Most of us don’t think twice about where we keep our cell phones as we go about our daily business. However, for people with implanted cardiac devices, storing the phone in a shirt or jacket pocket near the chest could have serious unintended consequences.
Pacemakers and implantable cardioverter defibrillators (ICDs) are both small battery-powered devices placed in the chest to help regulate cardiac rhythm. Pacemakers supply electrical currents to the heart muscle and prompt the heart to beat normally.1 ICDs monitor heart rhythm and deliver electrical shocks when dangerous rhythms (ventricular fibrillation or ventricular tachycardia) are detected.2 Both devices can function inappropriately when in close contact with magnets.
When a magnet is in close proximity to a pacemaker, the pacemaker will pace the heart asynchronously. This means that an electrical impulse will be delivered regardless of the patient’s heart rhythm.3 On the other hand, an ICD has a magnetic safety switch that deactivates the device when an external magnet is placed above it -- a feature designed to turn the ICD off in case of malfunction and prevent it from delivering inappropriate electrical shocks.3
Dr. Joshua C. Greenberg, an electrophysiology fellow at Henry Ford Hospital, was diligently reading about his new iPhone 12 Pro when he learned that it contained a strong magnet designed to improve use with wireless charging devices. The Apple iPhone 12 series has a circular array of magnets located around a central charging coil that align the phone on a wireless charger and facilitate the use of other peripheral accessories. 4 The magnet is reportedly strong enough to attach the phone to a refrigerator. Greenberg said, “I’m thinking if this thing is strong enough to attach to a refrigerator I wonder what it would do to a potential device”.3,5
It’s estimated that 1 in 4 cell phones sold last year was an iPhone 12 and more than 300,000 people in the United States undergo procedures to implant pacemakers or ICDs each year.4 Due to the high demand for these magnet containing devices and the prevalence of pacemakers and ICDs in the community, Dr. Greenberg and his colleagues set out to determine if his suspicions were valid.
They decided to test the iPhone 12 Pro on a patient with a Medtronic ICD to determine if it would have the same effects as other magnets known to be capable of deactivating the device.6 They hypothesized that the magnet wouldn’t be strong enough to, in fact, deactivate an ICD. To their surprise, when they placed the iPhone over the skin covering the ICD, the defibrillator was deactivated. Wondering if they could reproduce the results, they repeated the sequence; every time the iPhone was held close to the ICD implantation site, the ICD was deactivated. Dr. Gurjit Singh, a cardiologist at the Henry Ford Heart and Vascular Institute, said, “When we brought the iPhone close to the patient’s chest the defibrillator was deactivated. We saw on the external defibrillator programmer that the functions of the device were suspended and remained suspended. When we took the phone away from the patient’s chest, the defibrillator immediately returned to its normal function.”
To date, they haven’t tested their theory with pacemakers, but are working towards getting approval to conduct a similar study involving all major brands of pacemakers and ICDs.4
Their findings illustrate the unintended danger of keeping or operating magnet-containing smartphones in close proximity to medical devices. Should an ICD be inadvertently deactivated by a smartphone or other device, the ICD would fail to deliver the electrical shock necessary to correct a deadly arrhythmia. This underlines the importance of cautioning patients with implanted devices, like ICDs and pacemakers, and those caring for them to keep their iPhone 12, other similar electronic devices, or magnetic phone cases at least 6 inches away from the chest during routine use and 12 inches away from the chest while wirelessly charging to prevent accidental deactivation or malfunction.6
These cautions apply to patients where continued cardiac device function is desirable. In the hospice setting, magnets are commonly used to prevent painful ICD shocks as the patient goes through the dying process. Not every hospice practitioner walks around with a magnet in their pocket for this purpose. However, many will undoubtedly carry the extremely popular iPhone 12. Might it someday prove to be a useful tool for the hospice clinician wishing to deactivate an ICD in a terminally ill patient?
Melissa Corak, PharmD
John Corrigan, PharmD
OnePoint Patient Care Clinical Pharmacists
- American Heart Association. Updated September 30, 2016. Accessed May 3, 2021. https://www.heart.org/en/health-topics/arrhythmia/prevention--treatment-of-arrhythmia/pacemaker
- Implantable Cardioverter Defibrillator (ICD). American Heart Association. Updated September 30, 2016. Accessed May 3, 2021. https://www.heart.org/en/health-topics/arrhythmia/prevention--treatment-of-arrhythmia/implantable-cardioverter-defibrillator-icd
- Shamus K. Henry Ford Docs Spot Potentially Fatal iPhone 12 Problem with Pacemakers, Defibrillators. Detroit Free Press. February 4, 2021. Accessed May 3, 2021 at https://www.freep.com/story/news/health/2021/02/03/apple-iphone-12-pacemakers-defibrillators/4382911001/
- Greenberg J, Altawil M, Singh G. Letter to the Editor – Lifesaving Therapy Inhibition by Phones Containing Magnets. Heart Rhythm Society. Published online January 4, 2021. doi:10.1016/j.hrthm.2020.12.032
- “Henry Ford Cardiologists Find Apple iPhone 12 Magnet Deactivates Implantable Cardiac Devices”. February 4, 2021. Accessed March 4, 2021. https://www.henryford.com/news/2021/02/iphone-12-deactivates-defibrillator