Phantom pacemaker programming.

Spurious or "phantom" programming of programmable pacemakers may occur as the result of two phenomena. One is change in rate and/or output of the generator from an anomalous source (dysprogramming); the other is a generator response different from that intended and set on the conventional programmer (misprogramming). In either case, the result is a nuisance, at best. Conceivably, at worst, an irreversible subthreshold output could be induced. Despite wide usage of such devices, neither event has been reported. In the routine follow-up of 95 implanted Cordis Omni-Stanicor generators, we have observed three instances of dysprogramming upon application of a magnet commonly used to induce the asynchronous mode. Subsequent in vitro studies revealed magnetically induced programming reed switch vibration in 9 of 6,680 units, which could account for the in vivo observations. We also describe many instances of misprogramming, attributable, in most cases, to a faulty programmer emission count. In this series, none of the anomalies was clinically detrimental. However, anyone involved in pacemaker follow-up should be alerted to the existence of these potentially hazardous phenomena.