Inappropriate activation of pacemaker magnet response mode by CPAP masks

Background: While electromagnetic interference is widely recognized as a cause of noise detected by cardiac implanted electronic devices (CIEDs), we report on two cases of inappropriate activation of magnet response mode due to magnets in continuous positive airway pressure (CPAP) masks. Methods: Two patients with St. Jude Medical dual-chamber pacemakers (Assurity DR 2240; St. Jude Medical, St. Paul, MN, USA) were discovered on routine outpatient device interrogation to have magnet response events that correlated with nightly use of their CPAP masks. A magnet response event was reproduced by positioning one CPAP mask over the patient's pulse generator site. The magnetic flux density was measured using a Gauss meter. Results: It was found that their CPAP masks had magnetic clips that were used to secure the headgears. These appeared to be transiently positioned within sufficient proximity of the patients’ CIEDs to activate magnet response events during sleep. The measured magnetic field density adjacent to a mask magnet was 136 Gauss. Conclusion: Clinicians managing CPAPs and CIEDs should be aware of magnetic interference with the potential for inappropriate activation of magnet response mode. CPAP masks that are secured with magnetic clips should be avoided in patients with CIEDs, since this can result in inappropriate asynchronous pacing in pacemakers or potential failure to deliver life-saving tachytherapies in patients with implanted cardioverter-defibrillators.