2026 SCAI SHOCK Classification Expert Consensus Update: Refined Staging and Incorporation of Clinical Phenotypes and Patient Populations

Background The Society for Cardiovascular Angiography & Interventions (SCAI) SHOCK stage classification has been widely adopted since its introduction in 2019 as a framework for risk stratification, communication, and clinical assessment of cardiogenic shock (CS). Subsequent validation studies and real-world experience have identified opportunities to refine stage definitions and improve applicability across diverse clinical settings and patient populations. Methods A multidisciplinary writing group convened under the auspices of the SCAI Standards and Guidelines Committee conducted narrative literature reviews and iterative expert consensus discussions. Draft recommendations were developed and refined through structured review, consensus voting, external peer review, and organizational approval processes. Results The 2026 update refines and operationalizes the SCAI SHOCK classification through greater emphasis on objective assessment using physical examination findings, biochemical markers, and hemodynamic parameters. Updated definitions clarify stage A ("at risk"), reinforce hypoperfusion rather than hypotension as the key distinction between stages B and C, define stage D as failure of an initial support strategy with worsening (or not improving) hypoperfusion, and characterize stage E as actual or impending circulatory collapse. This update emphasizes serial reassessment and shock trajectory, clarifies use of the cardiac arrest modifier, and highlights that treatment intensity or device use alone should not determine shock stage. Additional guidance is provided for major shock phenotypes, including acute myocardial infarction-related CS, heart failure-related CS, right ventricular-predominant shock, mixed shock states, postcardiotomy shock, and pediatric CS. Practical recommendations for multidisciplinary implementation, clinical workflow integration, and future research are also presented. Conclusions This expert consensus update provides refined staging definitions and expanded clinical guidance intended to improve recognition, communication, risk stratification, and longitudinal assessment of CS across diverse care settings. By emphasizing objective measures of hypoperfusion, serial reassessment, and phenotype-specific considerations, the updated SCAI SHOCK classification aims to support both clinical practice and research while preserving the simplicity and broad applicability that have driven its widespread adoption.