Low Voltage Definition

• Sensitive Definition
  • QRS amplitudes in leads I+II+III < 15 mm
  • Or QRS amplitudes in leads V₁+V₂+V₃ < 30 mm
• Specific Definition
  • QRS amplitudes in limb leads all < 5 mm
  • Or QRS amplitude in all precordial leads < 10 mm

Low Voltage QRS Differential

• “Low Power”
  • Myxedema (severe hypothyroidism)
  • Infiltrative diseases (Amyloid, Sarcoid, etc.)
  • End stage cardiomyopathy​
• Conduction blockage
  • Fluid/Effusion (pericardial or pleural)
  • Fat (obesity)
  • Air (COPD)

Take home Points

• Pulmonary embolism and large pericardial effusions can often present similarly!
  • Both have similar patient risk factors
  • Both may present with: dyspnea, tachypnea, tachycardia, JVD, and hypotension when severe
  • Don’t forget about pericardial effusion in the differential diagnosis for patients with dyspnea and clear lungs!
• (Large) Pericardial effusion triad is not always present
  • Low voltage (best to compare to prior ECGs)
  • Tachycardia (medications may blunt a tachycardic response)
  • Electrical alternans (present in < 1/3 of cases)
  • When in doubt…do the bedside echo looking for an effusion!