The most common accessory pathways leading to WPW syndrome is
They occur across either an AV valve annulus or the septum, most frequently between the left atrium and free wall of the left ventricle, followed by posteroseptal, right free wall, and anteroseptal locations. If the AP conducts from atrium to ventricle (antegrade) with a shoer conduction time than the AV node and His bundle, then the ventricles are preexcited during sinus rhythm, and the ECG shows a sho P-R interval (<0.12 s), Ref Harrison 20th edition pg 1432
Left free wall
Posteroseptal
Right free wall
Anteroseptal
General anatomy