• In WPW, an accessory conduction pathway is present between the atria and the ventricles.Electrical impulses may be rapidly conducted to the ventricles.
• These rapid impulses slur the initial portion of the QRS; the slurred effect is called a delta wave.

Rate: Depends on rate of underlying rhythm

Rhythm: Regular unless associated with atrial fibrillation

P Waves: Normal (upright and uniform) unless atrial fibrillation is present

PR Interval: Short (less than 0.12 sec) if P wave is present

QRS: Wide (greater than 0.10 sec); delta wave present

Clinical Tip: WPW is associated with narrow-complex tachycardias, including A-flutter and A-fib.