How do magnets affect the functioning of a pacemaker?

Updated: Oct 11, 2019
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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Magnet use inhibits further ICD discharge. It does not, however, inhibit pacing. 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. Indications for ICD deactivation are as follows:

  • End-of-life care - After a discussion with the patient and family

  • Inappropriate shocks

  • During resuscitation

  • With transcutaneous pacing - External pacing can cause an ICD to fire

  • During procedures such as central lines or surgery with electrocautery

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