Risk of CIED Interference From Smartphones, High-Voltage Power Lines Low but Possible, Say Studies

Deborah Brauser

July 01, 2015

MILAN, ITALY — Patients with cardiac implantable electronic devices (CIEDs) should take commonsense precautions when it comes to the "rare but present" risk of electromagnetic interference (EMI) from high-voltage power lines or smartphones, suggest two new studies.

In the first, 40 standalone cardiac devices were exposed in a lab to electric fields up to 20 kV/m. The public-exposure recommendation from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) is 4.2 kV/m, and the International Standards Organization states that pacemakers and implantable cardioverter defibrillators (ICDs) should be resistant up to 5.4 kV/m.

Study results showed that when pacemakers were programmed to the usual configuration (normal settings, in bipolar mode), there were no significant concerns up to 8.6 kV/m[1]. However, the EMI threshold dropped to as low as 1.5 kV/m when the devices were programmed to higher sensitivity levels or in unipolar mode.

Lead author Dr Katia Dyrda (Montreal Heart Institute and University of Montreal, QC) told heartwire from Medscape that although the risk for malfunction was low, clinicians should warn the minority of patients who have the latter type of device programming to pass quickly when walking or riding bicycles under high-voltage power lines—and to not linger under them for long periods of time.

In the second study, only one of 308 patients with a CIED was affected by EMI from a smartphone[2]. Still, lead author Dr Carsten Lennerz (German Heart Center, Munich) told heartwire that clinicians should tell patients that this type of interference is a possibility—and that smartphones should be kept away from a CIED, including in a shirt's front pocket.

Both posters were presented at the European Heart Rhythm Association (EHRA) EUROPACE-CARDIOSTIM 2015 meeting.

Overhead Danger?

Dr Katia Dyrda

Dyrda reported that because power-utility substations can have electric fields up to 15 to 20 kV/m, the investigators chose that top number in determining the threshold for EMI. High-voltage power lines can "theoretically reach up to about 9 kV/m at mid-span," she noted.

"When it comes to power lines, there's just been no information. Yet there's been a lot of interest in designing parks or bicycle paths under power lines because it's potentially unused space," said Dyrda. "The question came up: could there be a danger to our patients?"

For the study, the researchers mounted 21 pacemakers and 19 ICDs from five manufacturers in a saline tank at the height of a human torso within a high-voltage research lab.

All of the pacemakers programmed to nominal parameters and in bipolar mode were resistant to EMI up to 8.6 kV/m, and all of the ICDs in this mode were resistant up to 2.9 kV/m. However, "some" of the resistance dropped to 1.5 kV/m when programmed to higher parameters or in unipolar mode.

EMI threshold levels were not significantly different between the left-sided and right-sided implants.

No Need for Panic

"The results reconfirm the need for individualized decision making for the safety of employees with [CIEDs] in their work environment," note the investigators in the poster. "For the general safety of the public, no significant concern should arise" in the patients who have pacemakers in nominal settings.

However, before implantation and during follow-up, clinicians should talk with patients who will be receiving devices in unipolar or sensitive settings about these issues, noted Dyrda.

"Things are always changing. So tell them that there are risks of EMI out there," she said. "However, don't live in fear. In this study, the risk was very small, which should reassure people and not create panic."

Dr Tommaso Infusino (Sant'Anna Hospital, Catanzaro, Italy) told heartwire that he has a particularly strong interest in this study because many people in his region of Italy live in housing that's underneath big power lines. And there have been several reports by these residents of interference with device monitoring.

"In this study, they didn't see a problem for the patients who were at normal, standard settings. And I don't know anybody who programs in unipolar mode," said Infusino, who was not involved with this research.

"But still, of course, I'll tell patients to keep this in mind. I'd say, 'don't stand under high-voltage wires' and to make sure all settings are perfect."

Keep Your Distance

Dr Carsten Lennerz

For the smartphone study, Lennerz reported that the US Food and Drug Administration, the Deutsches Bundesamt fur Strahlenschutz, and device manufacturers all recommend a distance of 15 cm between a mobile phone and a generator. However, because these recommendations were created based on 10-year-old pacemaker studies, the investigators sought to assess more modern smartphones and cardiac devices.

They enrolled a total of 308 participants (72% men; mean age 65 years), of whom 103 had pacemakers, 103 had ICDs, and 66 had CRT devices.

Three smartphones (Samsung Galaxy 3, Nokia Lumia, and HTC One XL) were placed one at a time directly over each individual's CIED and were taken through a standardized protocol of connecting, ringing, and talk settings. In addition, alternations between the current mobile network standards of GSM, UMTS, and LTE were used.

Continuous six-lead ECG recordings were examined for any possible abnormalities in sensing or pacing during a total of 11 tests per patient.

The one man who ended up being affected by EMI had an MRI-compatible ICD. Both ventricular and atrial oversensing occurred after the ICD was exposed to the HTC phone when operating at UMTS testing standards and to the Nokia phone when operating at GSM standards. When phones were operating at the LTE standard, no EMI occurred with any of the phones.

"Modern MRI-compatible devices don't seem to be better shielded against EMI in daily life," said Lennerz. "The main message is: current recommendations on the importance of keeping a safe distance between devices should be upheld."

The first study was funded by Electric Power Research Institute and TransÉnergie, Hydro-Québec. Dyrda reported no relevant financial relationships. Lennerz reported receiving lecture fees, travel expenses, and research support from Biotronik, St Jude Medical, and Sorin Group.

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