Experience shows that in practice, power lines do not cause interference with Implanted Medical Devices, specifically Implanted Heart Devices. But scientists have been able to produce interference in laboratory settings.
One of the issues is that the design of these devices has improved over the years. We know that earlier devices were susceptible to interference. Newer devices are much less so.
EPRI produced a report in 2004 summarising our current state of knowledge about interference to implanted cardiac pacemakers and defibrillators from electric and magnetic fields in the frequency range of 1 hertz (Hz) to 3 kilohertz (kHz). It found that electric and magnetic fields could alter the function of pacemakers and defibrillators, but electric fields appear to be the most likely source of interference. The magnitude or intensity of the magnetic field required to alter the function of these devices varies widely with frequency and waveform. Their summary figures are:
Electric fields: sensitivity reported at levels ranging from 1.5 kV/m upwards, though some units are immune at 20 kV/m
Magnetic fields: 100 µT to 1.2 mT may produce interference
There have been very few studies investigating the effects of external EMFs on pacemaker and ICD function. Recently Trigano et al., (2005) examined the risk of interference by magnetic fields with permanent pacemakers. These investigated the effects of 100 µT on various patients with differing models of pacemakers. All pacemakers were set to their maximum sensitivity settings and subjects walked through the uniform magnetic field. During the tests only a small incidence of interaction with the magnetic field was observed. A switch to asynchronous mode was observed in three patients with devices set to unipolar sensing configuration. In one patient pacing inhibition occurred after a sustained mode switch. The conclusions drawn from this large study are that magnetic fields have a low incidence of interactions at levels up to the ICNIRP public magnetic field reference levels.
|
J Am Coll Cardiol. 2005 Mar 15;45(6):896-900. Trigano A, Blandeau O, Souques M, Gernez JP, Magne I. Department of Cardiology, Centre Hospitalier Universitaire Nord, Marseille, France. [email protected] OBJECTIVES: This study examined the risk of interference by high magnetic flux density with permanent pacemakers. BACKGROUND: Several forms of electromagnetic energy may interfere with the functions of implanted pacemakers. No clinical study has reported specific and relevant information pertaining to magnetic fields near power lines or electrical appliances. METHODS: A total of 250 consecutive tests were performed in 245 recipients of permanent pacemakers during 12-lead electrocardiographic monitoring. A dedicated exposure system generated a 50-Hz frequency and maximum 100-microT flux density, while the electrical field was kept at values on the order of 0.10 V/m. RESULTS: A switch to the asynchronous mode was recorded in three patients with devices programmed in the unipolar sensing configuration. A sustained mode switch was followed by symptomatic pacing inhibition in one patient. No effect on devices programmed in bipolar sensing was observed, except for a single interaction with a specific capture monitoring algorithm. CONCLUSIONS: The overall incidence of interaction by a magnetic field was low in patients tested with a wide variety of conventionally programmed pacemaker models. A magnetic field pulsed at power frequency can cause a mode switch and pacing inhibition in patients with devices programmed in the unipolar sensing configuration. The risk of interference appears negligible in patients with bipolar sensing programming. |