Cardiogenic shock – hemodynamic profile

Cardiogenic shock is a state of inadequate organ perfusion caused by primary failure of the heart as a pump. Hemodynamically it is defined by the combination of a low cardiac index (CI < 2.2 L/min/m² without circulatory support), elevated left ventricular filling pressures (PCWP > 18 mmHg) and a compensatorily raised systemic vascular resistance. This combination of too little forward flow and too much backward pressure distinguishes it from every other form of shock. Mixed venous saturation falls because tissues must extract a greater fraction of a reduced oxygen supply.

For educational use only. Not for clinical use.

Hemodynamic profile

ParameterDirectionTypicalNormal range
CI↓< 2.2 L/min/m²2.5-4.0
SVR↑> 1400 dyn·s·cm⁻⁵800-1200
PCWP↑> 18 mmHg6-15
ZVD↑normal to elevated2-6
SvO2↓< 60 %65-75

Differentiation

Differentiate fromDiscriminating parameterExplanation
Hypovolemic shockPCWPPCWP separates the two: elevated in cardiogenic shock (> 18 mmHg), low in hypovolemic shock (< 8 mmHg). Cardiac output is low and vascular resistance high in both.
Obstructive shockZVDA markedly elevated CVP with equalisation of diastolic pressures points to an obstructive cause such as tamponade; in pulmonary embolism PCWP is normal or low despite high PA pressures.
Septic shockSVRSystemic vascular resistance separates the two: compensatorily elevated in cardiogenic shock, reduced in septic shock (< 800 dyn·s·cm⁻⁵).

Causes

  • Acute myocardial infarction, particularly large anterior infarction
  • Acutely decompensated chronic heart failure
  • Myocarditis
  • Sustained tachyarrhythmia or bradyarrhythmia
  • Acute valvular regurgitation, for example papillary muscle rupture
  • Post-cardiotomy syndrome following cardiac surgery

Clinical context

Clinically there is hypotension, cool and mottled extremities, prolonged capillary refill and oliguria. The combination of raised PCWP and low CI explains why pulmonary congestion and peripheral hypoperfusion occur together. Cardiac power output (CPO = MAP × CO / 451) is the parameter most strongly associated with in-hospital mortality; values below 0.6 W identify a particularly high-risk group. A low PAPI alongside an elevated CVP indicates concomitant right ventricular involvement, which worsens the prognosis further.

Frequently asked questions

Which values define cardiogenic shock hemodynamically?
A cardiac index below 2.2 L/min/m² without circulatory support together with a PCWP above 18 mmHg. Systemic vascular resistance is typically elevated above 1400 dyn·s·cm⁻⁵.
How do you distinguish cardiogenic from hypovolemic shock?
By the PCWP. Both show low cardiac output and high vascular resistance, but PCWP is elevated in cardiogenic shock and low in hypovolemic shock. Without that value the two cannot be separated hemodynamically.
What does cardiac power output (CPO) tell you?
CPO combines pressure and flow into a single value describing the work the heart actually performs. The normal value is around 1.0 W; values below 0.6 W are associated with markedly increased mortality.
Why is mixed venous saturation reduced?
When oxygen delivery falls, tissues extract a larger proportion of the oxygen offered. The oxygen extraction ratio rises and venous saturation falls correspondingly below 60 per cent.
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