Patients with an implantable cardioverter defibrillator (ICD) should be warned that some newer models of smartphones equipped with magnets, such as the iPhone 12, can disable their device, inhibiting its lifesaving functions, according to investigators who tested and confirmed this effect.
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“Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted which persisted for the duration of the test,” reported the investigating team led by Joshua C. Greenberg, MD, who is an electrophysiology fellow at Henry Ford Hospital, Detroit. The results were published in Heart Rhythm.
The American Heart Association has already cautioned that magnetic fields can inhibit the pulse generators for ICDs and pacemakers. On the AHA website, there is a list of devices and their potential for functional interference, but cell phones and other common devices are identified as posing a low risk.
The most recent iPhone and perhaps other advanced smartphones appear to be different. According to the authors of a study that tested the iPhone 12, this model has a circular array of magnets around a central charging coil. This array interacts with Apple’s proprietary MagSafe technology, which accelerates charging. The magnets also serve to orient the phone on the charger and enable other MagSafe accessories.
The authors of the new study were concerned that this array of magnets might be sufficiently strong to interfere with ICDs or other devices at risk. In a previously published study, the strength of a magnetic field sufficient to interfere with implantable cardiac devices was estimated to be at least 10 gauss.
Tests were performed on a patient wearing a Medtronic ICD.
“Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted,” according to the authors of the study. The functional loss of the ICS persisted for the duration of proximity. It was reproduced multiple times and with multiple phone positions.
Previous studies have provided evidence that earlier models do not share this risk. In a study testing the iPhone 6 and an Apple Watch in 148 patients with various types of implantable electronic devices, including pacemakers, cardioverter defibrillators, resynchronization defibrillators, and resynchronization pacemakers, only one instance of interference was observed in 1,352 tests.
With wand telemetry, iPhone-induced interferences could be detected with the iPhone 6 in 14% of the patients, but these did not appear to be clinically meaningful, and this type of interference could not be detected with the Apple Watch, according to the report. The single observed interaction, which was between an iPhone 6 and a dual-chamber pacemaker, suggested device-device interactions are uncommon.
More recently, a woman with a single-chamber Medtronic ICD who went to sleep wearing an Apple Watch was awoken by warning beeps from her cardiac device, according to a case report published online. The Apple watch became the prime suspect in causing the ICD warning when proximity of the watch reproduced the warning during clinical examination. However, the magnetic interference was ultimately found to be emanating from the wristband, not the watch.
This case prompted additional studies with Fitbit and other Apple Watch wristbands. Both wristbands contain magnets used to track heart rate. Both were found capable of deactivating ICDs at distances of approximately 2 cm. On the basis of these results, the authors concluded that patients should be counseled about the risk posed by wristbands used in fitness tracking, concluding that they should be kept at least 6 inches away from ICDs and not worn while sleeping.
On their website, Apple maintains a page that specifically warns about the potential for interactions between iPhone 12s and medical devices . Although there is an acknowledgment that the iPhone12 contains more magnets than prior iPhone models, it is stated that iPhone 12 models are “not expected to pose a greater risk of magnetic interference to medical devices than prior iPhone models.” Nevertheless, the Apple instructions advise keeping the iPhone and MagSafe accessories more than 6 inches away from medical devices.
Dr. Greenberg and coinvestigators concluded that the iPhone 12 does pose a greater risk to the dysfunction of ICDs and other medical devices because of the more powerful magnets. As a result, the study brings forward “an important public health issue concerning the newer generation iPhone 12.”
Well aware of this issue and this study, Bruce L. Wilkoff, MD, director of cardiac pacing and tachyarrhythmia devices, Cleveland Clinic, agreed. He said the focus should not be restricted to the iPhone 12 series but other wearable devices as alluded to in the study.
“Pacemakers and implantable defibrillators are designed to respond to magnets for important reasons, but magnets have many common uses,” he said. These can change the function of the implantable cardiac devise, but “it is temporary and only when placed in close proximity.”
The solution is simple. “Patients should be careful to avoid locating these objects near these devices,” Dr. Wilkoff said.
However, the first step is awareness. According to the study authors, devices with magnets powerful enough to impair function of implantable devices, such as the iPhone 12 “can potentially inhibit lifesaving therapy.”
Patients should be counseled and provided with practical steps, according to the authors. This includes keeping these devices out of pockets near implantable devices. They called for more noise from makers of smartphones and other devices with strong enough magnets to alter pacemaker and ICD function, and they advised physicians to draw awareness to this issue.
Dr. Greenberg reported no potential conflicts of interest.