This was a very interesting case:

A Very Fast Regular Narrow Complex, Followed by an Equally Fast Regular Wide Complex

It had a very fast narrow complex rhythm, then a very fast wide complex rhythm, then converted to sinus with a very short PR interval.

We surmised that there must be accelerated AV conduction AND an accessory pathway.

The EP results are back, and:

1. Accelerated AV conduction

2. Left lateral accessary pathway.  It was ablated.