By: Richa Tamakuwala, PharmD Candidate c/o 2022

              There has been a dramatic rise in the number of patients with cardiovascular implantable electronic devices (CIEDs), such as permanent pacemakers and implantable cardioverter‐defibrillators (ICDs), due to an increasing aging population and clinical trials showing benefits in mortality and morbidity.  Multiple studies investigating the use of ICDs concluded that the use of these devices has been associated with decreased incidence of deaths from arrythmias, thus prolonging life span.¹ Combatting these proposed benefits is the proliferation of technology that emits electromagnetic signals, whose electromagnetic interference (EMI) potentially interferes with CIED function.² While most manufacturers attempt to create devices that are “EMI-proof”, clinical consequences still occur.  These consequences will differ depending on the type of interaction, type of device, and the patient’s characteristics. In this article, the topic of focus will be the potentially life-threatening interactions between ICDs and smartphones due to the latter’s ubiquitous role in everyday life.

Implantable cardioverter-defibrillators are small, battery-powered devices that are placed in the chest to detect and stop abnormal heartbeats, or arrhythmias. An ICD continuously monitors heartbeat and delivers electric shocks, when needed, to restore a normal heart rhythm.  These devices are often used in patients who have ventricular tachycardia or fibrillation, which are conditions that result in a dangerously fast heartbeat, because this prevents the heart from supplying sufficient blood to the rest of the body.  There are two basic types of ICDs: (1) a traditional ICD, which requires invasive surgery to implant the device in the chest and attach the leads to the heart, and (2) a subcutaneous ICD (s-ICD) which is implanted under the skin at the side of the chest, below the armpit, and is attached to an electrode that runs along the breastbone.³ Because these devices work to regulate heart rate via transmission of electric signals to the heart, there is a possibility that devices that also use electric signals, such as mobile devices, security systems, medical equipment, etc., can cause interference with these ICDs. 

In the mid-1990s, several investigators conducted in vitro and in vivo tests, and reported several effects of EMI on CIEDs including temporary inhibition of output from oversensing emitted electrical signals from the cell phone, noise reversion or asynchronous pacing, and unwanted ventricular tracking from cellphone signals detected by the atrial lead.² The highest incidence of this interference was when the cellphone was placed directly over the pacemaker itself, whereas the lowest incidence of interference came with use of the cellphone at the ear without any clinically significant events.  Early on, more EMI interference was observed in cell phones with Global System for Mobiles (GSM) technology, because of its high-power usage and continuous pulsing associated with digital signals.  In response to GSM – which now entails more than 80% of the mobile communications market – and the increased possibility of EMI interactions with cell phones, CIED manufacturers have developed special filters to isolate cell phone frequencies in the feedthroughs (which are conductors used to carry a signal through an enclosure or printed circuit board).  Since this change was implemented, bipolar leads were used in pacing systems programmed to nominal sensitivity values, reducing the prevalence of interactions between cellphones and ICDs to only 0.3%, according to an in vivo study of 679 patients. ⁴

Another study analyzed various CIEDs, including 51 pacemakers, 5 cardiac resynchronization therapy pacemakers, 46 implantable cardioverter-defibrillators, 43 cardiac resynchronization therapy defibrillators, and 3 implantable loop recorders, to determine a possible correlation of certain distances between the smartphone (iPhone 6) and the smartwatch (Apple Watch A1553) and the CIED.  The Apple products were placed in close proximity to the  implanted devices, directly above for the phone, and at the right for the watch.  All possible activations of the iPhone and the Apple Watch, including the standby, dialing, and connecting modes, were tested.  The incidence and characteristics of interferences were also tested with interrogation telemetry. ⁵ Interrogation telemetry is a more selective, automatic measurement and wireless transmission of data from remote sources.  There was only one case of cell phone- induced electromagnetic interference observed. Utilization of wanded telemetry – a method that utilizes low-frequency radiowaves and simple digital modulation techniques at relatively slow rates for sequential data transmission – indicated 14% of patients experienced iPhone-induced magnetic interferences.  There were no interferences observed with the Apple Watch.  Based on these results, the overall risk of electromagnetic interferences of the iPhone 6 and the Apple Watch with CIEDs is low, but close proximity of the iPhone to implanted devices can cause telemetry interferences.⁵

              The most recent publication about implanted devices and cell phones focused specifically on the newer generation iPhone 12, because it contains a circular array of magnets around a central charging coil that makes the phone compatible with MagSafe accessories.  While these magnets make the phones more efficient at aligning with wireless chargers and peripheral accessories, and increasing wireless charging speeds, there were some concerns regarding possible device-device interactions, due to the presence of a strong magnetic array in the iPhone and MagSafe compatible cases.  To test these concerns, a study was conducted on a patient with a Medtronic Inc. ICD, and the results were shocking.  Once the iPhone was brought close to the ICD over the left chest area, immediate suspension of ICD therapies was noted and persisted for the duration of the test.  This result was reproduced multiple times with different positions of the phone over the left chest pocket.⁶ In response to these results, the authors reported an important public health issue concerning the iPhone 12: it can potentially inhibit lifesaving therapy in a patient, particularly when the phone is carried in an upper chest pocket.  Apple also updated its website to include warnings about avoiding any potential interactions with sensor-based medical devices, recommending a safe distance of more than 6 inches / 15 cm apart or more than 12 inches / 30 cm apart if wirelessly charging.⁷  Ultimately, Apple claims that despite the fact that the iPhone 12 model does contain more magnets than prior models, the risk of magnetic interference to medical devices is not inherently greater than in previous iPhone models.

Despite the lack of overwhelming evidence contraindicating the use of newer cellphone models in patients with ICDs, physicians should recommend positioning the CIED contralateral to the ear and avoiding close physical proximity between the CIED and the cell phone, such as when keeping the phone in a breast pocket near the CIED.  

References

1. Smith T, Jordaens L, Theuns DA, van Dessel PF, Wilde AA, Hunink MG. The cost-effectiveness of primary prophylactic implantable defibrillator therapy in patients with ischaemic or non-ischaemic heart disease: A European analysis. European Heart Journal. 2012;34(3):211-219. doi:10.1093/eurheartj/ehs090. Accessed October 1, 2021.
2. Misiri J, Kusumoto F, Goldschlager N. Electromagnetic interference and implanted cardiac devices: the nonmedical environment (part I). Clin Cardiol. 2012;35(5):276-280. doi:10.1002/clc.21998. Accessed August 1, 2021
3. Implantable cardioverter-defibrillators (ICDs), https://www.mayoclinic.org/tests-procedures/implantable-cardioverter-defibrillators/about/pac-20384692. Accessed October 1, 2021.
4. Tandogan I, Temizhan A, Yetkin E, et al. The effects of mobile phones on pacemaker function. Int J Cardiol. 2005;103(1):51-58. doi:10.1016/j.ijcard.2004.08.031. Accessed October 1, 2021
5. Lacour P, Parwani AS, Schuessler F, et al. Are Contemporary Smartwatches and Mobile Phones Safe for Patients with Cardiovascular Implantable Electronic Devices? JACC Clin Electrophysiol. 2020;6(9):1158-1166. doi:10.1016/j.jacep.2020.04.033. Accessed October 1, 2021.
6. Greenberg JC et al. Life-saving therapy inhibition by phones containing magnets. Heart Rhythm 2021 Jan 4; [e-pub]. doi.org:10.1016/j.hrthm.2020.12.032. Accessed October 1, 2021
7. About the magnets inside iPhone 12, iPhone 12 mini, iPhone 12 Pro, iPhone 12 Pro Max, and MagSafe accessories, https://support.apple.com/en-us/HT211900. Accessed October 1, 2021 
8. Burri H, Mondouagne Engkolo LP, Dayal N, et al. Low risk of electromagnetic interference between smartphones and contemporary implantable cardioverter defibrillators. Europace. 2016;18(5):726-731. doi:10.1093/europace/euv374. Accessed October 1, 2021
9. Link M. New Smart Phone Can Temporarily Inactivate ICDs. NEJM Journal Watch. https://www.jwatch.org/na53134/2021/01/29/new-smart-phone-can-temporarily-inactivate-icds. Published 01/29/2021.
10. Tzeis S, Asvestas D, Moraitis N, et al. Safety of smartwatches and their chargers in patients with cardiac implantable electronic devices. Europace. 2021;23(1):99-103. doi:10.1093/europace/euaa220. Accessed October 1, 2021.

Published by Rho Chi Post