Hidden Magnets Fritz Heart Devices
Implantable Defibrillators, Pacemakers Affected by Small, Powerful Magnets in Jewelry, Clothing
WebMD News Archive
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
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
The magnets can throw pacemakers out of synch. And they can shut down
ICDs without warning -- leaving vulnerable patients unprotected against their
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
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
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.
"Notably, only small magnets were tested," Wolber and colleagues
observe. "Larger NdFeB magnets are likely to cause interference at greater
Wolber and Li agree that while the magnets affect pacemakers, their effects
are potentially much more serious for ICD patients.
"The ability of ICDs to detect and treat life-threatening arrhythmias is
temporarily suspended as long as the magnet switch of the device is
activated," Wolber tells WebMD. "This may put the patient at
substantial risk if the device is inactivated for a longer period of time, as
might be the case with nametags, necklaces, and brooches worn close to the
Wolber advises heart patients with electronic implants to be on the lookout
for jewelry, accessories, or even clothing that may carry NdFeB magnets. And he
warns patients not to test magnets by themselves.
What about patients who discover they have been wearing magnets?
"Don't panic, use common sense. Removal of the magnet resolves the
problem immediately," Wolber says.
Wolber's study -- and an editorial by Li -- appear in the December issue of