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After some back-and-forth in the medical community, it has generally been decided that iPods and MP3 players do not seriously interfere with pacemaker functions.
However, a study points to an entirely new concept of the risk involved with these devices. It is not the music player itself that can cause disruption. Rather, say researchers at Beth Israel Deaconess Medical Center in Boston, it is the headphones, which rely on magnets to operate.
"It has long been recognized that implantable medical devices such as pacemakers and defibrillators can be affected by magnets," William H. Maisel, senior author of the study and director of the Medical Device Safety Institute at Beth Israel, told TechNewsWorld. "What has not been appreciated is that these headphones have magnets."
Measuring the Fields
Researchers tested eight different models of MP3 player headphones including both the clip-on and earbud models using a gauss meter, which measures the strength of magnetic field produced. Field strength of 10 gauss at the site of the pacemaker or defibrillator has the potential to interact with the implantable device, the study said. The researchers found that some of the headphones had field strengths as high as 200 gauss or more.
Given that, it was not surprising that of the 60 patients tested, a "detectable interference" was observed in 15 percent of the pacemaker patients and 30 percent of the defibrillator patients.
The headphones were placed directly over the patients' chests; however, once they were moved -- even slightly -- the interference stopped.
There were no interactions when the headphones were at least 1.2 inches from the skin's surface, Maisel said.
Suggested Guidelines
Maisel suggested a few guidelines doctors should give patients as a result of the study.
First, while concerns about iPods and MP3 players may have been debunked, the headphones are still a concern. "If you use them, be careful to keep them away from your chest," he said.
Also, brand names are unimportant. The report's findings covered several different types of headphones, he added.
It also is wise to always question what could impact a pacemaker or other implantable device, he continued. The most common questions are about microwaves -- these have no effect -- and the antitheft devices in retail stores, he said. The latter also pose a small risk, but only if the patient stands in front of them for a long period of time. "Always ask your doctor if there are any questions."
Maisel was unaware of any adverse events caused by MP3 headphones. "Both devices -- headphones and pacemakers -- are very common. We simply want patients to understand the risks," he said.
Growing Risks
But even keeping Maisel's brand-neutral warning in mind, it is difficult to ignore the number of cautions the medical community has been throwing up against next-gen portable players, with the iPod the primary target. Hearing specialists have warned users that the iPod in particular can damage hearing because the sound can get very loud when played at the highest levels over time.
There was also controversy over whether the iPod -- the device itself, not the headphones -- could interfere with an implantable device.
This past February, the Food and Drug Administration weighed in on the subject with a study that found the iPod's interference with the pacemaker device to be non-existent. FDA researchers measured the magnetic fields produced by four different iPod models as well as the voltages delivered inside the pacemaker by the magnetic fields from the iPods. All measurements indicated there would be no effects on users with cardiac pacemakers.
In March another study affirmed the iPod's safety for pacemaker patients, but with some caveats. Cardiac electrophysiologists at Children's Hospital Boston reported findings for a study conducted between September and December in 2007 on 51 patients that had active pacemakers or implantable cardioverter-defibrillators. The study used four digital music players -- Apple's (Nasdaq: AAPL) iPod nano, Apple's iPod video, SanDisk (Nasdaq: SNDK) Sansa and Microsoft (Nasdaq: MSFT) Zune. All patients were lying down during the tests and each digital player was placed directly over the pacemaker or ICD. There was no interference with intrinsic device functioning -- the patients' EKG recordings showed no change in any of 255 separate tests, and no patients had symptoms, Gregory Webster, a cardiac fellow in training at Children's, and co-author of the report, told TechNewsWorld.
However, in 41 percent of patients, the music players interfered with telemetry, or communications between the programmer and the pacemaker or ICD itself. The programmer is a computerized device used by physicians to check and recalibrate the pacemaker/ICD.
The study concluded that patients should not use digital music players while their doctor is reprogramming their medical device.
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