Washington, November 10 : An American research team has shown that headphones for MP3 players can interfere with pacemakers and implantable cardioverter defibrillators (ICDs) if placed within an inch of such devices.
Researchers at the Medical Device Safety Institute at Beth Israel Medical Center in Boston, Massachusetts, presented their findings at the American Heart Association's Scientific Sessions 2008.
The researchers revealed that they undertook the study after an FDA report concluded earlier this year that interactions between MP3 players and implanted cardiac devices were unlikely to occur
The team further said that they investigated the effects of MP3 player headphones, most of which contain the magnetic substance neodymium, on the operation 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 senior author of the study Dr. William H. Maisel, director of the Medical Device Safety Institute at Beth Israel Medical Center in Boston, Massachusetts.
During the study, the researchers tested eight different models of MP3 player headphones, including both the clip-on and earbud varieties, 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 research team observed that there was a detectable interference with the device by the headphones in 14 patients, about 23 per cent.
Maisel revealed that about 15 per cent of the pacemaker patients, and 30 per cent of the defibrillator patients, had a magnet response.
"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. Exposure of a defibrillator to the headphones can temporarily deactivate the defibrillator," he said.
The researcher said that removal of the headphones was found to restore normal device function in most cases.
Maisel said that the team also tested the magnetic field strengths of each of the headphone models using a gauss meter, considering that field strength of 10 gauss at the site of the pacemaker or defibrillator has the potential to interact with the implantable devices.
He said that some of the headphones had field strengths as high as 200 gauss or more
"Even at those high levels, we did not observe any interactions when the headphones were at least 3 cm, or about 1.2 inches, from the skin's surface," Maisel said.
"Patients should not focus on the brands we tested but instead should simply be instructed to keep their headphones at least 3 cm from their implantable devices," he added.
The researcher suggested that patients do not place headphones in their pocket or drape them over their chest.
"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," he said.