What are the features of preexcitation during antidromic SVT in 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

During antidromic SVT, a premature atrial extrastimulation that shortens the SVT cycle length with no change in QRS morphology or that terminates SVT with an atrial depolarization (ie, not followed by a QRS) rules out VT. In the first case, the premature atrial depolarization conducts to the ventricles through the AP. In the second case, the premature atrial depolarization reaches the AP’s effective refractory period terminating the SVT in the antegrade limb, also proving that the AP participated in the SVT (ie, it is an AP-mediated SVT and not a VT).


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