Low QRS Voltage on the ECG

  • Post category:ECGs

Small QRS complexes indicate that relatively little of the voltage generated by ventricular depolarization is reaching the ECG electrodes.

Diagnostic criteria

  • The amplitudes of all the QRS complexes in the limb leads are < 5 mm
  • The amplitudes of all the QRS complexes in the precordial leads are < 10 mm


Small QRS complexes may simply reflect a variant of normal. However, always check for:

  • Incorrect ECG calibration (should be 1 mV = 10 mm).

For easy memorizing of the causes you can use the mnemonic FFAIL:

  • Fluid: Pericardial effusion; Pleural effusion
  • Fat: Obesity
  • Air: Emphysema; Pneumothorax
  • Infiltrative / Connective Tissue Disorders
    • Myxoedema
    • Infiltrative myocardial diseases — i.e. restrictive cardiomyopathy due to amyloidosis, sarcoidosis, haemochromatosis
    • Constrictive pericarditis
    • Scleroderma
  • Loss of viable myocardium:
    • Previous massive MI
    • End-stage dilated cardiomyopathy

ECG Example

Pericardial Effusion / Tamponade ECG
  • Sinus Tachycardia
  • Low QRS Voltage
  • Alternating QRS Amplitude (Electrical Alternans)

This patient had Pericardial Effusion / Tamponade