SCAI Shock Classification
Definition
A five-stage (A–E) clinical severity staging system for cardiogenic shock developed by the Society for Cardiovascular Angiography and Interventions (SCAI), updated in 2022 with incorporation of validation studies. Endorsed by the ACC 2025 Concise Clinical Guidance as the standard CS severity classification tool.
Key Concepts
Staging System Overview
The SCAI stages classify CS severity from "at risk" to "extremis." Each stage is defined by clinical, hemodynamic, and biochemical criteria sources/cardiogenic-shock-acc-2025 (very high) sources/cardiogenic-shock-nejm-2026 (very high):
- Stage A (At Risk): No signs or symptoms of CS, but at risk (e.g., large AMI, HF exacerbation). Normal hemodynamics. Lactate ≤2 mmol/L.
- Stage B (Beginning): Clinical evidence of relative hypotension or tachycardia without hypoperfusion. Elevated filling pressures possible. Lactate ≤2 mmol/L.
- Stage C (Classic): Hypoperfusion requiring intervention. Lactate >2 mmol/L; CI <2.2 L/min/m²; PCWP >15 mmHg. The classic CS presentation.
- Stage D (Deteriorating): Rising or persistently elevated lactate; escalating vasopressor doses or addition of MCS. Hemodynamic deterioration despite support.
- Stage E (Extremis): Lactate >8 mmol/L; profound hypotension despite maximal hemodynamic support; often includes cardiac arrest/CPR.
Key Prognostic Implications
- In-hospital mortality stepwise (Jentzer et al.; n=10,004; Mayo Clinic CICU 2007–2015): Stage A 3.0%, Stage B 7.1%, Stage C 12.4%, Stage D 40.4%, Stage E 67.0% sources/mcs-jic-2023 (high)
- In-hospital mortality increases stepwise from Stage A (~3%) to Stage E (~67%)
- Stage B is the critical intervention window: highest risk of worsening shock severity within 24 hours from CS diagnosis sources/cardiogenic-shock-acc-2025 (very high)
- Most patients change SCAI stage within the first 24 hours — serial reassessment within this window is essential
- SCAI trajectory predicts outcome (Hanson et al.; n=300 AMI-CS; NCSI registry): Stage C at admission — maintained C at 24h: 84% survival; worsened C→D: 55% survival; worsened C→E: 17% survival — trajectory after 24h is a key outcome driver sources/mcs-jic-2023 (high)
- The 24-hour period from CS diagnosis is the critical management window for escalation decisions
Clinical Application
- SCAI staging does not require invasive hemodynamics for initial classification — clinical and biochemical data sufficient
- Used for triage (Level 1 transfer decisions), shock team activation thresholds, tMCS escalation decisions
- For Level 2/3 CS hospitals: SCAI Stage + Shock Academic Research Consortium classification among the key questions for regional Level 1 consultation
- Serial SCAI staging guides escalation and de-escalation of support
Modifications and Subclassifications
- Pediatric CS requires modified SCAI criteria (pediatric presentations differ from adult)
- ACC 2025 presents the CS Working Group–SCAI adaptation (Figure 2) for practical use
- Etiology subclassification (AMI-CS, HF-CS, postcardiotomy CS, secondary CS) adds additional context beyond SCAI stage alone
Contradictions / Open Questions
- SCAI staging validated primarily in AMI-CS populations; performance and calibration in HF-CS less established
- Stage B interventions: no randomized evidence for preemptive escalation at Stage B; DanGer Shock enrollment was in Stage C/D equivalent STEMI-CS patients
- Stage E outcomes with advanced support (VA-ECMO/CPR): highly variable; patient selection and timing of withdrawal are major unresolved questions
Connections
- Related to concepts/Cardiogenic-Shock
- Related to concepts/Temporary-Mechanical-Circulatory-Support
- Related to concepts/IABP
- Related to concepts/ECPELLA
- Related to concepts/Invasive-Hemodynamic-Monitoring-CS