WPW syndrome, left posterior pathway, intermittent pre-excitation

A 19 years old male came with the history of palpitation on and off since last six months.  There was no history of giddiness or syncope. Patient ECG is shown below.

ECG (Click on the image to enlarge it)

ECG is showing sinus rhythm at rate 64 beats per minutes, left axis (as lead I is positive and lead avF is equivocal) PR interval is 80 msecs, positive delta wave present in lead I, V1, negative delta waves are present in lead III,avF so the ECG is suggestive of pre-excitation with short PR interval or WPW syndrome. Now if we apply Arruda algorithm then because V1 is positive with R/S >1 so accessory pathway is located on the left side. Now because the lead avF is negative so the pathway is located in the left posterior or left posterolateral in location.

ECG of the patient was showing intermittent pre-excitation. The second ECG of the patient does not shows any pre-excitation. 

ECG 2(Click on the image to enlarge it)  

ECG is showing normal sinus rhythm at rate 110 beats per minute, normal axis, PR interval 160 msec, there is no evidence of any delta wave or pre-excitation in this ECG.

So the final diagnosis is WPW syndrome with left posterior pathway with intermittent pre-excitation.

Lets discuss how to localise pathway in WPW syndrome.

There are two algorithm.

First one

Another algorithm

Thank you

Praveen Gupta