Washington, Nov 10 (IANS) Don’t allow MP3 headphones to get too close to pacemakers and implantable defibrillators; they could be potentially dangerous. Researchers investigated the effects of MP3 headphones, most of which contain the magnetic substance neodymium, on the operation of implanted cardiac devices.

An MP3 player is a popular digital music player. Earlier this year a US government report concluded that interactions between MP3 players, such as the popular iPod, and implanted cardiac devices are unlikely to occur.

“We became interested in knowing whether the headphones which contain magnets - not the MP3 players, themselves - would interact with implanted cardiac devices,” said William H. Maisel, study co-author and director of Medical Device Safety Institute at Beth Israel Medical Centre in Boston.

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 them looking for abnormal heart rhythms.

Implanted cardiac devices that react in these ways to magnets outside the clinical setting can be potentially dangerous for patients who rely on their lifesaving technologies, according to a Beth Centre release.

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 a detectable interference with the device by the headphones in 14 patients (23 percent). Specifically, they observed that 15 percent of the pacemaker patients and 30 percent of the defibrillator patients had a magnet response, Maisel said.

“For patients with pacemakers, exposure to the headphones can force the device to deliver signals to the heart, causing it to beat without regard to the patients’ underlying heart rhythm,” he said.

“Exposure of a defibrillator to the headphones can temporarily deactivate the defibrillator,” he said. In most cases, removal of the headphones restores normal device function.

However, other studies did not find adverse reactions to pacemakers and defibrillators from iPods or Bluetooth headsets, iPhones, electric blankets, hand-held airport metal detectors or pills swallowed to perform video endoscopy.

These findings were presented at the American Heart Association’s Scientific Sessions 2008.