Even if the overall risk of interference is considered low by experts: Anyone who has an implanted pacemaker should not carry a smartphone directly above their chest - in their shirt pocket, for example.

A distance of 15 centimetres is sensible, and shouldn't result in any restrictions in everyday life, says cardiologist Philipp Lacour from the Charite hospital in Berlin.

In most cases, this shouln't even be necessary, he adds. As a general rule, however, Lacour advises having a possible interaction between your smartphone and implanted device checked out by a cardiologist, if you can.

"The best person to contact is a cardiologist who can check the implanted device," explains Lacour. A mere consultation is not enough to determine or rule out a potential malfunction, he says.

Warning from heart doctors

The issue was recently brought into focus thanks to an article in the medical journal Heart Rhythm. Heart doctors in the US placed the new iPhone 12 on the chest of a patient with a pacemaker - the functionality of the implant was immediately suspended, they wrote, warning that the latest iPhones could potentially prevent life-saving features - especially if carried in a shirt pocket.

Cardiologist Florian Blaschke, a colleague of Lacour from Berlin's Charite hospital, says the circular array of 18 individual magnets in the iPhone 12 (called MagSafe) seems to be strong enough to deactivate the implanted pacemaker for the period of time the smartphone is placed on the device.

In everyday clinical practice, magnets are used to deactivate a pacemaker "with unnecessary shocks in the event of malfunction" if no corresponding programming device is available, says Blaschke.

While the magnet is placed on the chest, the shock function is deactivated, but the pacemaker function is not - and after removing the magnet, it is fully functional again. In the clinic this happens in a controlled manner. In everyday life, however, such malfunctions can be dangerous.

Apple recommends distance

Apple has responded to the report in the medical journal: iPhone 12 users should keep a safe distance between the implant and the smartphone, as well as other MagSafe accessories such as protective cases and inductive charging stations.

This is to avoid possible interactions, the manufacturer writes on its online support page. Specifically, Apple advises a distance more than 15 centimetres, and more than 30 centimetres if the smartphone is being charged wirelessly on a station.

In 2020, Blaschke and Lacour, together with other researchers, examined possible interactions between smartphones and pacemakers in a study - with an iPhone 6. Interactions like those with the iPhone 12 did not occur, explains Blaschke. However, the iPhone 6 did not use the MagSafe wireless system.

Their publication nevertheless came to the conclusion that patients should have their smartphone tested on an individual basis to see if it affects the functionality of their implant.

And, according to Blaschke, the test should look at the “worst case scenario” - that is, when the smartphone is placed on your chest directly above the implant - and everyday situations - such holding the smartphone up to your ear.

 - dpa