Author + information
- Carsten Lennerz, MD∗ (, )
- Herribert Pavaci, MD,
- Christian Grebmer, MD,
- Verena Semmler, MD,
- Felix Bourier, MD,
- Bernhard Haller, Dipl.-Stat,
- Tilko Reents, MD,
- Gabriele Hessling, MD,
- Isabel Deisenhofer, MD and
- Christof Kolb, MD
- ↵∗Deutsches Herzzentrum München, Lazarettstrasse 36, 80636 München, Germany
Patients with pacemakers or implantable cardioverter defibrillators (ICDs) are advised to keep mobile phones at least 6 inches (15 cm) away from these devices to avoid electromagnetic interference. This is because electromagnetic fields emitted by phones can be misinterpreted as intrinsic cardiac electrical activity and subsequently lead to pacing inhibition, premature triggered stimulation of pacemakers, or inappropriate shock delivery in defibrillators (1). Current recommendations include using the contralateral ear and avoid placing an activated phone next to the generator pocket (2). However, these recommendations are based upon studies conducted >10 years ago. The intervening decade has seen considerable advancement of pacemaker and ICD technology, including filtering properties and noise protection algorithms. Significant evolution in mobile communication technology has occurred, too. Smartphones have largely replaced conventional mobile phones, and new mobile standards have become widespread, for example, Long-Term Evolution (LTE) versus Global System for Mobile Communication (GSM). Our hypothesis was that technological advances may have rendered current recommendations obsolete. Therefore, we sought to determine the incidence and consequences of mobile phone–produced electromagnetic interference (EMI) on the current generation of implantable cardiac devices.
We screened 349 patients with implanted devices who attended our clinic for routine follow-up (July 2012 to May 2013). Thirty-five declined to provide consent, and 7 met exclusion criteria (base rate and lead problems). Power analysis indicated 300 subjects were sufficient to detect ≥1 EMI-related event with 95% to 99% probability, based on event rates of 1.0% to 2.5% reported previously. All 307 subjects (72% men, mean age of 65.5 years) underwent initial testing to ensure normal operation of all components and functions of their implanted devices. Our protocol simulated multiple aspects of phone use: connection to a cellular network, call reception, 30 s of connection including digital data transfer, and “handover” between network standards. We applied maximum transmitting power for all network standards (2G, GSM; 3G, Universal Mobile Telecommunication System [UMTS]; and 4G, LTE) and modulated maximal transmitting power (50-Hz mode) for each supported standard (UMTS, LTE) using a radio communication tester (CMW500, Rohde & Schwarz, Munich, Germany).
We examined 3 smartphones (Samsung Galaxy S3, Samsung Electronics, Suwon, South Korea; Nokia Lumia, Nokia Corp, Espoo, Finland; HTC One XL, HTC Corp., New Taipei City, Taiwan) held directly above the implanted devices in random order. During testing, patients received permanent ventricular pacing and were monitored using a 6-lead electrocardiogram (ECG). Two cardiologists independently analyzed ECG recordings, and device Holters were ancillarily used to confirm potential EMI abnormalities.
Only 1 patient’s implanted device was affected by electromagnetic interference (1 of 307; 0.3%; 95% confidence interval: 0.01% to 1.80%) (Figure 1A). This resulted in repeated pacing inhibition and premature ventricular pacing during exposure to 2 smartphones (Nokia and HTC) and 2 standards (GSM and UMTS) (Figure 1B). Nevertheless, even though ventricular pacing inhibition is potentially dangerous, the ventricular oversensing we observed (pauses <2 s) was not clinically significant. This may explain why EMI associated with mobile phones use is rarely reported.
Phone placement directly above implanted devices represents the worst-case exposure. However, it is a likely occurrence; for example, smartphones in standby-mode (i.e., switched on) are often carried in shirt or jacket pockets. Our finding that close proximity of smartphones could produce interference is consistent with results obtained using older mobile phone types. Conversely, one recent study failed to find EMI between two 4G smartphones and ICDs (3). Sixty-three patients subjected to 882 tests may be insufficient to draw definitive conclusions. However, we, too, saw no interference with 4G operation, which, generally, uses lower transmission power and higher frequencies than the other network modes investigated.
Our selection process produced a wide variety of tested devices (51 pacemaker and 64 ICD models from 8 manufacturers) and leads (52 lead families from 12 manufacturers) representative of contemporary practice. However, the process also produced several unique device–lead combinations. Such variety together with only 1 affected patient prevented direct assessment of differential susceptibility to electromagnetic interference in different devices or device–lead combinations. For example, we found no evidence of interference in 2 patients with the same cardiac resynchronization therapy (CRT)-ICD model as the patient who experienced pacing inhibition. It is certainly possible that other factors besides those already mentioned influence interference susceptibility, for example, spatial alignment of the smartphone antenna relative to the defibrillator head. It should also be acknowledged that we only examined 3 different phones; notably, we did not test an Apple iPhone for technical reasons.
In our series of 307 patients subjected to more than 3,300 individual tests, the incidence of EMI from smartphones was rare (0.3%) and of minimal clinical significance even when phones at maximal transmission power were placed immediately adjacent to the generator. We therefore suggest the current recommendation to maintain a 15-cm gap between phone and generator may be too stringent and thereby cause unnecessary apprehension. Nonetheless, the rapid evolution of implantable cardiac device and mobile phone technology obliges us to be aware that such safety recommendations require continual re-evaluation.
Please note: Dr. Lennerz has received lecture fees from Biotronik; travel support from Biotronik, Sorin Group, and St. Jude Medical; and educational fellowships supported by St. Jude Medical, Biotronik, and European Heart Academy (ESC). Dr. Pavaci has received educational fellowships supported by St. Jude Medical and European Heart Rhythm Association (EHRA). Dr. Semmler has received travel support from St. Jude Medical, Sorin Group, and from Boston Scientific. Dr. Reents has received travel support from Boston Scientific, St. Jude Medical, and Biosense Webster. Dr. Deisenhofer has received lecture honoraria from St. Jude Medical. Dr. Kolb has received lecture honoraria/travel support from Biotronik, Boston Scientific, Medtronic, Sorin Group, and St. Jude Medical; has been a consultant to Biotronik, Boston Scientific, and Sorin Group; and has performed clinical studies supported by Biotronik, Medtronic, Boston Scientific, Sorin Group, and St. Jude Medical. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. The resources and facilities of the German Heart Centre Munich were used. There was no direct or indirect funding from the industry (notably pacemaker, ICD or smartphone manufacturers). (Safety of Smartphones Among Patients With Cardiac Implantable Electronic Devices; NCT01819896)
- 2017 American College of Cardiology Foundation