INTERFERENCE OF CELLULAR PHONES WITH IMPLANTED PERMANENT PACEMAKERS

Background and hypothesis: Occasional reports have suggested that cell ular phones may interfere with permanent pacemakers. Our investigation sought to determine systematically the effects of commercially availa ble cellular phones on the performances of different pacing modes and sensing lead configurations of permanent implanted pacemakers. Methods : We conducted the study in 29 patients implanted with single- or dual -chamber bipolar rate-adaptive permanent pacemakers (a total of nine d ifferent models and six different sensors: minute ventilation, activit y sensing using either accelerometer or piezoelectric crystal, QT and oxygen saturation sensing) from four different manufacturers. Three di fferent cellular phones with analog or digital coding with maximum pow er from 0.6 to 2 W were used to assess the effect of pacemaker interfe rence. Each cellular phone was positioned at (1) above the pacemaker p ocket, (2) the ear level ipsilateral to the pacemaker pocket, and (3) the contralateral ear level. Surface electrocardiograms, intracardiac electrograms, and marker channels were recorded where possible during the following maneuvers at each position: (1) calls made by a stationa ry phone to a cellular phone, and (2) calls made from the cellular pho ne to a stationary phone. A total of eight different pacing modes [DDD (R), VDD(R), AAI(R) and VVI(R)] in both unipolar and bipolar sensing c onfigurations was tested. Results: Interference was demonstrated durin g cellular phone operation in 74 of 2,418 (3.1%) episodes in eight pat ients. Three types of interference were observed: inhibition of pacing output, rapid ventricular tracking in DDD(R) or VDD(R) mode, and asyn chronous pacing. All were observed only with the cellular phone positi oned above the pacemaker pocket. Interference occurred prior to and af ter the termination of the ringing tone of the cellular phone in 57% o f cases. Cellular phones with either digital or analog technology coul d cause interference. Unipolar atrial lead was most susceptible to int erference (relative frequency of interference: unipolar 1.8%, bipolar 0.4%, p<0.05; atrial 2.9%, ventricular 1%, p<0.05). There was no senso r-driven rate acceleration during all tests. In all patients, reprogra mming of the sensitivity level successfully prevented cellular phone i nterference. Conclusions: Commercially available cellular phones can c ause reversible interference to implanted single- or dual-chamber perm anent pacemakers. The effect is maximal with high atrial unipolar sens itivity, especially in single pass VDD(R) systems. Both digital and an alog cellular phones can lead to interference. Pacemaker interference can occur prior to a warning sign (ringing tone) of the phone and may have significant implications in patient safety.