[Sources of interference for cardiac pacemakers. Technical improvements of pacemakers--risks in the medical realm]

Such new technologies are associated with potential problems for patients with pacemakers which have not yet been adequately investigated. External sources of interference may inhibit or, in the case of dual chamber devices, trigger, the pacemaker, change its program or cause thermal damage to electrode tips leading to elevation of the stimulation threshold, or may destroy both hardware and software components. To prevent such problems, protective measures such as screening, sensitivity filters, asynchronous stimulation, and the bipolar electrodes have been developed. Detection by the pacemaker of a constant source of interference automatically activates an anti-interference circuit providing a fixed stimulating frequency. In contrast, interference by a pulsed or strongly amplitude-modulated signal can inhibit pacemaker function for a lengthy period and thus cause symptoms and possibly syncope.