SCAI Shock Definition Tracks Well With Mortality in Cardiac ICU

A new cardiogenic shock classification scheme proposed by the Society for Cardiovascular Angiography and Interventions (SCAI) earlier this year is useful for predicting short-term mortality risk across risk categories in patients admitted to the cardiac intensive care unit (CICU), new data show.

Unadjusted in-hospital mortality rates ranged from 3.0% among patients in the lowest-risk stage A to 67.0% among those in the highest-risk stage E (P < 0.001). Each shock stage was associated with an elevated risk of dying compared with the lowest-risk group after multivariable adjustment.

“We validated that the shock classification is indeed helpful and that as you go from A to B there’s an increase in mortality, but it’s fairly subtle until you get to C where the mortality is roughly triple what it would be in the A classification,” said study author Srihari Naidu, MD (Westchester Medical Center and New York Medical College, Valhalla, NY), who chaired the group behind the SCAI clinical expert consensus statement on classification of cardiogenic shock, released in May. “Then when you go up to D and E, it goes to four- and almost six- or sevenfold higher. So it shows that C, D, and E are the worst, but there’s also still gradations between C and D and E, and that’s what we wanted to show.”

The study, with lead author Jacob Jentzer, MD (Mayo Clinic, Rochester, MN), was published online September 20, 2019, ahead of print in the Journal of the American College of Cardiology.

SCAI Shock Categories

The classification scheme developed by SCAI and endorsed by the American College of Cardiology, the American Heart Association, the Society of Critical Care Medicine, and the Society of Thoracic Surgeons, consists of five stages:

• A (“At-risk”): Patients who are hemodynamically stable but who have acute cardiovascular disease that puts them at risk for developing cardiogenic shock.
• B (“Beginning”): Patients who are starting to show signs of hemodynamic instability, including hypotension/tachycardia, but who do not have cardiogenic shock.
• C (“Classic”): Patients who have cardiogenic shock characterized by hypoperfusion without deterioration.
• D (“Deteriorating”): Patients who have cardiogenic shock and whose hemodynamic instability and/or hypoperfusion does not respond to initial interventions.
• E (“Extremis”): Patients who have cardiogenic shock, are being supported by multiple interventions, and who may be experiencing cardiac arrest with ongoing CPR and/or extracorporeal membrane oxygenation.

“The SCAI shock classification was developed using expert consensus for the purpose of describing cardiogenic shock severity to clarify communication of patient status between providers in different care settings to facilitate patient triage and selection for advanced therapies,” the authors explain. “In addition, the SCAI classification of cardiogenic shock stages was designed to facilitate clinical research by simplifying the heterogeneity inherent to cardiogenic shock populations and help determine whether treatment interactions exist as a function of [shock] severity.”

There remained a need to validate the scheme’s ability to discriminate mortality risk across categories, Naidu said, noting that the current study was already in the works when the classification was released earlier this year.

The investigators retrospectively examined data on 10,004 patients (mean age 67.4 years; 37.4% women) who were admitted to the CICU at Mayo Clinic Hospital, St. Mary’s Campus, between 2007 and 2015. Overall, 43.1% of patients presented with ACS, 46.1% with heart failure, and 12.1% with cardiac arrest (categories are not mutually exclusive); 27.3% had neither ACS nor heart failure.

The patients were placed into the new SCAI categories based on the presence of hypotension/tachycardia, hypoperfusion, deterioration, and refractory shock. The proportions of patients in the five stages, from A to E, were 46.0%, 30.0%, 15.7%, 7.3%, and 1.0%. The prevalence of cardiac arrest increased across categories from 7.3% in stage A to 55.8% in stage E.

In-hospital mortality risk increased across categories, both before and after multivariable adjustment. The presence of cardiac arrest was associated with an increase in mortality within each stage and overall (adjusted OR 3.99; 95% CI 3.27-4.86).

In-Hospital Mortality Risk at Each Stage

^aP < 0.001 for all.

The results were consistent in patients with ACS, heart failure, or neither diagnosis.

“These data support the validity of the recent SCAI classification of cardiogenic shock stages for mortality risk stratification as a framework for future . . . clinical practice and research,” the authors say.

Guiding Aggressiveness

Naidu told TCTMD that having a better idea of short-term mortality risk for any given patient will be helpful in that it will allow clinicians to determine how aggressively to act in a given situation.

“People should use the [SCAI classification system] more because it does track with mortality,” Naidu said. If a patient moves into one of the higher-risk stages, he said, “that’s an incentive or hopefully a drive for people to say, ‘I need to get more people involved, we need to be much more aggressive, we need to recheck labs very quickly, we need to reassess hemodynamics very quickly, and try to prevent this patient from going to D or E because we know where the mortality is going at that point.’”

It’s important to note, Naidu said, that even though mortality associated with cardiogenic shock has been reported to be stuck at about 50% for years, this study shows that it varies greatly across stages.

“In the old studies of cardiogenic shock, the overall mortality is 40% to 50%, and what you can see now is that that really isn’t all shock,” he said. “Stage C shock does not have that mortality. Stage E shock does have that mortality. So that means that many of those trials initially were picking the worst of the worst and not taking classic shock into consideration.”

These new data provide benchmarks for mortality at each stage, which can be used both in randomized trials and registries of various therapies aimed at making a dent in cardiogenic shock mortality, he said.

And the classification scheme can be adapted to databases even if only some of the information used to classify patients is available, Naidu said. “You should be able to use whatever data you have to classify patients into the different stages,” he said. “And that shows actually, in my opinion, a strength of the classification, which is that it’s very flexible and versatile and allows you to classify shock with fairly limited data or more robust data or whatever data’s in front of you.”

Moving forward, the ability of the SCAI system to discriminate mortality risk should be corroborated in additional databases, according to Naidu, who said that investigators of prior randomized trials should apply it to their cohorts to see whether certain subsets of shock patients derived benefits from the therapies studied. It could be that additional trials enriched for these types of patients are warranted, he said.