iPhone, Apple Watch could disrupt pacemakers

The magnets in some new phones are powerful enough to affect implanted cardiac devices.

Emma Jones 3 minute read September 16, 2021
iphone pacemaker

The iPhone 12 can disrupt the function of a pacemaker, according to several new studies as well as Apple itself. (Brendon Thorne / Bloomberg) Brendon Thorne / Bloomberg

Wireless charging devices may pose a risk for patients with pacemakers and other implanted medical devices, according to a recent study.

In a study published in the Journal of the American Heart Association, researchers placed an iPhone 12 Pro Max on participants’ skin, directly over their implantable cardiac device. The strong magnets contained in these devices were enough to alter how the device functions. This did not happen when the researchers placed the iPhone 6 in the same position.

A separate study published in the journal Heart Rhythm found that all iPhone 12 models, from max to mini, as well as the Apple Watch 6, can cause this same interference.

The culprit is the strong rare-earth magnet that these devices use to align with wireless charging devices. With approximately 0.06 per cent of the Canadian population using pacemakers, and strong magnets becoming increasingly common in everyday products, the odds that a patient may come into close contact with such a magnet are starting to creep up.

Patients [should] keep any consumer electronic devices that may create magnetic interference, including cell phones and smart watches, at least 6 inches away from implanted medical devices, in particular pacemakers and cardiac defibrillators,” reads the study in HeartRhythm.

Apple has acknowledged the concern, releasing a list of 28 products that should always be kept at least 15 cm (6 inches) away from implanted medical devices, and 30 cm (12 inches) away while wirelessly charging. It remains to be seen whether the new host of products Apple announced at their conference on Tuesday will also be added to the list.

Apple is not the only manufacturer whose products necessitate this kind of warning. With strong magnets becoming increasingly common in everyday tech, the American Heart Association recommends that those with pacemakers keep all cell phones six inches away form their implanted device, and ensure they use it on the ear on the opposite side of the body than the pacemaker was implanted. Headphones should also be kept six inches away.

“Magnet mode” a necessary function of pacemakers
Pacemakers are devices that are implanted in the chest when the heart is not able to keep up an adequate heart rate. In traditional pacemakers, the pulse generator, fuelled by a lithium-iodine battery, stimulate the heart muscles to contract through an electrical impulse delivered by one or more leads (insulated wires ending in electrodes) connected to the heart. The leads also relay information about the heart’s rhythm back to the pacemaker, which the pulse generator may use to optimize the heart rate or deliver a shock in case of serious heart arrhythmias.

Because pacemakers are designed to deliver and sense electrical impulses within the heart muscles, they are sensitive to other electrical fields close to the chest. This can cause problems during routine medical procedures or tests that may also occur around the heart — not unrealistic considering a patient with heart problems may require other medical interventions.

To avoid the pacemaker improperly altering its delivered rhythms during medical procedures, many cardiac rhythm management devices such as pacemakers have a “magnet mode.” Magnet mode allows healthcare professionals to quickly turn off the sensing aspect of the pacemaker — especially important in some emergencies — by holding a strong magnet close to the sensor, allowing it to continue to deliver a regular pulse without interference. Once the procedure is completed, the sensing function can be turned back on.