Warning over smartphone interference inhibiting ICD therapy


A letter published in the journal Heart Rhythm has warned of possible interference to implantable cardioverter defibrillator (ICD) therapy caused by magnets in the iPhone 12.

The letter, authored by Joshua Greenberg and colleagues from the Henry Ford Heart and Vascular Institute, Detroit, USA, notes that when an external magnet is applied to a defibrillator, high voltage shock therapy for ventricular tachycardia and ventricular fibrillation is suspended.

The authors note that the iPhone 12 series has a circular array of magnets around a central charging coil for the phone. Greenberg raised concerns for possible device-device interaction due to the presence of a strong magnetic array in the iPhone, and the interaction was tested on a patient with a Medtronic ICD.

Greenberg and colleagues write: “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.”

The authors acknowledge that contemporary studies have shown minimal risk of electromagnetic interference between ICDs and prior smartphones without magnetic arrays, but note that a recent case report highlighted magnetic interference with a fitness tracker wrist band deactivating an ICD up to distances of 2.4cm.

“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,” the authors write, adding: “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.”


  1. Once, While on my back holding a transistor radio above me, I dropped it on my ICD. The ICD beeped in alarm and even though I was quick to remove it, I felt ill for about 12 hours until the ICD reset itself.
    According to data downloaded from my ICD I have been free of AF and other arrythmias for over 12 months. I believe I caused and episode of tachycardia recently through rolling over onto my Motorola Moto G5+ during the night while listening to an audiobook duting a restless night. I had placed the phone over 12 inches away on the bed.


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