12-lead electrocardiogram (ECG) of a left lateral accessory AV pathway

Electrocardiogram in sinus rhythm from a patient with the Wolff-Parkinson-White syndrome shows a maximally preexcited QRS. The PR is short, the QRS has a right bundle branch block morphology, there is a prominent RS complex in V1, the QRS is negative, and the delta wave is isoelectric in leads I and aVL, localizing the accessory pathway to the left lateral annulus.