Why is there a delta wave seen in wolff-parkinson-white (wpw) syndrome?

Pre-excitation: Wpw syndrome is commonly diagnosed on the basis of the surface ECG in an asymptomatic individual. In this case it is manifested as a delta wave, which is a slurred upstroke in the qrs complex that is associated with a short pr interval. The short pr interval and slurring of the qrs complex is actually the impulse making it through to the ventricles prematurely (across the accessory pathway) withou.

Pathway: The impulse is conducted through the accessory pathway which conducts fast er than he normal av node.