# What is the algorithm for location of AP in Wolff-Parkinson-White (WPW) syndrome based on the polarity of the delta wave?

Updated: Jan 08, 2017
• Author: Christopher R Ellis, MD, FACC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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A more specific algorithm for location of the AP, based on the polarity of the delta wave or first 40 ms of the QRS, predicts the following AP locations:

• Left lateral wall - Negative delta waves in lead I and aVL; positive or isoelectric delta waves in II, III, aVF (inferior leads), and V1-4; and negative or isoelectric delta waves in V5-6
• Left posterior free wall - Positive delta waves in lead I and aVL; negative delta waves in II, III, and aVF; positive delta waves in V1-5; and negative or isoelectric delta wave in V6
• Posteroseptal - Positive delta waves in lead I and aVL with negative delta waves in II, III, and aVF; isoelectric or positive delta waves in V1; and positive delta waves in the rest of the precordial leads (see the images below)
• Right free wall - Positive delta waves in I and II, negative delta waves in aVR, isoelectric or negative delta wave in aVF, isoelectric delta wave in V1, isoelectric or positive delta waves in V2-3, and positive delta waves in V4-6
• Left anteroseptal - Positive delta waves in I, II, and aVF; negative delta wave in aVR; isoelectric or positive delta wave in V1; and positive delta waves in V2-6
• Right anteroseptal - Positive delta waves in I, II, and aVF; negative delta wave in aVR; negative or isoelectric delta waves in V1-3; and positive delta waves in V4-6
Electrocardiogram of asymptomatic 17-year-old male who was incidentally discovered to have Wolff-Parkinson-White pattern. It shows sinus rhythm with evident preexcitation. To locate accessory pathway (AP), initial 40 ms of QRS (delta wave) is evaluated. Note that delta wave is positive in I and aVL, negative in III and aVF, isoelectric in V1, and positive in rest of precordial leads. Therefore, this is likely posteroseptal AP.
12-lead electrocardiogram from asymptomatic 7-year-old boy with Wolff-Parkinson-White pattern. Delta waves are positive in I and aVL; negative in II, III, and aVF; isoelectric in V1; and positive in rest of precordial leads. This predicts posteroseptal location for accessory pathway.