This is the case of a 20 year old young man who suffered from palpitations for 10 years. His WPW was only recognized when he finally came to the Emergency room. His ECG below shows a typical left sided accessory pathway (note the Delta wave in leads V1, II, III and AVf.
Typical left lateral Wolff Parkinson White ablation

As ablation is the current therapy in most situations in patients with symptomatic WPW, an electrophysiologic procedure was scheduled. A reentrant tachycardia going retrogradely through the accessory pathway was easily induced. During the tachycardia the high speed tracing below was recorded: note that the first depolarization of the atria is located at the site of the distal coronary sinus catheter (CS 12), verifying the lateral position of the accessory pathway. Note also that the tachycardia created a functional right bundle branch block (rsR complex in V1).

An ablation catheter was introduced through the right femoral artery to the mitral annulus, and positionned at a site where conduction between the atria and the ventricle was very fast. Note the "fusion" between the atrial and ventricular signals.

 

Ablation was attempted at that site and was successfull in less than 2 seconds. Note the normalization of the ECG, with disparition of the delta wave and of the repolarization abnormalities in the precordial leads.