Getting too close to magnets can have fatal consequences for heart patients

Dec 4 2006

According to Swiss researchers some magnets which are used in many new commercial products can interfere with implanted heart devices such as pacemakers and the consequences can be fatal.

It appears that magnets made from neodymium-iron-boron are increasingly being used in computer hard drives and "in-ear" headphones, and this is of concern because being close to such magnets can disrupt the normal functioning of cardiac devices.

Ordinary iron or ferrite magnets, which are a dull grey colour with a low magnetic strength, such as those used to stick badges on fridges are apparently not a problem; it is the powerful magnets made from neodymium-iron-boron, which are shiny and silver in colour that are the worry.

Because of their high magnetic field strength and low production costs, they are being used in computer hard drives, headphones and hi-fi speakers, and in toys and jewellery.

The researchers from the University Hospital of Zurich tested the effect of neodymium magnets in 70 heart patients, 41 with pacemakers and 29 with implantable cardioverter defibrillators.

They found that the small 8g magnets they tested interfered with all of the patients' devices, regardless of their make or type, when they were in a maximum range of 3cm.

The researchers say larger neodymium magnets are likely to cause interference at greater distances than this and though the heart implants worked normally again once the magnet was removed, the scientists warn that permanent damage might occur with prolonged exposure, such as the wearing of a magnetic name badge.

Dr. Thomas Wolber, from the University Hospital of Zurich, who led the study says doctors should warn patients about the risks associated with the magnets and he believes the packaging of the magnets should carry information on the potential risks that may be associated with them.

Makers of pacemakers say they are manufactured to the highest standards, are rigorously tested, and most have a protective case to shield them from outside interference.

The findings are published in the journal Heart Rhythm.