How is the AP identified and ablation site selected in the treatment 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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First, perform EPS (1) to determine that the AP is part of the tachycardia reentrant circuit and (2) to locate the optimal site for ablation. APs may be located in the left or right free wall or septum of the heart. In approximately 5-10% of patients, multiple pathways are present.

The ventricular insertion site is indicated by the earliest onset of the ventricular electrogram in relation to the delta wave during sinus rhythm or atrial pacing. The atrial insertion site is indicated by the region of the shortest VA interval during orthodromic tachycardia (ie, AVRT) or ventricular pacing. Mechanical trauma during mapping, “bump mapping”, often may occur at the site of pathway insertion and signals a potential effective ablation site.

During EPS, direct recordings of the AP potential indicate the optimal site for ablation, followed by areas of AV or VA fusion. Successful ablation sites show stable fluoroscopic and electrical features. During orthodromic AVRT, the time between the ventricular and atrial potentials is short and an AP potential may be observed.

Tip temperatures of at least 50°C are required for permanent elimination of AP conduction. Often, a single, well-placed RF lesion will cure the patient (see the image below). The RF ablation creates a conduction block that can be seen on intracardiac electrography (ie, during EPS) between the atrial activation and the AP potential.

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