ECG-Capable Smartwatches Can Induce Magnet Mode in Cardiac Implantable Electronic Devices

Smartwatches are increasingly used for screening of tachyarrhythmias and for ECG recording. We therefore investigated possible mechanisms of magnet-mode induction of smartwatches in cardiac implantable electronic devices (CIED).

Fifteen CIED (5 pacemakers, 10 implantable cardioverter-defibrillators) from all manufacturers were implanted in a subcutaneous and submuscular location in an isolated porcine thorax and connected to an interactive heart simulator. Eight different smartwatches (3 Apple, 3 Samsung, 1 Huawei, 1 Withings) were placed on top of the implantation site in 3 different configurations, and signs of magnet mode induction were recorded.

When the faces of smartwatches were placed on top of subcutaneously implanted CIED, only 1 instance of magnet mode induction was recorded in 120 measurements (<1%). When turning around the smartwatches and placing the backs on the implantation site, signs of magnet mode were recorded in 36 of 120 measured instances (30%). Smartwatches connected to respective chargers induced magnet mode in 28 of 120 measurements (23%). Magnet mode induction in submuscularly implanted CIED was seen in 5 of 360 measurements (1%). The smartwatch with physical charging connectors was the only one not to induce magnet mode in any CIED, resulting from a lower-than-average magnetic field strength likely due to its different charging mechanism.

ECG-capable smartwatches can induce magnet mode in CIED. Although the risk for patients wearing smartwatches on their wrist is low, patients should be discouraged from placing their watch close to their CIED. Smartwatch charging mechanism and CIED implantation depth influence the risk of magnet mode induction.