Research found that neodymium, a magnetic substance contained in the MP3 player headphones, appears to impede proper functioning of the technology, posing a potential grave risk to patients who rely on the devices.
"Exposure of a defibrillator to the headphones can temporarily deactivate the defibrillator," said William Maisel, senior author of the study and director of the Medical Device Safety Institute at Beth Israel Medical Center in Boston, Massachusetts.
The study, presented at an American Heart Association conference, concluded that in order to be operated safely, headphones accompanying the popular MP3 digital music players must be at least 1.2 inches (3 centimeters) from the implanted devices.
Scientists said patients using heart devices should not place MP3 player headphones in their pocket or drape them over their chest.
"For family members or friends of patients with implantable defibrillators," said Maisel, "they should avoid wearing headphones and resting their head right on top of someone's device."
Maisel and his research team determined that outside studies have found no adverse reactions to pacemakers and defibrillators from other portable electronic devices like iPods, Bluetooth headsets, iPhones, electric blankets or hand-held airport metal detectors.