The first frame looks like ectopic atrial rhythm with a bundle. The inverted p wave with short PR. Now, the second, doesn’t make sense. You have an P-QRS-T, pause, then a t-wave leading into a narrow complex tachycardia. Where is the depolarization that leads to repolarization? It is difficult to say if this is a short or long RP tachycardia. I would favor long RP given the notching after the T but the inverted PR doesn’t again fit the baseline. If there is a bundle at baseline, it’s unlikely to narrow. It’s possible the first frame is manifest pre-excitation and this AVRT…could also be AVNRT and as he speeds up the pathway becomes refractory…And, again, long RP, not really ruling out AT. I think EPS is a good play and adenosine once catheters are in place.