M. Zhou et al.: Radioprotection 2025, 60( 4), 373 – 381 379
No abnormality was found on PM-I and PM-II in terms of Source-I and Source-II. Certain cardiac signals were missing when PM-I and PM-II in unipolar setting with the maximum sensitivity( 1 mV) were subjected to Source-III. As for ICD-I and ICD-II( possess only bipolar sensing), erroneous cardiac signal detections and incorrect VF detections were observed when they are subjected to Source-II with maximum sensitivity, plus ICD-II with nominal sensitivity. Except for ICD-I with maximum sensitivity, no abnormality was found in terms of Source-I. In terms of Source-III, dysfunctions were observed in all the cases of ICDs, except ICD-I with 3rd sensitivity( 0.6 mV). d. Further investigation Additional tests were carried out to obtain the interference thresholds in these cases. By increasing the injected voltage in VIS, the maximum exposure level at which no dysfunction was observed, was identified as the interference threshold. Each threshold was tested three times as well to ensure reproducibility. Figure 4 illustrates the thresholds identified through the immunity tests conducted for all the cases. The sources are represented by three planes. Interference threshold surpassing the plane indicates that no dysfunction occurred for such source. e. Documentation As stated in EN 50527, a final report of the investigation shall be completed and in the possession of the employer to evaluate the situation of the CIED-employees, including overall risk assessment process, method chosen, rationale for the choice, findings, and conclusions.
4 Discussion
In this work, a risk assessment system VIS was designed based on the experimental investigation of the induced voltages on the cardiac implants under EF exposures. This system requires only a phantom setup and a voltage source. By controlling the voltage injection toward the phantom, the EF exposure in the implantation area may be characteristically reproduced. For many enterprises, due to their diversity, conducting immunity tests in laboratory EF exposure, which requires rigorous experimental configuration and maintenance, is neither practical nor efficient. In contrast, in the VIS assessment, the phantom ensures the reproduction of exposure characteristics, while its easy setup ensures that the process is portable and accessible. It presents an ideal alternative for conducting tests for cardiac implants, being simple and not requiring complex materials. Therefore, VIS assessment is proposed for the non-clinical investigation in the process of specific assessing for CIED-employees in the workplace.
Experimental measurements of induced voltages at the input of cardiac implants in VIS were carried out using the measuring system designed previously. The bipolar sensing mode demonstrates a significant reduction of induced voltage, which is consistent with previous studies [ 29 ]. Comparing the measurement and simulation results of induced voltage on the lead, there is a difference of 15.6 % for unipolar sensing and a difference of 3.4 % for bipolar sensing. Considering the small scale of the voltage, the results are in reasonable agreement. Two lookup tables( Fig. 3) were established, one for unipolar sensing and another for bipolar sensing, to determine the exposure dose for conducting equivalent tests of real-case exposure in the laboratory EF exposure system and VIS. The associations in the lookup tables are based on induced voltage’ s studies conducted previously( Zhou et al., 2024) and in this paper. According to the lookup tables, microvolt-level voltages can reproduce equivalent exposures up to 35 kV / m( the exposure limit) in VIS. Its efficiency and easy setup facilitate the experimental study of CIEDs under EF exposures.
A thorough non-clinical investigation for four CIEDs( two PMs and two ICDs) in specific risk assessment process was carried out as the application illustration of VIS assessment. The process utilized VIS assessment to determine whether the devices are subjected to severe interference from the assigned exposures. Considering the diversity of human cardiac signals, we tested the devices at maximum, nominal, and an additional higher sensitivity( 3rd Sen.) representing patients with higher amplitude cardiac signals. The amplitude of cardiac signals delivered from the ECG Unit varies accordingly. The findings indicate that cardiac implants at maximum sensitivity are more susceptible to EF exposures than at other settings. Interference was observed in all devices for Source-III( High AL in Directive 2013 / 35 / EU), except for pacemakers in bipolar sensing mode. We may notice the influence of the variety of sensitivity, but it is important to note that the maximum sensitivity represents an extreme scenario. At nominal sensitivity, the most common setting, no abnormalities were found in any of the devices for Source-I( public exposure); both ICDs with nominal settings were perturbed before Source-III, indicating they are more susceptible than pacemakers. Immunity tests for these cases were conducted under laboratory EF exposure. Approximate thresholds were obtained( Fig. 5), further validating the performance of VIS. Despite the cohort size is small( N = 4), these results highlight the importance of conducting assessments for specific cases. 5 Conclusion
In this paper, we established an exposure system VIS for evaluating occupational hazards associated with cardiac implants exposed to high-intensity EFs at power frequency in the workplace. In this system, we conducted investigations on the interference thresholds of cardiac implants and experimental measurements of induced voltages. Measurement and numerical results showed good agreement. The correspondences between in vitro testing and real-case exposures based on the findings of measurement were built up in two lookup tables. Equivalent exposure to real case may be produced by applying the exposure dose indicated in the lookup tables in in vitro testing. This system may be used in non-clinical investigation during specific assessing of an occupational exposure case. To illustrate the application of VIS, we conducted a complete process of specific assessing for four CIEDs. An assessment approach, along with the analysis method, was provided for further applications in the workplaces.