Here is a VT tracing misinterpreted as SVT because of the chamber onset discrimination algorithm. Nothing special except the following sequence (4 and 5th ventricular events):
The 4th ventricular event is sensed and marked "-" (discrepancy between the current interval which is fast and the average of the 4 last intervals). Immediately after, we see a AP at the sensor rate which is followed by a BIV stimulation (BP) within the vulnerable period of the ventricular cycle. The atrial pacing interval is not altered by the PVC which is expected to trigger a PVARP.
Does somebody have an explanation for that?