Researchers investigated the effects of MP3 player headphones, most of which contain the magnetic substance neodymium, on the effectiveness of implanted cardiac devices.

“We became interested in knowing whether the headphones which contain magnets — not the MP3 players, themselves — would interact with implanted cardiac devices,” said researcher Dr William H. Maisel of the Medical Device Safety Institute in Boston, US.

Maisel said doctors traditionally use magnets in the clinical setting to test pacemakers, which treat slow heart rhythms. When exposed to magnets, these devices automatically pace, sending low-energy signals to the heart to make it beat. Defibrillators, which treat slow and dangerously fast heart rhythms, send either low- or high-energy signals to the heart. However, ICDs near magnets may temporarily stop working.

Implanted cardiac devices that react in these ways to magnets can be potentially dangerous for patients who rely on their lifesaving technologies.

Researchers tested eight different models of MP3 player headphones (including both the clip-on and earbud variety) with iPods® on 60 defibrillator and pacemaker patients.

“We placed the headphones on the patients’ chests, directly over where their devices are located, monitoring them for evidence of an interaction,” Maisel said.

The researchers found that in around a quarter of patients, headphones interfered with heart devices – 15 percent of the pacemaker patients and 30 percent of the defibrillator patients.

In most cases, removal of the headphones restores normal device function.
The researchers say that patients should not place headphones in their pocket or drape them over their chest.

“Patients should keep their headphones at least 3 cm from their implantable devices,” Maisel concluded.

“For family members or friends of patients with implantable defibrillators, they should avoid wearing headphones and resting their head right on top of someone’s device.”