What are the signs, symptoms, and causes of cardiogenic shock?

Cardiogenic Shock: Signs, Symptoms, and Causes

Cardiogenic shock is defined by persistent hypotension (systolic blood pressure <90 mmHg) despite adequate filling status, combined with clinical signs of tissue hypoperfusion including cold extremities, confusion, oliguria, and elevated lactate levels >2 mmol/L. 1

Clinical Signs and Symptoms

Hemodynamic Criteria

• Systolic blood pressure <90 mmHg for >30 minutes or requiring pharmacological/mechanical support to maintain adequate pressure 1, 2
• **Cardiac index <2.2 L/min/m²** with central filling pressure >20 mmHg 1, 2
• Elevated lactate >2 mmol/L indicating tissue hypoperfusion 1

Clinical Manifestations of End-Organ Hypoperfusion

• Cold, clammy extremities reflecting peripheral vasoconstriction 1
• Altered mental status or confusion from cerebral hypoperfusion 1
• Oliguria (reduced urine output) indicating renal hypoperfusion 1
• Tachycardia as a compensatory mechanism 2
• Tachypnea and dyspnea from pulmonary congestion 1

Echocardiographic Findings

• Depressed left ventricular ejection fraction with regional or global wall motion abnormalities 1
• Decreased stroke volume and cardiac output 1
• Elevated left ventricular filling pressures with secondary mitral regurgitation 1
• Right ventricular dysfunction may show dyssynergy, dilatation, and decreased TAPSE in RV infarction 1

Causes of Cardiogenic Shock

Primary Cardiac Causes

Acute Myocardial Infarction (Most Common)

• ST-elevation myocardial infarction (STEMI) is the leading cause, complicating 5-12% of AMIs 2, 3
• Typically requires >40% loss of left ventricular myocardium to precipitate shock 1, 2, 3
• Right ventricular infarction most often associated with inferior AMI 1

Mechanical Complications of AMI

• Ventricular septal rupture with incidence of 0.2% 1
• Acute severe mitral regurgitation from papillary muscle rupture 1
• Free wall rupture with cardiac tamponade—the most serious complication with near 100% mortality without surgery 1
• Left ventricular free wall rupture may present as acute catastrophic collapse or insidious pericardial effusion 1

Other Cardiac Causes

• Acute decompensated heart failure in advanced end-stage chronic heart failure 1
• Severe valvular heart disease (acute or chronic) 1, 3
• Severe acute myocarditis 1
• Cardiomyopathy (various etiologies) 1, 3
• Myocardial contusion from trauma 1
• Acute aortic dissection 1
• Post-cardiotomy cardiogenic shock 3

Pathophysiological Cascade

The pathophysiology creates a vicious cycle of deterioration 2, 3:

• Diminished cardiac output leads to systemic hypoperfusion 1, 2, 3
• Tissue ischemia triggers inflammatory mediator release causing systemic vasodilation 2, 3
• Renal hypoperfusion leads to fluid retention and increased preload 2
• Myocardial ischemia worsens from reduced coronary perfusion, further decreasing cardiac output 2, 3

Critical Diagnostic Approach

Immediate ECG and echocardiography are mandatory in all patients with suspected cardiogenic shock 1. Echocardiography serves as the excellent initial tool for confirming the diagnosis, identifying the underlying cause, assessing hemodynamic status, and ruling out other shock etiologies 1. When transthoracic echocardiography is suboptimal, transesophageal echocardiography should be performed 1.

Complications and Prognosis

Multiorgan system failure develops in severe cases with nearly 50% in-hospital mortality 2, 3. Specific complications include:

• Acute kidney injury 1, 2
• Acute liver injury 1
• Respiratory failure 1
• Coagulopathy 1
• Metabolic acidosis 1
• Arrhythmias 1

Overall mortality remains 40-50% despite advances in treatment, with one-year mortality reaching 50-60% 1, 2. Shock due to left ventricular dysfunction remains the leading cause of mortality in AMI (50-70%) 1.