Cardiogenic Shock Criteria
Cardiogenic shock is characterized by increased systemic vascular resistance (SVR), not increased cardiac output or decreased pulmonary wedge pressure—the correct answer is C.
Hemodynamic Profile of Cardiogenic Shock
The defining hemodynamic features of cardiogenic shock include 1, 2:
- Decreased cardiac index (<2.2 L/min/m²) due to primary myocardial dysfunction and impaired contractility 1, 2
- Increased systemic vascular resistance (SVR) as a compensatory mechanism—the body attempts to maintain blood pressure despite falling cardiac output through systemic vasoconstriction 1, 2
- Elevated pulmonary capillary wedge pressure (PCWP) (>15 mmHg) reflecting left ventricular failure and volume overload 1, 2
- Elevated central venous pressure (CVP) (>15 mmHg) resulting from elevated right-sided filling pressures and backward failure 1, 2
Why the Other Options Are Incorrect
Option A (Increased Cardiac Output) is wrong: Cardiogenic shock is fundamentally defined by decreased cardiac output and cardiac index <2.2 L/min/m². The failing myocardium cannot generate adequate output despite elevated filling pressures 1, 2.
Option B (Decreased Pulmonary Wedge Pressure) is wrong: Cardiogenic shock features elevated PCWP (>15 mmHg), not decreased. Decreased PCWP characterizes hypovolemic shock, which is the opposite hemodynamic pattern 1, 2.
Complete Diagnostic Criteria
The American College of Cardiology requires all three core hemodynamic parameters when invasive monitoring is available 1:
- Cardiac index <2.2 L/min/m²
- PCWP >15 mmHg
- Systolic BP <90 mmHg
Clinical criteria must include both sustained hypotension (systolic BP <90 mmHg for >30 minutes OR mean arterial pressure <60 mmHg OR need for vasopressors) AND evidence of end-organ hypoperfusion 1:
- Decreased mentation/altered mental status
- Cold extremities with livedo reticularis
- Urine output <30 mL/hour
- Lactate >2 mmol/L
- Metabolic acidosis
Critical Distinction from Other Shock Types
Cardiogenic shock is distinguished by elevated PCWP, elevated CVP, and elevated SVR 1, 2.
Distributive shock (septic, neurogenic) presents with decreased SVR, normal or increased cardiac output initially, and warm extremities—the opposite pattern 1, 2.
Hypovolemic shock shows low PCWP (<15 mmHg), low CVP, and cold extremities but responds to fluid challenge 1.
Pathophysiologic Mechanism
The damaged myocardium cannot generate adequate cardiac output, triggering compensatory neurohormonal activation that causes systemic vasoconstriction to maintain perfusion pressure, thereby increasing SVR 2. This increased afterload further impairs the already failing heart, creating a vicious cycle 2. The elevated SVR represents the body's attempt to compensate for inadequate cardiac function, distinguishing cardiogenic shock from distributive states where pathological vasodilation predominates 2.