INTERFERENCE WITH CARDIAC-PACEMAKERS BY CELLULAR TELEPHONES

Background A growing body of evidence suggests that electromagnetic in terference may occur between cardiac pacemakers and wireless hand-held (cellular) telephones, posing a potential public health problem. Elec tromagnetic interference may occur when the pacemaker is exposed to an electromagnetic field generated by the cellular telephone. Methods In this multicenter, prospective, cross-over study, we tested 980 patien ts with cardiac pacemakers with five types of telephones (one analogue and four digital) to assess the potential for interference. Telephone s were tested in a test mode and were programmed to transmit at the ma ximal power, simulating the worst-case scenario; in addition, one tele phone was tested during actual transmission to simulate actual use. Pa tients were electrocardiographically monitored while the telephones we re tested at the ipsilateral ear and in a series of maneuvers directly over the pacemaker. Interference was classified according to the type and clinical significance of the effect. Results The incidence of any type of interference was 20 percent in the 5533 tests, and the incide nce of symptoms was 7.2 percent. The incidence of clinically significa nt interference was 6.6 percent. There was no clinically significant i nterference when the telephone was placed in the normal position over the ear. Interference that was definitely clinically significant occur red in only 1.7 percent of tests, and only when the telephone was held over the pacemaker. Interference was more frequent with dual-chamber pacemakers (25.3 percent) than with single-chamber pacemakers (6.8 per cent, P < 0.001) and more frequent with pacemakers without feed-throug h filters (28.9 to 55.8 percent) than with those with such filters (0. 4 to 0.8 percent, P = 0.01). Conclusions Cellular telephones can inter fere with the function of implanted cardiac pacemakers. However, when telephones are placed over the ear, the normal position, this interfer ence does not pose a health risk. (C) 1997, Massachusetts Medical Soci ety.