SCAI updates expert consensus to SCAI Shock classification

Cardiogenic shock (CS) is a serious and life-threatening condition that occurs when the heart is unable to pump enough blood to the body's vital organs and is commonly triggered by heart attack or heart failure. Mortality from cardiogenic shock complicating myocardial infraction (MI) remains high, approaching or exceeding 50%, despite the development of percutaneous mechanical circulatory support technologies and the national standard of emergent angioplasty and stenting.

SCAI developed the original shock classification in 2019 to provide a first-of-its-kind universal standardized vocabulary that would translate across settings and providers from emergency room physicians to critical care physicians, heart failure physicians, interventional cardiologists, and surgeons, as well as those on the frontline such as emergency medical technicians. While the system has been widely adopted for its simple and intuitive framework, and ability to discern gradations of severity of CS for the first time, recent validation studies conducted since 2019 have provided new detailed information to make the definition more powerful.

To produce this update, the writing group reviewed validation studies of the original classification in detail to identify potential areas of refinement. The statement clarifies the precise role of the SCAI SHOCK classification within a more comprehensive 3-axis model incorporating other predictors of mortality, such as etiology and phenotype and nonmodifiable risk factors such as age and frailty, and provides more granularity to the cardiac arrest modifier and the constituent domains of the classification, including physical examination, biochemical, and hemodynamic criteria.

"The new updated definition is easier to use, with tables that have eliminated relatively unnecessary variables and highlighted the more commonly present ones in each shock stage, a more useful cardiac arrest modifier, and a 3-axis model that places the shock stages in context of other variables that need to be considered for the patient in front of you," said Srihari S. Naidu, MD, FSCAI, Chair of the writing group, Director of the Cardiac Catheterization Laboratory at Westchester Medical Center, and SCAI Trustee. "Further, we have made it much clearer how patients move up and down the stages if they deteriorate or recover, what these changes do to survival, and how support strategies such as mechanical support devices or vasopressors tie into the various stages."

In addition, the cardiac arrest modifier was adjusted based on available data to only include an arrest with concern for anoxic brain injury. According to Timothy D. Henry, MD, MSCAI, Vice-Chair of the document and President of SCAI, "Cardiac Arrest remains an important predictor of mortality in patients with cardiogenic shock, but we clarify the risk is in patients with unclear neurogenic status."

SCAI and the endorsing societies anticipate the classification to continue to evolve over time as new data accrue, but believe the updated criteria and associated tables and figures will be able to aid in acute clinical care for these patients, inter-hospital and within hospital communication, and in addition should facilitate clinical trials that will ultimately improve mortality in this high risk population.

Key summary points

1. The SCAI SHOCK stage is an indication of shock severity and comprises one component of mortality risk prediction in patients with CS, along with etiology/phenotype and other risk modifiers; a 3-axis model of risk stratification in CS has been proposed to position the SCAI SHOCK stage in context.

2. Validation studies have underscored the correlation of the SCAI SHOCK stage with mortality across all clinical subgroups, including CS with and without acute coronary syndrome (ACS), cardiac intensive care unit (CICU) patients, and those presenting with out-of-hospital cardiac arrest (OHCA).

3. Progression across the SCAI SHOCK stage continuum is a dynamic process, incorporating new information as available, and patient trajectories are important both for communication among clinicians and for decision-making regarding the next level of care and therapeutics.

4. A hub and spoke model for transfer of higher-risk patients including those with a deteriorating SCAI SHOCK stage has been proposed.

5. Cardiac arrest (CA) as described herein relates to that accompanied by coma, defined as the inability to respond to verbal stimuli, most commonly associated with Glasgow Coma Scale <9, where there is concern for significant anoxic brain injury.

6. The SCAI SHOCK pyramid and associated figure now reflect gradations of severity within each stage and pathways by which patients progress or recover.

7. A streamlined table incorporating variables that are most typically seen, and the revised CA modifier definition, is also provided and incorporates lessons learned from validation studies and clinician experience.

8. The lactate level and thresholds have been highlighted to detect hypoperfusion but may be dissociated from hemodynamics in cases such as chronic heart failure (HF). In addition, patients may demonstrate other manifestations of end-organ hypoperfusion with a normal lactate level, and there are also important causes of an elevated lactate level other than shock.

https://www.jscai.org/article/S2772-9303(21)00008-9/fulltext