When I posed the above question to few cardiologists including electro physiologists , the answer I got was surprising . In the process , I could understand why cardiology is such fascinating subject ! Each one gave a different answer and all the 5 responses were forth coming .
The following post in my blog which I wrote years ago tries to decode the reason for such wide variation in our understanding of AVRT of WPW.
By the way , is there a real risk for an ortho-dromic AVRT into anti-dromic AVRT by a definite block in AV node ?