Figure 2. Response during ventricular overdrive pacing
Overdrive pacing from right ventricular apex (RVa 1-2) during tachycardia resulted in a post pacing V-A-V response and a long PPI-TCL of 177ms. This maneuver excludes a ventricular nodal/Hisian mechanism. It also demonstrates that the retrograde fast pathway is capable of conducting faster than the TCL.
Intracardiac electrograms as follows: HRA= high right atrium, CS= coronary sinus, HIS= His bundle, RVa= right ventricular apex.