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Magnetic Field Susceptibility Standards for Pacemakers and Other Active Implants

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Time-varying magnetic fields are present in many aspects of modern life, arising from power-distribution systems, household appliances, wireless charging devices, transportation infrastructure, and increasingly from electrically intensive environments. While these fields are a familiar part of today’s technological landscape, they can interact in specific ways with electronic systems, including those found in active implantable medical devices (AIMDs) such as pacemakers and defibrillators. Because these devices contain sensitive sensing circuits and conductive leads, even moderate external fields may induce voltages or interfere with their operation under certain conditions.

Under certain conditions, this may result in pacing inhibition, unintended therapy delivery, or temporary changes in device operating mode (see ICNIRP (1998) on device interference caveats; and Driessen et al. (2019) for a systematic review of such effects).

Because of this increased susceptibility, dedicated electromagnetic compatibility (EMC) standards have been developed alongside general public exposure guidelines. The primary foundation is the ICNIRP 1998 guideline on time-varying electric and magnetic fields, which underpins the EU Council Recommendation 1999/519/EC and many national exposure frameworks.

Although ICNIRP has since updated its low-frequency guidelines (2010), 1999/519/EC still reflects the 1998 framework. ISO 14117 builds on the exposure limits in the EU Recommendation 1999/519/EC, itself based on ICNIRP 1998, and defines standardized EMC test methods and field levels to assess how pacemakers and other active implantable devices perform under specified magnetic and electromagnetic field conditions.

From human exposure limits to implant susceptibility

ICNIRP 1998 as the starting point

In 1998, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) published guidelines that later became the main reference for limiting human exposure to time-varying electric, magnetic, and electromagnetic fields up to 300 GHz. These guidelines set out a two-level framework:

  1. First, they defined basic restrictions inside the body. These limits relate to quantities such as induced current density at low frequencies and specific absorption rate at higher frequencies. Those limits are directly linked to established biological effects.
  2. Second, ICNIRP defined reference levels outside the body. These are expressed as electric field strength and magnetic flux density and are frequency dependent. The reference levels provide a practical way to assess compliance without measuring internal quantities directly.

For extremely low-frequency fields, such as the 50 Hz fields associated with power systems, ICNIRP 1998 set a general-public reference level of 100 microtesla for magnetic flux density. This value was derived primarily to prevent acute effects such as nerve and muscle stimulation at power frequencies. In the higher frequency range, additional limits address excessive tissue heating.

These values were rapidly adopted into regulatory frameworks worldwide. The EU Council Recommendation 1999/519/EC mirrors the ICNIRP 1998 limits with minimal modification.

ICNIRP 1998 is designed to protect intact biological tissue from direct effects of electromagnetic fields. The guidelines explicitly note that compliance may not prevent interference with implanted medical devices such as cardiac pacemakers and defibrillators, and do not provide detailed limits or models for how such devices behave in external fields, even though they can react at field levels below the thresholds for biological effects.

Why implants need their own susceptibility criteria

Active implantable medical devices operate under very different conditions than human tissue. Pacemakers, implantable cardioverter defibrillators, cardiac resynchronization devices, and similar systems include features that inherently increase their sensitivity to magnetic fields.

These devices use long conductive leads that can form loops and couple efficiently to external fields. Their sensing amplifiers are designed to detect signals at the microvolt level. Many also incorporate additional sensors and wireless telemetry circuits.

Because of this, magnetic fields that remain well within ICNIRP general-public limits can still interfere with normal device operation. This gap is explicitly recognized in standards such as ISO 14117, which notes that achievable electromagnetic immunity for implantable cardiovascular devices may lie below exposure limits derived for biological safety.

The regulatory response has been split into two layers. ICNIRP guidelines (as reflected in the EU Council Recommendation 1999/519/EC) define acceptable environmental field levels for the general population. In parallel, implant-specific EMC standards such as ISO 14117 specify the immunity levels and test methods that pacemakers and ICDs must meet when exposed to those fields.

ISO 14117: EMC standard for cardiac AIMDs

Scope and relationship to ICNIRP 1998

ISO 14117:2019, titled Active implantable medical devices — Electromagnetic compatibility — EMC test protocols for implantable cardiac pacemakers, implantable cardioverter defibrillators and cardiac resynchronization devices, defines the main standard used today to review electromagnetic immunity of cardiac AIMDs.

The introduction of the standard clarifies several important points about the test protocols it defines:

  • First, the scope is intentionally broad. The test methods cover frequencies from 0 Hz up to 3,000 MHz, spanning static fields, power-frequency magnetic fields, intermediate frequencies, and radiofrequency exposure.
  • Second, the tests are built around real-world exposure sources. These include broadcast transmitters, mobile phones, RFID systems, electronic article surveillance gates, induction-based equipment, and a range of medical and industrial devices that patients may realistically encounter.
  • Third, and most importantly for exposure rationale, the standard explicitly anchors its test levels to ICNIRP 1998. Annex M gives the rationale for using ICNIRP 1998 levels and shows how the device test voltages correspond to external fields, with particular discussion for emitters above 10 MHz.

Subsequent technical analyses maintain this alignment. For devices using unipolar lead configurations  (which have larger effective loop areas), the applied test levels trace back to EU Recommendation 1999/519/EC, which itself is derived from the ICNIRP 1998 general-public exposure limits.

In essence, ISO 14117 examines how cardiac implants behave when exposed to fields that comply with ICNIRP 1998 public limits, and where their immunity margins may be insufficient

Test philosophy

ISO 14117 does not directly use ICNIRP reference levels as a pass or fail threshold. Instead, the standard defines a structured immunity evaluation process.

Standardized laboratory setups are used to represent the human torso, typically a saline-filled tank with the device and leads positioned in controlled and repeatable geometries. Electric and magnetic fields are then applied using calibrated coils or antennas at defined frequencies and amplitudes.

Device behavior is evaluated against functional performance criteria. These include the absence of sustained pacing inhibition, no inappropriate delivery of therapy, and no lasting change to device operation.

For magnetic fields, testing explicitly includes both power-frequency exposure at 50 and 60 Hz and intermediate-frequency exposure in the kilohertz range associated with induction systems, wireless power transfer, RFID, and selected industrial platforms.

The objective is to characterize and improve device immunity so that, for typical exposure conditions up to ICNIRP-based public limits, compliant pacemakers and defibrillators are unlikely to experience hazardous malfunctions (for a modelling example, see Vivarelli et al. (2025)), while also identifying scenarios where interaction can still occur.

How ISO 14117 translates ICNIRP 1998 levels into immunity tests

The connection between public exposure limits and implant immunity testing follows a defined and technical process. The intent is to convert environmental reference levels into test conditions that are meaningful for implanted devices (see Annex M in ISO 14117 (2019)).

  1. The starting point is the magnetic and electric field reference levels defined in ICNIRP 1998. These levels are also reflected in EU Recommendation 1999/519/EC and represent limits intended to protect the general public from established adverse effects, for continuous exposure.
  2. The next step is to evaluate how such external fields couple into an implanted system. ISO 14117 assumes a realistic but conservative situation, where the implant leads form a loop inside the human torso. To cover worst case coupling, the standard specifies lead configurations with relatively large loop areas. A commonly cited example is a planar semicircular loop with an area of 225 cm², selected to maximize induced voltage (see Vivarelli et al. (2025) and Campi et al. (2023) for explicit use of the 225 cm² loop).
  3. Based on this coupling model, the standard defines immunity test levels. These are expressed either as induced voltage on the lead or as an equivalent external field that would generate the same effect. Additional margins are applied to account for uncertainty and variability.
  4. Separate test levels are defined for unipolar and bipolar systems. Unipolar leads form larger effective loops, so their immunity levels are derived directly from ICNIRP based environmental limits. Bipolar leads have much smaller loop areas, and therefore the applied test levels are typically about ten percent of the unipolar level.

This method does not attempt to cover every possible electromagnetic condition. Instead, it targets a controlled set of worst case scenarios that are grounded in ICNIRP exposure limits and realistic implant geometries.

China C-GCAP’s grading for vehicles with respect to implants

A recent illustration of how implant immunity criteria are applied at the vehicle level can be found in the China Green Car Assessment Program (C-GCAP). In its 2024 Detailed Rules for Health Assessment, electromagnetic protection is defined as one of three main health indicators, with separate evaluation tracks for the general public and for sensitive populations, including people with medical implants.

For the general public, C-GCAP measures magnetic fields from 10 Hz to 400 kHz. Tests under different conditions, following the procedures of GB/T 37130-2018. The results are then reported as a margin, in decibels, relative to the public reference limits in GB 8702-2014..

  • A margin of 25 dB or higher receives the full score.
  • Lower margins reduce the score in stages.
  • Any result below 3 dB earns zero points for this part of the electromagnetic protection item.

For sensitive populations, the assessment follows a different method. Low-frequency magnetic fields in the range covered by IEC 62764-1:2022 (1 Hz to 100 kHz) are measured under different operating conditions (stationary, constant speed, acceleration, deceleration, charging and discharging). These measurements are then compared against implant-specific limits defined in ISO 14117:2019 and ISO 14708-2/-3/-4. Where C-GCAP extends the assessment to higher frequencies, it must use additional RF exposure frameworks beyond IEC 62764-1.

Instead of public reference limits, C-GCAP compares these measurements to implant-specific limits defined in ISO 14117:2019 and ISO 14708-2/-3/-4. This ties the results directly to pacemaker and other active implant immunity requirements.

The scoring for this category is handled as a penalty rule:

  • When the smallest margin between the measured fields and the relevant implant limit is at least 25 dB, the vehicle passes with no deduction.
  • If the margin drops below 25 dB in any test state, the item fails and 5 points are deducted from the electromagnetic protection score.
  • If this failure occurs while the public-protection score is already below 5 points, the full electromagnetic protection score is set to zero

This builds a defined safety buffer for pacemakers and other implants into its health rating. Vehicles must maintain strong margins relative to ISO-based implant limits in realistic operating modes. This also gives manufacturers a clear reason to address implant compatibility and general EMF exposure together.

The possible implications

For clinicians and patients

A medical device that is declared compliant with ISO 14117 has undergone immunity testing against a wide range of magnetic and electromagnetic fields, covering frequencies up to 3 GHz. The applied test levels are derived from exposure limits that originate in ICNIRP guidance for the general public.

In practical terms, ISO 14117 compliance provides assurance against most everyday exposure scenarios.

Compliance, however, does not eliminate the need for judgment in all situations. Certain environments involve field levels or coupling conditions that are outside typical everyday exposure. Examples include industrial equipment that carries very high currents, welding systems, magnetic resonance imaging, or very close proximity to strong wireless power transfer systems. Occupational risk assessments for workers with active implantable medical devices consistently show that most common sources pose no problem, while a limited number of specific scenarios require case-by-case evaluation (see occupational and implant guidance in Driessen et al. (2019), Mattei et al. (2019), Zradziński et al. (2018), and the EC EMF Guide (2013)).

For engineers and manufacturers

ICNIRP 1998 defines environmental exposure ceilings. ISO 14117 and related standards convert those ceilings into concrete design targets and electromagnetic compatibility test procedures for pacemakers and other cardiac AIMDs.

When new emission sources appear, such as wireless charging systems for electric vehicles or new large-scale wireless deployments, their relevance to implant safety should be evaluated against ISO 14117-based immunity requirements, and not solely against general population exposure limits.

Susceptibility standards for active implants rely on a two-layer framework. Public exposure limits define the external environment, and implant-specific standards verify that device performance remains clinically acceptable within that environment. Maintaining alignment between these layers, and revising them when technology changes, remains a central requirement for long-term patient safety.

Reference

  1. International Commission on Non-Ionizing Radiation Protection (ICNIRP) (1998). Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz)
  2. International Commission on Non-Ionizing Radiation Protection (ICNIRP) (2010). Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz)
  3. IInternational Organization for Standardization (2019). ISO 14117:2019 – Active implantable medical devices — Electromagnetic compatibility — EMC test protocols for implantable cardiac pacemakers, implantable cardioverter defibrillators and cardiac resynchronization devices
  4. Driessen, S., Napp, A., Schmiedchen, K., Kraus, T., & Stunder, D. (2019). Electromagnetic interference in cardiac electronic implants caused by novel electrical appliances emitting electromagnetic fields in the intermediate frequency range: A systematic review
  5. Vivarelli, C., Calcagnini, G., Censi, F., et al. (2025). A tool for the assessment of electromagnetic compatibility in active implantable devices: The pacemaker physical twin
  6. Campi, T., Cruciani, S., Maradei, F., Feliziani, M., et al. (2023). Electromagnetic interference in cardiac implantable electronic devices due to dynamic wireless power systems for electric vehicles
  7. Mattei, E., Calcagnini, G., Censi, F., Pinto, I., Bogi, A., & Falsaperla, R. (2019). Workers with active implantable medical devices exposed to EMF: In vitro test for the risk assessment
  8. Zradziński, P., Karpowicz, J., Gryz, K., et al. (2018). Evaluation of the safety of users of active implantable medical devices (AIMD) in the working environment in terms of exposure to electromagnetic fields – Practical approach to the requirements of European Directive 2013/35/EU
  9. European Commission. (2013). Non-binding guide to good practice for implementing Directive 2013/35/EU – Guide for SMEs
  10. China Green Car Assessment Program (C-GCAP) (2024). Detailed Rules for Health Assessment