QRS Complex - Parameters

Parameters

Parameter Normal value Value comments Clinical significance
QRS duration 0.06 - 0.10 sec Shorter in children and in tachycardia Prolonged duration indicates e.g. hyperkalemia. or bundle branch block
QRS amplitude
  • S amplitude in V1 + R amplitude in V5 < 3.5 millivolt (mV)
  • R+S in a precordial lead < 4.5 mV
  • R in V5 or V6 < 2.6 mV
 Increased amplitude indicates cardiac hypertrophy
Ventricular
activation
time (VAT)
  • < 0.05sec in V5 or V6
  • < 0.03sec in V1
 Measured in increased QRS amplitude
Q wave
  • Duration more than 0.04 secs in leads other than III and AVR
  • Amplitude less than 1/3 QRS amplitude (R+S)
  • Amplitude less than 1/4 of R wave
 Abnormality indicates presence of infarction

The QRS complex is also included in estimating the QT interval.

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