Electromagnetic Interference in Patients with
Implanted Cardioverter-Defibrillators and Implantable Loop Recorders
Marcos de Sousa, Gunnar Klein,
Thomas Korte, Michael Niehaus
Department of Cardiology and
Angiology, Medical School Hannover, Germany
Address for correspondence: Dr.
Michael Niehaus, MD, Dept. of Cardiology and Angiology, Hannover
Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
Email: niehaus.michael@mh-hannover.de
Introduction:
Modern life exposes us all to an ever-increasing number of potential
sources of electromagnetic interference (EMI) and patients with
Implantable rhythm devices (IRD) like pacemakers, implantable
cardioverter defibrillators
or implantable loop recorders often ask about the use of microwave
ovens,
walking through airport metal detectors and the use of cellular phones.
Electromagnetic interference occurs when electromagnetic waves emitted
by one device impede the normal function of another electronic device.
The potential for interaction between implanted pacing systems and
cardioverter-defibrillators (electromagnetic interference, EMI) has
been recognized for years.1,2,3,4. It has been shown that EMI
can produce clinically significant effects
on patients with implanted pacemakers and ICDs. For these reasons the
following text discusses the influence of several EMI generating
devices
on IRD .
Mobile phones:
These phones have the potential to interfere with pacemaker- or ICD
function. Several studies have shown that cellular phones might cause
electromagnetic interference with complex medical equipment5,6 including pacemakers 7,8,9,10,11.
The effects of digital cellular telephones on patients with ICDs have
been studied in a relatively small number of patients with various ICD
models provided by a single manufacturer. The static magnetic field
generated
by the cellular telephone when placed at very close proximity to the
ICD
during in vitro testing has caused temporary suspension of ventricular
tachycardia and ventricular fibrillation detection.
European cellular phones are different from those used in North
America: The NADC-phones (North American Digital Cellular) work on a
carrier frequency of 835 MHz. For data transmission a pulse amplitude
modulation of 50 pulses/s is used (TDMA-50) and the peak power of the
handset is limited to 0.6W. In contrast, the peak power of digital
phones used in the European GSM-net is 2W for D-net and 1W for E-net.12,13. The D-net works on a
carrier frequency of 900 MHz modulated with 217 Hz; the E-net works on
a carrier frequency of 1800 MHz.
How
the North American cellular phones are different to those used in
Europe the susceptibility of tiered single chamber ICDs to EMI or other
dysfunction caused by commercially available digital mobile telephones
was evaluated in our own study. For our evaluations, two different
types of European
digital cellular phone systems were used.
We
prospectively analyzed 97 patients with different ICDs and exposed them
to two different types of European digital cellular handy phones
(Ericsson GH337, 900 MHz and NOKIA NHK1EA, 1,8GHz). The effect of high
radiofrequency-output (RF) was tested during continuous recording of
the marker channel and intracardiac ECG. During the recordings the
handsets were put in a calling position
close to the patient´s ear and on top of the device. We noticed
interferences (loss of communication or temporary inactivation of the
device during
interrogation) in 38 patients; most of them (93%) during testing close
to the device.
Main
finding of our study was that electromagnetic interference transmitted
by digital cellular handheld D- or E-net phones, commonly used in
Europe
did not interfere with normal ICD-function of tested single-chamber
devices under daily-life conditions. Inappropriate sensing and
detection of ventricular tachyarrhythmias were not found. These
observations are in accordance
with the results described by Fetter et al.17,
Occhetta14, Barbaro et al.15 and Jimenez et al.16.
In contrast to Fetter et al. we did not see any temporary suspension of
the ICD function by static magnetic field (magnetic reversion
counter=0)
generated by the speaker in the cellular phone´s earpiece which
may
be in part explained by a less strong static magnetic field of the
evaluated
GSM-phones. Implantation technique did not have any relation to
interference
with the function of the ICD.
We
concluded that there is no evidence of harm related to the use of the
tested European GSM handsets for the tested single chamber ICDs
independent
of the used GSM-net. Since most interferences were seen when the
GSM-phones were in a short distance to the ICDs, patients should be
advised not to
carry their GSM-phone close to the device. This is in accordance to in
vitro
studies with American GSM-phones18.
As
ICD-interrogation is the most susceptible phase for interference, the
use of GSM-phones should be prohibited in hospital areas where
interrogation takes place.
For
implantable loop recorders there are only small experiences so far17. It could be shown that GSM phones did not
affect appropriate function of the implantable loop recorder.
Microwave ovens:
Although no recent studies have been performed which test the effect of
household microwave energy on pacemakers and ICDs, it is widely
believed and accepted that all modern pacemakers are adequately
shielded from microwave energy produced by modern appliances18. Pacemaker manufacturers therefore recommend
that patients with implanted devices
do not need to take special precautions in the use of microwave ovens
or
other common household equipment such as televisions, radios, toasters
and electric blankets.
Metal-detector gates:
The
effect of metal-detector gates on implanted pacemakers has been studied
more than 10 years ago19. In 103 patients
who were monitored as they passed through typical metal detectors
alarms invariably were activated when the patients walked through the
gates. In none of the patients the pacemaker function was affected:
None of the devices was reset to the programmed noise-protection mode
(most often VOO) or spontaneous fixed rate mode of function, nor were
any of the devices´ outputs inhibited
in paced patients, or inappropriately delivered in patients who had
normal
cardiac rhythm. Test series with ILRs did not show any interference
with metal detector gates. It is therefore accepted practice to advise
the patient
that while airport screening devices may detect the pacemaker, ICD or
ILR
metal case the device will not be adversely affected. Patients should
carry
their device identification card for the purpose of obtaining security
clearance.
Electronic article surveillance systems:
Electronic article surveillance systems have recently been recognized
as having the potential to interact with implanted rhythm devices20. The commercial use of such scanning devices
is widespread, and case reports have been published in which patients
received inappropriate ICD therapies while lingering between or
touching electronic article surveillance gates. Because a very large
number of electronic article surveillance devices are in use, and
because only very few episodes of possible interaction between
electronic article surveillance devices and pacemakers or ICDs have
been reported, it is likely that too much is being made of
this issue.
Electronic surveillance systems use three different technologies to
detect the presence of a metal alloy tag within an electromagnetic
field created between two parallel gates: magnetic audio frequency,
swept frequency, and acoustomagnetic or pulsed low-frequency. The
detection of such a tag signals a theft.
The literature suggests, that significant EMI with implanted rhythm
devices is most likely to occur with the acoustomagnetic mode of
electronic article surveillance, and that pacemakers are more likely to
be affected than
ICDs, likely due to electromagnetic fields of six different electronic
article surveillance devices, no instance of significant interference
with normal ICD function was seen. The testing protocol included
positioning
the patients for five minutes between the electronic article
surveillance
gates while rotating 360° as well as leaning against the electronic
article surveillance transmitter. In another study, patients with ICDs
with pacing capability performed routine walking through electronic
article
surveillance gates as well as prolonged exposure within the gates, with
and without pacing from the implanted device. The absence of
significant
interaction between electronic article surveillance gates and ICDs was
confirmed
during walking at a normal slow pace through the gates. Under
conditions
of extreme exposure, however, seven of 169 patients exhibited some
interaction
between the ICD and the electronic article surveillance device,
manifested
by noise-sensing that resulted in complete or prolonged inhibition of
the
device output. Such output inhibition might have been clinically
relevant, and could also have resulted in inappropriate ICD shocks had
this function
not been suspended during the testing protocol. Older-generation
devices,
and those implanted in the abdomen were more likely than
newer-generation
subpectorally implanted ones to manifest these interactions. In
general,
electronic surveillance systems do not pose a threat to the tachycardia
functions of ICDs under reasonably normal conditions. More prolonged
exposures
or closer proximity to the transmitter can result in inappropriate
shocks.
In
contrast to ICDs, acoustomagnetic electronic surveillance devices can
interact with permanent pacemakers. Asynchronous pacing
(noise-reversion),
atrial and ventricular oversensing and surveillance device-induced
pacing
have been described during a real-life walk through the gates. No
pacemaker
was reprogrammed, and no patient experienced severe symptoms. No
difference
in electronic article surveillance device effect on pacemakers was
observed
between unipolar and bipolar sensing configurations. Since these
effects
on pacemakers occur only while the patient is within the electronic
article
surveillance device's magnetic field, it is prudent to advise patients
to avoid prolonged exposure to electronic article surveillance systems,
lingering within the surveillance gates and direct contact with the
gates.
Acoustomagnetic electronic surveillance devices can interact with
permanent pacemakers. Asynchronous pacing (noise-reversion), atrial and
ventricular oversensing and surveillance device-induced pacing have
been described during a real-life walk through the gates. No difference
in electronic article surveillance device effect on pacemakers was
observed between unipolar and bipolar sensing configurations. Since
these effects on pacemakers occur only while the
patient is within the electronic article surveillance device´s
magnetic
field, it is prudent to advise patients to avoid prolonged exposure to
electronic article surveillance systems and direct contact with the
gates.
Although data are lacking, it is likely that the same considerations
and
cautions apply to the pacing functions of ICDs which are part of all
currently
available systems.
For ILR systems it has been
shown recently that their function can be impaired by electronic
surveillance systems.
Magnetic resonance imaging:
The
safety of magnetic resonance imaging in patients with IRD has been
debated for years. In general, the presence of these devices is an
absolute contraindication to the performance of magnetic resonance
imaging, since cardiac pacing
and total inhibition of output can occur during magnetic resonance
exposure21. However, it has been suggested
that if patients are positioned so that the thorax does not enter the
magnet bore no significant interaction occurs. Furthermore, it has been
shown22 that MR imaging at 0.5 T can be
safely performed in patients with implanted pacemakers in carefully
selected clinical circumstances when appropriate strategies
(programming to an asynchronous mode, adequate monitoring techniques,
limited RF exposure) are used.
These data need to be confirmed before magnetic resonance imaging of
the extremities can be allowed in patients with implanted devices.
First test series with ILRs have resulted in an irreversible error in
one nonimplanted device 18. Therefore MRI
diagnostics should be scheduled before implantation of an ILR system.
Electrocautery devices:
Electrocautery devices have long been known to have the potential for
interfering with pacemaker function. These devices generate a high
energy electromagnetic field with a frequency that may pass through the
filters
of ICDs. This may result in oversensing, independent of unipolar or
bipolar
coagulation mode is used. This oversensing leads to a pacemaker
inhibition
or false detection of ventricular tachyarrhythmias. Therefore, for
surgical
procedures using electrocautery devices, pacemaker-dependent patients
should
be programmed into an asynchronous pacing mode. Usually, ICD-patients
should
be programmed to detection-off using a programmer. Nevertheless,
detection
of ICDs may be temporarily inactivated using a pacemaker magnet placed
above the device on condition that monitoring and an external
defibrillator
are available.
Radiotherapy:
The
CMOS electronic circuitry of pacemaker, ICD and ILR-devices which is
currently used in all pacemakers and ICDs is responsible for the high
sensitivity of these devices to ionizing radiation. Nevertheless, no
large recent studies have been performed which test the effect of
radiotherapy on pacemakers and ICDs. 1991 Rodriguez et al.23 could show severe malfunctions of pacemakers
and ICDs: Of the 17 pacemakers exposed to photon radiation eight failed
before 50 Gy, whereas four of the six
pacemakers exposed to electron radiation failed before 70 Gy. For the
ICDs,
detection and charging time increased with accumulated radiation dose
and charging time increased catastrophically at less than 50 total
pulses delivered when compared with the charging time of six ICDs
implanted at the same
time. In 1995 Roethig et al.24 showed
similar
results using 9-MV photon radiation. Our own experience in 3
ICD-patients
who underwent radiation therapy with a cumulative dose of <5 Gy
showed
no damage of the device, oversensing or inhibition of pacing.
Therefore, direct radiation of pacemakers or ICDs at therapeutic levels
should be
strictly avoided. Furthermore, pacemaker and ICDs have to be controlled
in short periods during and after radiation therapy, and pacemaker or
ICDs
should be exchanged after the radiotherapy when accumulative dose on
the
pacemaker exceeds 5 Gy.
References
1. Altamura G,
Toscano S, Gentilucci G, Ammirati F, Castro A, Pandozi C, Santini M.
Influence
of digital and analogue cellular telephones on implanted pacemakers.
Eur
Heart J 1997;18:1632-1641.
2. Irnich
W. Interference in Pacemakers. Pacing Clin Electrophysiol
1984;7:1021-1048
3.
Marco D,
Eisinger G, Hayes DL. Testing of work environments for electromagnetic
interference. Pacing Clin Electrophysiol 1992;15:2016-2022
4.
Barbaro V, Bartolini P, Tarricona A. Evalution of static magnetic field
levels interfering with pacemakers. Physica Medica 1991;2:73-76
5.
Naegeli B, Deola M, Eicher B, Osswald S. Pacemaker dysfunction caused
by interference with Natel-D mobile phones (Abstr.) Pacing Clin
Electrophysiol 1995;18:842
6. Irnich
W, Batz L, Muller R, Tobish R. Electromagnetic interferences of
pacemaker by mobile phones. Pacing Clin Electrophysiol 1996;19:1431-1446
7. Naegeli
B, Osswald S, Deola M, Burkart F. Intermittent pacemaker dysfunction
caused by digital mobile telephones. J Am Coll Cardiol
1996;27(6):1471-1477
8. Hofgartner
F, Muller T, Sigel H. Could C- and D-network mobile phones endanger
patients with pacemakers? Dtsch. Med. Wochenschr 1996;121(20):645
9. Grimm
W. Is the cardiac pacemaker patient at risk by using mobile telephone
devices in D-net? Internist 1994;35:580
10. Fahraeus
T, Almquist LO. Cellular telephones may interfere with cardiac
stimulators. Yuppie telephones and alarms are hazardous for patients
with pacemakers. Lakartidningen 1995; 92(43):4009-4010
11. Barbaro
V, Bartolini P, Donato A, Altamura G, Ammirati F, Santini M. Do
European GSM mobile cellular phones pose a potential risk to pacemaker
patients? Pacing Clin Electrophysiol 1995;18:1218-1224.
12.
Hayes DL, Carillo RG, Findly GK, Embrey M: State of the science:
pacemaker and defibrillator interference from wireless communication
devices. Pacing Clin Electrophysiol 1996;19(10):1419-30
13. Niehaus
M, Gille K, Cierpka R, Korte T, Tebbenjohanns J: Interference of two
common European digital cellular phones with implantable
cardioverter-defibrillators. EHJ 2002;23(7):586-588
14.
Occhetta E, Plebani L, Bortnik M, Sacchetti G, Trevi C. Implantable
cardioverter defibrillators and cellular phones: Is there any
interference? Pacing Clin Electrophysiol 1999;22:983-9
15.
Barbaro V, Bartolini P, Caruso F, Donato A, Gabrielli D, Militello C,
Montenero A, Zecchi P. Electromagnetic interference of digital and
analog cellular telephones with implantable cardioverter
defibrillators: In vitro and in vivo studies. Pacing Clin
Electrophysiol 1999;22:626-634
16. Jimenez
A, Hernandez Madrid A, Pascual J, Gonzalez Rebollo JM, Fernandez
E,Sanchez A, Ortega J, Lozano F, Munoz R, Moro C. Electromagnetic
interference between automatic defibrillators and digital and analog
cellular telephones. Rev Esp Cardiol 1998;51(5):375-82
17. de
Cock CC, Spruijt HJ, van Campen LM, Plu AW, Visser CA: Electromagnetic
interference of an implantable loop recorder by commonly encountered
electronic
devices. Pacing Clin Electrophysiol 2000 Oct;23:1516-8
18. Bonney
CH, Rustan PL, Fond GE. Evaluation of effects of microwaves oven (915
and 23450 MHz) and radar (2810 and 3050 MHz) electromagnetic radiation
on noncompetetive cardiac pacemakers. IEEE Trans Biomed Eng
1973;20:357-364
19.
Copperman Y, Zarfati D, Laniado S. The effect of metal detector
gateways on implanted permanent pacemakers. Pacing Clin Electrophysiol
1988;11:1386-1387.
20. Groh W, Boschee
SA, Engelstein ED, Miles WM, Burton MK, Forster PR et al.. Interaction
between electronic surveillance systems and implantable
cardioverter-defibrillators. Circulation 1999;100:387-392 .
21. Lauck G, von
Smekal A, Wolke S, Seelos KC, Jung W, Manz M, Luederitz B. Effects of
nuclear magnetic resonance imaging on cardiac pacemakers. Pacing Clin
Electrophysiol 1995; 18(8):1549-1555.
22. Sommer T,
Vahlhaus C, Lauck G, von Smekal A, Reinke M, Hofer U, Block W, Traber
F, Schneider
C, Gieseke J, Jung W, Schild H. MR imaging and cardiac pacemakers:
in-vitro evaluation and in-vivo studies in 51 patients at 0.5 T.
Radiology 2000; 215(3):869-79.
23. Rodriguez F,
Filimonov A, Henning A, Coughlin C, Greenberg M. Radiation-induced
effects in multiprogrammable pacemakers and implantabale
defibrillators. Pacing Clin Electrophys 1991;14: 2143-2153 .
24. Roethig H,
Herrmann T, Kopcsek H. Experience in dealing with artificial pacemaker
patients during therapy with ionizing radiation. Strahlenther Onkol
1995;171:398-402.
