of which practitioner is taking care of these patients—it really had to ultimately not just be easy to use and available, but it had to be effective” in risk stratification and mortality prediction, and also when used in clinical trials.

An improved ability to estimate risk can guide treatment decisions, Naidu noted. “Then you can start using it to say, ‘Well, we know that this kind of patient has a mortality of 80 to 90%—it's not 40 to 90, it’s 80 to 90—and we have to make some serious decisions about transfer versus end-of-life care and those types of issues.”

They sought to make the SCAI SHOCK framework apply throughout the continuum of care to be helpful across diverse hospital settings, not just large tertiary care centers.

Additionally, Naidu stressed, a wide swath of professional societies across specialties have endorsed the update: the American College of Cardiology, American College of Emergency Physicians, American Heart Association, European Society of Cardiology Association for Acute Cardiovascular Care, International Society for Heart and Lung Transplantation, Society of Critical Care Medicine, and Society of Thoracic Surgeons.

‘A Huge Advance’

William O'Neill, MD (Henry Ford Hospital, Detroit, MI), who co-authored the 2019 document, told TCTMD the 2022 update represents “a huge advance in treatment and research for cardiogenic shock, because one of things that’s really confounded us is that there’s lots of experiences from multiple centers,” with variations in patients, practices, and outcomes.

“Not every shock patient is the same,” said O’Neill, adding that the SCAI SHOCK categories “help us provide a little bit of a level playing field for what the prognosis is based on presentation.”

Maya Guglin, MD (Indiana University Health, Indianapolis), speaking with TCTMD, also praised the update. “They refined the criteria,” she said. “They made it more succinct, more straightforward, [and] more, I would say, data-driven. So I think there is improvement from the original classification.”

Guglin, an advanced heart failure cardiologist, said she uses the SCAI SHOCK system in her own work. “It is very logical, so I see clinicians using it increasingly,” she commented, pointing to the paper’s Table 3, which describes shock stages based on physical exam, biomarkers, and hemodynamics, as “extremely helpful.”

Beyond the unified approach to describing severity, the consensus document helps standardize when patients should be referred to specialized centers through a hub-and-spoke model, said Guglin. “What is extremely important to realize is that when [shock] progresses to stage D, which is deteriorating despite pharmacological or mechanical circulatory support, it is time to refer the patient to a higher order of center.” Some centers may have access to some kinds of support, she added, but not the whole spectrum of options.

From Theory to Practice

Overall, Naidu said, feedback on the update thus far has been good, from clinicians and researchers, as well as from industry. For the latter, having a classification system is a positive thing, he added, in that enables trialists to target specific scenarios that might benefit from therapy.

Indeed, the classification system is meant to generate consistency among studies. Thiele pointed out DOREMI, published last fall in the New England Journal of Medicine, is “the first time that the SCAI SHOCK stage definition has been applied in a randomized trial.” And, as Naidu noted, the SCAI-B study of intra-aortic balloon pump in acute MI is slated to do the same.

Thiele predicted that as studies using the categories begin to accumulate, the feedback they provide will enable further revisions to SCAI SHOCK.

Researchers of the National Cardiogenic Shock Initiative (NCSI), which released final results earlier this year, retrospectively applied the SCAI SHOCK categories to their own data set, O’Neill noted. They found they had no patients in stages A and B. One-third were stage C, while 10% were D and a full 40% were E. “So we were treating really high-risk patients with crash-and-burn cases,” he said. Despite this, “they actually did very well, at almost a 60% survival in class E. So I think that it really does show that if you use these tools, you'll be able to have apples-to-apples comparison with folks.”

[The categories] help us provide a little bit of a level playing field for what the prognosis is based on presentation. William O’Neill

Another contribution of the document, said O’Neill, is that it may further discussions with the US Food and Drug Administration on how best to obtain informed consent during such a rapidly changing, complex scenario. Patients defined as having stage E shock, as of now rarely enrolled in randomized trials, might be the “perfect population” in which to explore new strategies for consent, he added.

“One of the reasons that they've been able to do multiple randomized trials in Germany and Europe is that the format there is two doctors agree that the patient qualifies for the trial and then they get into the trial,” he explained. Only afterwards do the researchers go back to the patient or their family to ask if they’d like to continue participating. “Here in the United States, you have to find someone to consent, and it's just really traumatic for [them].”

According to O’Neill, the RECOVER IV investigators are in active discussions with the FDA about the possibility of it being an Exception From Informed Consent (EFIC) trial. “It’s a really incredibly elaborate thing. It’s going to take a year to set it up, but I think it really will dramatically facilitate enrollment,” he said. Both RECOVER IV and the NCSI’s CERAMICS registry, set to begin in a few months, will prospectively use the SCAI categories, O’Neill added.