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AIMS: The aim of this study was to test pacemakers with feedthru filters for interference with a digital cellular telephone. METHODS: The study comprised 100 patients having their first pacemaker implantation between January 2001 and May 2003. A GSM-standard cellular phone was tested in the standby, dialing and operating mode against 23 single-chamber and 77 dual-chamber pacemakers. Continuous surface electrocardiograms, intracardiac electrograms, and marker channels were recorded when calls were made by a land phone to the cellular phone. RESULTS: In 2 patients we observed pacing inhibition with the cellular phone positioned directly above the pacemaker pocket. The unipolar and bipolar ventricular sensitivity setting was 0.25 mV in one dual-chamber pacemaker, and when we changed the sensitivity to 0.50 mV and higher no interference could be detected. The second inhibition occurred in a single-chamber pacemaker with unipolar and bipolar ventricular sensitivity setting of 0.5 mV, where a sensitivity change to 1.0 mV eliminated the interference. CONCLUSION: Anticipating a correct setting of ventricular sensitivity, currently available pacemakers equipped with feedthru filters do not show any interference with cellular phones. Since interference was only observed with sensitivity settings below 0.50 mV, we recommend that permanent programming of ventricular sensitivity should be set at 2.0 mV and higher.
Khosro Hekmat (Wed,) studied this question.