What is the role of accessory pathways in the pathogenesis of Wolff-Parkinson-White (WPW) syndrome?

Updated: Jan 08, 2017
  • Author: Christopher R Ellis, MD, FACC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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Answer

The presence of an AP sets up the potential for reentrant tachycardia circuits to be established or for preexcited tachycardia in the setting of atrial fibrillation, atrial flutter, or SVT with a bystander accessory pathway. This reentrant mechanism is the typical cause of the SVT of which patients with preexcitation are at risk. The genesis of reentrant SVT involves the presence of dual conducting pathways between the atria and the ventricles [9] :

  • The natural AV nodal His-Purkinje tract
  • One or more AV accessory tract(s) (ie, AV connection or AP, Kent fibers, Mahaim fibers)

These pathways usually exhibit different conduction properties and refractory periods that facilitate reentry. The effective refractory period (ERP, the time necessary for the electrical recovery needed to conduct the next impulse) of the accessory tract is often longer than that of the normal AV nodal His-Purkinje tract and requires time for conduction to recover before allowing reentry.


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