July 08, 2015
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Smartphones, power lines may affect some implantable cardiac devices

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Smartphones and high-voltage power lines could cause electromagnetic interference with some implantable cardiac devices, according to results of two studies presented at Cardiostim 2015.

Device manufacturers and regulators such as the FDA recommend that patients with pacemakers or implantable cardioverter defibrillators maintain a distance of 15 cm to 20 cm from smartphones. However, there are no recommendations about whether such people should keep a distance from power lines, according to a press release from the European Society of Cardiology.

Smartphones

Carsten Lennerz, MD, and colleagues evaluated whether the recommended safety distance between smartphones and those with pacemakers or ICDs, which was determined more than 10 years ago, is still appropriate given the advent of new smartphones, networks and cardiac devices.

Carsten Lennerz, MD

Carsten Lennerz

The researchers evaluated 308 recipients of cardiac devices who visited an outpatient clinic; of those, 103 had pacemakers, 103 had ICDs and 66 had cardiac resynchronization therapy devices. They interrogated each device, adjusted the base rate or atrioventricular delay to achieve permanent ventricular pacing and disabled the shock function in ICDs. Then, all patients were exposed to the electromagnetic fields of three commercially available smartphones (Samsung Galaxy 3, Nokia Lumia and HTC One XL) in all current network standards (GMS, UMTS, LTE) and at standard mode and 50 Hz mode, in a protocol of the calling process, including connecting, ringing, talking and disconnecting.

During each test, a 6-lead ECG was recording and then investigated for sensing and pacing abnormalities.

One patient (0.3%) was affected by electromagnetic interference. That patient had an MRI-compatible ICD, which misdetected electromagnetic waves from the Nokia and HTC smartphones operating on the GSM or UMTS networks as intracardiac signals, according to data presented at the conference.

“Interference between smartphones and cardiac devices is uncommon, but can occur, so the current recommendations on keeping a safe distance should be upheld,” Lennerz, cardiology resident in the Clinic for Heart and Circulatory Diseases, German Heart Centre, Munich, said in the press release. “Interestingly, the device influenced by [electromagnetic interference] in our study was MRI-compatible, which shows that these devices are also susceptible.”

High-voltage power lines

Katia M. Dyrda, MD, MSc, and colleagues investigated whether pacemakers and ICDs were affected by high electric field thresholds such as high-voltage power lines and utility substations.

Katia Dyrda

Katia M. Dyrda

International Standards Organization standards call for pacemakers and ICDs to offer resistance up to 5.4 kV/m, higher than the international recommendation for public exposure of 4.2 kV/m. The researchers exposed pacemakers and ICDs to electric fields up to 20 kV/m to determine the electric field threshold for electromagnetic interference. According to the study background, high-voltage power lines can attain up to 9 kV/m at mid-span.

The researchers mounted 40 device models (21 pacemakers, 19 ICDs including CRT-D) from five manufacturers in a saline tank at human torso height, set up as left- and right-sided pectoral implants, and exposed them to voltage up to 20 kV/m.

When programmed to nominal parameters in bipolar mode, all pacemakers were immune to electromagnetic interference up to 8.6 kV/m (least resistant, 8.6 kV/m; most resistant, > 20 kV/m), Dyrda and colleagues found. However, when programmed to higher sensitivity levels or in unipolar mode, the electromagnetic interference threshold declined to as low as 1.5 kV/m for some devices.

When programmed to nominal parameters, all ICDs were immune to electromagnetic interference up to 2.9 kV/m (least resistant, 2.9 kV/m; most resistant, > 20 kV/m), according to the results.

Electromagnetic interference threshold values did not differ for left- vs. right-sided implants, but in many cases a slight decrease in sensitivity level was associated with much greater resistance to electromagnetic interference, according to the researchers.

“There is no significant concern for patients with pacemakers programmed in the usual configuration (normal settings, in bipolar mode),” Dyrda, cardiologist at Montreal Heart Institute, University of Montreal, said in the release. “For the minority of patients with devices in unipolar mode or with very sensitive settings, counseling should be given at implantation or at medical follow-up. There is no need for patients with a pacemaker or ICD to avoid crossing under power lines (> 230 kV), but patients should avoid staying in a stationary position under them.” – by Erik Swain

References:

Dyrda KM, et al. Abstract P137.

Lennerz C, et al. Abstract P867. Both presented at: Cardiostim 2015; June 21-24, 2015; Milan.

Disclosure: Dryda reports receiving funding for the study from Electric Power Research Institute and TransÉnergie, Hydro-Québec. Lennerz reports receiving lecture fees from Biotronik and travel expenses from Biotronik, St. Jude Medical and Sorin Group.