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\DOI{10.5802/crphys.187}
\datereceived{2023-08-01}
\daterevised{2024-01-24}
\datererevised{2024-04-30}
\dateaccepted{2024-05-02}
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\dateposted{2024-07-11}
\begin{document}

\begin{noXML}

%\makeatletter
%\def\TITREspecial{\relax}
%\def\cdr@specialtitle@english{Energy in the heart of EM waves: modelling, measurements and management}
%\def\cdr@specialtitle@french{L'\'energie au c{\oe}ur des ondes \'electromagn\'etiques : mod\'elisation, mesures et gestion}
%\makeatother

\CDRsetmeta{articletype}{research-article}

\title{Electromagnetic compatibility of active cardiovascular implants
to occupational magnetic field environments: impact of the field
direction}

\alttitle{Etude de la compatibilit\'{e} \'{e}lectromagn\'{e}tique des
dispositifs cardiaques actifs aux champs magn\'{e}tiques industriels
basses fr\'{e}quences : impact de l'orientation du champ}

\author{\firstname{Lucien} \lastname{Hammen}\IsCorresp}
\address{Laboratoire d'Electromagn\'{e}tisme, Vibrations et Optique Institut national de recherche et de s\'{e}curit\'{e} (INRS) Vand\oe{}uvre-l\`{e}s-Nancy, France}
\address{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Universit\'{e} Paris-Saclay, CentraleSupelec, CNRS Gif-sur-Yvette, France} 
\address{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Sorbonne Universit\'{e}, CNRS Paris, France}
\email[L. Hammen]{lucien.hammen@inrs.fr}

\author{\firstname{Lionel} \lastname{Pichon}\CDRorcid{0000-0002-3402-5498}}
\addressSameAs{2}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Universit\'{e} Paris-Saclay, CentraleSupelec, CNRS Gif-sur-Yvette, France} 
\addressSameAs{3}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Sorbonne Universit\'{e}, CNRS Paris, France}

\author{\firstname{Yann} \lastname{Le Bihan}\CDRorcid{0000-0001-5563-9192}}
\addressSameAs{2}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Universit\'{e} Paris-Saclay, CentraleSupelec, CNRS Gif-sur-Yvette, France} 
\addressSameAs{3}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Sorbonne Universit\'{e}, CNRS Paris, France}

\author{\firstname{Mohamed~}\lastname{Bensetti}\CDRorcid{0000-0002-4755-5113}}
\addressSameAs{2}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Universit\'{e} Paris-Saclay, CentraleSupelec, CNRS Gif-sur-Yvette, France} 
\addressSameAs{3}{Laboratoire de G\'{e}nie Electrique et Electronique de Paris Sorbonne Universit\'{e}, CNRS Paris, France}

\author{\firstname{G\'{e}rard} \lastname{Fleury}}
\addressSameAs{1}{Laboratoire d'Electromagn\'{e}tisme, Vibrations et Optique Institut national de recherche et de s\'{e}curit\'{e} (INRS) Vand\oe{}uvre-l\`{e}s-Nancy, France}

\keywords{\kwd{AIMD} 
\kwd{Pacemaker} 
\kwd{EMC} 
\kwd{Occupational exposure} 
\kwd{Magnetic fields} 
\kwd{Helmholtz coil}}

\altkeywords{\kwd{DMIA} 
\kwd{Pacemaker} 
\kwd{Exposition professionnelle} 
\kwd{Champ magn\'{e}tique} 
\kwd{Bobines d'Helmholz} 
\kwd{CEM}}

\def\thanksname{Note}
\thanks{This article follows the URSI-France workshop held on 21 and 22
March 2023 at Paris-Saclay.}

\begin{abstract}
Active Implantable Medical Devices (AIMD) are nowadays a part of
everyday life, with for example more than one million pacemakers (PMs)
implanted each year worldwide. Like every electronic devices they are
sensitive to electromagnetic interferences but the consequences are
potentially severe. A large number of publications deals with
electromagnetic compatibility (EMC) with common equipment but only a
few concern industrial sources. Furthermore, the field encountered at
workplace is potentially higher. Taking these into account, a new test
method to assess the EMC of AIMDs against occupational magnetic field
sources was developed. It is based on an experimental approach using a
specific test bench able to generate a controlled magnetic field in all
space directions up to the high occupational exposure limits between
50~Hz and 3~kHz. To do this, three Helmholtz coil systems are combined
on three orthogonal space directions. This specificity makes it
possible to take into account the high variability of the operator's
position compared to the industrial source. 

In this paper, the study focused on the impact of the magnetic field
direction on the PM's functioning with bipolar leads, as is the case
for the vast majority of devices implanted nowadays. It appears that
the magnetic field direction has an impact on the PM's functioning
and is consequently a relevant parameter for evaluating their EMC.
These observations led us to the hypothesis that the lead in bipolar
mode is more sensitive to electric field than magnetic field. This
assumption remains to be confirmed by further studies.
\end{abstract}

\begin{altabstract}
Les dispositifs m\'{e}dicaux implantables actifs (DMIA) font
aujourd'hui partie de la vie courante, en effet plus d'un million de
pacemakers sont implant\'{e}s chaque ann\'{e}e dans le monde. Comme
tous les appareils \'{e}lectroniques, ceux-ci sont susceptibles
d'\^{e}tre perturb\'{e}s par les champs \'{e}lectromagn\'{e}tiques
environnants. De telles interf\'{e}rences peuvent avoir des
cons\'{e}quences dramatiques sur la sant\'{e} du porteur. Un grand
nombre de publications traitent de la compatibilit\'{e}
\'{e}lectromagn\'{e}tique (CEM) des DMIA avec des \'{e}quipements de la
vie courante. Cependant, peu d'\'{e}tudes concernent les sources de
champ industrielles. De plus, les limites d'exposition
professionnelle \'{e}tant sup\'{e}rieures \`{a} celles pour la
population g\'{e}n\'{e}rale, l'exposition est potentiellement plus
intense au poste de travail. Compte tenu de ces \'{e}l\'{e}ments, une
nouvelle m\'{e}thode d'essai pour \'{e}valuer la CEM des DMIA en milieu
industriel a \'{e}t\'{e} mise au point. Elle repose sur l'utilisation
d'un banc d'essai sp\'{e}cifique capable de g\'{e}n\'{e}rer un
champ magn\'{e}tique entre 50 Hz et 3 kHz dans toutes les directions de
l'espace et jusqu'aux limites hautes concernant l'exposition
professionnelle. Pour ce faire, trois syst\`{e}mes de Helmholtz ont
\'{e}t\'{e} combin\'{e}s selon trois directions de l'espace
orthogonales. Cette sp\'{e}cificit\'{e} permet de consid\'{e}rer la
grande variabilit\'{e} du positionnement de l'op\'{e}rateur
vis-\`{a}-vis d'une source industrielle.

L'\'{e}tude pr\'{e}sent\'{e}e dans cet article s'est port\'{e}e sur
l'impact de l'orientation du champ magn\'{e}tique sur le
fonctionnement des pacemakers munis de sondes bipolaires, comme c'est
le cas de la quasi-totalit\'{e} des dispositifs implant\'{e}s de nos
jours. Il appara\^{i}t que la direction du champ magn\'{e}tique a un
impact sur le fonctionnement des pacemakers et constitue ainsi un
param\`{e}tre pertinent pour l'\'{e}valuation de la CEM. Ces
observations nous ont conduit \`{a} formuler l'hypoth\`{e}se selon
laquelle la sonde en mode bipolaire serait plus sensible aux champs
\'{e}lectriques qu'aux champs magn\'{e}tiques. Cette hypoth\`{e}se
demande \`{a} \^{e}tre confirm\'{e}e par d'autres \'{e}tudes.
\end{altabstract}

\shortrunauthors

\maketitle

\end{noXML}

\vspace*{-1pt}


\section{Introduction}

Cardiac implants are now part of everyday life, with more than one
million pacemakers (PMs) implanted each year worldwide~\cite{bib1}
and around 67,000 in France~\cite{bib2}. PMs have two main
functions: sensing cardiac activity and stimulating the heart muscle if
an irregularity is detected. Like every electronic device, they are
sensitive to interactions with electromagnetic fields. The principal
mechanism of interaction is a perturbation of the measured signals,
leading to a lack or inadequate stimulation. Such interference can lead
to potentially severe consequences. These Electromagnetic Compatibility
(EMC) issues of PMs are the topic of a large number of publications,
especially concerning everyday life equipment~\cite{bib3,bib4,bib5}.
The patients are generally well informed about the potential risk and
they are advised to stand away from some common sources. For example,
the device manufacturers specify a minimal distance between the
pacemaker and a cell phone, which is usually around 20~cm. Except some
studies about power distribution~\cite{bib6}, only a few deal with
EMC at workplace~\cite{bib7,bib8,bib9,bib10}. It is therefore
difficult for an occupational physician to correctly assess the risks
in the case of an employee equipped with a PM. Furthermore, a worker is
likely to be more exposed to electromagnetic fields at work. Indeed, in
Europe, occupational exposure limits~\cite{bib11} are generally
higher than the general public ones~\cite{bib12}. No major pacemaker
malfunction in industrial environment was published, but several
articles~\cite{bib7,bib10} or standards~\cite{bib13} highlight the
potential adverse effects using \textit{in vitro} tests. The
absence of documented accident at workplace could be explained by
various suggestions: malfunctions are generally reversible and do not
directly threaten patient safety, this type of malfunction is not
reported by the cardiologist and high-risk workers are generally
properly protected from electromagnetic sources. 


Cardiac implants are more sensitive to low-frequency (LF) magnetic
fields. Indeed, these devices are designed to pick up cardiac signals
which are LF with a frequency range up to 500~Hz~\cite{bib14}. The
higher frequencies are generally filtered out at the device input
stage. According to an internal study, the industrial sources, such as
a spot welding gun, an induction oven or an arc welding station,
generally emit LF magnetic field. 


In order to comply with European directives, implant manufacturers
perform EMC tests according to international standards
\cite{bib14,bib15}. These standards combine different approaches:
injection tests for which the signals are directly injected at the
pacemaker input stage through a ``tissue-equivalent interface circuit''
and a radiative test using a simple coil for magnetic field exposure.
Some magnetic field thresholds between 0~Hz and 3~GHz are defined to
guarantee the implant functioning during daily life situation, that's
why they follow or generally exceed the public exposure limits. For
information, these limits reach $100~\upmu\mathrm{T}$ (RMS) at 50~Hz,
then decrease in inverse proportion to frequency up to 800~Hz and
remain constant at $6.25~\upmu\mathrm{T}$ (RMS) up to 150~kHz. To
determine the voltage amplitude required for injection tests from the
magnetic field thresholds, the standards consider the induced voltage
through the inductive loop formed by the pacemaker and its leads. A
``worst case'' loop dimension, taking into account the length of the
leads and the clinical implantation, is considered for the calculation,
which tends to maximise the test voltages. This inductive loop
consideration is only valid for unipolar (single electrode) mode leads,
however almost all PMs implanted in Europe nowadays operate in bipolar
(two electrodes) mode~\cite{bib1}, which is only partially considered
by the literature or international standards~\cite{bib14,bib15}.
Historically the lead polarity was only unipolar, in this mode the
sensing and the pacing are made between an electrode at the lead
extremity and the pacemaker case itself which is metallic. Electrical
continuity is ensured by the conductivity of the intermediate tissues.
In bipolar mode, the electrocardiogram (ECG) monitoring and the pacing
are made between two electrodes at the lead extremity. In this case,
there is no inductive loop formed by the leads. The differences between
these two lead configurations are illustrated in Figure~\ref{fig1}.
Bipolar probes are thus reputed to be less sensitive to electromagnetic
interference, that is why standards EMC tests consider an injected
voltage for this mode ten times lower than for unipolar mode
\cite{bib14,bib15}. Considering that, the tests proposed by the
international standards are limited in some aspects: the considered
mechanism of interaction only concerns the case of unipolar leads, the
magnetic field exposure test does not consider the PM's leads and the
magnetic field is only applied along three mutually perpendicular
directions, no signal corresponding to real exposure situations
is\unskip\break tested, etc.

\begin{figure}
\includegraphics{fig01}
\caption{Differences between unipolar and bipolar lead configurations.
The unipolar lead has a single electrode (cathode) at its extremity,
detection and stimulation are made between it and the pacemaker housing
(anode). The bipolar lead has two electrodes at its extremity,
detection and stimulation are made between them.\label{fig1}}
\end{figure}

According to the previous considerations, there is a need to develop a
new test method for estimating the EMC of PMs to occupational LF
magnetic fields. The method proposed here is based on an experimental
approach using a test bench. It makes it possible to determine the
impact of different parameters on the implant behaviour. In our case,
the study focused on the impact of the magnetic field direction on the
PM with bipolar leads.


\section{Material and method}


A test bench was designed using the numerical simulation software CST
studio suite. A frequency domain solver for LF applications based on
the finite element method (FEM) was used. As the system dimensions are
significantly smaller than the wavelength at the considered
frequencies, the magneto-quasistatic approximation was made, i.e.~the
displacement current is neglected compared to the conduction current in
Maxwell--Ampere equation. Like the human body, the saline solution used
to test the PMs has a relatively low electrical conductivity, which
implies---considering the system's dimensions---an induced current
too low to generate a significant magnetic field. In these conditions
and with a test setup made of non-magnetic material ($\mu_{r}\approx
1$), the magnetic field distribution is not impacted by its presence.
Also, considering the range of frequencies and the type of biological
tissues around the pacemaker, using an equivalent homogeneous solution
is a standard experimental approach widely used in the literature
\cite{bib6,bib7,bib10,bib16}. The aim of the test bench is to generate
a homogeneous and controlled LF magnetic field over a volume that can
encompass an implant with its leads in a configuration approaching a
clinical implantation. In order to take into account the high
variability of the implant's position relatively to the source, the
field can be generated in every space direction. In order to cover a
wide range of industrial sources, the test bench was designed to
operate between 50~Hz and 3~kHz. In terms of magnitude, the magnetic
field is able to reach the high occupational exposure limits over the
frequency range, which is theoretically the maximum level that an
implant can be exposed. For information, these limits reach 6~mT (RMS)
at 50~Hz and decrease in inverse proportion to frequency up to 3~kHz.
Concerning the field homogeneity, a maximal variation of ${\pm}$5\% over
a volume that encompasses the pacemaker and its leads is researched.
The test bench is also able to reproduce a non-sinusoidal magnetic
field representative of a real exposure at workplace.

The solution adopted to ensure the technical specifications mentioned
above was to combine 3 Helmholtz coil systems in three orthogonal
spatial directions (see Figure~\ref{fig2}). Numerical simulation was
particularly useful to characterise the field homogeneity inside the
test bench and to determine the coil inductances, which is essential
for selecting the power supply solution. The coils are thus supplied by
5 power amplifiers (model~7548 from AETechron). The geometrical
characteristics of the coils are given in Table~\ref{tab1}. The
high-voltage supply generates unwanted electric fields that can
interfere with implants. To avoid these parasitic fields and obtain a
source of magnetic field only, the coils are shielded with a conductive
layer (see Figure~\ref{fig3}). Aluminium was used due to its relative
magnetic permeability close to unity, which does not significantly
affect the magnetic field distribution.


\begin{figure}
\includegraphics{fig02}
\caption{Test bench functional block diagram.\label{fig2}}
\vspace*{5pt}
\end{figure}


\begin{figure}
\includegraphics{fig03}
\caption{Test bench composed of the set of coils with shielding, the
phantom and 5 power amplifiers: 2 in series for the $x$ and $y$ axes and
only one for the $z$-axis, which requires less power.\label{fig3}}
\vspace*{5pt}
\end{figure}


\begin{table}
\caption{Coil geometrical characteristics\label{tab1}}
\begin{tabular}{ccc}
\thead
 & Average diameter (cm) & N$^*$ for LF test bench \\
\endthead 
X coils & 62 & 148 \\
Y coils & 53 & 127 \\
Z coils & 44 & 105 
\botline
\end{tabular}
\tabnote{$^*$ Number of turns.}   
\end{table}


The test bench was characterised and complies with the specifications
detailed above. The simulated magnetic field distribution presents, in
the centre of the test bench when the 3 axes generate a same field
intensity, a maximum variation in intensity of ${\pm}$5\% and a variation
of field direction below 8\textdegree\ over a volume of $24\times
22\times 3~\mathrm{cm}^{3}$ that can encompass the pacemaker
implantation. A good agreement of the generated magnetic field for a
given voltage excitation was observed between the numerical simulation
and the experimental measurements, with less than 1\% difference.


For more information about the test bench, a related conference paper
details its functioning, design and characterisation~\cite{bib17}.

To test the implant's behaviour to magnetic field, it is immersed in
a saline solution that simulates the electromagnetic properties of the
human body. The solution conductivity is around 0.54~S/m, which
corresponds to the average conductivity of human blood~\cite{bib18}.
The whole system---composed of a plexiglass container with the saline
solution, the PM under test and a plastic grid to support it---is
placed at the middle of the Helmholtz coils as illustrated in
Figure~\ref{fig4}. The implant's functioning is monitored during the
magnetic field exposure.


\begin{figure}
\includegraphics{fig04}
\caption{Test setup: monitoring and positioning of the pacemaker inside
the phantom.\label{fig4}}
\end{figure}


Concerning the pacemaker's settings, the tested device is configured
in bipolar mode and operates in DDD mode corresponding to the standard
setting for a dual-chamber pacemaker, which is the most implanted
device configuration in Europe~\cite{bib1}. According to the
international nomenclature, these three letters indicate that sensing
and stimulation can be carried out on the atrium and on the ventricle,
and that the device can either compensate cardiac stimulation
irregularities or be inhibited if spontaneous cardiac activity is
detected. This configuration permits to test the PM's sensing
function as well as its stimulation function. The detection sensitivity
is set to the most sensitive case, i.e.~the lowest value: 0.1~mV. It
corresponds to a worst-case situation. Indeed, the more the detection
is sensitive, the more the PM is subject to electromagnetic
interference. The PM with its leads is placed inside the container in a
position approaching a typical left-sided pectoral implantation, which
is the most common implantation (see Figure~\ref{fig3}).

In our case, the study focused on the effect of the magnetic field
direction, the other parameters are fixed. Eight different directions
equi-distributed in space are considered (see Figure~\ref{fig7}(a)).
The frequency is set to 50~Hz which corresponds to many industrial
applications in Europe. The~different magnetic field amplitudes applied
are between $0~\upmu\mathrm{T}$ and $400~\upmu\mathrm{T}$ with a step
size of $10~\upmu\mathrm{T}$. 

The implant monitoring is made with two coaxial wires immersed in the
saline solution; the stimulation wire is used to send an ECG signal
which simulates the atrial contraction and the monitoring wire is used
to detect the ventricular stimulation response generated by the PM (see
Figure~\ref{fig4}). 

In ``normal'' operating mode, the PM detects the dummy atrial
contraction signal and the absence of ventricular contraction, and thus
generates a stimulation pulse on the ventricular lead after a
pre-programmed delay. During the magnetic field exposure, if a decrease
of 50\% of the pulse amplitude or a variation of more than 20\% on the
delay between the atrial contraction and the ventricular stimulation is
observed, it is considered as a malfunction \cite{bib16}. A comparison
between a normal operating mode and a malfunctioning situation is
presented in Figure~\ref{fig5}. The limits considered for proper
operation are defined from a reference measurement made without
magnetic field (see Figure~\ref{fig6}). For each considered magnetic
field amplitude, a sequence of 100 cardiac cycles is played at a rate
of 60~bpm and the number of malfunctions is recorded. It is then
possible to plot the percentage of malfunctions versus the applied
magnetic field for each considered direction.




\begin{figure}
\includegraphics{fig05}
\caption{Comparison between a normal operating mode and a
malfunctioning situation.\label{fig5}}
\end{figure}


\begin{figure}
\includegraphics{fig06}
\caption{Determination of the proper functioning limits.\label{fig6}}
\end{figure}


\section{Results}

The spatial orientations of the eight considered field directions
relative to the PM (numbered from 1 to 8) are illustrated in
Figure~\ref{fig7}(a), the coordinates of the associated unit vectors
are given in Table~\ref{tab2}. The percentage of malfunction versus the
magnetic field amplitude is given for these eight directions in
Figure~\ref{fig7}(b). In order to better visualise and compare the
results in Figure~\ref{fig7}(b), the measurements for each direction
are fitted by a power function which matches well to the observed
trend.

\begin{figure}
\includegraphics{fig07}
\caption{(a) Visualisation of the unit vectors associated with the 8
considered field directions (the pacemaker and its leads are in the
$xy$-plane). 
(b) Percentage of malfunction in function of the magnetic field
amplitude for the 8 considered field directions when exposed to a 50~Hz
sinusoidal magnetic field.\label{fig7}}
\end{figure}


\begin{table}
\caption{Unit vectors associated with the 8 considered field
directions\label{tab2}}
\begin{tabular}{cccc}
\thead
\xmorerows{1}{Orientation} & \multicolumn{3}{c}{Coordinates} \\ \cline{2-4}
&  $x$ &  $y$ &  $z$ \\
\endthead
1 &  0 &  0 &  1 \\ 
2 &  ${-}$0.74 &  \mn0.59 &  \mn0.32 \\ 
3 &  ${-}$0.60 &  ${-}$0.05 &  ${-}$0.80 \\ 
4 &  \mn0.88    &  \mn0.34    &  \mn0.32 \\ 
5 &  ${-}$0.70 &  ${-}$0.70 &  \mn0.16 \\ 
6 &  \mn0.45    &  ${-}$0.88 &  \mn0.16 \\ 
7 &  \mn0.14    &  \mn0.92    &  ${-}$0.35 \\ 
8 &  \mn0.55    &  ${-}$0.22 &  ${-}$0.80 
\botline
\end{tabular}
\end{table}

The direction of the magnetic field has a significant impact on the
operation of the pacemaker in bipolar mode.

No malfunctioning was observed between 0 and $400~\upmu\mathrm{T}$ for
the 6th direction. However it occurs for higher
magnetic field amplitudes.

After exposure to the magnetic field, the PM resumes a normal activity.
No long-term effect of the magnetic field on the PM is observed. These
intermittent malfunctions imply a desynchronisation of the atrial and
ventricular contractions which may lead to discomfort. This situation
is not suitable especially at workplace---where exposure is repeated
and prolonged---and should be avoided. However, this is not
life-threatening for the PM holder, except for patients who are
entirely PM-dependant.

\section{Discussion}

The magnetic field direction has an impact on the PM's functioning
in bipolar mode. The direction with the highest malfunction rate
doesn't correspond to the direction considered as the reference for
EMC testing by international standards~\cite{bib14,bib15} and the
literature~\cite{bib16,bib19}. This reference direction corresponds
to orientation~1, i.e.~the magnetic field perpendicular to the plane
formed by the PM and its leads, a situation where a unipolar PM senses
the maximum of magnetic flux.

The rational given by international standards and literature, based on
an inductive area formed by the electrodes, seems inadequate for a
bipolar PM. Indeed for this latter one, the highest malfunction rate
doesn't correspond to the highest magnetic flux through an inductive
area. Our hypothesis, based on this observation and others, is that the
lead in bipolar mode is more sensitive to electric field than magnetic
field. Indeed, in bipolar mode the induced voltage cannot be derived
easily from the evaluation of a magnetic flux through a given surface,
but it can be expressed directly as a line integral of the electric
field along a path between the two electrodes. In bipolar polarity
mode, the lead seems to interact more like a short monopole antenna. In
our case, the interfering electric field inside the phantom derives
from the time-varying magnetic field (Maxwell--Faraday). Unlike the
magnetic field, the electric field distribution over the phantom,
obtained by numerical simulation, is inhomogeneous. Indeed, its
distribution principally depends on the phantom geometry, the magnetic
field direction and the material inside the container, such as the grid
or the PM itself. It's therefore relatively complex to accurately
predict the electric field distribution over the phantom. However, the
fact that the electric field distribution varies according to the
magnetic field direction could explain its impact on the PM's
functioning.

No long-term effect on the PM is observed, which is in accordance with
the requirements of the international standards. However, a relatively
high malfunction rate is observed for magnetic field, even below the
general public exposure limits. This could be explain by a detection
sensitivity of 0.1~mV, which is outside the scope of international
standards. It is indeed a key parameter regarding to electromagnetic
interference.

\section{Conclusion}

A new method for assessing the EMC of AIMDs was developed and
characterised, then applied to PMs. The first tests showed that the
direction of the magnetic field is a relevant parameter for the EMC
study of PMs in bipolar mode. Furthermore, the induced voltage cannot
be derived easily from the evaluation of a flux through an inductive
surface. These observations led us to the hypothesis that the leads in
bipolar mode are more sensitive to electric field than magnetic field.
This assumption remains to be confirmed by further studies.

The impact of other parameters on the PM's functioning such as the
saline solution conductivity, the field frequency or the device
positioning is tested using the test bench. A comparative study between
different PMs from different manufacturers is also carried out.

This test method could be applied or adapted to other AIMDs such as
implantable cardioverter defibrillators or neurostimulators.

\section*{Declaration of interests} 
The authors do not work for, advise, own shares in, or receive funds
from any organization that could benefit from this article, and have
declared no affiliations other than their research organizations.

\section*{Acknowledgement}
The authors would like to thank Dr.~Mathieu Echivard, cardiologist from
the CHRU of Nancy (F), for his valuable help.

\back{}

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