Presenter: Dr. Jacob C. Jentzer

Although rare, cardiogenic shock is the most common cause of death in patients with acute myocardial infarction (AMI). The overall in-hospital mortality rate is 39%, rising to 55% in those 75 years and older. SCAI first proposed the classification system for cardiogenic shock in 2019 in a bid for standardization, categorizing at-risk patients from low to high – from A, an at-risk patient not currently experiencing signs or symptoms of cardiogenic shock, to E, a patient with circulatory collapse, frequently in refractory cardiac arrest(1). Researchers at the time said such a system was previously missing in any robust form and that: “The outcome of cardiogenic shock complicating MI has not appreciably changed in the last 30 years despite the development of various percutaneous mechanical circulatory support options.”

The SCAI Shock Classification system was, however, developed on the basis of expert consensus rather than a data-driven approach, lead researcher Jacob C. Jentzer, MD, of the Mayo Clinic, Rochester, Minnesota, said during his presentation(2). Therefore, the aim of the current study was to find whether the approach was “testable in reality” and whether the shock stages could provide a mortality risk-stratification tool, “the presumption here being that patients with a greater severity of shock would be sicker and, therefore, more likely to die,” Jentzer said. The researchers identified 14 manuscripts on PubMed for studies examining clinical outcomes as a function of SCAI shock stage in any population. The studies included more than 15,000 unique patients including cardiogenic shock, cardiac arrest, and cardiac intensive care unit cohorts; one study was prospective, and none were clinical trials. They examined seven separate definitions of the SCAI shock stages, yielding a prevalence of each SCAI shock stage as follows: A, 0-46%; B, 0-41%; C, 13-61%; D, 7-55%; E, 1-31%. The data confirmed that each proposed SCAI shock stage from A to E carried a stepwise increase in in-hospital or 30-day mortality, said Jentzer, adding that mortality risk factors included cardiac arrest, systemic inflammation, poor hemodynamics, worsening shock, and older age. 

“Every single study we looked at, regardless of whether they included low-risk patients or just cardiogenic shock patients, there was a very clear stepwise increase in (short-term) mortality … as the SCAI stage increased,” he said. Mortality at each SCAI stage also varied according to the study population and definition, the researchers added, noting ranges for the five groups as follows: A, 1-5%; B, 0-34%; C, 11-54%; D, 24-68%; E, 42-77%.

Nevertheless, “patients in stage E or refractory shock uniformly had higher risk of mortality, on average at least 50%,” Jentzer added, noting: “There was a lot more variability in some of the lower SCAI stages depending on who was included and what the baseline cohort was. This was a very important finding for us,” he said, clarifying that even though different definitions of SCAI shock stages were being used across the studies, “it was uniformly able to provide significant mortality risk stratification.” The results also show that despite variations in the definitions of the SCAI shock stages used in the studies, for instance with some using criteria that were not “necessarily explicit,” such as physician review of the charts, Jentzer stressed that some variables were commonly used across the board, such as lactate or vital signs.

Alongside its classification system, SCAI originally proposed that cardiac arrest was a “special circumstance that modified the risk,” Jentzer said. “We wanted to see if that was actually true based on the published studies.” The data clearly demonstrate that fact, he said, noting: “At every single SCAI shock stage, patients who were in cardiac arrest were more likely to die.” He showed charts demonstrating that cardiogenic shock patients in stage E had an in-hospital mortality rate of around 80% for various types of cardiac arrest. Meanwhile, in patients with cardiac arrest, the presence of shock was also associated with higher mortality, he noted, adding: “There was this very clear, graded association showing that for mortality risk stratification, you cannot only focus on either the presence or absence of cardiac arrest, or the presence or absence of shock. They’re both very important variables that need to be taken into account simultaneously.” 

Besides shock severity, Jentzer and colleagues noted other important components of mortality risk stratification related to the clinical characteristics of the patient, including age, poor hemodynamics, abnormal echocardiography, systemic inflammation, and acute kidney injury. For instance, the researchers found a “dramatic relation between patients that are young and have mild shock severity versus patients that are older and have high shock severity,” he said. “These findings confirm the efficacy of the SCAI shock stage classification, allowing physicians a staged approach communicate with their colleagues and the broader heart team how sick a patient is in a very consistent way," said Jentzer in an accompanying press statement. "Our analysis should enhance physician confidence in the protocol to appropriately identify high-risk and low-risk patients, ultimately helping tailor therapy based on level of shock to improve patient outcomes."

The data gleaned from the current study will help better inform an update on the stages in SCAI Shock Classification, which should be presented in the fall, at the SCAI Shock 2021 meeting, Jentzer concluded. 

All Authors: Giorgio A. Medranda, MD; Brian C. Case, MD; Jason P. Wermers, BS, Natalie Morrison, BA (Hons); and Ron Waksman, MD, MSCAI. 

References

1. David A. Baran, MD, FSCAI (Co-Chair); Cindy L. Grines, MD, MSCAI; Steven R. Bailey, MD, MSCAI; Daniel Burkhoff, MD, PhD; Shelley A. Hall, MD; Timothy D. Henry, MD, MSCAI; Steven M. Hollenberg, MD; Navin K. Kapur, MD, FSCAI; William O'Neill, MD, MSCAI; Joseph P. Ornato, MD; Kelly Stelling, RN; Holger Thiele, MD; Sean van Diepen, MD; Srihari S. Naidu, MD, FSCAI. SCAI clinical expert consensus statement on the classification of cardiogenic shock: This document was endorsed by the American College of Cardiology (ACC), the American Heart Association (AHA), the Society of Critical Care Medicine (SCCM), and the Society of Thoracic Surgeons (STS) in April 2019. Catheter Cardiovasc Interv 2019;94:29-37.
2. SCAI Shock Classification for Mortality Risk Stratification: Survey of Published Evidence. Accessed April 29, 2021.