Cardiac pacemakers in electric and magnetic fields of 400-kV power lines

Phantom Model Testing of Active Implantable Cardiac Devices at 50/60 Hz Electric Field

Exposure to external extremely low-frequency (ELF) electric and magnetic fields induces the development of electric fields inside the human body, with their nature depending on multiple factors including the human body characteristics and frequency, amplitude, and wave shape of the field. The objective of this study was to determine whether active implanted cardiac devices may be perturbed by a 50 or 60 Hz electric field and at which level. A numerical method was used to design the experimental setup. Several configurations including disadvantageous scenarios, 11 implantable cardioverter-defibrillators, and 43 cardiac pacemakers were tested in vitro by an experimental bench test up to 100 kV/m at 50 Hz and 83 kV/m at 60 Hz. No failure was observed for ICNIRP public exposure levels for most configurations (in more than 99% of the clinical cases), except for six pacemakers tested in unipolar mode with maximum sensitivity and atrial sensing. The implants configured with a nominal sensitivity in the bipolar mode were found to be resistant to electric fields exceeding the low action levels, even for the highest action levels, as defined by the Directive 2013/35/EU. Bioelectromagnetics. 2020;41:136-147. © 2020 Bioelectromagnetics Society.

Workers with Active Implantable Medical Devices Exposed to EMF: In Vitro Test for the Risk Assessment

The occupational health and safety framework identifies workers with an active implantable medical device (AIMD), such as a pacemaker (PM) or an implantable defibrillator (ICD), as a particularly sensitive risk group that must be protected against the dangers caused by the interference of electromagnetic field (EMF). In this paper, we describe the results of in vitro testing/measurements performed according to the EN50527-2-1:2016 standard, for the risk assessment of employees with a PM exposed to three EMF sources: (1) An electrosurgical unit (ESU); (2) a transcranial stimulator (TMS); and (3) an arc welder. The ESU did not affect the PM behavior in any of the configurations tested. For the TMS and the arc welder, interference phenomena were observed in limited experimental configurations, corresponding to the maximum magnetic field coupling between the EMF source and the implant. The in vitro measurements presented can be considered an example of how the specific risk assessment for a worker with a PM can be performed, according to one of the methodologies proposed in the EN50527-2-1:2016, and can be used as scientific evidence and literature data for future risk assessments on the same EMF sources.

Evaluation of the inter-person variability of hazards to the users of BAHA hearing implants caused by exposure to a low frequency magnetic field

PURPOSE

In this work, the inter-person variability of hazards caused by a low frequency magnetic field exposure (of various polarization and homogeneity near to the magneto therapy applicator) to users of bone anchored hearing aid (BAHA) hearing implants were investigated with respect to various head structures.

MATERIAL AND METHODS

The effects of exposure were evaluated by numerical simulations of the electric field (E_in) induced in head phantoms (regular or with implant model). Phantoms mimic head dimensions and thicknesses of layers of skin, fat, skull bones, and brain.

RESULTS

The values of E_in obtained in the phantom of the BAHA user's head were several times (up to 4.5) higher than in a regular person. The highest differences in E_in values were found in the skin and fat tissues - up to 80% in phantoms of various structures (statistically significant differences related to various tissues thicknesses, not-significant with relation to phantom dimensions - Kruskal-Wallis test with Bonferroni correction, p < .017) and up to 3 times with magnetic field spatial distribution (statistically significant with different polarization).

CONCLUSIONS

The results support the need to assess the electromagnetic fields hazards to individual implant user exposed to the magnetic field at a level approaching the exposure limits set by international guidelines.

Computation of Pacemakers Immunity to 50 Hz Electric Field: Induced Voltages 10 Times Greater in Unipolar Than in Bipolar Detection Mode

Thisstudy aims to compute 50 Hz electric field interferences on pacemakers for diverse lead configurations and implantation positions. Induced phenomena in a surface-based virtual human model (standing male grounded with arms closed, 2 mm resolution) are computed for vertical exposure using CST EM^® 3D software, with and without an implanted pacemaker. Induced interference voltages occurring on the pacemaker during exposure are computed and the results are discussed. The bipolar mode covers 99% of the implanted pacing leads in the USA and Europe, according to statistics. The tip-to-ring distance of a lead may influence up to 46% of the induced voltage. In bipolar sensing mode, right ventricle implantation has a 41% higher induced voltage than right atrium implantation. The induced voltage is in average 10 times greater in unipolar mode than in bipolar mode, when implanted in the right atrium or right ventricle. The electric field threshold of interference for a bipolar sensing mode in the worst case setting is 7.24 kV·m⁻¹, and 10 times higher for nominal settings. These calculations will be completed by an in vitro study.

The Possibility of Decreasing 50-Hz Electric Field Exposure near 400-kV Power Lines with Arc Flash Personal Protective Equipment

Various guidelines for the protection of human beings against possible adverse effects resulting from exposure to electromagnetic fields (EMFs) have been published with a view towards continual improvement; therefore, decreasing exposure is an important research area. The aim of this study was to investigate the possibility of decreasing electric field exposure with arc flash rated personal protective equipment (PPE), which in this case was a set of coveralls, and to compare the measurement results to calculations using the helmet-mask measuring system. We collected the data under a 400-kV power line. The test person stood on isolated aluminum paper, and the current between the ground and the aluminum paper was measured. When the test subject wore the arc flash PPE, the current to the ground was only 9.5% of the current measured when wearing normal clothes, which represents a clear decrease in exposure.

Occupational exposure to electric and magnetic fields during tasks at ground or floor level at 110 kV substations in Finland

The aim was to investigate occupational exposure to electric and magnetic fields during tasks at ground or floor level at 110 kV substations in Finland and to compare the measured values to Directive 2013/35/EU. Altogether, 347 electric field measurements and 100 magnetic field measurements were performed. The average value of all electric fields was 2.3 kV/m (maximum 6.4 kV/m) and that of magnetic fields was 5.8 µT (maximum 51.0 µT). It can be concluded that the electric and magnetic field exposure at ground or floor level is typically below the low action levels of Directive 2013/35/EU. The transposition of the directive will not create new needs to modify the work practice of the evaluated tasks, which can continue to be performed as before. However, for workers with medical implants, the exposure may be high enough to cause interference.

Possible Influences of Spark Discharges on Cardiac Pacemakers

Exposure to spark discharges may occur beneath high voltage transmission lines when contact is initiated with a conductive object (such as a motor vehicle) with the spark discharge mediated by the ambient electric field from the line. The objective of this study was to assess whether such exposures could interfere with the normal functioning of implanted cardiac pacemakers (PMs). The experiment consisted of PMs implanted in a human-sized phantom and then exposed to spark discharge through an upper extremity. A circuit was designed that produced spark discharges between two spherical electrodes fed to the phantom's left hand. The circuit was set to deliver a single discharge per half cycle (every 10 ms) about 10 μs in duration with a peak current of 1.2-1.3 A, thus simulating conditions under a 400-kV power line operating at 50 Hz. Of 29 PMs acquired, all were tested in unipolar configuration and 20 in bipolar configuration with exposure consisting of 2 min of continuous exposure (one unit was exposed for 1 min). No interference was observed in bipolar configuration. One unit in unipolar configuration incorrectly identified ventricular extra systoles (more than 400 beats min(-1)) for 2 s. The use of unipolar configuration in new implants is extremely rare, thus further minimizing the risk of interference with the passage of time. Replication of this study and, if safety for human subjects can be assured, future testing of human subjects is also advisable.

Cardiac pacemakers in magnetic fields of a shunt reactor at a 400 kV substation

The use of cardiac pacemakers (PMs) increases in Western countries. The aim of the study is to investigate cardiac pacemakers (PMs) using a human-shaped phantom in magnetic fields of a shunt reactor at a 400 kV substation. We performed seven PM experiments using a phantom. Two locations close to the shunt reactors were chosen. The magnetic field exposure was over 1000 µT in one location and over 600 µT in the other one. The magnetic field exposure did not disturb the tested five different PMs (in unipolar or bipolar configurations). It can be stated that in our experiment, the magnetic field exposure (over 600 µT and over 1000 µT) did not disturb the PMs (in unipolar or bipolar configurations). Since we only studied some PMs, it is possible that the magnetic field exposure at 400 kV substations can cause disturbances to other PMs. However, the risk of disturbances does not seem to be high.

Testing of common electromagnetic environments for risk of interference with cardiac pacemaker function

Background

Cardiac pacemakers are known to be susceptible to strong electromagnetic fields (EMFs). This in vivo study investigated occurrence of electromagnetic interference with pacemakers caused by common environmental sources of EMFs.

Methods

Eleven volunteers with a pacemaker were exposed to EMFs produced by two mobile phone base stations, an electrically powered commuter train, and an overhead high voltage transmission lines. All the pacemakers were programmed in normal clinically selected settings with bipolar sensing and pacing configurations.

Results

None of the pacemakers experienced interference in any of these exposure situations. However, often it is not clear whether or not strong EMFs exist in various work environments, and hence an individual risk assessment is needed.

Conclusions

Modern pacemakers are well shielded against external EMFs, and workers with a pacemaker can most often return to their previous work after having a pacemaker implanted. However, an appropriate risk assessment is still necessary after the implantation of a pacemaker, a change of its generator, or major modification of its programming settings.

Implantable cardioverter defibrillators in electric and magnetic fields of 400 kV power lines

BACKGROUND

Implantable cardioverter defibrillator (ICD) therapy has increased in Western countries. The aim of the study was to investigate the function of ICDs using a human-shaped phantom in electric and magnetic fields of 400 kV power lines.

METHODS

The phantom was used in the following manner: isolated from the ground, earthed from a foot, or earthed from a hand.

RESULTS

We performed 37 ICD tests using 10 different ICD devices. When the electric fields varied from 6.8 kV/m to 7.5 kV/m (humidity 70.5%) and the magnetic field was 2.0 μT, one of the ICDs tested recorded 258 ventricular beats/min when a simulated heart signal was applied to ICD electrodes. When the exposure was 5.1 kV/m, the same ICD had a similar disturbance; however, in a 0.9 kV/m field, it worked correctly.

CONCLUSIONS

Consequently, no effect on ICDs functioning was observed up to 0.9 kV/m, while anomalous behavior in some conditions was observed when levels exceeded 5.1 kV/m; ICD malfunctioning seems possible within 11.5 m from 400 kV power lines or in conditions inducing exposures exceeding 5 kV/m. Further development of this research field is needed.

Setups for in vitro assessment of RFID interference on pacemakers

The aim of this study is to propose setups for in vitro assessment of RFID (radiofrequency identification) interference on pacemakers (PM). The voltage induced at the input stage of the PM by low-frequency (LF) and high-frequency (HF) RFID transmitters has been used to quantify the amount of the interference. A commercial PM was modified in order to measure the voltage at its input stage when exposed to a sinusoidal signal at 125 kHz and 13.56 MHz. At both frequencies, two antennas with different dimensions (diameter = 10 cm and 30 cm, respectively) were used to generate the interfering field, and the induced voltage was measured between the lead tip and the PM case (unipolar voltage), and between the tip and ring electrodes (bipolar voltage). The typical lead configurations adopted in similar studies or proposed by international standards, as well as lead paths closer to actual physiological implants were tested. At 125 kHz, the worst-case condition differs for the two antennas: the 10 cm antenna induced the highest voltage in the two-loop spiral configuration, whereas the 30 cm antenna in the 225 cm(2) loop configuration. At 13.56 MHz, the highest voltage was observed for both the antennas in the 225 cm(2) loop configuration. Bipolar voltages were found to be lower than the unipolar voltages induced in the same configurations, this difference being not as high as one could expect from theoretical considerations. The worst-case scenario, in terms of the induced voltage at the PM input stage, has been identified both for LF and HF readers, and for two sizes of transmitting antennas. These findings may provide the basis for the definition of a standard implant configuration and a lead path to test the EMI effects of LF and HF RFID transmitters on active implantable devices.

Influence of relative humidity on analyzing electric field exposure using ELF electric field measurements

The objective of the study was to investigate the influence of humidity on analyzing electric field exposure using extremely low frequency (ELF) electric field measurements. The study included 322 measurements in a climate room. We used two commercial three-axis meters, EFA-3 and EFA-300, and employed two measurement techniques in the climate room where we varied the temperature from 15 to 25 °C, the relative humidity from 55% to 95%, and the electric field from 1 to 25 kV/m. We calculated Pearson correlations between humidity and percentage errors for all data and for data at different levels of humidity. When the relative humidity was below 70%, the results obtained by the different measurement methods in terms of percentage errors were of the same order of magnitude for the considered temperatures and field strength, but the results were less reliable when the relative humidity was higher than 80%. In the future, it is important to take humidity into account when electric field measurement results will be compared to the values given in different exposure guidelines.

Non-physiological increase of AV conduction time in sinus disease patients programmed in AAIR-based pacing mode

PURPOSE

The EVOCAV(DS) trial aimed to quantify the paradoxal atrioventricular (AV) conduction time lengthening in sinus node (SD) patients (pts) paced in AAIR-based pacing mode.

METHODS

SD pts, implanted with dual-chamber pacemaker programmed in AAIR-based pacing mode, were randomized in two arms for a 1-month period: the low atrial pacing (LAP; basic rate at 60 bpm, dual sensor with minimal slope) and the high atrial pacing (HAP; basic rate at 70 bpm, dual sensor with optimized slope, overdrive pacing) arm. At 1 month, crossover was performed for an additional 1-month period. AV conduction time, AV block occurrence and AV conduction time adaptation during exercise were ascertained from device memories at each follow-up.

RESULTS

Seventy-nine pts participated to the analysis (75 ± 8 years; 32 male; PR = 184 ± 38 ms; bundle branch block n = 12; AF history n = 36; antiarrhythmic treatment n = 53; beta-blockers n = 27; class III/Ic n = 18; both n = 8). The mean AV conduction time was significantly greater during the HAP (275 ± 51 ms) vs. LAP (263 ± 49 ms) period (p < 0.0001). Class III/Ic drugs were the only predictors of this abnormal behaviour. Degree II/III AV blocks occurred in 49 % of pts in the HAP vs. 19 % in the LAP period (p < 0.0001). Fifty-two patients (66 %) presented a lengthening of AV conduction time during exercise.

CONCLUSION

AAIR-based pacing in SD pts may induce a significant lengthening of pts' AV conduction time, including frequent abnormal adaptation of AV conduction time during exercise.