12-lead electrocardiogram of a patient in sinus rhythm with Wolff-Parkinson-White pattern

Nearly full preexcitation is manifest in normal sinus rhythm on the 12-lead electrocardiogram in this patient with a short accessory pathway refractory period. The ventricular complex in preexcitation is a fusion of the impulse that preexcites the ventricles due to rapid conduction through an accessory pathway and of the impulse that takes the usual route through the atrioventricular node; this fusion creates the delta wave that is characteristic of Wolff-Parkinson-White electrocardiogram pattern.

Normal sinus rhythm at a rate of 71 beats/minute, a P wave axis of 45°, and a PR interval of 0.15 seconds.