Cardiogenic Shock

Cardiogenic Shock

Cardiogenic shock is a life-threatening syndrome of sustained systemic hypoperfusion due to primary cardiac dysfunction, characterized by inadequate cardiac output to meet metabolic demands, with clinical and biochemical evidence of end-organ hypoperfusion, often (but not always) associated with hypotension or the need for vasopressors or mechanical support.

Pathophysiology: Primary cardiac dysfunction → ↓ cardiac output (cardiac index ≤2.2 L/min/m²) → ↓ oxygen delivery → tissue hypoxia → anaerobic metabolism → lactate elevation → metabolic acidosis → multiorgan dysfunction

• Early: compensatory vasoconstriction (↑ SVR) to maintain perfusion
• Consequence: ↑ afterload → further ↓ cardiac output (vicious cycle)
• Late: systemic inflammation → vasodilation → mixed cardiogenic and distributive shock

Core mechanism: ↓ cardiac output + ↑ SVR → impaired oxygen delivery → end-organ failure

1. Etiology

1. Acute myocardial infarction (most common cause, high mortality)
2. Acute decompensated heart failure
3. Right ventricular failure, including RV infarction or acute RV failure states
4. Mechanical complications (high yield, sudden deterioration):
1. Papillary muscle rupture → acute mitral regurgitation with pulmonary edema
2. Ventricular septal rupture → new harsh holosystolic murmur with shock
3. Free-wall rupture → cardiac tamponade and pulseless electrical activity
5. Myocarditis or Takotsubo cardiomyopathy
6. Arrhythmias (reversible causes):
1. Ventricular tachycardia or ventricular fibrillation
2. Complete heart block
7. Severe valvular disease (for example acute MR or critical aortic stenosis)
8. Post-cardiotomy or cardiac surgery

Always consider myocardial infarction first in undifferentiated shock

2. Clinical Features

2.1 Classic features

1. Hypotension
1. SBP less than 90 mmHg
2. MAP less than 65 mmHg
3. Requirement for vasopressors to maintain perfusion
2. Hypoperfusion (defining feature)
1. Cold, clammy extremities
2. Oliguria (less than 0.5 mL/kg/h)
3. Altered mental status
4. Lactate greater than 2 mmol/L
3. Congestion
1. Pulmonary edema (common in left ventricular dominant shock)
2. Elevated jugular venous pressure

2.2 Other features

1. Tachycardia (compensatory)
2. Dyspnea or hypoxemia
3. Narrow pulse pressure
4. Cool or mottled skin
5. Chest pain (ischemic cause)

2.3 Key signs

1. Cold and congested patient with hypotension suggests cardiogenic shock
2. Cold and congested patient with preserved blood pressure suggests normotensive cardiogenic shock
3. Shock index (heart rate divided by systolic blood pressure) greater than 0.9 suggests high risk

A cold, poorly perfused phenotype favors cardiogenic shock, but mixed shock should be considered

3. Classification

3.1 SCAI Stages

1. Stage A At risk
2. Stage B Beginning (preshock):
1. Relative hypotension and/or tachycardia
2. No clear hypoperfusion
3. Stage C Classic:
1. Hypoperfusion with or without hypotension requiring intervention
4. Stage D Deteriorating:
1. Worsening despite initial therapy or escalating support
5. Stage E Extremis:
1. Refractory circulatory collapse or cardiac arrest

Early recognition in stages B and C is critical

3.2 Hemodynamic Phenotypes

1. Left ventricular dominant (most common)
1. Cardiac index less than 2.2 L/min/m²
2. Pulmonary capillary wedge pressure greater than 18 mmHg
3. Pulmonary congestion is common
2. Right ventricular dominant
1. Right atrial pressure greater than 10 to 15 mmHg
2. Pulmonary capillary wedge pressure normal or low
3. Clear lungs with elevated jugular venous pressure
3. Biventricular failure
1. Both right atrial pressure and wedge pressure elevated
2. Associated with worse prognosis

Phenotype helps guide therapy and device selection

4. Diagnosis

4.1 ECG

1. ST-elevation or non–ST-elevation myocardial infarction
2. Arrhythmias

4.2 Echocardiography (key test)

1. Left ventricular dysfunction
2. Right ventricular dysfunction
3. Regional wall motion abnormalities suggesting ischemia
4. Mechanical complications

Urgent bedside echocardiography is essential in suspected cardiogenic shock

4.3 Hemodynamics (pulmonary artery catheter in selected patients)

1. Cardiac index less than 2.2 L/min/m²
2. Pulmonary capillary wedge pressure greater than 18 mmHg suggesting left ventricular failure
3. Right atrial pressure greater than 10 mmHg suggesting right ventricular failure
4. Pulmonary artery pulsatility index reduced in right ventricular dysfunction
5. Cardiac power output less than 0.6 watts associated with high mortality

Most useful in refractory, mixed, or unclear shock

4.4 Laboratory findings

1. Lactate elevation (key marker of hypoperfusion)
2. Troponin elevation
3. Rising creatinine indicating renal dysfunction
4. Elevated liver enzymes (shock liver)
5. BNP or NT-proBNP

Serial lactate trends help assess response and prognosis

5. Management

5.1 Immediate management

1. Oxygen supplementation with or without ventilatory support
2. Intravenous access and arterial line placement
3. Continuous hemodynamic monitoring
4. Rapid identification of the underlying cause
5. Early activation of a multidisciplinary shock team

5.2 Pharmacologic therapy

1. Norepinephrine (first-line vasopressor)
1. Target mean arterial pressure at least 65 mmHg
2. Inotropes (if low cardiac output persists)
1. Dobutamine (commonly used first inotrope)
2. Milrinone (alternative inotrope and vasodilator; may be useful in right ventricular failure or lower SVR states)
3. Adjunct agents:
1. Vasopressin
2. Epinephrine (reserved for refractory shock due to higher risk of arrhythmias and lactate elevation)
4. Diuretics:
1. Consider in patients with congestion and adequate perfusion
5. Fluids:
1. Only if hypovolemia is suspected

Avoid unnecessary fluid loading in left ventricular failure

5.3 Definitive management

1. In myocardial infarction–related cardiogenic shock, immediate percutaneous coronary intervention is the main evidence-based mortality-reducing intervention
2. Early invasive strategy for non–ST-elevation myocardial infarction
3. Urgent repair of mechanical complications
4. Immediate treatment of arrhythmias

5.4 Temporary mechanical circulatory support

Selective, phenotype-driven use; not routine

1. Impella (microaxial flow pump)
1. Consider in selected patients with left ventricular dominant myocardial infarction–related shock
2. Provides left ventricular unloading
2. Venoarterial ECMO
1. Consider in refractory or biventricular shock
2. Provides circulatory and respiratory support
3. May require left ventricular unloading
3. Intraaortic balloon pump
1. No routine mortality benefit
2. May be used selectively in specific situations
4. Right ventricular support devices
1. Consider in right ventricular dominant shock

Careful patient selection is essential, as only a subset benefit

6. ICU Management

1. Frequent reassessment:
1. Lactate levels
2. Urine output
3. Hemodynamics
2. Ventilation:
1. Lung-protective strategy
2. Avoid excessive positive end-expiratory pressure in right ventricular failure
3. Renal support:
1. Maintain mean arterial pressure at least 65 to 70 mmHg
2. Initiate renal replacement therapy if indicated
4. Monitor for complications:
1. Bleeding
2. Limb ischemia
3. Infection

7. Prognosis

1. Mortality:
1. Approximately 30 to 50 percent in the short term
2. Poor prognostic factors:
1. Biventricular failure
2. Persistent lactate elevation
3. Multiorgan dysfunction

8. Clinical Pearls

1. Shock is defined by hypoperfusion, not hypotension
2. A cold and congested patient suggests cardiogenic shock
3. Early echocardiography is essential
4. Start norepinephrine first, then add an inotrope if needed
5. Early revascularization improves survival in myocardial infarction–related cardiogenic shock
6. Routine intraaortic balloon pump use is not recommended
7. Hemodynamic parameters guide therapy
8. Early recognition and escalation improve outcomes

References

1. Thiele H et al. Cardiogenic shock. N Engl J Med. 2026;394:62–77
2. van Diepen S et al. Contemporary management of cardiogenic shock. Circulation. 2017;136:e232–e268
3. Naidu SS et al. SCAI shock classification update. J Am Coll Cardiol. 2022;79:933–946