Life Saving Therapy Inhibition by Phones Containing Magnets

The Heart Rhythm Society has issued the following information regarding the use of the new iPhone 12 Series and ICDs.

“Implantable Cardioverter Defibrillator (ICD) remains the cornerstone therapy in the management of malignant ventricular arrythmia’s for patients with high risk cardiac conditions. An ICD system contains a battery, capacitors, sensing/ pacing circuit together with an intra-or extra-cardiac lead. All ICD’s have an in-built switch (Reed switch, Hall-effect sensors, Giant magneto sensitive resistors or coils) which respond 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.

Recently, Apple Inc. launched the iPhone 12 series which has a circular array of magnets around a central charging coil for the phone to be compatible with “MagSafe” accessories. MagSafe technology contains a magnetometer and single coil Near Field Communications (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 Watts). The first author (JG) raised the concerns for possible device-device interaction due to presence of a strong magnetic array in the iPhone and MagSafe compatible cases. We thus tested this interaction on a patient with a Medtronic Inc. (Minneapolis, MN, USA) ICD. Institutional Review Board approved the study. Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted which persisted for the duration of the test. This was reproduced multiple times with different positions of the phone over the pocket.

We hereby bring an important public health issue concerning the newer generation iPhone 12 which can potentially inhibit lifesaving therapy in a patient particularly while carrying the phone in upper pockets. Contemporary studies have shown minimal risk of electromagnetic interference with ICDs and prior smartphones without magnetic arrays. A recent case report highlighted magnetic interference with a fitness tracker wrist band deactivating an ICD up to distances of 2.4 cm. Apple Inc. website does mention magnetic interference with medical devices and prior consulting with physician and medical device manufacturers. Medical device manufacturers and implanting physicians should remain vigilant in making patients aware of this significant interaction of the iPhone 12 and other smart wearables with their cardiac implantable electronic devices”.


If you have an interesting case, ECG or EGM please consider submitting a report. It’s a great opportunity to show CPD and share experiences for others to learn from.

Submissions should include a brief case background, a question with multiple choice possible answers, the answer, an explanation, a brief discussion section if relevant and a minimum of one reference and be sent to with the subject heading ‘BHRS Challenge Feature’

As part of our ongoing collaboration with Radcliffe Cardiology we are planning to co-publish successful submissions on the BHRS website and on a new case-based web platform, led by Professor Angelo Auricchio and the Radcliffe Group called the Arrhythmia Academy

As an incentive to submit cases the editor in chief of Arrhythmia and Electrophysiology Review (AER) journal, Dr Demosthenes Katritsis would like to select a ‘winning case’ each quarter and invite the author of these best cases to write a review or an expert opinion piece on the topic addressed, that would be published in the AER journal and indexed on PubMed.