Cardinal ECG Features of WPW Syndrome

The cardinal ECG features of WPW syndrome are:

In sinus rhythm

  • The ECG may be completely normal or there may be a short PR interval (Fig 1)
  • There may be a slurred upstroke of the R wave known as a delta wave
  • There may be right (type A) or left (type B) bundle branch block pattern QRS abnormalities (Fig 2)
Fig 1: ECG showing WPW Fig 2: QRS abnormalities in WPW
During episodes of re-entry tachycardia
  • Orthodromic narrow complexes, no delta wave, inverted P waves follow QRS
  • Antidromic wide aberrant complexes, no visible P waves