Cardiogenic Shock

Meet the patient

A 64-year-old man is in the coronary care unit, six hours after a primary PCI for an anterior STEMI. The stent is open, the pain has gone, and the team is reassuring his wife — when the nurse notes his urine output has stopped and he has become confused and restless.^[1]

His blood pressure is 88/60, his heart rate 118, his peripheries are cool and mottled to the elbows, and a bedside lactate comes back at 5.2 mmol/L. The chest has bibasal crackles — the clinical picture of cardiogenic shock: hypotension with cool extremities, falling urine output and biochemical evidence of tissue hypoperfusion.^[14][24] The registrar reads this as "blood pressure holding, probably just a bit low after the procedure" — and that is the moment the spiral deepens, because the cuff is the last thing to fall.

The exam question hiding in this bed is cardiogenic shock complicating acute MI, and the lethal habit it exposes is treating the blood pressure instead of the perfusion. Everything below exists to make you stage the patient with SCAI, defend the MAP with an inotrope and a vasopressor, and reach for early revascularisation and mechanical support before the spiral is irreversible.^[6][13]

What cardiogenic shock is — and why the cuff is the last sign to fall

Cardiogenic shock is a clinical syndrome of inadequate tissue perfusion due to cardiac pump dysfunction. The heart cannot deliver sufficient cardiac output to meet the metabolic demands of the body, despite adequate or even raised intravascular volume.^[6][13]

The most widely used diagnostic criteria, as set out in current reviews of the syndrome:^[14]

• Clinical criteria — a systolic blood pressure at or below 90 mmHg for at least 30 minutes, OR vasopressors to maintain systolic blood pressure at least 90 mmHg, with urine output at or below 30 mL/hour or cool extremities;
• Haemodynamic criteria — a depressed cardiac index (at or below 2.2 L/min/m2 of body surface area) and an elevated pulmonary capillary wedge pressure (over 15 mmHg in the SHOCK trial; Forrester subset IV uses over 18 mmHg) — the wedge criterion confirms the cause is cardiac rather than hypovolaemic;
• Biochemical evidence of tissue hypoperfusion — a raised serum lactate;
• Exclusion of hypovolaemia, sepsis, and other non-cardiac causes as the primary driver.^[14]

The clinical importance of cardiogenic shock is its lethality: it complicates up to 10 percent of acute MIs, is the leading cause of in-hospital death after AMI, and — even with modern revascularisation, inotropes and mechanical circulatory support — carries nearly 40 percent 30-day and about 50 percent 1-year mortality (in-hospital series 40 to 50 percent). The exam skill lies in (1) recognising shock early, before SBP collapses (perfusing organs fail before blood pressure falls — watch lactate, urine output, mentation, skin); (2) distinguishing cardiogenic shock from its mimics (septic, hypovolaemic, obstructive, distributive), because the management is the opposite; (3) identifying the cardiac cause and the reversible subgroup (MI, tamponade, massive PE, mechanical complication, arrhythmia); and (4) running the shock funnel to definitive therapy.^[9][13]

Classification — SCAI stages, Forrester subsets, and aetiology

Cardiogenic shock is classified by SCAI staging (the modern prognostic standard), by Forrester haemodynamic subset (the bedside physiological model), and by aetiology (which determines treatment).^[1]

SCAI SHOCK stages A to E — the modern prognostic standard

^[6]

The SCAI staging was published in 2019 (Baran et al.) and updated in 2022 (Naidu et al.); the B-to-C boundary is the appearance of hypoperfusion (a verbatim concept from the consensus statement), and stages track in-hospital mortality in a steep gradient validated across multiple registries (Jentzer et al., Naidu et al.).^[6][7][8]

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Forrester subsets — two numbers at the bedside

The older Forrester haemodynamic subsets (Forrester, Diamond, Chatterjee; NEJM 1976) classify the patient at the bedside using two numbers: pulmonary capillary wedge pressure (a proxy for left-sided filling) and cardiac index.^[10][11]

• Subset I — warm and dry: wedge below 18 mmHg, CI above 2.2 L/min/m2. Normal perfusion, no congestion. Mortality 2.2 percent.
• Subset II — warm and wet: wedge over 18 mmHg, CI above 2.2 L/min/m2. Pulmonary oedema, good peripheral perfusion. Mortality 10.1 percent.
• Subset III — cold and dry: wedge below 18 mmHg, CI below 2.2 L/min/m2. Hypoperfusion without congestion — usually relative hypovolaemia; treat with a cautious fluid challenge. Mortality 22.4 percent.
• Subset IV — cold and wet: wedge over 18 mmHg, CI below 2.2 L/min/m2. This is classic cardiogenic shock. Mortality 55.5 percent in the 1977 correlative series.^[26]

Aetiology — the classification that drives treatment

The headline categories are: acute MI (LV failure — the commonest), acute mechanical complication of MI (papillary muscle rupture, VSR, free-wall rupture), right ventricular infarction, acute decompensated chronic heart failure or cardiomyopathy, fulminant myocarditis, acute severe valvular disease (MR, AR, MS), arrhythmia (VT, bradyarrhythmia, AF with rapid rate), cardiac tamponade, massive pulmonary embolism (the right ventricle failing against acute afterload), post-cardiotomy shock, drug toxicity (beta-blocker, calcium-channel blocker, digoxin), and rejection of a transplanted heart.^[1]

^[1]

Epidemiology and risk factors

Cardiogenic shock complicates up to 10 percent of acute MIs immediately after infarction (EURO SHOCK quotes 10 percent of patients presenting with AMI) and is the leading cause of in-hospital death after AMI.^[16][22][1]

Demographic and clinical risk factors (the high-yield list):^[1]

• Age — SHOCK-trial mean age was 66 plus or minus 10 years; the 1-year survival benefit of early revascularisation was confined to those under 75.^[1][2]
• Female sex — the SHOCK trial was 32 percent women.^[1]
• Anterior STEMI — large anterior (especially proximal LAD) infarcts are the single most common infarct location to cause CS, because of the large area of myocardium at risk.^[1]
• Large infarct size — peak CK or troponin, reduced LV ejection fraction, wall-motion score index, and lack of collateral circulation or incomplete reperfusion (TIMI flow below 3, no-reflow).
• Prior MI or known LV dysfunction — the second hit on an already-compromised ventricle tips the patient into shock.
• Diabetes mellitus, chronic kidney disease, peripheral arterial disease — common comorbidities that worsen outcome.
• Delay to presentation or reperfusion — delayed presentation and delayed reperfusion worsen the downward spiral; early revascularisation is the SHOCK-trial standard of care.^[1]
• Multivessel coronary disease — supply-side failure; downstream culprit-only versus multivessel PCI is a key decision (CULPRIT-SHOCK).^[4]
• Mechanical complications of MI — typically occur days after infarction (classically taught as later in the first week, though timing is not a hard rule in the fetched sources), in patients with smaller infarcts (subendocardial or first MI): papillary muscle rupture (inferior MI — the posteromedial papillary muscle has a single blood supply), ventricular septal rupture, free-wall rupture.^[9]

Non-ischaemic causes — fulminant myocarditis (young patients with a recent viral illness, sudden severe LV dysfunction — a high recovery rate if supported); peripartum cardiomyopathy; acute severe valvular regurgitation (endocarditis, traumatic); drug overdose (beta-blocker, calcium-channel blocker, digoxin); advanced cardiomyopathy with a precipitant.^[12]

Pathophysiology — the self-perpetuating downward spiral

The pathophysiology of cardiogenic shock is best understood as a self-perpetuating downward spiral in which cardiac dysfunction, neurohormonal activation, systemic inflammation and end-organ failure reinforce one another.^[1][13]

1. The initiating insult — pump failure. A large enough loss of functioning muscle reduces stroke volume and cardiac output (CO equals heart rate times stroke volume). When the remaining viable myocardium cannot compensate, cardiac index falls below 2.2 L/min/m2. The same injury — through the Frank-Starling mechanism — raises left ventricular end-diastolic pressure (LVEDP), which transmits back to the left atrium and pulmonary capillaries, raising filling pressure and producing pulmonary congestion and oedema. SHOCK-trial haemodynamics used PCWP over 15 mmHg; Forrester subset IV used wedge over 18 mmHg.^[10][26]

2. The vicious spiral — coronary hypoperfusion. Reduced cardiac output lowers diastolic blood pressure and hence coronary perfusion pressure (diastolic BP minus wedge pressure). The subendocardium is most vulnerable (it is perfused in diastole only, against the highest intramyocardial pressure). Worsened subendocardial ischaemia further reduces contractility of the surviving myocardium, which drops stroke volume further — a spiral that terminates in asystole or pulseless electrical activity unless interrupted. This spiral is the biological reason early reperfusion works.^[1]

3. Compensatory neurohormonal activation — initially helpful, ultimately harmful. Baroreceptors sense falling blood pressure and activate the sympathetic nervous system (tachycardia, vasoconstriction, increased contractility — raising myocardial oxygen demand in an ischaemic ventricle) and the renin-angiotensin-aldosterone system (vasoconstriction, sodium and water retention). Vasopressin (ADH) rises. These responses initially maintain central organ perfusion, but in established shock they increase afterload, worsen subendocardial ischaemia, and drive further decompensation — the rationale for vasodilator (GTN) and beta-blockade strategies in the chronic phase, and the danger of indiscriminate fluids in the acute phase.^[1]

4. The systemic inflammatory response syndrome (SIRS) in CS. In established shock the gut becomes hypoperfused, the endothelium is injured, and a pro-inflammatory cytokine cascade (TNF-alpha, IL-1, IL-6) is released from ischaemic and necrotic myocardium. This produces inducible nitric oxide synthase, excess nitric oxide and peroxynitrite, vasoplegia (pathological vasodilatation on top of pump failure), capillary leak, and myocardial depression — the so-called "septic-like" phenotype of late cardiogenic shock. This is why some CS patients become warm and vasoplegic rather than cold and vasoconstricted, and why noradrenaline rather than dobutamine alone is needed. The NOS inhibitor tilarginine (L-NMMA) was tested in TRIUMPH and failed.^[5]

5. End-organ hypoperfusion — the clinical face of CS.^[14]

• Kidney — falling renal perfusion drops glomerular filtration; oliguria (urine output at or below 30 mL/hour) is one of the earliest bedside signs, and progressive renal injury follows sustained hypoperfusion.
• Brain — confusion, agitation, obtundation.
• Liver — ischaemic (hypoxic) hepatitis ("shock liver"): a massive but transient rise in serum aminotransferases caused by anoxic necrosis of centrilobular liver cells, with cardiac failure a leading underlying condition.^[21]
• Gut — hypoperfusion and ileus; mesenteric ischaemia in extreme cases.
• Skin — cool, clammy, mottled peripheries with delayed capillary refill — vasoconstriction shunts blood to vital organs.
• Skeletal muscle — lactic acidosis from anaerobic metabolism; a raised serum lactate is the biochemical marker of tissue hypoperfusion and hypoxia.^[14]

6. The role of the right ventricle. RV infarction (with inferior MI) is a special pathophysiology: the dilated, failing RV causes systemic venous congestion (raised JVP, hepatomegaly) with clear lung fields (the LV is underfilled because the RV cannot deliver preload), and hypotension that is exquisitely preload-sensitive — nitrates, diuretics and beta-blockers precipitate collapse; volume challenge and reperfusion are the answer. RV failure on top of LV failure (biventricular CS) is the most lethal phenotype and demands biventricular mechanical support (VA-ECMO rather than isolated LV assist).^[1]

7. The macro- and microcirculation dissociate. In late CS, macro-haemodynamics may improve on inotropes while the microcirculation remains failed — the so-called "lost in translation" phenomenon. This underlies the search for microcirculatory monitoring (sublingual SDF imaging) and the failure of pure pressure-based endpoints.^[13]

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Clinical presentation — hypoperfusion plus congestion plus a cardiac cause

The clinical face of cardiogenic shock is the triad of hypoperfusion plus congestion plus a cardiac cause.^[13]

Symptoms (the patient is usually too sick to give a long history):^[1]

• Cardiac symptoms of the underlying cause — chest pain of acute MI (crushing central, radiation to arm or jaw, autonomic features), palpitation (VT, AF), syncope (arrhythmia, PE, tamponade), the breathlessness of pulmonary oedema.
• Hypoperfusion symptoms — dizziness, light-headedness, syncope, fatigue, confusion, oliguria or anuria, cold extremities.
• Pulmonary congestion — orthopnoea, paroxysmal nocturnal dyspnoea, frothy pink sputum (frank pulmonary oedema) — unless the cause is RV infarct, massive PE, or tamponade, in which case the lungs are clear despite shock.^[1]

Vital signs (the first clue):^[1]

• Hypotension — SBP at or below 90 mmHg for at least 30 minutes, or vasopressors to maintain SBP at least 90 mmHg. Assess perfusion as well as pressure — hypoperfusion can be present before profound hypotension.^[14]
• Tachycardia — compensatory.
• Tachypnoea — from pulmonary oedema, metabolic acidosis (Kussmaul breathing), or anxiety.
• Hypoxaemia — pulmonary oedema, V/Q mismatch.
• Cool peripheries, delayed capillary refill, mottled skin — vasoconstriction; cool extremities are part of the clinical criteria.^[14]
• Oliguria — catheterise early; urine output at or below 30 mL/hour.^[14]
• Altered mental status — confusion, agitation, obtundation.^[14]

Examination (organ by organ):^[1]

• JVP — typically raised (biventricular failure, RV infarct, tamponade, PE); a flat JVP suggests hypovolaemia or vasodilatory shock and prompts a fluid challenge.
• Precordium — a diffuse, weak apex (LV failure); an RV heave (RV infarct, PE, pulmonary hypertension); a right parasternal heave in massive PE; an absent apex with muffled sounds in tamponade.
• Auscultation — an S3 gallop (the auscultatory hallmark of severe LV failure), bibasal crackles (pulmonary oedema), a new pansystolic murmur at the apex radiating to the axilla (papillary muscle rupture — acute severe MR) or at the lower left sternal edge with a thrill (VSR); a diastolic murmur of acute severe AR (dissection, endocarditis); a pericardial rub (tamponade or myopericarditis); a silent precordium (a large effusion or tamponade, cardiac arrest).
• Abdomen — tender pulsatile hepatomegaly with hepatojugular reflux (right-heart failure).
• Periphery — cool, clammy, mottled, peripheral cyanosis; a weak and thready pulse; a narrow pulse pressure (low stroke volume).^[1]

Atypical presentations (high-yield)

• Elderly or diabetic — a painless MI with confusion, falls, breathlessness, fatigue as the only clues; shock may be the first sign of infarction.
• Right ventricular infarction (with inferior MI) — the clear-lung-fields shock: raised JVP, hypotension, a Kussmaul sign (the JVP rises paradoxically with inspiration), a clear chest; worsens catastrophically with nitrates or diuretics.^[9]
• Mechanical complication days after MI — a sudden new murmur with haemodynamic collapse in a patient who had been recovering; papillary muscle rupture (pansystolic apical, often no thrill because LA pressure equalises with LV) or ventricular septal rupture (a loud pansystolic lower-left-sternal-edge murmur with a thrill).
• Cardiac tamponade — Beck triad (hypotension, raised JVP, muffled heart sounds), pulsus paradoxus (a drop in SBP over 10 mmHg on inspiration), electrical alternans on ECG; emergency pericardiocentesis.
• Massive pulmonary embolism — sudden syncope, pleuritic pain, a right-heart failure pattern on ECG (S1Q3T3, right-axis deviation, T-wave inversion V1 to V3, RBBB), hypoxaemia with a clear CXR; right ventricular strain on echo.
• Drug overdose (beta-blocker, calcium-channel blocker, digoxin) — bradycardia in shock is the clue; specific antidotes (glucagon, high-dose insulin euglycaemic therapy, digoxin Fab, calcium, lipid emulsion).^[1]

The differential — separate cardiogenic from its mimics, because the treatment is opposite

The first task is to separate cardiogenic shock from its mimics, because the management is the opposite (cardiogenic needs an inotrope, a vasopressor and decongestion; hypovolaemic and distributive need fluid; obstructive needs a needle or treatment of the obstruction).^[13]

• Hypovolaemic shock — blood loss (GI bleed, trauma, ruptured AAA, postpartum haemorrhage), fluid loss (vomiting, diarrhoea, burns). Distinguish: a flat JVP, dry then cold peripheries, a wedge that is not raised, no chest pain. Treat with fluid (crystalloid, then blood if bleeding).
• Septic or distributive shock — infection, warm peripheries early (vasodilatation), wedge normal or low, high cardiac output (until late), SVR low, often a leucocytosis and a source. Treat with prompt fluids (at least 30 mL/kg crystalloid is the Surviving Sepsis 2021 starting dose, though a weak recommendation), antimicrobials within 1 hour, vasopressors and source control.^[20] A common pitfall: late sepsis can become cold with low-output myocardial depression, mimicking CS — the bedside echo (looking for a primary cardiac problem) and the wedge help.
• Obstructive shock — massive PE, tension pneumothorax, cardiac tamponade. Each is immediately reversible:
  • Tamponade — Beck triad, pulsus paradoxus, equalisation of diastolic pressures, a swinging heart on echo; pericardiocentesis.
  • Tension pneumothorax — tracheal deviation, hyper-resonance, absent breath sounds on one side; needle decompression then a chest drain.
  • Massive PE — sudden syncope, RV strain on ECG and echo, raised D-dimer, CT pulmonary angiogram; systemic thrombolysis or catheter-directed thrombolysis or surgical embolectomy — reperfusion modalities used in massive PE alongside extracorporeal support in refractory collapse.^[24]
• Anaphylactic shock — exposure, urticaria, angioedema, bronchospasm, hypotension within minutes; treat with prompt intramuscular adrenaline first, then fluids and adjunct medications — the World Allergy Organization guidelines place IM adrenaline at the centre of first aid and adjuncts only after it.^[19]
• Acute adrenal crisis (Addisonian crisis) — weakness, abdominal pain, hyponatraemia, hyperkalaemia, hypoglycaemia, pigmentation; acute adrenal crisis is a life-threatening condition requiring immediate treatment, with parenteral glucocorticoid (hydrocortisone) and fluids.^[25]
• Cardiogenic mimics of shock — other cardiac disorders (valve disease, conduction system disease, pericardial disease, drug toxicity) can themselves produce a cardiogenic-shock picture and must be sought deliberately.^[14]

The single best discriminator is the bedside echocardiogram combined with wedge pressure or cardiac index measurement (where available) — a globally hypokinetic, dilated LV with raised wedge and low CI confirms cardiogenic shock; a normal LV with low wedge points to hypovolaemia; a dilated RV with raised JVP and clear lungs points to RV infarct or PE.^[1]

Bedside assessment — perfusion, not pressure

ABCDE first. Cardiogenic shock is a perfusion diagnosis, so assess perfusion, not just pressure:^[13]

Bedside perfusion assessment (the earliest signs):^[1]

• Capillary refill time — press, release, and watch the refill; delayed capillary refill and mottled skin mark advanced shock.
• Urine output — catheterise early; oliguria (urine output at or below 30 mL/hour) is one of the earliest signs of failing perfusion.^[14]
• Mental status — confusion, agitation, obtundation.
• Lactate — arterial or venous; a raised or rising lactate despite therapy is the biochemical marker of ongoing tissue hypoperfusion.^[14]
• Skin temperature — cool peripheries (cold shock) versus warm (vasoplegic late shock).^[14]

JVP assessment at 45 degrees: raised in CS (biventricular failure, RV infarct, PE, tamponade); a flat JVP challenges the diagnosis and prompts a cautious fluid challenge.^[1]

Pulsus paradoxus — a drop in SBP over 10 mmHg on inspiration — points to tamponade, severe asthma or COPD, tension pneumothorax, massive PE.^[1]

The "shock bundle" at the bedside (the National Cardiogenic Shock Initiative or Tehrani et al. 2020 protocol):^[13]

1. Arterial line (continuous BP) — the brachial or femoral route; the radial under-reads in severe vasoconstriction.
2. Two large-bore IV cannulae and central venous access (right internal jugular or femoral, given the need for a PA catheter and possible ECMO cannulation).
3. Bedside echo within minutes — confirm the cardiac cause, identify mechanical complications, RV function, valve lesions, effusion or tamponade.
4. Pulmonary artery (Swan-Ganz) catheter — for the deteriorating or vasopressor-dependent patient: gives wedge, cardiac output (thermodilution), mixed venous saturation (SvO2), and calculates cardiac power output (CPO equals MAP times CO over 451, in Watts). In the SHOCK registry, cardiac power was the strongest haemodynamic correlate of in-hospital mortality; contemporary shock protocols often target CPO above 0.6 W as a haemodynamic goal.^[27][31]
5. Lactate, ABG, full blood count, U and E, LFT, troponin, BNP or NT-proBNP, group-and-save, cross-match, coagulation — baseline labs.
6. ECG — STEMI (drive to emergency PCI), tachy or bradyarrhythmia, a PE pattern, tamponade (electrical alternans).
7. CXR — pulmonary oedema, cardiomegaly, a widened mediastinum (dissection), pneumothorax.^[1]

Investigations — echo is the test; haemodynamics confirm

First-line (in parallel with resuscitation):^[9][13]

• 12-lead ECG — STEMI drives emergency revascularisation; ST elevation in II, III or aVF with V4R suggests RV infarct; S1Q3T3, right-axis deviation, RBBB, T-wave inversion V1 to V3 suggests massive PE; electrical alternans suggests tamponade; a wide QRS or hyperkalaemia — beware acidosis-induced arrhythmia.
• Chest X-ray — pulmonary oedema (Bat's-wing alveolar shadowing, Kerley B lines, cardiomegaly, pleural effusions); clear lung fields with shock suggest RV infarct, PE, tamponade, hypovolaemia.
• Echocardiography (transthoracic, emergency bedside) — the single most important diagnostic test. Look for: global LV hypokinesis (large MI, myocarditis, cardiomyopathy), regional wall-motion abnormality in a coronary distribution (acute MI), a dilated failing RV with preserved LV (RV infarct, massive PE), severe MR with a flail leaflet (papillary muscle rupture), a ventricular septal defect with a high-velocity left-to-right jet on colour Doppler (VSR), a pericardial effusion with diastolic RV collapse and a swinging heart (tamponade), regional wall-motion abnormality of the aortic valve (acute severe AR), an LV apical thrombus. Echo also estimates LVEF and pulmonary artery systolic pressure (the TR jet).
• Arterial blood gas — metabolic acidosis (low pH, low bicarbonate, raised lactate), hypoxaemia, a raised base deficit (correlates with lactate and outcome).
• Lactate — arterial or venous; clearance is a target of therapy (failing to clear lactate is an indication to escalate).
• Troponin — confirms myocardial injury (but may already be high in chronic HF or renal failure; trend the rise).
• BNP or NT-proBNP — high in CS (a cardiac cause); a low BNP argues against a cardiac cause.
• Renal function, electrolytes, liver function, coagulation, full blood count — baseline and end-organ function.
• Drug levels — digoxin, salicylate, paracetamol (an overdose screen), beta-blocker or CCB (history).^[1]

Invasive haemodynamics (PA catheter) — for the deteriorating or refractory patient:^[10][13]

• Pulmonary capillary wedge pressure (PCWP) — over 15 mmHg in the SHOCK trial; Forrester subset IV uses over 18 mmHg. Below 18 mmHg with a low CI is "Forrester III — cold and dry" and should prompt a cautious fluid challenge rather than a diuretic.
• Cardiac index (CI) — below 2.2 L/min/m2 in CS.
• Mixed venous saturation (SvO2) — a low mixed venous saturation indicates inadequate oxygen delivery relative to consumption.
• Systemic vascular resistance (SVR) — typically high (compensatory vasoconstriction) in early CS, low in vasoplegic late CS.
• Cardiac Power Output (CPO) equals (MAP times CO) over 451 (in Watts) — Fincke et al. found cardiac power the strongest haemodynamic correlate of in-hospital mortality in the SHOCK registry; CPO above 0.6 W is used as a protocol haemodynamic goal.^[27][31]

Coronary angiography — mandatory in MI-related CS; it identifies the culprit lesion, drives immediate revascularisation (culprit-lesion-only PCI per CULPRIT-SHOCK), and identifies the surgical or mechanical problem.^[4]

Advanced (case by case): CT coronary angiography (if a non-ischaemic cause is suspected and the patient is stable enough), cardiac MRI (myocarditis, cardiomyopathy, infiltrative disease — usually once stabilised), CT pulmonary angiogram (massive PE), endomyocardial biopsy (giant-cell myocarditis, sarcoidosis, transplant rejection), a drug screen (overdose).^[1]

Named scores and criteria — reproduced verbatim

SCAI SHOCK stages (Baran 2019, Naidu 2022)^[6][7]

^[8]

The B-to-C boundary is the appearance of overt hypoperfusion.^[6]

Forrester haemodynamic subsets (Forrester, Diamond, Chatterjee; NEJM 1976)^[10][11]

^[26]

SHOCK trial entry criteria (Hochman 1999)^[1]

• SBP below 90 mmHg for at least 30 minutes OR requiring inotropes or vasopressors to maintain SBP at least 90 mmHg;
• CI below 2.2 L/min/m2 AND PCWP over 15 mmHg (the original trial used 15);
• plus clinically evident hypoperfusion (oliguria, cold peripheries, altered mentation).^[1]

^{[14] [16] [22]}

Resuscitation — the shock funnel begins

Enlarge

^{[16] [17]}

ABCDE first, in parallel with the diagnostic work-up. Cardiogenic shock is a time-critical emergency — every minute of hypoperfusion deepens the spiral.^[9][13]

Airway and breathing:^[1]

• High-flow oxygen, titrated to the patient's saturations and the presence of hypercapnic lung disease; escalate to high-flow nasal cannula or non-invasive ventilation (CPAP or BiPAP) for pulmonary oedema — NIV reduces the work of breathing, recruits alveoli and lowers preload and afterload.
• Intubate and mechanically ventilate if the patient is tiring, comatose, or in cardiac arrest — positive-pressure ventilation also reduces LV afterload (a useful haemodynamic effect in CS) but reduces venous return, so titrate carefully and ensure adequate preload.^[1]

Circulation — early vascular access and monitoring:^[1]

• Large-bore and central venous access, an arterial line for continuous BP, and a urinary catheter, with invasive haemodynamic assessment (a PA catheter for the deteriorating or vasopressor-dependent patient) — the standardised protocols emphasise early intervention and ongoing haemodynamic assessment.^[13]
• A cautious fluid challenge only where hypovolaemia is suspected — and avoiding iatrogenic harm (fluid overload worsens congestion) is an explicit principle of contemporary CS management.^[24]

Circulation — pharmacological haemodynamic support (the core of early therapy):^[13]

The goal is to restore perfusion while preserving coronary perfusion, without worsened arrhythmia or ischaemia. The choice of agent depends on the haemodynamic phenotype, and no single agent has shown a mortality benefit in CS:^[17]

• Cold, hypotensive CS (low CI, low MAP, raised wedge — the classic form) — an inotrope to raise cardiac output plus a vasopressor to defend pressure:

  • Noradrenaline — the first-line vasopressor of choice in CS (supported by the OptimaCC trial and the SOAP-II comparison with dopamine).^[15][17]
  • Dobutamine — the standard first-line inotrope in most CS.
  • Milrinone — an inodilator alternative; the CAPITAL DOREMI trial found milrinone not superior to dobutamine (primary composite 49 versus 54 percent, RR 0.90, P=0.47).^[28]
  • Levosimendan — efficacy against placebo in early CS is still being tested (LevoHeartShock); not established therapy.^[17]
  • Inotrope selection should be guided by physician experience, availability, cost and the individual patient's response.^[17]

• Warm vasoplegic CS (low SVR despite an inotrope — the late, SIRS-like phenotype) — noradrenaline remains the first-line vasopressor; evidence for specific add-on agents in CS vasoplegia is limited.^[17]

• Dopamine — no longer first-line: the SOAP-II trial randomised shock patients to dopamine versus noradrenaline as first-line vasopressor; dopamine caused more arrhythmic events (24.1 percent versus 12.4 percent, P under 0.001), and in the cardiogenic-shock subgroup (280 patients) dopamine was associated with an increased rate of death at 28 days.^[15]

The "shock funnel" — escalation triggers: escalate when the patient is SCAI stage D or E, has a rising lactate despite an inotrope, worsening end-organ function, high inotrope or vasopressor doses, or cardiac arrest or peri-arrest.^[13]

Adjunctive therapy in MI-related CS:^[9]

• Dual antiplatelet therapy and parenteral anticoagulation — follow the standard acute coronary syndrome pathway (aspirin plus a P2Y12 inhibitor; parenteral anticoagulation per local protocol), with agent choice and dosing individualised to bleeding risk.
• High-intensity statin therapy.
• Glycaemic control — avoid hypoglycaemia; dose insulin per unit protocol.
• Revascularisation — see Definitive Management.^[9][16]

Definitive management — cause-specific, team-based, escalate to MCS

The definitive management of CS is cause-specific and team-based: identify and treat the cardiac cause, support the circulation to break the spiral, and escalate to mechanical circulatory support (MCS) as a bridge to recovery, decision, transplant or durable LVAD.^[1][13]

Step 1 — Identify and treat the cause (within minutes to hours)

The single biggest mortality-reducing intervention in MI-CS is early coronary revascularisation.^[1]

• STEMI-CS — immediate revascularisation of the infarct-related artery is the only treatment for MI-related CS supported by randomised clinical trials (Samsky et al., JAMA 2021), with primary PCI the default strategy.^[16]
• NSTEMI-CS — an immediate invasive strategy with PCI.^[16]
• CULPRIT-lesion-only PCI is preferred over immediate multivessel PCI in MI-CS (the CULPRIT-SHOCK trial, Thiele 2017): culprit-lesion-only PCI reduced the composite of death OR severe renal failure needing RRT (45.9 percent versus 55.4 percent; relative risk 0.83, P equal to 0.01). Staged complete revascularisation is performed later once stabilised.^[4]
• Mechanical complications of MI — emergency surgical repair for papillary muscle rupture, VSR, free-wall rupture; surgical and MCS options are reviewed in the AHA scientific statement, with MCS as a bridge to surgery.^[24]
• Acute severe valvular disease — emergency valve surgery.^[24]
• Cardiac tamponade — emergency pericardiocentesis.^[24]
• Massive PE — systemic thrombolysis or catheter-directed thrombolysis or surgical embolectomy — the reperfusion modalities used in massive PE.^[24]
• Arrhythmia — DC cardioversion for an unstable tachyarrhythmia; temporary then permanent pacing for symptomatic bradyarrhythmia or AV block.^[24]
• Drug overdose — specific antidotes and supportive care per toxicology protocols, with MCS as a bridge in refractory drug-induced pump failure.^[24]
• Fulminant myocarditis — supportive MCS (often VA-ECMO) through the acute phase.^[24]
• End-stage cardiomyopathy or transplant rejection — an MCS bridge to transplant or a palliative pathway.^[24]

Step 2 — Mechanical circulatory support (MCS) — bridge to recovery or decision

MCS unloads the failing ventricle, restores end-organ perfusion, and buys time for definitive therapy. It is not a destination for most (post-cardiotomy support being the exception).^[13]

^[13]

The choice of MCS depends on the primary failing chamber, the oxygenation need, the anticipated duration, and the centre expertise. A practical algorithm: LV-dominant CS — Impella (or IABP if Impella is unavailable); RV-dominant or biventricular CS, or CS with hypoxaemia or arrest — VA-ECMO; combine (ECMO plus Impella equals "ECPELLA") when LV distension is a problem.^[13]

Step 3 — Decongestion, oxygen delivery and metabolic support

• Diuresis — an intravenous loop diuretic for congestion once perfusion is defended; cautious in RV infarct (preload-dependent).^[24]
• Ventilation — see Resuscitation; NIV for pulmonary oedema, invasive ventilation for the tiring or comatose patient.
• Correct electrolytes and acidosis — renal replacement therapy for severe acidosis, hyperkalaemia, or fluid overload unresponsive to diuretics.^[24]
• Thromboprophylaxis, stress-ulcer prophylaxis, and early enteral nutrition once stable, per critical-care protocol — the AHA statement frames these as part of contemporary best supportive practice.^[24]

Step 4 — De-escalation and disposition

• Wean MCS and inotropes as the underlying cause recovers — guided by lactate clearance, CI, CPO, and echocardiographic recovery of EF. Wean VA-ECMO by reducing the sweep gas and then the flow over hours; decannulate surgically.
• Long-term HF therapy — once euvolaemic and stable, introduce the four pillars of HFrEF (ARNI or ACE-inhibitor, beta-blocker, MRA, SGLT2 inhibitor) cautiously and uptitrate.
• Bridge to transplantation or durable LVAD for those who cannot wean (end-stage cardiomyopathy); a palliative pathway for those who are not candidates.^[1]

Special situations you will actually meet

• Acute MI with LV failure (the commonest CS) — the most common cause of cardiogenic shock is acute MI; treat with immediate revascularisation of the infarct-related artery, an inotrope plus noradrenaline, and MCS as a bridge; culprit-lesion-only PCI.^[14][16][4]
• Right ventricular infarction (with inferior STEMI) — the clear-lung-fields shock; a raised JVP, hypotension, a clear chest; preload-dependent. Current AHA and ESC guidance recommends that nitrates are not administered in RVMI because dropping preload in a ventricle with compromised ejection may reduce cardiac output and precipitate hypotension — though a 2023 systematic review and meta-analysis found the contraindication is not supported by the available evidence (no arrest or death after sublingual nitroglycerin in pooled studies; only transient adverse events). Manage with cautious volume expansion, avoidance of preload-reducing agents, and reperfusion.^[18]
• Acute mechanical complications of MI — a sudden haemodynamic collapse with a new murmur:
  • Papillary muscle rupture — acute severe MR, a pansystolic apical murmur, pulmonary oedema, shock. Echo shows a flail leaflet and an eccentric MR jet. Emergency surgery, with MCS as a bridge.
  • Ventricular septal rupture — a loud pansystolic murmur at the lower left sternal edge with a thrill, biventricular failure; echo with colour Doppler shows a left-to-right shunt. Emergency surgical closure, with MCS as a bridge.
  • Free-wall rupture — sudden chest pain, pericardial tamponade, electromechanical dissociation, usually fatal; emergency surgery if recognised.
• Fulminant myocarditis — a young patient, a viral prodrome, sudden severe LV dysfunction with or without arrhythmia and AV block. VA-ECMO support through the acute phase.^[24]
• Acute decompensated heart failure or end-stage cardiomyopathy — chronic HF with a precipitant (ischaemia, arrhythmia, infection, anaemia, an NSAID, non-adherence); treat the precipitant and decongest; consider MCS or transplant.^[24]
• Acute severe valvular disease — acute severe MR (papillary muscle rupture, endocarditis), acute severe AR (aortic dissection, endocarditis). Emergency valve surgery.^[24]
• Massive pulmonary embolism — sudden syncope, RV strain on ECG and echo, hypoxaemia with a clear CXR, raised D-dimer, confirmed on CTPA. Systemic thrombolysis, catheter-directed thrombolysis or surgical embolectomy, with extracorporeal life support in refractory collapse.^[22]
• Cardiac tamponade — Beck triad, pulsus paradoxus, electrical alternans, diastolic RV or RA collapse on echo. Emergency pericardiocentesis; treat the cause.
• Drug overdose — specific antidotes and supportive care per toxicology protocols; MCS (VA-ECMO) may be needed as a bridge when standard inotropes fail.^[24]
• Post-cardiotomy shock — failure to wean from cardiopulmonary bypass; temporary MCS support; a high mortality.
• Takotsubo cardiomyopathy — stress-induced apical ballooning; may present with shock; supportive and MCS management per phenotype.^[24]
• Pregnancy-related CS — peripartum cardiomyopathy (heart failure presenting towards the end of pregnancy or in the months after delivery) is the characteristic pregnancy-related cause; the ESC EORP registry describes its global presentation, management and outcomes, with disease-specific therapies such as bromocriptine under active investigation.^[23]

How patients with cardiogenic shock come to harm (the preventable list)

• Treating CS as if it were septic or hypovolaemic shock — fluid overload harms a congested patient; contemporary CS management explicitly warns against iatrogenic harm. Check the wedge, the JVP and the echo before fluids.^[24]
• Failing to recognise RV infarct — AHA and ESC guidance advises withholding nitrates in RVMI (preload-dependent collapse risk); know the clear-lung-fields phenotype.^[18]
• Delaying revascularisation for investigations — every minute of delay deepens the spiral; the SHOCK trial is the proof.^[1]
• Using dopamine as the first-line vasopressor — SOAP-II showed more arrhythmic events (24.1 versus 12.4 percent) and, in the cardiogenic-shock subgroup, more deaths at 28 days with dopamine than noradrenaline; noradrenaline is the first-line vasopressor in CS.^[15]
• Relying on blood pressure alone — hypoperfusion can be present before profound hypotension; monitor urine output, mentation, skin and lactate.^[14]
• Misclassifying a mechanical complication as "worsening LV failure" — a new murmur post-MI is papillary muscle rupture or VSR until proven otherwise; urgent echo.^[24]
• Forgetting the differential of shock — tamponade, tension pneumothorax, massive PE, anaphylaxis, adrenal crisis are all immediately reversible; missing them is fatal.^[14]
• Indiscriminate IABP use after IABP-SHOCK II — routine IABP does NOT reduce 30-day mortality (39.7 versus 41.3 percent); reserve for selected cases.^[3]

Prognosis and disposition

In-hospital mortality of CS remains about 40 to 50 percent in contemporary series, 30-day mortality is nearly 40 percent and 1-year about 50 percent after AMI-CS, and SCAI E hospital mortality was 67.0 percent in Jentzer's CICU validation — not an 80-percent-plus figure.^[16][22][8]

Predictors of poor outcome: older age (especially over 75), lower EF, lower cardiac index, lower CPO, higher wedge, rising lactate, renal dysfunction, hyperlactataemia not clearing, biventricular failure, mechanical complications, delay to revascularisation, out-of-hospital cardiac arrest, SCAI stage D or E at presentation, multi-organ failure.^[7][8]

Disposition:^[1]

• All CS patients belong in a critical-care environment (a cardiac ICU or coronary care unit with MCS capability) with invasive monitoring and rapid access to PCI, surgery and MCS.
• Early transfer to a regional shock centre for the deteriorating patient or for MCS or transplant consideration.
• Survivors need lifelong cardiology follow-up — GDMT for HFrEF, device therapy (ICD or CRT) once stable, secondary prevention, cardiac rehabilitation, and a palliative-care discussion for the non-recoverable, non-transplant candidate.^[1]

Pregnancy and special populations

• Elderly (over 75) — atypical presentation, higher mortality; of the 10 prespecified subgroup analyses in the SHOCK trial, only age interacted significantly with treatment — the early-revascularisation survival benefit was apparent only for patients younger than 75 years (1-year survival 51.6 versus 33.3 percent), so decisions are made with the patient and family.^[2]
• Pregnancy — peripartum cardiomyopathy is the characteristic cause of peripartum cardiogenic shock; the ESC EORP registry (739 women, 49 countries) describes its clinical presentation, management and 6-month outcomes, and disease-specific therapy such as bromocriptine remains under investigation. Care is multidisciplinary (obstetric-cardiology-anaesthetic).^[23]
• Post-cardiac-arrest — CS after cardiac arrest carries a very high mortality; early revascularisation if there is STEMI.^[24]

Evidence, guidelines and regional differences

Key guidelines: the 2023 ESC ACS Guidelines (Byrne et al.) for the acute MI-CS pathway (early revascularisation, culprit-lesion-only PCI); the 2022 AHA/ACC/HFSA Heart Failure Guideline (Heidenreich et al.) for HF-CS; the SCAI SHOCK classification (Baran 2019, Naidu 2022) for staging; the National Cardiogenic Shock Initiative standardised protocol (Tehrani et al., JACC:HF 2020) for the shock funnel.^{[6][7][9][12][13]}

Landmark trials and statements every exam candidate must know:^[1]

• SHOCK trial (Hochman et al., NEJM 1999) — randomised early revascularisation (PCI or CABG within 48 hours) versus initial medical stabilisation in MI-CS. Early revascularisation did NOT significantly reduce 30-day all-cause mortality (46.7 percent versus 56.0 percent, P equal to 0.11) but DID reduce 6-month mortality (50.3 percent versus 63.1 percent, P equal to 0.027) — cite it for the 6-month and 1-year survival benefit, NOT for a 30-day mortality win.^[1]
• SHOCK 1-year follow-up (Hochman et al., JAMA 2001) — 1-year survival 46.7 percent versus 33.6 percent (P under 0.03), with the benefit confined to age under 75. This trial established early revascularisation as the standard of care in MI-CS.^[2]
• IABP-SHOCK II (Thiele et al., NEJM 2012) — routine IABP in MI-CS did NOT reduce 30-day mortality (39.7 percent versus 41.3 percent, P equal to 0.69). Routine IABP is no longer used as default support in AMI-CS planned for early revascularisation. The IABP retained a role in selected mechanical-complication cases.^[3]
• CULPRIT-SHOCK (Thiele et al., NEJM 2017) — in MI-CS with multivessel disease, culprit-lesion-only PCI reduced the composite of death OR severe renal failure needing RRT (45.9 percent versus 55.4 percent; RR 0.83, P equal to 0.01). Death alone RR 0.84 (P equal to 0.03); RRT alone RR 0.71 (P equal to 0.07, not significant). Cite the composite. Multivessel PCI is deferred to a staged procedure.^[4]
• TRIUMPH (Alexander et al., JAMA 2007) — the NOS inhibitor tilarginine (L-NMMA) in MI-CS did NOT reduce 30-day mortality (48 versus 42 percent, P=0.24); enrolment was stopped at 398 patients for futility. A landmark negative trial — targeted NO modulation in CS does not work.^[5]
• SOAP-II (De Backer et al., NEJM 2010) — dopamine versus noradrenaline as first-line vasopressor in shock: no significant difference in 28-day death overall, but more arrhythmic events with dopamine (24.1 versus 12.4 percent, P under 0.001), and in the cardiogenic-shock subgroup dopamine was associated with an increased rate of death at 28 days — the basis for noradrenaline as the preferred first-line vasopressor in CS.^[15]
• SCAI 2019 (Baran et al.) and 2022 update (Naidu et al.) — the 5-stage classification (A to E) with the B-to-C boundary defined by the appearance of hypoperfusion; validated against in-hospital mortality across registries (Jentzer CICU: A 3.0, B 7.1, C 12.4, D 40.4, E 67.0 percent).^[6][7][8]
• CAPITAL DOREMI (Mathew et al., NEJM 2021) — milrinone versus dobutamine in CS: primary composite 49 versus 54 percent (RR 0.90, P=0.47) — neither inotrope is superior.^[28]
• ISAR-SHOCK (Seyfarth et al., JACC 2008) — Impella versus IABP: greater CI rise (0.49 versus 0.11) but identical 30-day mortality (46 percent both arms).^[29]
• DanGer Shock (Møller et al., NEJM 2024) — Impella CP plus standard care versus standard care in STEMI-CS: 180-day death 45.8 versus 58.5 percent (HR 0.74, P=0.04); more safety events (24.0 versus 6.2 percent).^[30]

Regional deltas:^[1]

• US (SCAI or AHA) — SCAI SHOCK staging drives triage; early revascularisation in MI-CS; culprit-lesion-only PCI (CULPRIT-SHOCK adopted); Impella and VA-ECMO at tertiary shock centres; the National Cardiogenic Shock Initiative standardised protocol.
• UK (NICE or NHS England) — a developing national CS network with regional shock centres, ECMO retrieval; routine IABP use declined post-IABP-SHOCK II; early revascularisation via cardiac networks.
• Europe (ESC) — the 2023 ESC ACS Guidelines endorse early revascularisation and culprit-only PCI; levosimendan is used in some countries for refractory CS.
• India (NEET-PG or INICET context) — primary PCI is not universally available; fibrinolysis remains common as first reperfusion in many hospitals; delayed presentation is typical; resource limits constrain PA catheter, Impella and VA-ECMO availability — concentrated in tertiary centres; a high prevalence of rheumatic valvular disease and cardiomyopathy as non-MI causes; cost-benefit discussions with the family are central; dobutamine and noradrenaline are widely available and affordable.

Current controversies: (1) the optimal MCS choice (Impella versus VA-ECMO versus ECPELLA — RECOVER IV, DanGer Shock, ECLS-SHOCK); (2) routine use of steroids for vasoplegia; (3) superurgent complete revascularisation timing after CULPRIT-SHOCK; (4) microcirculatory monitoring; (5) outcome prediction with machine-learning models; (6) the ethical allocation of MCS and transplant.^[1]

The mantra, and the viva honesty line

^[1]

The mantra: watch the perfusion not the pressure, stage with SCAI, revascularise early, defend the MAP, and escalate to a pump before the spiral is irreversible.^[6][13]

Ward-round test — three stems, thirty seconds each

Stem 1 — the post-PCI patient from the top of the topic (answer)ShowHide

A 64-year-old man, six hours after primary PCI for an anterior STEMI, becomes confused with oliguria; BP 88/60, HR 118, cool mottled peripheries, bibasal crackles, lactate 5.2 mmol/L. What is the diagnosis, the stage, and the immediate management? Model: Cardiogenic shock complicating acute MI — SCAI stage C (classic): hypoperfusion with hypotension, raised wedge (the crackles), raised lactate. Perfusion is failing while the cuff is still being debated. Immediate management: ABCDE and oxygen, arterial line and central access, a bedside echo to exclude a mechanical complication, an inotrope plus the first-line vasopressor noradrenaline titrated to perfusion (no single agent has proven mortality benefit), careful diuresis for the congestion, and re-discussion of revascularisation (the stent is open, so support the circulation and watch for recovery; if deteriorating, escalate to MCS). Do not flood him with fluid — the wedge is already high.^[6][13][17]

Stem 2 — the clear-lung-fields shock (answer)ShowHide

A 70-year-old with an inferior STEMI has BP 84/58, a raised JVP with a Kussmaul sign, and clear lung fields; he has just been given sublingual GTN by the nurse and has dropped his pressure further. What is this, and what is the single most important change in management? Model: Right ventricular infarction — the clear-lung-fields shock. The RV is preload-dependent and the GTN has dropped preload. Stop the nitrates — AHA and ESC guidance recommends nitrates are not administered in RVMI because reduced preload may cut cardiac output and precipitate hypotension (a 2023 systematic review found this contraindication is not actually evidence-supported — but in the shocked patient, stop them) — avoid other preload-reducing agents (diuretics), give cautious volume expansion, and reperfuse the RCA (PCI).^[18]

Stem 3 — the day-4 new murmur (answer)ShowHide

A 58-year-old woman, four days after an inferior STEMI that was managed medically, suddenly develops pulmonary oedema and shock with a harsh pansystolic murmur and a thrill at the lower left sternal edge. What is the diagnosis, the investigation, and the disposition? Model: Ventricular septal rupture (typically days after MI) — a loud pansystolic murmur with a thrill at the lower left sternal edge plus biventricular failure is VSR until proven otherwise (distinguish from papillary muscle rupture, which is apical, radiates to the axilla, and usually has no thrill). Emergency bedside echo with colour Doppler confirms the left-to-right shunt. Disposition: emergency surgical closure (or a percutaneous device in selected cases), with MCS (IABP or Impella) as a bridge and a vasodilator (nitroprusside) to reduce afterload if BP tolerates. This is a surgical emergency — mortality without surgery is catastrophic.^[9]

References31ShowHide

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