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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Critical Care

The SCAI Staging System: Measuring the Severity of Shock

At a Glance

The SCAI Staging System ranks cardiogenic shock severity from Stage A (at risk) to Stage E (extreme emergency). ICU doctors use markers like lactate levels, mental status, skin temperature, and urine output to determine the stage and dynamically adjust life-support treatments.

In the ICU, doctors use a specific shorthand to describe how severe cardiogenic shock is and how fast they need to act. This is called the SCAI Staging System (named after the Society for Cardiovascular Angiography and Interventions) [1]. It ranks shock from Stage A (lowest risk) to Stage E (highest risk) [2][3].

Think of these stages like a weather warning system for the heart. Knowing the “stage” helps you understand the current “storm level” your loved one is facing.

The Five Stages of Shock

  • Stage A: At Risk. The patient has heart disease or had a heart attack, but their blood pressure and organ function are currently stable. The “storm” hasn’t hit yet, but the clouds are forming [1][4].
  • Stage B: Beginning. The heart rate might be high or blood pressure low, but the organs (like the kidneys and brain) are still getting enough blood. This is like a “weather warning”—the system is starting to struggle [5][6].
  • Stage C: Classic. This is true cardiogenic shock. The heart cannot pump enough blood, and organs are showing signs of starving for oxygen (hypoperfusion) [1]. The patient usually needs medications or mechanical pumps to stay stable [6].
  • Stage D: Deteriorating. The initial treatments (like medications) aren’t working well enough. The patient’s condition is getting worse despite the team’s efforts, and they may need to “escalate” to stronger machines or different therapies [1][4].
  • Stage E: Extremis. This is the most severe “emergency” stage. The patient has had a cardiovascular collapse, often requiring active CPR or multiple advanced life-support machines to maintain any blood flow [2][7].

Why the Stage is “Dynamic”

A patient’s stage is not a permanent label; it is dynamic, meaning it can change from hour to hour [8][5]. The first 24 to 48 hours are the most volatile [9][10].

  • Moving “Down” (e.g., C to B): This is the goal. It means the treatments are working, the organs are getting blood, and the body is stabilizing [11].
  • Moving “Up” (e.g., C to D): This signals that the heart failure is winning the tug-of-war, and the medical team needs to change their strategy quickly [12][8].

How the Stage is Determined

Doctors don’t just guess the stage; they look at specific “red flags” [13]:

  1. Lactate Levels: This is a blood test marker. High levels (>2 mmol/L) tell doctors that cells are struggling to survive without enough oxygen [14][15].
  2. Mental Status: If the brain isn’t getting enough blood, a patient may become confused, agitated, or very sleepy (Altered Mental Status) [16][17].
  3. Skin Temperature: Cold or “mottled” (blotchy) skin on the hands and feet is a sign the body is pulling blood away from the skin to protect the brain and heart [18][19].
  4. Urine Output: If the kidneys aren’t getting enough blood, they stop making urine. This is often one of the first signs of Stage C or D shock [12][17].

Asking the doctor, “What SCAI stage are they in today?” is a powerful way to get a clear, standardized update on your loved one’s status [20].

Common questions in this guide

What is the SCAI staging system?
The SCAI staging system is a five-tier classification tool doctors use to measure the severity of cardiogenic shock. It ranges from Stage A (lowest risk) to Stage E (extreme emergency) and helps the ICU team quickly communicate how much life support is needed.
What does Stage C cardiogenic shock mean?
Stage C represents classic cardiogenic shock. In this stage, the heart cannot pump enough blood, and vital organs begin starving for oxygen. Patients in Stage C typically need intravenous medications or mechanical pumps to stabilize their blood flow.
Why does the SCAI stage change over time?
Cardiogenic shock is highly dynamic, meaning a patient's condition can improve or worsen quickly, especially in the first 24 to 48 hours. A patient's stage will change based on how well their organs respond to medical treatments and life-support machines.
How do doctors determine a patient's SCAI stage?
Doctors use a combination of physical signs and blood tests to monitor organ health. They track key warning signs like high blood lactate levels, confusion or extreme sleepiness, cold or blotchy skin, and low urine output.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my loved one's current SCAI stage (A through E)?
  2. 2.Has their stage changed since they were admitted to the ICU?
  3. 3.What specific markers—like lactate or kidney function—are you tracking to decide if they are moving into a 'deteriorating' stage?
  4. 4.If they move from Stage C to Stage D, what is the 'escalation plan' for more support?
  5. 5.How often are you reassessing the stage during these first 48 hours?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (20)
  1. 1

    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.

    Baran DA, Grines CL, Bailey S, et al.

    Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions 2019; (94(1)):29-37 doi:10.1002/ccd.28329.

    PMID: 31104355
  2. 2

    The Range of Cardiogenic Shock Survival by Clinical Stage: Data From the Critical Care Cardiology Trials Network Registry.

    Lawler PR, Berg DD, Park JG, et al.

    Critical care medicine 2021; (49(8)):1293-1302 doi:10.1097/CCM.0000000000004948.

    PMID: 33861557
  3. 3

    Prognostic validation and risk stratification of the Society for Cardiovascular Angiography and Interventions cardiogenic shock classification in a large, real-world intensive care unit cohort in South Korea.

    Cho H, Kang J, Han M, et al.

    Acute and critical care 2026; (41(1)):117-125 doi:10.4266/acc.004500.

    PMID: 41834637
  4. 4

    Criteria for Defining Stages of Cardiogenic Shock Severity.

    Kapur NK, Kanwar M, Sinha SS, et al.

    Journal of the American College of Cardiology 2022; (80(3)):185-198 doi:10.1016/j.jacc.2022.04.049.

    PMID: 35835491
  5. 5

    Application of the SCAI classification in a cohort of patients with cardiogenic shock.

    Schrage B, Dabboura S, Yan I, et al.

    Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions 2020; (96(3)):E213-E219 doi:10.1002/ccd.28707.

    PMID: 31925996
  6. 6

    Etiology, Management, and Outcomes of Society for Cardiovascular Angiography and Interventions Stage B Cardiogenic Shock.

    Mehta C, Has P, Mehta A, et al.

    Circulation. Heart failure 2026; e013814 doi:10.1161/CIRCHEARTFAILURE.125.013814.

    PMID: 41711037
  7. 7

    Cardiogenic shock trajectories: is the Society for Cardiovascular Angiography and Interventions definition the right one?

    Dorian D, Thomson RJ, Lim HS, Proudfoot AG

    Current opinion in critical care 2024; (30(4)):324-332 doi:10.1097/MCC.0000000000001168.

    PMID: 38841918
  8. 8

    SCAI stage reclassification at 24 h predicts outcome of cardiogenic shock: Insights from the Altshock-2 Registry.

    Serrao G, Dangas G

    Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions 2023; (101(3)):676 doi:10.1002/ccd.30566.

    PMID: 36748779
  9. 9

    Prognostic performance of the SCAI shock classification at admission and during ICU treatment: A retrospective, observational cohort study.

    Britsch S, Britsch M, Hahn L, et al.

    Heart & lung : the journal of critical care 2024; (68()):52-59 doi:10.1016/j.hrtlng.2024.06.012.

    PMID: 38924856
  10. 10

    PROGNOSTIC PERFORMANCE OF SERIAL DETERMINATION OF THE SOCIETY FOR CARDIOVASCULAR ANGIOGRAPHY AND INTERVENTIONS SHOCK CLASSIFICATION IN ADULTS WITH CRITICAL ILLNESS.

    Jentzer JC, Sanghavi D, Patel PC, et al.

    Shock (Augusta, Ga.) 2024; (61(2)):246-252 doi:10.1097/SHK.0000000000002292.

    PMID: 38150371
  11. 11

    Serial Shock Severity Assessment Within 72 Hours After Diagnosis: A Cardiogenic Shock Working Group Report.

    Ton VK, Li S, John K, et al.

    Journal of the American College of Cardiology 2024; doi:10.1016/j.jacc.2024.04.069.

    PMID: 39217545
  12. 12

    Patterns of Disease Progression and Outcomes of Inferior ST-Elevation Myocardial Infarction Complicated by Cardiogenic Shock: The Multicenter INSTINCT Registry.

    Botti G, Pieri M, Cappannoli L, et al.

    Journal of clinical medicine 2025; (14(7)) doi:10.3390/jcm14072231.

    PMID: 40217681
  13. 13

    Application of Cardiogenic Shock Working Group-defined Society for Cardiovascular Angiography and Interventions (CSWG-SCAI) Staging of Cardiogenic Shock to the Medical Information Mart for Intensive Care IV (MIMIC-IV) database.

    John KJ, Stone SM, Zhang Y, et al.

    Cardiovascular revascularization medicine : including molecular interventions 2023; (57()):82-90 doi:10.1016/j.carrev.2023.06.019.

    PMID: 37400345
  14. 14

    Association Between the Acidemia, Lactic Acidosis, and Shock Severity With Outcomes in Patients With Cardiogenic Shock.

    Jentzer JC, Schrage B, Patel PC, et al.

    Journal of the American Heart Association 2022; (11(9)):e024932 doi:10.1161/JAHA.121.024932.

    PMID: 35491996
  15. 15

    Association between serum lactate levels and mortality in patients with cardiogenic shock receiving mechanical circulatory support: a multicenter retrospective cohort study.

    Scolari FL, Schneider D, Fogazzi DV, et al.

    BMC cardiovascular disorders 2020; (20(1)):496 doi:10.1186/s12872-020-01785-7.

    PMID: 33234107
  16. 16

    Altered mental status predicts mortality in cardiogenic shock - results from the CardShock study.

    Kataja A, Tarvasmäki T, Lassus J, et al.

    European heart journal. Acute cardiovascular care 2018; (7(1)):38-44 doi:10.1177/2048872617702505.

    PMID: 28403620
  17. 17

    Kidney and liver dysfunction in cardiogenic shock.

    Lassus J

    Current opinion in critical care 2020; (26(4)):417-423 doi:10.1097/MCC.0000000000000746.

    PMID: 32520812
  18. 18

    Clinical impact of congestion in patients admitted for cardiogenic shock.

    Cherbi M, Roubille F, Bonnefoy E, et al.

    Archives of cardiovascular diseases 2026; (119(3)):201-209 doi:10.1016/j.acvd.2025.08.006.

    PMID: 40967978
  19. 19

    Performance of Early Capillary Refill Time Measurement on Outcomes in Cardiogenic Shock: An Observational, Prospective Multicentric Study.

    Merdji H, Curtiaud A, Aheto A, et al.

    American journal of respiratory and critical care medicine 2022; (206(10)):1230-1238 doi:10.1164/rccm.202204-0687OC.

    PMID: 35849736
  20. 20

    What is cardiogenic shock? New clinical criteria urgently needed.

    Ostadal P, Belohlavek J

    Current opinion in critical care 2024; (30(4)):319-323 doi:10.1097/MCC.0000000000001172.

    PMID: 38841985

This page explains the SCAI staging system for educational purposes. Always rely on your loved one's ICU team for specific updates on their cardiogenic shock status, organ function, and medical care plan.

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