Reversion mode activation by myopotential sensing in a ventricular inhibited demand pacemaker.

Pacemaker follow-up in a 72-year-old woman revealed occasional failure to sense and pace, which was confirmed by Holter monitor. Neither reprogramming the pacemaker sensitivity nor repositioning the lead resolved the problem. A recheck of the Holter recordings revealed pacing and sensing failures were concurrent with "baseline artifact," suggestive of myopotentials. Furthermore, the inappropriate pacing spikes occurred at a rate of 90 pulses per minute (ppm). It was theorized that myopotential sensing was alternately inhibiting the pacer and activating the reversion mode, an asynchronous rate of 90 ppm. Reprogramming the unit to a lower sensitivity restored normal pacer function.