[Pacemaker dysfunction during use of a mobile telephone].

Ubiquitious electronic equipment increases the number of potential sources of electromagnetic interference with sufficient energy to influence a pacemaker function. Besides others the mobile phone play important role. A 76 year-old female patient with pacemaker was hospitalized because of bilateral congestive heart failure. During ECG telemetry a short episode of pacemaker dysfunction was recorded. In a period of 15 seconds at first a pulse output inhibition occurred, then an undersensing was present. In all the 24-hour recording no other similar episode was observed. Such an utterly atypical picture lead to a direct question on mobile telephone calling. The patient confirmed that during a visit of her relatives she was really using a mobile phone. The GSM (Global System for Mobile Communication) phones operate on a carrier frequency of 900 MHz which is modulated generally in pulses about 8 Hz and 2 Hz. These signals can be falsely detected as an intrinsic heart activity by a pacemaker or they are analysed to be an electromagnetic interference. As a result a pacemaker inhibition, an asynchronous pacing and in dual chamber systems also a ventricular triggering can be present. These reactions usually do not occur if the distance between phone and pacemaker is higher than 10 cm. With some measures patients with pacemakers can safely use mobile phones. In pacemaker dependent patients a careful approach is necessary.