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Newest cellphones may pose 'significant risk' to pacemakers and ICDs

There has been little compelling evidence that smartphones pose a significant danger to users of medical devices such as implantable cardiac defibrillators (ICD). Until now, with the arrival of Apple’s iPhone12, argues an article in MedPage Today, citing recent research in HeartRhythm.

Apple announced its iPhone 12 in late 2020 as "the best iPhone ever" with "a powerful 5G experience and advanced technologies that push the boundaries of innovation for users who want the most out of iPhone." One innovation that users may not have anticipated was the ability of this iPhone iteration to deactivate their implantable cardiac defibrillators (ICD), writes Dr Anthony Pearson in MedPage Today.

Pearson, a noninvasive cardiologist and professor of medicine at St Louis University School of Medicine, writes:

ICDs and cardiac pacemakers are designed to respond to nearby magnets by changing their function. In essence, these sophisticated devices are rendered dumb. Amongst the advanced technologies Apple put in the iPhone 12 was "an array of magnets around the wireless charging coil" for pairing with various MagSafe fitted chargers and accessories:

An electrophysiologist at Henry Ford, Dr Joshua Greenberg, became concerned about possible adverse interactions between iPhone's magnets and implantable cardiac devices and performed a test on a patient with an ICD manufactured by Medtronic. In a letter to the editor of HeartRhythm in early January of this year, he and his co-authors describe what happened: "Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted and persisted for the duration of the test."

This is a big deal because "suspension of life-saving therapies" means that, should the patient go into ventricular tachycardia or fibrillation during this time, they would just drop dead without receiving a life-saving shock from the ICD. Electrophysiologist Dr Mike Eskander, recently tweeted a video showing the iPhone 12 can convert standard pacemakers to asynchronous (magnet) mode as well.

Greenber et al write:

"The implantable cardioverter-defibrillator (ICD) remains the cornerstone therapy for the management of malignant ventricular arrhythmias in patients with high-risk cardiac conditions. An ICD system contains a battery, capacitors, and a sensing/pacing circuit together with an intracardiac or extracardiac lead. All ICDs have an in-built switch (reed switch, Hall effect sensors, giant magnetosensitive resistors or coils) that responds to an externally applied magnetic field. When an external magnet is applied to a defibrillator, high-voltage shock therapy for ventricular tachycardia and ventricular fibrillation is suspended. It has been estimated that a magnetic field stronger than 10 gauss is strong enough to activate these switches.

"Apple recently launched the iPhone 12 series, which has a circular array of magnets around a central charging coil that makes the phone compatible with MagSafe accessories. MagSafe technology contains a magnetometer and a single-coil, near-field communication (NFC) reader. The magnets aids in properly aligning the iPhone on a wireless charger and other peripheral accessories and increases wireless charging speeds (up to 15 W). The first author raised concerns regarding possible device–device interaction due to the presence of a strong magnetic array in the iPhone and MagSafe compatible cases.

"We thus tested this interaction on a patient with a Medtronic ICD. The study was approved by the institutional review board. Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted and persisted for the duration of the test. This result was reproduced multiple times with different positions of the phone over the pocket.

"We hereby report an important public health issue concerning the newer-generation iPhone 12, which potentially can inhibit lifesaving therapy in a patient, particularly when the phone is carried in an upper chest pocket … Medical device manufacturers and implanting physicians should remain vigilant about making patients aware of this significant interaction of the iPhone 12 and other smart wearables with their cardiac implantable electronic devices."

Previous advice and evidence

Patients with ICDs and pacemakers have long been given recommendations to keep cell phones more than 6 inches from their pacemakers. The concern is that cell phone-emitted electromagnetic fields could be misinterpreted by the devices as intrinsic cardiac electrical activity with subsequent inhibition of pacing activity or inappropriate activity. Patients are routinely instructed to use the ear opposite the pacemaker site and not to put the phone in a shirt or jacket pocket adjacent to the site.

However, these recommendations are based on studies performed decades ago and since then both cardiac device technology and cell phone technology has evolved and advanced and heretofore there has been no evidence for adverse interactions. In fact, reports of adverse interactions were so rare that a 2017 paper in the Journal of the American College of Cardiology (JACC) tested the hypothesis that "technological advances may have rendered current recommendations obsolete."

They tested three different smartphones (Samsung Galaxy S3, Nokia Lumia, and HTC One XL) held directly above the implanted cardiac devices of 307 patients (52% ICD, 48% pacemaker from eight manufacturers) and found only one device was affected by electromagnetic interference. The authors concluded: "We therefore suggest the current recommendation to maintain a 15-cm [6-in] gap between phone and generator may be too stringent and thereby cause unnecessary apprehension."

A more recent study in JACC: Clinical Electrophysiology showed minimal risk of electromagnetic interference from ICDs and smartphones without a magnetic array. This study evaluated the interaction of iPhone 6 or Apple Watch (first generation) with "51 pacemakers, 5 cardiac resynchronization therapy pacemakers, 46 implantable cardioverter-defibrillators, 43 cardiac resynchronization therapy defibrillators, and 3 implantable loop recorders."

With unusual prescience, the authors of the 2017 JACC study noted that "the rapid evolution of implantable cardiac device and mobile phone technology obliges us to be aware that such safety recommendations require continual re-evaluation."

Magnetic wristbands and ICDs

A case report in HeartRhythm describes the wristband magnets in Fitbit and Apple Watch deactivating a Medtronic ICD up to distances of 2.4 and 2.0 cm (0.9 and 0.8 in), respectively:

"A 55-year-old woman with history of sustained ventricular tachycardia secondary to arrhythmogenic right ventricular dysplasia was treated with a dual-chamber ICD for secondary prevention. She was recommended to avoid strenuous exercise to reduce arrhythmic risk. She subsequently purchased an Apple Watch with fitness tracking capabilities to monitor her heart rate, which she wore sometimes overnight. While asleep one night, she was awoken by several beeps emanating from her implanted cardiac device. Subsequent interrogation of the device showed no alerts or abnormal parameters. Upon further investigation, it was found that the device had reverted to magnet mode, owing to magnetic interference from the fitness watch's wristband. No other possible sources of interference were identified. This was replicated in the office, where interrogation of the ICD confirmed magnetic reversion when placed in proximity to the wristband. The watch itself did not have magnetic interference."

Apple's response

On January 23, 2021, three weeks after the Greenberg letter, Apple issued a confusing press release regarding the iPhone 12 and magnetic interference with medical devices:

"Though all iPhone 12 models contain more magnets than prior iPhone models, they're not expected to pose a greater risk of magnetic interference to medical devices than prior iPhone models."

Apple went on to give this advice:

"Medical devices such as implanted pacemakers and defibrillators might contain sensors that respond to magnets and radios when in close contact. To avoid any potential interactions with these devices, keep your iPhone and MagSafe accessories a safe distance away from your device (more than 6 inches / 15 cm apart or more than 12 inches / 30 cm apart if wirelessly charging). But consult with your physician and your device manufacturer for specific guidelines."

Apple is implying that the iPhone 12 is no more likely to shutdown ICDs than other cell phones or that earlier iPhone versions have this capability but we didn't know it. It is possible that any cell phone with wireless charging capabilities could interact with ICDs and pacemakers in the same manner.

Beware cellphone magnets With an ICD or pacemaker

If you are, like me, perpetually unaware of the location of your iPhone or Apple Watch (whether on or off my body), it is highly likely they will not infrequently come within 6 inches of your left (or, for some individuals, right) upper chest region. Depending on your device, this could render you unprotected by your ICD from ventricular rhythm abnormalities or put your pacemaker into an asynchronous pacing mode.

Dr Phil Mar, an electrophysiologist at Saint Louis University School of Medicine, agrees that this is a significant, heretofore-unrecognised issue. Our advice to patients with pacemakers or ICDs (or the future possibility of one) would be to not buy an iPhone 12 or wearable wristband with magnets. In fact, Mar would extend this to spouses of ICD patients, since most couples sleep in the same bed.

This was not a problem with earlier iPhones without the array of magnets and was not seen with Apple Watch without the magnetic wrist bands, but it is possible it extends to any cell phone with wireless charging.

It occurs to me that the safest approach for patients would be to have their personal cell phone tested for interaction with their cardiac device by their cardiologist or electrophysiologist early after implantation. Such a check will become the norm for my patients.


[link url=""]MedPage Today full text (Restricted Access)[/link]


[link url="
"]Heart Rhythm Journal full text (Open Access)[/link]


[link url=""]Heart Rhythm Journal Case Report (Open Access)[/link]


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