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Many forms of electromagnetic energy have been reported to interfere with the function of implanted cardiac pacemakers in hospitals. Lithotripsy devices and magnetic resonance imaging scanners can result in interference with pacemaker function, and there have been reports that other sources such as welding and degaussing equipment may also affect pacemaker function in small numbers of patients. In 1991, reports started to surface that cellular telephones could potentially interfere with implanted pacemaker function.1-3 Because of the rapidly expanding use of this technology, the U.S. government and researchers in many laboratories started to assess the prevalence of interference and the potential risk of a serious clinical event resulting from exposure of permanently implanted pacemakers to the electromagnetic energy being emitted from a cellular telephone.4-7
Hayes and associates from the Mayo Clinic tested 980 patients with cardiac pacemakers in a multicenter, prospective, crossover study with five different types of cellular telephones. They found that they were capable of producing interferences in 20% of 5533 tests and that the incidence of symptoms was 7.2%. Clinically significant interference occurred in only 1.7% of tests and only when the telephone was held directly over the pacemaker. Interference was more frequent with dual-chamber pacemakers than it was with single-chamber pacemakers and when digital telephones were used when compared with analogue telephones. The authors conclude that when telephones are placed in the normal position over the ear, interference of cellular telephones with pacemaker function does not pose a significant health risk.
Aberrant electromagnetic signals may be sensed through the implanted pacemaker leads or in the vicinity of the interface where the leads are connected to the internal circuitry of the pulse generators. These signals may inappropriately inhibit pacing and/or trigger pacing stimuli by a variety of techniques, all of which, fortunately, are temporary and occur only when the interference is actively present and of sufficient intensity. These electromagnetic signals are, for a variety of technical reasons, potentially more harmful in patients who have dual-chamber pacemakers and are capable of producing palpitations or even inducing ventricular tachycardia. The rapidly expanding use of cellular telephones has heightened the concern regarding the potential effects of the electromagnetic energy emanating from the telephones on implanted pacemaker function.
Previous studies have demonstrated that pacemaker function may be affected by various digital telephones, whereas analogue telephones appear to cause no interference.5-7 Hayes et al confirmed these previous impressions and found that digital technology interfered with more pacemakers (23.7%) than did phones using analogue-system technology (2.5%). In addition, the highest incidence of interference occurred when the telephone was placed directly over the pacemakers. The majority of symptoms were simply palpitations, although pre-syncopal episodes could occur. The greatest frequency of pre-syncopal episodes occurred among patients who were at least intermittently or completely dependent upon their pacemaker.
Ideally, every possible combination of cellular telephone and pacemaker models should be bench tested to assess the type and degree of interference to be expected from each combination, but it is obviously not practical to test each and every system. Such testing becomes more important when one recognizes that interference in the function of a pacemaker by electromagnetic energy coming from cellular telephones is not an important clinical problem in patients who are not pacemaker-dependent since, when an underlying rhythm such as normal sinus rhythm is present, occasional inhibition of pacing will almost certainly go unnoticed, and inappropriate stimuli will produce, at most, only occasional palpitations. Any potential problems in pacemaker function produced by cellular telephones is virtually totally eliminated if pacemaker patients use analogue telephones, and, even if they are using digital telephones, symptom production is extremely rare if the cellular telephone is kept away from the pacemaker pulse generator when carrying, dialing, or talking into the telephone. Telephones obviously should not be carried in a pocket directly over the pacemaker and, when in use, should be kept in the normal position next to the ear farthest from the pacemaker and not moved over the pacemaker.
Observing these simple precautions will almost certainly eliminate any interference of cardiac pacemakers by cellular telephones, and pacemaker patients should therefore not alter their cellular telephone usage nor should they be concerned about colleagues who are using cellular telephones in their environment.
1. Barbaro V, et al. GSM cellular phone interference with implantable pacemakers: In vitro and in vivo observations. Presented at the Biomagnetics Society 16th Annual Meeting. Copenhagen Denmark, June 12-17, 1994, poster.
2. Eicher B, et al. In: Bioelectromagnetics 16th Annual Meeting abstract book. Frederick, MD; Bioelectromagnetics Society, 1994:64.
3. Joyner KH, et al. In: Bioelectromagnetics 16th Annual Meeting abstract book. Frederick, MD; Bioelectromagnetic Society, 1994;67-68.
4. Imich W, et al. In: Bioelectromagnetics 18th Annual Meeting abstract book. Frederick, MD; Bioelectromagnetic Society, 1996:121-122.
5. Barbaro V, et al. Pacing Clin Electrophysiol 1995; 18:1218-1224.
6. Barbaro V, et al. In Bioelectromagnetics 17th Annual Meeting abstract book. Frederick MD; Bioelectromagnetic Society, 1995:24-26.
7. Naegeli B, et al. Pacing Clin Electrophysiol 1995;18:842.