Wolff-Parkinson-White pattern

Precordial leads in a patient with preexcitation due to the WPW syndrome. The three characteristic findings are the short PR interval (0.09 sec in this case), the wide QRS, and the delta wave (slurring of the QRS upstroke) that is best seen in leads V5 and V6 (arrows).

Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75°.