What are the diagnostic criteria for cardiogenic shock?

Diagnostic Criteria for Cardiogenic Shock

Cardiogenic shock is defined as evidence of tissue hypoperfusion induced by heart failure after correction of pre-load, characterized by sustained hypotension with systolic blood pressure <90 mmHg (or mean BP <60 mmHg) for >30 minutes or requiring vasopressors to maintain adequate blood pressure, along with signs of end-organ hypoperfusion despite adequate intravascular volume. 1, 2

Essential Diagnostic Criteria

Clinical Criteria (must meet both)

1. Hypotension

   • Systolic BP <90 mmHg for >30 minutes OR
   • Mean BP <60 mmHg for >30 minutes OR
   • Requirement of vasopressors to maintain systolic BP ≥90 mmHg or mean BP ≥60 mmHg 1

2. Evidence of Hypoperfusion (at least one of the following)

   • Decreased mentation
   • Cold extremities, livedo reticularis
   • Urine output <30 mL/h
   • Lactate >2 mmol/L 1

Hemodynamic Criteria (when invasive monitoring is available)

• Cardiac index <2.2 L/min/m²
• Pulmonary capillary wedge pressure >15 mmHg 1, 2

Additional Hemodynamic Parameters

• Cardiac power output ([CO × MAP]/451) <0.6 W
• Shock index (HR/systolic BP) >1.0 1

Right Ventricular Shock Specific Criteria

• Pulmonary artery pulse index [(PASP-PADP)/CVP] <1.0
• CVP >15 mmHg
• CVP-PCW >0.6 1

Severity Classification (SCAI)

The Society for Cardiovascular Angiography and Interventions (SCAI) classification system provides a standardized approach to categorizing cardiogenic shock severity 2:

Stage	Description
A (At Risk)	Patient not in shock but at risk (e.g., large MI)
B (Beginning)	Hypotension but normal perfusion (SBP <90 mmHg, normal mentation)
C (Classic)	Hypotension with hypoperfusion (altered mentation, decreased urine output, impaired renal function)
D (Deteriorating)	Worsening despite initial interventions
E (Extremis)	Cardiac arrest, refractory shock, requiring CPR or escalating support

Diagnostic Approach

1. Initial Clinical Assessment

   • Evaluate for hypotension and signs of hypoperfusion
   • Check vital signs, mental status, urine output, peripheral perfusion
   • Assess for cold extremities, weak pulses, and altered mentation 2

2. Laboratory Evaluation

   • Lactate levels (>2 mmol/L suggests tissue hypoperfusion)
   • Renal and liver function tests (elevated BUN, creatinine, liver enzymes)
   • Cardiac biomarkers (troponin, BNP) 2

3. Immediate Echocardiography

   • Essential for assessment of:
     • Ventricular function (LV, RV, or biventricular failure)
     • Mechanical complications
     • Valvular abnormalities 2

4. Invasive Hemodynamic Monitoring (when indicated)

   • Provides definitive hemodynamic parameters
   • Confirms diagnosis and guides therapy
   • Particularly useful in complex or unclear cases 1, 2

Common Pitfalls and Caveats

• Pre-shock misdiagnosis: Patients with compensatory vasoconstriction may maintain near-normal systolic blood pressure despite significant malperfusion. These patients represent a high-risk cohort with lower average cardiac output and high mortality (43% in-hospital) 2

• Delayed recognition: Early recognition and prompt intervention are critical for improving survival. Failure to identify shock in its early stages can lead to worse outcomes 2

• Failure to identify shock phenotype: Not distinguishing between LV, RV, or biventricular failure may lead to inappropriate therapy selection. Tailoring treatment to the specific phenotype is essential for optimal outcomes 2

• Relying solely on blood pressure: Hypotension alone is insufficient for diagnosis; evidence of end-organ hypoperfusion must also be present 1

• Overlooking mechanical causes: Mechanical complications of acute MI, valvular disease, and other structural problems must be identified promptly through echocardiography 2

Remember that cardiogenic shock exists on a spectrum from pre-shock to refractory shock, and early recognition with prompt intervention is essential for improving outcomes.