What is magnet inhibition in pacemakers?

Updated: Oct 11, 2019
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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In most devices, placing a magnet over a permanent pacemaker temporarily "reprograms" the pacer into asynchronous mode; it does not turn the pacemaker off. Each pacemaker type has a unique asynchronous rate for beginning of life (BOL), elective replacement indicator (ERI), and end of life (EOL). Therefore, if the device company parameters are known, application of a magnet can determine if the pacer's battery needs to be replaced. Further interrogation or manipulating of the device should be performed by an individual skilled in the technique.

Although many different branded pacemaker/implantable cardioverter-defibrillator (ICD) magnets are available, emergency physicians should be aware that, in general, any pacemaker/ICD magnet can be used to inhibit delivery of shock therapy from the device. When a magnet is applied to an ICD, pacing therapy is not inhibited.

The majority of devices have a magnet response; however, some devices can be programmed to not respond to magnet application and thus will need a device programmer to change the parameters.

In some devices, application of a magnet produces a soft beep for each QRS complex. If the magnet is left on for approximately 30 seconds, the ICD is disabled and a continuous tone is generated. To reactivate the device, the magnet must be lifted off the area of the generator and then replaced. After 30 seconds, the beep returns for every QRS complex.

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