MP3 player headphones may throw off cardiac devices

Tucking the headphones for your iPod into your coat pocket might not be exactly heart-stopping, but it could interfere with the normal functioning of your implanted cardiac device.

Harvard researchers presenting Sunday at the American Heart Association's annual scientific sessions, in New Orleans, report that magnets in these headphones might throw off pacemakers and implantable cardioverter defibrillators (ICDs) when placed within an inch of the devices.

Although interference is unlikely to cause life-threatening problems, the authors of the study advise those with ICDs and pacemakers to keep headphones at least 1.2 inches from their device.

Others agreed.

""Don't put the device near your torso,"" recommended Dr. Peter Cheung, an assistant professor of internal medicine at Texas A&M Health Science Center College of Medicine and a cardiologist with Scott & White Hospital. ""Instead of your breast pocket, put it in your pants pocket or purse, and don't let the speakers hang from your shoulder or neck.""

""People need to take just as much care with their MP3 as much as they do with other sources of electromagnetic interference,"" said Dr. Daniel Morin, a staff electrophysiologist with Ochsner Health System in New Orleans.

Other possible interference can come from microwaves, theft detection devices in malls and stores, and other sources, but patients should be fine with routine use. ""Just don't hug the microwave,"" Morin said.

Previous research has indicated that iPods have little, if any, effect on pacemakers and ICDs, and a statement from the U.S. Food and Drug Administration confirmed that interactions between MP3 players and implanted devices are unlikely.

But less attention has been placed on headphones.

The authors of this latest study tested eight different types of MP3 headphones with iPods on 60 patients with defibrillators or pacemakers.

The headphones were placed on patients' chests right over their devices. Fifteen percent of patients with pacemakers and 30 percent of those with defibrillators had a response to the magnets.

But even higher-strength magnets had no effect when kept at least 1.2 inches above the device location.

""It's good information, but I don't think it's going to be a big deal,"" said Dr. Spencer Rosero, an associate professor of medicine in the electrophysiology unit at the University of Rochester Medical Center. ""In very unusual circumstances, it can interfere, but the situation has to be just right, which doesn't really apply for daily living. . . It would not kill you.""

And even a front shirt or jacket pocket is unlikely to be right above a pacemaker or defibrillator, he added. ""Pacemakers are usually two-to-three fingerbreadths below the collar bone. Most pockets are not that high,"" Rosero said.

Two other studies being presented at the heart meeting also absolved other devices from interfering with pacemakers and ICDs.

According to one set of researchers from Massachusetts, Bluetooth cell phone technology, and capsules equipped with tiny cameras that are swallowed to view internal organs, did not interfere with the devices.

And another group of researchers from California found that electric blankets and hand-held airport security metal detectors, in addition to iPods, iPhones and Bluetooth, did not affect pacemakers or ICDs.