Pacing on the T Wave: PAVB, Not PVAB

To the Editor:

In the “Focus on ECGs” section of the February 2016 issue, Gahremanpour and colleagues described an interesting case of pacing on the T wave.¹ We completely agree that it was not a sensing issue with the pacemaker and that answer “C” was appropriate. However, in the answer section, the authors described the premature ventricular contraction (PVC) as falling in the post-ventricular atrial blanking period (PVAB). The PVAB is the interval after a sensed or paced ventricular event, during which any atrial activity is not seen by the pacemaker.^2,3 In the authors' presented case, there was an atrial pacing stimulus right at the time of the PVC. Therefore, the PVC fell in the post-atrial ventricular blanking period (PAVB) and not in the PVAB.³

The PAVB is the interval after an atrial pacing stimulus during which the ventricular event is not seen by the ventricular channel of the pacemaker.⁴ In this case, the pacemaker was not inhibited, and there was subsequent ventricular pacing on the T wave. In that the myocardium was in the refractory period because of the PVC, the V-pacing on the T wave led to physiologic failure to capture, and there was no QRS complex following that V-pacing stimulus.