Definition, Causes & Recognition
Cardiogenic shock is end-organ hypoperfusion caused by the heart's failure to generate an adequate cardiac output despite an adequate — or raised — intracardiac filling pressure. The clinical bind is that the failing pump cannot be simply "filled"; the problem is forward output, and the same congestion that floods the lungs is a marker of, not the cure for, the low output. Acute myocardial infarction remains the commonest cause, but the differential is wide.
Summarised from the Washington Manual of Critical Care — Cardiogenic Shock.Haemodynamic definition (typical thresholds)
- SBP <90 mmHg for >30 min (or vasopressors needed to maintain it) plus signs of hypoperfusion (oliguria, cool peripheries, altered mentation, lactate >2 mmol/L).
- When measured: cardiac index <1.8 L/min/m² without support (or <2.2 with support) and PCWP >15 mmHg.
Aetiology — not just infarction
- Acute MI with LV failure (commonest) — and its mechanical complications: papillary muscle/chordal rupture (acute MR), VSD, free-wall rupture/tamponade — always get an early echo.
- RV infarction — hypotension with clear lungs and raised JVP; preload-dependent.
- Decompensated chronic heart failure, fulminant myocarditis, stress (Takotsubo) cardiomyopathy, arrhythmia, valvular catastrophe, and post-cardiotomy shock.
- Obstructive mimics to exclude fast: massive PE, tamponade, tension pneumothorax (see Shock).
Classic cardiogenic shock is cold (hypoperfused — low output/high SVR) and wet (congested — high filling pressures). But up to a fifth are "warm and wet" with a SIRS-like vasodilated picture, and the danger is mistaking them for sepsis and pouring in fluid. Anchor on the echo and the lactate, not the skin alone.
Pathophysiology — the Downward Spiral
The hallmark of cardiogenic shock is a self-reinforcing spiral: a fall in cardiac output lowers coronary perfusion, which worsens myocardial ischaemia, which further reduces output. Compensatory vasoconstriction and tachycardia defend blood pressure at the cost of raising afterload and myocardial oxygen demand, accelerating the decline. Interrupting this spiral early — restoring coronary flow and unloading the ventricle — is the whole of treatment.
Summarised from Marino PL. The ICU Book, 5th Ed — Acute Heart Failure Syndromes.Bedside phenotyping (the Stevenson/Forrester quadrants) drives therapy: assess perfusion ("cold" vs "warm") and congestion ("wet" vs "dry") independently.
- Warm & dry — compensated; optimise oral therapy.
- Warm & wet — congested but perfusing → vasodilators + diuretics.
- Cold & wet — the classic shock quadrant → inotrope ± vasopressor, then diurese/unload once perfusion returns.
- Cold & dry — hypoperfused & underfilled → cautious fluid, then inotrope.
Vasoactive drugs buy time but every inotrope raises myocardial oxygen demand and is arrhythmogenic — they are a bridge, not a destination. Definitive care is reversing the cause (revascularise the infarct, cardiovert the arrhythmia, drain the tamponade, fix the valve) and, where the heart cannot recover on drugs alone, mechanically unloading it with circulatory support as a bridge to recovery, decision, or transplant/LVAD.
Classification & Evidence
B — Beginning (compensated: tachycardia/hypotension, no hypoperfusion).
C — Classic (hypoperfusion needing an intervention — inotrope/pressor/mechanical support).
D — Deteriorating (failing to respond, escalation needed).
E — Extremis (circulatory collapse, often on CPR/ECMO).
Stage rises with a rising lactate and mounting support — restage frequently.
DanGer Shock (NEJM 2024): a microaxial flow pump (Impella CP) in selected STEMI cardiogenic shock reduced 180-day mortality — but at the cost of more bleeding, limb ischaemia and renal-replacement; patient selection is everything.
ECLS-SHOCK (2023): routine early VA-ECMO in AMI–cardiogenic shock did not reduce mortality and increased complications — reserve for selected/refractory cases in expert centres (see ECMO).
Rheumatic valvular disease and late-presenting STEMI mean mechanical complications and large infarcts are common, often reaching hospital late. Access to primary PCI and mechanical support is concentrated in tertiary centres — recognise cardiogenic shock early, thrombolyse where timely PCI is unavailable, and transfer rather than persist on escalating inotropes locally. A bedside echo (to catch acute MR, VSD, RV infarct, tamponade) is the highest-value early investigation and is widely available. Levosimendan and dobutamine are accessible; Impella is not, so VA-ECMO in a capable centre is the realistic escalation for refractory shock.
Vasoactive & Adjunct Drugs
| Drug | Role | Dose | Notes |
|---|---|---|---|
| Noradrenaline | First-line vasopressor | 0.05–0.5 µg/kg/min IV | Restores MAP with fewer arrhythmias than dopamine/adrenaline (SOAP II, OptimaCS) |
| Dobutamine | Inotrope (low output) | 2.5–10 µg/kg/min | β1 inotropy + vasodilation; add once MAP restored; tachyarrhythmia |
| Adrenaline | Refractory low output | 0.01–0.5 µg/kg/min | Potent but ↑ lactate & arrhythmia; reserve/peri-arrest |
| Milrinone | Inotrope (PDE-3 inhibitor) | 0.125–0.75 µg/kg/min | Inodilator; good for RV failure/pulmonary HTN & chronic β-blockade; causes hypotension; renally cleared |
| Levosimendan | Ca²⁺-sensitiser inotrope | 0.05–0.2 µg/kg/min (12.5 mg vial); usually no bolus in shock | Inotropy without ↑ O₂ demand; long-acting metabolite; hypotension |
| Furosemide | Decongestion (once perfusing) | Bolus or infusion; IV dose ≈ oral | Treat congestion after perfusion restored; not a fix for low output |
| GTN | Afterload/preload reduction | 10–200 µg/min IV | Warm-&-wet / hypertensive pulmonary oedema; avoid if hypotensive/RV infarct |
| Noradrenaline + dobutamine | Typical combination | Titrate to MAP ≥65 & perfusion | Vasopressor for pressure + inotrope for output |
| Heparin | Anticoagulation (ACS/MCS) | Per ACS / device protocol | For infarct + any mechanical support circuit |
Management Algorithm
Recognise & find the cause
- Hypotension + hypoperfusion (lactate, oliguria, cool/altered) with adequate/high filling pressure
- Immediate ECG + bedside echo — infarct? mechanical complication? RV? tamponade? valve?
- Exclude obstructive mimics (PE, tamponade, tension pneumothorax)
Treat the cause urgently
- AMI → emergency culprit-lesion PCI (or thrombolysis if PCI unavailable, then transfer)
- Arrhythmia → cardiovert/rate control; tamponade → drain; acute valve/VSD → surgery
- RV infarct → cautious preload, avoid nitrates/over-diuresis
Support the circulation
- Phenotype (cold/warm × wet/dry); noradrenaline to MAP ≥65, add dobutamine for low output
- Oxygen/ventilation for pulmonary oedema (NIV/intubate); cautious fluids only if underfilled/RV
- Decongest with diuretics once perfusion restored
Escalate if refractory (SCAI D–E)
- Rising lactate/failing on 2 agents → discuss mechanical circulatory support early with a shock team
- Selected STEMI shock → microaxial pump (Impella); refractory/arrest → VA-ECMO in an expert centre
- IABP is not routine
Define the destination
- Bridge to recovery, decision, transplant or durable LVAD
- Restage (SCAI) & reassess perfusion/lactate frequently; wean support as the heart recovers
Common Mistakes in Cardiogenic Shock
Reflex boluses in a "cold and wet" patient worsen pulmonary oedema without improving output. Only give fluid if the echo/clinical picture shows underfilling (e.g. RV infarct) — otherwise support with inotropes and decongest.
Dopamine caused more arrhythmias and higher mortality than noradrenaline in the cardiogenic-shock subgroup of SOAP II. Noradrenaline is first-line.
Missing an acute mechanical complication (papillary muscle rupture, VSD, tamponade) or an RV infarct changes everything. An early bedside echo is the highest-yield test.
CULPRIT-SHOCK showed culprit-lesion-only PCI is better than routine immediate complete revascularisation. Fix the culprit, stage the rest.
IABP-SHOCK II (IABP) and ECLS-SHOCK (routine early VA-ECMO) were both negative for survival. Mechanical support is for selected patients and expert centres, decided by a shock team — not a reflex.
The RV-infarct patient is preload-dependent; nitrates and aggressive diuresis cause profound hypotension. Give cautious fluid and inotropic support instead.
Every added inotrope raises myocardial oxygen demand and arrhythmia risk. If two agents are failing and lactate is rising, escalate to mechanical support / transfer rather than climbing the infusion.
Exam Pearls
Q: Define cardiogenic shock haemodynamically.
Sustained hypotension (SBP <90 for >30 min or pressors needed) with hypoperfusion, plus (when measured) cardiac index <1.8 L/min/m² unsupported and PCWP >15 mmHg — i.e. low output despite adequate filling.
Q: What are the SCAI SHOCK stages?
A At risk, B Beginning (compensated), C Classic (hypoperfusion needing intervention), D Deteriorating, E Extremis. Restage with lactate and escalating support.
Q: First-line vasopressor and why?
Noradrenaline — fewer arrhythmias and lower mortality than dopamine (SOAP II) and less refractory shock/lactic acidosis than adrenaline (OptimaCS). Add dobutamine for low output.
Q: Culprit-only or multivessel PCI in AMI shock?
Culprit-lesion-only (CULPRIT-SHOCK) — routine immediate multivessel PCI increased death/renal-replacement at 30 days.
Q: Does IABP improve survival in AMI cardiogenic shock?
No — IABP-SHOCK II was neutral; it is no longer routinely recommended.
Q: What did DanGer Shock and ECLS-SHOCK show?
DanGer Shock (2024): a microaxial pump reduced mortality in selected STEMI shock but with more complications. ECLS-SHOCK (2023): routine early VA-ECMO did not reduce mortality — reserve for selected refractory cases.
Q: How do you spot and treat RV infarction shock?
Hypotension with clear lungs + raised JVP, inferior STEMI, ST-elevation in V4R. It is preload-dependent — give fluid, avoid nitrates/over-diuresis, support with inotrope, and revascularise.
Q: Milrinone vs dobutamine?
Milrinone (PDE-3 inhibitor) is an inodilator useful in RV failure/pulmonary hypertension and chronic β-blockade, but is renally cleared and more hypotensive; dobutamine is quicker to titrate but more tachycardia-prone.
References
- Naidu SS, Baran DA, Jentzer JC, et al. (SCAI). SCAI SHOCK Stage Classification Expert Consensus Update. J Am Coll Cardiol. 2022;79:933–946.
- McDonagh TA, Metra M, Adamo M, et al. (ESC). 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure (and 2023 focused update). Eur Heart J. 2021;42:3599–3726.
- Thiele H, Zeymer U, Neumann FJ, et al. (IABP-SHOCK II). Intra-aortic balloon support for myocardial infarction with cardiogenic shock. N Engl J Med. 2012;367:1287–1296.
- Thiele H, Akin I, Sandri M, et al. (CULPRIT-SHOCK). PCI Strategies in Patients with AMI and Cardiogenic Shock. N Engl J Med. 2017;377:2419–2432.
- Møller JE, Engstrøm T, Jensen LO, et al. (DanGer Shock). Microaxial Flow Pump in Infarct-Related Cardiogenic Shock. N Engl J Med. 2024;390:1382–1393.
- Thiele H, Zeymer U, Akin I, et al. (ECLS-SHOCK). Extracorporeal Life Support in Infarct-Related Cardiogenic Shock. N Engl J Med. 2023;389:1286–1297.
- De Backer D, Biston P, Devriendt J, et al. (SOAP II). Comparison of dopamine and norepinephrine in the treatment of shock. N Engl J Med. 2010;362:779–789.
- Marino PL. The ICU Book, 5th Edition. Acute Heart Failure Syndromes. Wolters Kluwer; 2025.
- Washington Manual of Critical Care, 4th Edition. Kollef MH, Witt CA (eds). Cardiogenic Shock. Wolters Kluwer; 2023.