Effect of magnet application on pacemakers and ICDs
The exact effect of magnet application on the various functions of pacemakers and ICDs (implantable cardioverter-defibrillator) will depend on the make of the device and the programmed parameters.
But in general, the effect on a pacemaker is that it stops sensing and functions in an asynchronous pacing mode. In case of ICDs, magnet application suspends all anti-tachycardia therapies, without affecting the pacing mode.
In most pacemakers, magnet application increases the pacing rate during the asynchronous pacing mode, but the actual rate and duration for which the higher rate is maintained will vary with each manufacturer/model. Some pacemakers can be programmed to initiate vario threshold checking on application of a magnet. Older pacemakers have a reed switch to initiate the magnet mode while newer devices have a Hall sensor.