Discussion for 90 year old male CC: Chest pain– Revisited

We are revisiting the Discussion for 90 year old male CC: Chest pain.  You may wish to review the case.

You may recall we pointed out that the VT appeared be regularly irregular, with alternating cycle lengths:

What follows is a "Guest Post" by Jason Roediger, CCT/CRAT, and Ken Grauer, M.D. (www.kg-ekgpress.com):

"The rhythm represents VT for all of the morphologic reasons discussed in your explanation. The reason for the repetitive regular irregularity of this ventricular rhythm is that the tracing represents VT with retrograde 3:2 Wenckebach Exit block out of the ventricular focus. The discharge rate of the ectopic ventricular focus is ~240/minute.

This results in a manifest ventricular rate that is about 2/3 the presumed discharge rate and reduces the manifest rate to ~160/minute. Note the characteristic Wenckebach periodicity conducting retrograde (with a 3:2 ratio) out of the ventricular focus in the laddergram below. FINAL point: in addition to the bizarre marked axis deviation, the entirely negative QRS in V6 with delayed nadir and other morphologic clues you state in support of the diagnosis of VT-WPW can be ruled out by the negative QS complexes in V4-V6 (Brugada)."

Many thanks to Jason and Ken for their insightful analysis. We are always learning!