FDA warns of pacemaker-iPhone interference

A study published this week in Heart Rhythm supported recommendations by the U.S. Food and Drug Administration that patients keep consumer electronic devices that may create magnetic interference, including cell phones and smart watches, at least six inches away from implanted medical devices.  

The study, which was coauthored by four investigators affiliated with the FDA’s Center for Devices and Radiological Health, built upon previous discoveries that the iPhone 12 Pro could trigger the “magnet mode” of a Medtronic implantable cardioverter-defibrillator.

“When a pacemaker enters magnet mode, the device continuously paces without sensing the patient’s own heart rhythm, which can result in symptoms (such as irregular heartbeats), abnormal heart rhythms, or, rarely, more serious patient harm,” wrote the researchers.   


The magnet modes of implantable pacemakers and ICDs are designed to be used when a patient is undergoing certain medical procedures, such as an MRI.

As the researchers explain, historically, magnets strong enough to trigger that mode have been very large or identifiable. Because the static magnetic field decays with distance, pacemaker patients could fairly easily maintain distance from them.  

However, small rare-earth magnets are increasingly used inside of technology such as headphones, locks for doors, and small phone speakers, along with smart watches and accessories.  

“For example, the MagSafe feature in the iPhone 12 series of phones uses a strong rare-earth magnet to align the phone for wireless charging,” the researchers wrote.  

“While the iPhone 12 is just another application with a strong magnet, it is a concern for patients because the phone can get very close to the implantable device (e.g. placing the phone in a front shirt or jacket pocket),” they continued.

The researchers explained that implantable pacemakers and ICDs that meet FDA standards are tested to ensure magnet mode will not be triggered by static magnetic fields below 10 gauss.  

They attempted to determine the minimum separation distance between electronic devices that may create magnetic interference – in this case, the iPhone 12 and Apple Watch 6 – and implantable pacemakers and ICDs where magnet mode can be triggered.   

The researchers found that all iPhone 12 and Apple Watch 6 models tested have static magnetic fields much greater than 10 G within 11 millimeters of the device, or slightly less than half an inch.  

Those numbers decrease to below 10 G between 11 millimeters and 20 millimeters.  

Notably, researchers found that the static magnetic field for the back of an Apple Watch 6 measured 983.14 G at 1 millimeter away.  

“If placed within close proximity, the fields are high enough to place implanted cardiac devices into magnet mode,” said the researchers.   

“This particular study focuses on the iPhone 12 and Apple Watch 6, but the results could be broadly applicable to any consumer electronic devices that may create magnetic interference, including other cell phones and smart watches,” they wrote.  

Apple did not respond to requests for comment, but it did publish a statement in early July warning about magnets potentially interfering with medical devices and recommending that users keep Apple products more than six inches away from them (or a foot if wirelessly charging).  

“If you suspect that your Apple product is interfering with your medical device, stop using your Apple product and consult your physician and your medical-device manufacturer,” said the statement.  


The FDA’s study reinforced a warning it issued in May of this year about the effect that magnets in some cell phones and smartwatches can have on pacemakers and other implanted medical devices.

“The FDA also conducted its own testing on some products that use the high field strength magnet feature and have confirmed the magnetic field is both consistent with the publications and strong enough to turn on the magnetic safety mode of the medical devices in question,” the agency said in the warning.  


“We believe the risk to patients is low and the agency is not aware of any adverse events associated with this issue at this time,” said Dr. Jeff Shuren, director of the FDA’s Center for Devices and Radiological Health, in a May statement about the issue.

“However, the number of consumer electronics with strong magnets is expected to increase over time,” he added. “Therefore, we recommend people with implanted medical devices talk with their healthcare provider to ensure they understand this potential risk and the proper techniques for safe use.”

Kat Jercich is senior editor of Healthcare IT News.
Twitter: @kjercich
Email: [email protected]
Healthcare IT News is a HIMSS Media publication.