Cardiogenic Shock

Overview & definition

Cardiogenic shock — the failure of the heart to maintain the cardiac output adequate for the tissue perfusion. The vicious cycle: the low CO triggers the compensatory vasoconstriction (the SVR rises to maintain the BP), but the increased afterload further reduces the stroke volume (the already-failing ventricle cannot pump against the high resistance), worsening the low CO. The mortality 40-60 per cent. The prompt recognition + the revascularisation (if the ACS) + the haemodynamic support + the mechanical support (if refractory) are the core.[1][1]

The formal definition — the cardiogenic shock is the inadequate tissue perfusion due to a primary cardiac pump failure, despite an adequate or elevated preload. The diagnostic hallmarks: the hypotension (SBP under 90 mmHg or MAP under 65 for over 30 min), the signs of hypoperfusion (the oliguria, the altered mental state, the cold peripheries, the lactate above 2 mmol/L), the cardiac dysfunction (the reduced LVEF, the low cardiac index under 2.2 L/min/m², the elevated filling pressures — the PCWP above 15 mmHg). The "despite adequate preload" is the key discriminator — the cardiogenic shock is NOT a problem of volume (the hypovolaemic) or of distribution (the distributive / vasodilatory); it is a problem of the pump. The corollary: a fluid challenge that fails to improve the perfusion points toward the cardiogenic (or the obstructive) rather than the hypovolaemic shock.[1][10]

SCAI classification — the five stages

The SCAI (Society for Cardiovascular Angiography and Interventions) classification stratifies the cardiogenic shock into five stages — A through E — moving from the at-risk patient to the extremis. The stages parallel the temporal and the severity progression of the shock; each stage carries a progressively higher mortality (A under 5 per cent through E over 80 per cent). The classification guides the escalation of the monitoring and the therapy — the higher the stage, the more aggressive and the more invasive the support.[10]

The stages:[10]

• Stage A — At risk. The patient with the risk factors but NOT yet in the shock (the large anterior STEMI, the known HFrEF with the acute decompensation). The haemodynamics normal; the perfusion normal. The mortality low.
• Stage B — Beginning shock. The hypoperfusion beginning; the hypotension may respond to the fluid or to the low-dose vasopressor. The SBP above 90, the lactate near-normal. The clinical vigilance high.
• Stage C — Classic shock. The hypoperfusion now overt — the SBP under 90 (or the MAP under 65), the lactate above 2 mmol/L, the oliguria, the cold peripheries. The inotrope and the vasopressor required to maintain the perfusion.
• Stage D — Deteriorating. The shock worsening DESPITE the inotrope and the vasopressor — the escalating doses, the failing perfusion. The indication for the prompt mechanical circulatory support.
• Stage E — Extremis. The circulatory collapse — the cardiac arrest, the ongoing CPR, the refractory VF, the crash. The ECMO / the eCPR the consideration.

The practical use of the SCAI classification — the early recognition at the stage A-B (before the overt shock of the stage C), so that the revascularisation and the haemodynamic support can prevent the progression. A patient admitted with the large anterior STEMI is the stage A — the high vigilance, the early inotrope at the first sign of the hypoperfusion, the early PCI. The escalation to the stage D-E is the failure of the early recognition.[1][10]

[10]

The haemodynamic profile — Forrester subsets and the catheter findings

The cardiogenic shock has a stereotyped haemodynamic profile. The cardiac pump fails → the cardiac output falls, the ventricular filling pressures rise, the systemic vascular resistance rises (the compensatory vasoconstriction), and the mixed venous (and the central venous) oxygen saturation falls (the tissues extract more oxygen from the sluggish flow). The profile, summarised:[1][2]

• Cardiac index — low (under 2.2 L/min/m², often under 1.8 in the established shock).
• Pulmonary capillary wedge pressure (PCWP) — high (above 15 mmHg, often 20-30 with the pulmonary oedema).
• Systemic vascular resistance (SVR) — high (the compensatory vasoconstriction; the SVR rises to defend the BP).
• Mixed venous oxygen saturation (SvO₂) — low (under 65 per cent, often under 50 in the severe shock; the tissues extract maximally from the slow flow).
• Central venous pressure (CVP) — elevated in the right-heart failure, the biventricular failure, or the tamponade. [1]

The Forrester haemodynamic subsets (the classic 1976 framework, still examined) combine the wedge pressure (the "warm" vs the "wet") with the cardiac index (the "warm" vs the "cold") into four quadrants. The cardiogenic shock occupies the subset IV — the high wedge (wet) AND the low cardiac index (cold): the "cold and wet" profile. The management implication: the patient needs the inotrope (to raise the cardiac index) and the diuresis / the unloading (to lower the wedge), not the further fluid.[14][1]

[14] [1] [1] [1]

The pathophysiology — the vicious cycle

The heart fails → the CO falls → the BP falls → the compensatory the sympathetic the drive (the tachycardia, the vasoconstriction) → the SVR rises → the afterload increases → the failing the ventricle cannot the pump against the high afterload → the stroke volume falls further → the CO falls further → the worsens.[1][1]

The cycle also involves the compensatory tachycardia (which increases the myocardial oxygen demand while reducing the diastolic filling time) and the renin-angiotensin-aldosterone system (the sodium and water retention → the preload overload → the pulmonary oedema).[1]

The systemic inflammatory response is the second amplifier. The cardiogenic shock is no longer seen as a purely haemodynamic problem — it triggers a systemic inflammatory response syndrome (SIRS) indistinguishable from the sepsis (the nitric oxide release, the cytokine cascade, the inducible NOS, the reperfusion injury). The inflammatory vasoplegia supervenes on the original compensatory vasoconstriction, producing a mixed shock phenotype (the cardiogenic PLUS the distributive). This is why some patients with the established cardiogenic shock have a LOWER-than-expected SVR and require the vasopressor in addition to the inotrope. The inflammation also drives the reperfusion injury (after the PCI), the microcirculatory failure, and the multi-organ dysfunction that dominates the late course.[1][10]

The causes

• The acute coronary syndrome (the commonest — 80 per cent of the cardiogenic shock). The large the infarct (the anterior, the multivessel) or the mechanical complication (the VSD, the papillary muscle rupture, the free wall rupture).[1][1]
• The decompensated heart failure (the chronic HFrEF with the acute decompensation).[1]
• The myocarditis (the fulminant — the young, the viral).[1]
• The arrhythmia (the VT, the AF with the rapid ventricular response, the complete heart block).[1]
• The valvular (the acute severe MR, the acute severe AR, the prosthetic valve thrombosis).[1]
• The drug toxicity (the beta-blocker, the CCB, the TCA — the negative inotropy).[1]
• The post-cardiotomy (the after the cardiac surgery).[1]

The ACS-related causes fall into three groups: the primary LV pump failure (the large infarct, the multivessel disease — the commonest), the mechanical complication (the ventricular septal rupture at 3-5 days, the papillary muscle rupture with the severe MR, the free wall rupture with the tamponade — the days 1-5), and the right ventricular infarct (the inferior MI with the RV involvement — the high right-sided filling pressures, the clear lung fields). Each has a distinct management: the pump failure → the revascularisation + the inotrope; the mechanical complication → the urgent surgical repair with the MCS as the bridge; the RV infarct → the fluid loading (the RV is preload-dependent) + the inotrope + the sinus rhythm maintained (the AV synchrony critical for the RV filling) + the AV sequential pacing if the block.[1][1]

[1] [1]

The clinical

The signs of the poor perfusion:[1][1]

• The cool, the clammy skin (the peripheral vasoconstriction).
• The oliguria (the renal hypoperfusion).
• The altered mental state (the cerebral hypoperfusion).
• The hypotension (the SBP below 90 or the MAP below 65).
• The pulmonary oedema (the LV failure) OR the clear lung fields (the RV failure — the isolated right).
• The echo: the reduced LV function (the low EF, the low CO), the RV dilatation (if the RV infarct), the mechanical complication (the VSD, the MR).[1]

The bedside echocardiogram is the single most important diagnostic test in the suspected cardiogenic shock. It answers the four critical questions within minutes: (1) Is the LV function reduced? (the global hypokinesis = the pump failure; the regional = the ACS); (2) Is there a mechanical complication? (the colour Doppler for the MR, the VSD; the effusion for the tamponade / the free wall rupture); (3) Is the RV involved? (the RV dilatation, the McConnell sign, the D-shape of the LV in the RV infarct or the massive PE); (4) Is the preload adequate or excessive? (the IVC size and the collapsibility, the dilated fixed IVC of the high right-sided pressures). The echo differentiates the cardiogenic from the obstructive (the tamponade, the tension pneumothorax, the PE) and from the distributive shock (the hyperdynamic LV of the sepsis — a KEY discriminator).[1][2]

The lactate is the marker of the anaerobic metabolism and the cornerstone of the resuscitation monitoring. A lactate above 2 mmol/L with the hypoperfusion signs defines the shock; the lactate clearance (the fall by at least 10 per cent per hour) is the marker of the adequate resuscitation. A rising or the static lactate signals the ongoing hypoperfusion despite the apparent haemodynamic stability.[2]

The management

[1] [2] [10]

1. The identify and treat the cause

• The ACS → the urgent revascularisation (the PCI, the CABG). The SHOCK trial — the early revascularisation reduces the long-term mortality (even though the 30-day mortality was not significantly different).[1]
• The arrhythmia → the cardioversion / the pacing.
• The valvular → the surgical repair / the replacement.
• The drug toxicity → the specific antidote (the calcium + the glucagon + the high-dose insulin for the CCB / the BB; the bicarbonate for the TCA).[1]

The SHOCK trial (Hochman, NEJM 1999) established the paradigm: in the AMI cardiogenic shock, the early revascularisation (the PCI or the CABG within 24 hours) reduced the 6-month and the 1-year mortality compared with the initial medical stabilisation (the 1-year mortality 53 per cent vs 63 per cent), even though the 30-day mortality was not significantly different. The 6-year follow-up (Hochman, JAMA 2006) confirmed the durable benefit. The lesson — the early revascularisation is the standard, and the long-term survival is the endpoint that matters, not the 30-day.[3][4]

The CULPRIT-SHOCK trial (Thiele, NEJM 2017) refined the revascularisation strategy: in the multivessel-disease AMI cardiogenic shock, the culprit-lesion-only PCI at the index procedure was superior to the immediate multivessel PCI — the 30-day mortality 17.5 per cent vs 43 per cent, and the less renal-replacement therapy. The lesson — in the AMI shock, fix ONLY the culprit lesion acutely; stage the non-culprit lesions once the patient stabilises. This is now the guideline standard.[7]

2. The pharmacological support

The inotrope (to increase the contractility):[1][2]

• Dobutamine (the beta-1 — the increased contractility and the HR; the also the beta-2 vasodilation → the reduced afterload; but the tachyarrhythmia, the increased myocardial oxygen demand).[1]
• Milrinone (the PDE-3 inhibitor — the increased cAMP; the inotropy AND the vasodilation; the long half-life; the caution in the renal failure).[1]
• Levosimendan (the calcium sensitiser — the inotropy without the increased intracellular calcium; the less the arrhythmia; the vasodilation; the expensive).[2]
• Adrenaline (the potent but the high the arrhythmia, the increased the lactate, the increased the myocardial oxygen demand).[1]

The vasopressor (to maintain the perfusion pressure):[1][2]

• Noradrenaline (the alpha-1 — the vasoconstriction; the preferred over the dopamine per the SOAP II).[1]
• The target the MAP 65 (or above 70-80 if the TBI / the known the vascular disease).[2]

The SOAP II trial (De Backer, NEJM 2010) compared the dopamine with the noradrenaline in the circulatory shock (the cardiogenic, the septic, the hypovolaemic). The result — the no difference in the overall mortality, BUT the dopamine had the more arrhythmia (the atrial fibrillation especially) and the more frequent rate of discontinuation for the adverse events. The cardiogenic subgroup showed a trend toward the higher mortality with the dopamine. The lesson — the noradrenaline is the preferred first-line vasopressor in the cardiogenic shock; the dopamine is avoided (the arrhythmia, the worse outcome).[8]

The SURVIVE trial (Mebazaa, JAMA 2007) compared the levosimendan with the dobutamine in the acute decompensated heart failure. The result — the no difference in the short-term or the long-term mortality, though the levosimendan showed a transient benefit in the subgroup with the prior beta-blocker use. The lesson — the levosimendan is NOT superior to the dobutamine; the dobutamine remains the first-line inotrope for the cost-effectiveness and the familiarity, with the levosimendan as the alternative (especially in the beta-blocked patient, where the beta-agonist dobutamine is less effective).[9]

[1] [2] [9] [1] [2] [8]

3. The mechanical circulatory support (MCS)

For the refractory (the pharmacological failure):[1][2]

• The IABP (the intra-aortic balloon pump) — the diastolic augmentation (the balloon inflates in the diastole, increasing the coronary perfusion; deflates in the systole, reducing the afterload). The IABP-SHOCK II trial — the no the mortality the benefit in the ACS the cardiogenic the shock (the routine the IABP not the recommended).[1]
• The Impella (the axial-flow catheter across the aortic valve — the continuous the LV unloading; the 2.5 to the 5.0 L/min).[1]
• The VA-ECMO (the venoarterial ECMO — the full the cardiopulmonary the bypass; the 3-5 L/min; the bridge to the recovery / the transplant / the decision).[1]
• The TandemHeart (the LA-to-femoral artery the bypass).[2]

The choice of the MCS depends on the centre, the expertise, the patient, and the cause.[1]

The three landmark device trials of the recent era have reshaped the MCS landscape:[5][11][12]

• The IABP-SHOCK II (Thiele, NEJM 2012, 600 patients) — the routine IABP in the AMI cardiogenic shock showed no mortality benefit at 30 days, 6 months, 12 months, or the long-term follow-up. The routine IABP is NOT recommended; the IABP is reserved for the mechanical complication (the VSR, the MR — the bridge to surgery) and for the centre without the more advanced MCS.[5][6]
• The DanGer-SHOCK (Møller, NEJM 2024, 360 patients) — the Impella CP vs the standard care (including IABP) in the AMI cardiogenic shock. The result — the reduced all-cause mortality at 180 days (66.7 per cent vs 80.0 per cent in the per-protocol analysis). This is the first positive MCS mortality trial in the infarct-related shock — but the caveat: the benefit was confined to the per-protocol population; the trial excluded the cardiac arrest and the moderate-severe AR; the bleeding and the haemolysis were more common with the Impella. The cautious adoption.[12]
• The ECLS-SHOCK (Akin, NEJM 2023, 420 patients) — the VA-ECMO vs the standard care in the infarct-related shock. The result — the no difference in the 30-day all-cause mortality (47.8 per cent vs 49.0 per cent), with the more bleeding and the more vascular complications in the ECMO group. The EURO-SHOCK (Møller-Helgestad, EuroIntervention 2023) similarly showed no mortality benefit of the VA-ECMO. The lesson — the VA-ECMO is NOT the routine first-line MCS in the AMI shock; it is reserved for the SCAI stage D-E, the profound shock, the refractory cardiac arrest (the eCPR), the bridge to the durable support.[11][13]

[1] [2] [5] [11] [12]

4. The supportive

• The oxygen / the ventilation (the non-invasive or the invasive; the lung-protective).[1]
• The renal replacement therapy (if the AKI / the fluid overload).[1]
• The correction of the electrolyte (the K, the Mg) + the acidosis (the pH above 7.2 for the inotrope the effectiveness).[1]
• The glycaemic control (the 6-10).[1]
• The DVT prophylaxis (the LMWH — the caution with the anticoagulation).[1]

The acidosis correction deserves the emphasis. The myocardium, the catecholamine receptors, and the vascular smooth muscle all dysfunction in the acidosis — the inotropes and the vasopressors become ineffective below the pH 7.2. The acidosis is BOTH the consequence of the shock (the hypoperfusion → the lactate) AND the amplifier (the depressed contractility, the receptor desensitisation). The correction: the adequate perfusion (the inotrope, the MCS) is the primary; the sodium bicarbonate is reserved for the pH under 7.1-7.2 with the refractory haemodynamic instability (the bicarbonate generates the CO₂ which worsens the intracellular acidosis if the ventilation is inadequate — so it is given only with the secured airway and the adequate ventilation).[1]

The landmark trials

[3] [4] [5] [6] [7] [8] [9] [12] [11] [13]

Prognosis

The mortality 40-60 per cent (the higher in the older, the comorbid, the delayed). The early revascularisation (the ACS), the appropriate pharmacological support, and the timely MCS (the refractory) reduce the mortality. The bridging to the transplant or the durable LVAD for the irreversible.[1][2][1]

The SCAI stage is the most powerful prognostic marker — the mortality rises steeply from the stage A (under 5 per cent) through the stage E (over 80 per cent). The other adverse markers: the lactate (the higher and the slower to clear, the worse), the renal failure (the creatinine rise and the need for the RRT), the age above 75, the out-of-hospital cardiac arrest, the anterior infarct, the multivessel disease, the delay to the revascularisation, and the biventricular failure. The SHOCK trial the only mortality-reducing intervention is the early revascularisation — every other therapy (the inotrope, the vasopressor, the MCS) is the supportive bridge, not the disease-modifier.[3][10]

Red flags

Clinical pearls

Exam practice

[1] [7] [8] [10] [11] [12] [1] [1] [10]

References

1. [1]Muller G, et al. ICU management of cardiogenic shock before mechanical support Curr Opin Crit Care, 2024.PMID 38872375
2. [2]Terkelsen CJ, et al. Hemodynamic management of cardiogenic shock in the intensive care unit J Heart Lung Transplant, 2024.PMID 38518863
3. [3]Hochman JS, Sleeper LA, Webb JG, et al. Early revascularization in acute myocardial infarction complicated by cardiogenic shock. SHOCK Investigators. Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock N Engl J Med, 1999.PMID 10460813
4. [4]Hochman JS, Sleeper LA, Webb JG, et al. Early revascularization and long-term survival in cardiogenic shock complicating acute myocardial infarction JAMA, 2006.PMID 16757723
5. [5]Thiele H, Zeymer U, Neumann FJ, et al. Intraaortic balloon support for myocardial infarction with cardiogenic shock N Engl J Med, 2012.PMID 22920912
6. [6]Thiele H, Zeymer U, Neumann FJ, et al. Intraaortic balloon support for cardiogenic shock N Engl J Med, 2013.PMID 23281982
7. [7]Thiele H, Akin I, Sandri M, et al. PCI Strategies in Patients with Acute Myocardial Infarction and Cardiogenic Shock N Engl J Med, 2017.PMID 29083953
8. [8]De Backer D, Biston P, Devriendt J, et al. Comparison of dopamine and norepinephrine in the treatment of shock N Engl J Med, 2010.PMID 20200382
9. [9]Mebazaa A, Nieminen MS, Packer M, et al. Levosimendan vs dobutamine for patients with acute decompensated heart failure: the SURVIVE Randomized Trial JAMA, 2007.PMID 17473298
10. [10]Baran DA, Grines CL, Bailey S, et al. 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 Catheter Cardiovasc Interv, 2019.PMID 31104355
11. [11]Akin M, Pauschinger M, Opitz F, et al. Extracorporeal Life Support in Infarct-Related Cardiogenic Shock N Engl J Med, 2023.PMID 37634145
12. [12]Møller JE, Holmvang L, Papo D, et al. Microaxial Flow Pump or Standard Care in Infarct-Related Cardiogenic Shock N Engl J Med, 2024.PMID 38587239
13. [13]Møller-Helgestad OK, Hyldebrandt JA, Banke A, et al. Venoarterial extracorporeal membrane oxygenation or standard care in patients with cardiogenic shock complicating acute myocardial infarction: the multicentre, randomised EURO SHOCK trial EuroIntervention, 2023.PMID 37334659
14. [14]Forrester JS, Diamond G, Chatterjee K, Swan HJ Medical therapy of acute myocardial infarction by application of hemodynamic subsets (second of two parts) N Engl J Med, 1976.PMID 790194