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Heart Disease Health Center

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Hidden Magnets Fritz Heart Devices

Implantable Defibrillators, Pacemakers Affected by Small, Powerful Magnets in Jewelry, Clothing
WebMD Health News
Reviewed by Louise Chang, MD

Dec. 6, 2006 -- Jewelry and accessories made with small, powerful magnets may have a fatal attraction for heart patients with implantable defibrillators or pacemaker implants.

Heart doctors always warn patients with electronic implants to avoid close contact with magnetic fields. But patients may not recognize that the jewelry they receive as a gift -- or the name badge they get at a conference -- could carry magnets far stronger than their size would suggest.

These aren't your average refrigerator magnets. The newer magnets are made from neodymium-iron-boron, or NdFeB. Dozens of brightly colored, pea-size NdFeB magnets can be placed together in various intriguing shapes -- without strings or clasps.

Is this really a problem? Minnesota Heart Clinic cardiologist Huagui Li, MD, PhD, recalls an urgent call from a 64-year-old woman whose implantable cardioverter defibrillator, or ICD, began beeping.

The beeping stopped when she took off her blouse -- to which a magnetic brooch was attached.

"It is those magnets that are not easy to identify that become a problem," Li tells WebMD. "Most people don't feel the difference right away."

The magnets can throw pacemakers out of synch. And they can shut down ICDs without warning -- leaving vulnerable patients unprotected against their heart disease.

Magnets an Inch From Trouble

Thomas Wolber, MD, of University Hospital, Zurich, tested NdFeB magnets on 41 patients with pacemaker implants and 29 patients with ICDs, which are designed to detect a dangerous heart rhythm and shock it back into normal rhythm.

Wolber and colleagues used four different NdFeB magnets: a sphere less than a third of an inch in diameter, a sphere less than a half-inch in diameter, a necklace made up of 45 small spherical magnets, and a magnetic name badge.

Under close medical supervision, they exposed the patients to the magnets.

None of the magnets affected patients' implants -- until they got within 1.2 inches of the patient's skin. Then the magnets switched off ICDs and affected the speed at which pacemakers ran.

None of the patients had any symptoms during the tests. And their devices resumed normal function once the magnets were removed.

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