Static magnetic field measurements of smart phones and watches and applicability to triggering magnet modes in implantable pacemakers and implantable cardioverter-defibrillators

Abstract

Implantable pacemakers and implantable cardioverter-defibrillators (ICDs) are designed to include a "magnet mode" feature that can be activated from magnets stronger than 10 G. This feature is designed to be used when a patient is undergoing a procedure where electromagnetic interference is possible, or anytime suspension of tachycardia detection and therapy is needed. A publication in Heart Rhythm demonstrates an iPhone 12 triggering the magnet mode of a Medtronic ICD. The purpose of this study is to determine the separation distance between consumer electronic devices that may create magnetic interference, including cell phones and smart watches, and implantable pacemakers and ICDs where magnet mode can be triggered. The static magnetic fields of the iPhone 12 models and Apple Watch were measured at several planes in 1 cm resolution using an FW Bell 5180 Gauss Meter with STD18-0404 Transverse probe (unidirectional probe). All iPhone 12 and Apple Watch 6 models tested have static magnetic fields significantly greater than 10 G in close proximity (1-11 mm), which attenuates to below 10 G between 11 and 20 mm. The findings of this study support the US Food and Drug Administration recommendation that patients 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.