Harvard Heart Letter

Heart Beat: Fatal attraction?

Heart Beat

Fatal attraction?

That magnetic brooch or necklace may set off more than your eyes or sweater "" it could also set off, or turn off, your pacemaker or implanted cardioverter/defibrillator (ICD).

Jewelry, reading glasses, name tags, and even some clothing sport a new breed of magnet. Called rare earth or neodymium-iron-boron magnets, they are more powerful than the traditional magnets used to stick things to a refrigerator or found inside stereo speakers.

Swiss researchers tested two jewel-sized pieces as well as a necklace and a name tag "" all made of neodymium-iron-boron magnets "" in 70 volunteers with a pacemaker or ICD. All four pieces interfered with the heart device at a distance of an inch or so. They made the pacemakers generate "beat now" signals at a fixed rate regardless of the heart's activity. More worrisome, they turned off the ICDs' ability to detect and stop a potentially deadly heart rhythm.

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