After-potential oversensing by a programmable pulse generator.

Oversensing and recycling due to a pacemaker stimulus after-potentials are recognized complications of non-competitive pacing. Often masquerading as T-wave sensing, after-potential oversensing may result in slowing or acceleration of pacing rate. We report two cases of after-potential oversensing in patients with R-wave inhibited (VVI) programmable pulse generators. In both cases, recycling of the pulse generators by the sensed after-potentials resulted in slowing of the pacing rates. This phenomenon was abolished non-invasively by decreasing the duration or width of the stimulus pulse which diminished the magnitude of the after-potential signal.