Interference and Implantable Cardiac Stimulators.

As pacemakers and defibrillators are electronic devices that elaborate electrical signals, they are by nature sensitive to electromagnetic signals. The crucial problem is not so much to establish which devices are susceptible to such physical phenomena, but rather to determine threshold levels and the precautions required to ensure that the devices function properly. The preferential pathways of interference between an external electromagnetic source and an implanted device are constituted by catheters, antennas used in telemetry, magnetic switches, and rate-responsive sensors; that is to say, those components which in some way communicate with the external environment. The human body, which is a fairly good conductor of electricity, acts as an effective shield against electrical fields surrounding the patient, thereby intrinsically protecting the implanted device. The internal microprocessor and electronic interfaces are based on the c-mos technology, which is sensitive to ionising radiation that can alter the conduction thresholds of the transistors. Moreover the electronic components and the ceramic base supporting them can be mechanically damaged by high power vibrations like high power ultrasounds. The aim of this review is to summarise the recommendations for all professionals managing patients with an implanted cardiac stimulator in case of interference most frequently encountered in hospital, at home and in everyday life. keywords: Pacemacker, DeWbrillator, Interference.