Patients may not realize that some of their newer-generation devices could interfere with their life-saving therapies, so implanting physicians should stay vigilant and talk with their patients about potential issues, the two specialists write in Heart Rhythm.
"Inbuilt magnets are capable of interacting with a defibrillator in a fashion similar to clinical external magnets," said co-author Dr. Gurjit Singh of the Henry Ford Heart and Vascular Institute in Detroit, Michigan.
ICDs contain a sensing circuit that deactivates the defibrillator when it comes close to a magnetic switch. Pacemakers and other devices may also deliver electrical impulses that don't match the patient's rhythm when near a magnetic field.
"If the phone is kept very close to the ICD site, the ICD may get deactivated," he told Reuters Health by email. "If a patient happens to develop a fatal cardiac rhythm, then the defibrillator will not sense the rhythm and will not deliver any shock therapy, which can be fatal."
Dr. Singh and colleague Dr. Joshua Greenberg tested a new iPhone 12 model after they discovered the smartphone contains a circular array of magnets around a central charging coil, which makes the phone compatible with Apple's MagSafe accessories. The MagSafe technology contains a magnetometer and a single-coil, near-field communication reader. The magnets help devices and chargers to align properly and increase charging speeds.
Drs. Singh and Greenberg checked for a device interaction on a patient with a Medtronic ICD. When the phone was moved close to the ICD over the left chest area, the device stopped immediately. The same pause happened several times as they tested the phone in different positions over the chest pocket.
Newer-generation phones could create a significant health issue for patients with ICDs, especially when carried in an upper chest pocket, Drs. Singh and Greenberg report. Although recent studies have shown that older-generation models without a magnetic array carry minimal risk of interference, new models could pose an issue.
"As of now, tests are being conducted to determine the distance from devices where the iPhone 12 starts interacting," Dr. Singh said. "I am also conducting studies to look for interactions from other devices, such as watches and phone cases."
For now, Drs. Singh and Greenberg recommend keeping phones six inches away from ICDs and pacemakers. Smartphone manufacturers, medical device manufacturers and physicians who implant cardiac devices should remain aware of potential interactions, they write.
"There are more and more magnets built into wearables and portable devices with enough magnetic strength to affect cardiovascular implantable electronic device functions," said Dr. Michael Wu of the Warren Alpert School of Medicine at Brown University in Providence, Rhode Island. Dr. Wu, who wasn't involved in the study, has written about potential magnetic interference from smartwatches and fitness trackers.
One of Dr. Wu's patients, a 55-year-old woman with ventricular tachycardia, woke up one night to a beeping sound from her Medtronic ICD. After testing, his research team found that the built-in magnet in her fitness tracker was powerful enough to deactivate the ICD when she wore it overnight (https://bit.ly/3rKukQG).
"We want patients to be aware of these potential interactions to avoid unwanted effects," he told Reuters Health by email.
Similar interferences have been reported across different ICD manufacturers and personal devices with magnets, such as portable headphones and tablet covers, and larger studies are needed, said Dr. Haran Burri of the Cardiac Pacing Unit at the University Hospital of Geneva in Switzerland. Dr. Burri, who also wasn't involved in the new report, has researched the risk of interference between smartphones and cardiac devices.
Manufacturers recommend keeping a distance of six inches between phones and implantable devices and won't likely change their current recommendations, Dr. Burri said.
"It is also important to stress that the cell phone will not damage the pacemaker/ICD, and that interference is transient, with resumption of normal device function once the phone is again at a distance from the implanted device," he told Reuters Health by email.
SOURCE: https://bit.ly/372G4FU Heart Rhythm, online January 4, 2021.
By Carolyn Crist
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