If you have a pacemaker and like listening to music, take note. Earphones used for portable music players may interfere with pacemakers if they're held close to the device, a new study suggests.
Researchers have found that neodymium, the magnetic substance found in most earphones, can temporarily stop defibrillators from detecting abnormal heart rhythms.
Defibrillators send either low- or high-energy signals to the heart to regulate or slow dangerously fast heartbeats.
The research team, which hailed from the Medical Device Safety Institute at Beth Israel Medical Center in Boston, Mass., tested eight models of headphones connected to iPods on 60 patients who had either a pacemaker or a defibrillator.
The researchers found that the earphones caused interference in 15 per cent of the subjects who had pacemakers and 30 per cent of the subjects with defibrillators.
Researchers noticed the effect whether or not the earphones were plugged into a music player.
"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," lead study author Dr. William H. Maisel said in a statement. "Exposure of a defibrillator to the headphones can temporarily deactivate the defibrillator."
When the headphones were removed, normal function of the devices was restored, Maisel said.
The research team presented its findings at the American Heart Association's Scientific Sessions 2008 in New Orleans.
During testing, the earphones were placed on the subjects' chests, directly over the implanted devices. Therefore, the results suggest that patients should avoid keeping earphones in shirt pockets or hanging off the neck.
The good news, according to researchers, is that they did not notice any interference when the earphones were kept at least three centimetres from the implantable device.
As well, the music players themselves are considered safe.
Earlier this year, the U.S. Food and Drug Administration (FDA) concluded that MP3 players, including iPods, are unlikely to interfere with defibrillators and pacemakers.
