Beware What You Wear with Your Pacemaker or ICD

New, powerful magnets in consumer products can threaten pacemaker and ICD function.

Relatively weak magnets in consumer products have always posed some risk, usually very low, to the function of pacemakers and implantable cardioverter-defibrillators (ICDs). However, stronger, potentially riskier magnets made from neodymium–iron–boron (Nd₂Fe₁₄B) are becoming more prevalent, due to their small size and low cost.

Researchers in Switzerland assessed the risk posed by commercially available NdFeB magnets to the function of pacemakers in 41 patients and ICDs in 29 patients. They tested two small spherical magnets (diameters, 8 and 12 mm), a necklace with magnets, and a magnetic name tag; no single magnet weighed more than 8.3 grams.

In all, 280 measurements were taken at distances ranging from direct skin contact over, to 3 cm away from, the implanted cardiac devices. Magnetic interference was observed in all patients. The frequency of interference ranged from 57% (name tag) to 99% (12-mm sphere). Pacemakers were affected at greater distances than were ICDs (mean, 2.1 cm vs. 1.7 cm), with no significant differences between single- and dual-chamber devices or by manufacturer.

Comment

An accompanying editorial describes an illustrative incident in which a patient’s brooch, worn on her blouse, inactivated her ICD for an extended period, until the blouse was removed and a magnet in the jewelry discovered. In the present study, small neodymium–iron–boron magnets had a high likelihood of causing pacemaker and ICD interference at distances up to 3 cm. The authors note that magnets larger than those tested are likely to be risky at greater distances. For ICD wearers in particular, magnetic interference could mean the device’s failure to detect a life-threatening arrhythmia and to deliver life-saving therapy. Physicians should discuss with their patients who have pacemakers and ICDs the risks from increasingly common NdFeB magnets.

Reviewing Author

Mark S. Link, MD

Citation(s):

Wolber T et al. Potential interference of small neodymium magnets with cardiac pacemakers and implantable cardioverter-defibrillators. Heart Rhythm 2007 Jan; 4:1-4.

Li H. Magnet decoration, beautiful but potentially dangerous for patients with implantable pacemakers or defibrillators. Heart Rhythm 2007 Jan; 4:5-6.