12-lead electrocardiogram (ECG) of a right posteroseptal accessory AV pathway

Electrocardiogram in sinus rhythm from a patient with Wolff-Parkinson-White syndrome shows a maximally preexcited QRS complex. There is early transition across the precordial leads, with R/S ratio of 1 occurring in lead V2. The delta waves are positive in the lateral leads I, aVL, and V6, and negative in leads III and aVF, localizing the pathway to the posteroseptal area. The positive delta wave in lead II and in the lateral leads localize the pathway to the right side.