Experimental study on malfunction of pacemakers due to exposure to different external magnetic fields.
OBJECTIVE
Cardiac pacemaker malfunction due to exposure to magnetic fields may cause serious problems in some work environments for workers having cardiac pacemakers. The aim of this study was to find the magnetic field interference thresholds for several commonly used pacemaker models.


METHODS
We investigated 16 pacemakers from three different manufacturers with the frequency range of 2 to 1,000 Hz, using sinusoidal, pulse, ramp, and square waveforms. The magnetic fields were produced by a computer-controlled Helmholtz coil system.


RESULTS
Pacemaker malfunction occurred in six of 16 pacemakers. Interaction developed almost immediately after high-intensity magnetic field exposure started. With each waveform, at least two pacemakers exhibited interference. In most exposure settings, there was no interference at magnetic field levels below the international occupational safety limits. Nevertheless, some frequencies using ramp or square waveforms interfered with pacemakers even at levels below public exposure limits. The occurrence of interference depended greatly on the waveform, frequency, magnetic field intensity, and the sensing configuration of the pacemaker. Unipolar configurations were more susceptible for interference than the bipolar ones. In addition, magnetic fields perpendicular to the pacemaker loops were more likely to cause interference than parallel fields.


CONCLUSIONS
There is a need for further investigations on pacemaker interference caused by different external magnetic fields to ensure safe working environment to workers with a pacemaker.
Safe New Technologies, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250, Helsinki, Finland. maria.tiikkaja@ttl.fi
Maria
M
Tiikkaja
Tommi
T
Alanko
Harri
H
Lindholm
Maila
M
Hietanen
Juha
J
Hartikainen
Lauri
L
Toivonen
D004868:Equipment Failure; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D060526:Magnetic Fields; D010138:Pacemaker, Artificial