CLINICAL RESEARCH
Europace (2013) 15, 388–394
doi:10.1093/europace/eus345
Pacing and resynchronization therapy
Electromagnetic interference with cardiac
pacemakers and implantable cardioverterdefibrillators from low-frequency
electromagnetic fields in vivo
Maria Tiikkaja 1*, Aapo L. Aro2, Tommi Alanko1, Harri Lindholm 3, Heli Sistonen 3,
Juha E.K. Hartikainen 4, Lauri Toivonen 2, Jukka Juutilainen 5, and Maila Hietanen 1
1
Safe New Technologies, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland; 2Department of Cardiology, Helsinki University Central Hospital,
Haartmaninkatu 4, 00029 Helsinki, Finland; 3Physical Work Capacity, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland; 4Heart Center,
Kuopio University Hospital and University of Eastern Finland, PO Box 1777, 70211 Kuopio, Finland; and 5Department of Environmental Science, University of Eastern Finland, PO
Box 1627, 70211 Kuopio, Finland
Received 28 June 2012; accepted after revision 20 September 2012; online publish-ahead-of-print 1 November 2012
Aims
Electromagnetic interference (EMI) can pose a danger to workers with pacemakers and implantable cardioverterdefibrillators (ICDs). At some workplaces electromagnetic fields are high enough to potentially inflict EMI. The
purpose of this in vivo study was to evaluate the susceptibility of pacemakers and ICDs to external electromagnetic
fields.
.....................................................................................................................................................................................
Methods
Eleven volunteers with a pacemaker and 13 with an ICD were exposed to sine, pulse, ramp, and square waveform
and results
magnetic fields with frequencies of 2–200 Hz using Helmholtz coil. The magnetic field flux densities varied to
300 mT. We also tested the occurrence of EMI from an electronic article surveillance (EAS) gate, an induction
cooktop, and a metal inert gas (MIG) welding machine. All pacemakers were tested with bipolar settings and
three of them also with unipolar sensing configurations. None of the bipolar pacemakers or ICDs tested experienced
interference in any of the exposure situations. The three pacemakers with unipolar settings were affected by the
highest fields of the Helmholtz coil, and one of them also by the EAS gate and the welding cable. The induction
cooktop did not interfere with any of the unipolarly programmed pacemakers.
.....................................................................................................................................................................................
Conclusion
Magnetic fields with intensities as high as those used in this study are rare even in industrial working environments. In
most cases, employees can return to work after implantation of a bipolar pacemaker or an ICD, after an appropriate
risk assessment. Pacemakers programmed to unipolar configurations can cause danger to their users in environments
with high electromagnetic fields, and should be avoided, if possible.
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Electromagnetic interference † Pacemaker † ICD † Low-frequency magnetic field † in vivo tests
Introduction
At present, the indications for implantation of cardiac pacemakers
and cardioverter-defibrillators (ICDs) are expanding, and, as a consequence, the number of working-age people with these implanted
devices is also increasing. At the same time, concerns have arisen
about electromagnetic interference (EMI) in implanted devices
from electromagnetic fields (EMFs) that exist in various work
environments.1 – 3 In workplaces with possible high EMF levels,
employees are usually assigned to other duties or have to retire
after receiving a pacemaker or an ICD. This solution is, however,
expensive for the employer and for society, and often unpleasant
also for the employee.
The interim European EMF Directive (2004/40/EC) requires
employers to specifically consider the safety of workers at particular risk.4 This group of workers includes those with a pacemaker or
* Corresponding author. Tel: +358 30 474 2750; fax: +358 30 474 2805, Email: [email protected]
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2012. For permissions please email: [email protected].
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Electromagnetic interference with cardiac pacemakers and implantable cardioverter-defibrillators
What’s new?
† After an implantation of a pacemaker or an implantable
cardioverter-defibrillator (ICD) an individual risk assessment concerning electromagnetic interference is required
in order to evaluate if the pacemaker/ICD patient can
safely return to work.
† ICDs and modern pacemakers with bipolar sensing configurations seem to be well shielded against external lowfrequency magnetic fields.
† Pacemakers programmed to unipolar sensing configurations
can be susceptible to electromagnetic fields that can occur
in working environments.
an ICD. Currently, safety provisions for workers with a pacemaker
or an ICD exposed to EMFs are poorly understood.
Static magnetic fields (0 Hz) produced by devices with permanent magnets have been shown to result in EMI in pacemakers/ICDs
or their interrogation telemetry. In pacemakers, an exposure to a
static magnetic field can cause a switch into asynchronous pacing
mode. In contrast, ICDs generally respond to a strong static
magnet field by temporarily withholding all therapies for tachyarrhythmias. Devices capable of producing static magnetic fields
are, e.g. hard drives of laptop – computers and portable media
players, portable headphones, and small neodymium magnets.5 – 9
Similarly, EMI is commonly caused by static magnetic fields of magnetic resonance imaging equipment.10,11 The data on EMI from alternating extremely low-frequency magnetic fields (,50 Hz) are,
however, scanty.
This study focused on testing the function of pacemakers and
ICDs in vivo during exposure to typical EMF sources in work life
and to relatively high-intensity magnetic fields produced with a
Helmholtz coil. We investigated if low-frequency EMFs cause interference in pacemaker and ICD function and programming, as suggested by some previous reports.12 – 18 We chose a Helmholtz coil,
an electronic article surveillance (EAS) gate, an induction cooktop,
and a cable of a welding machine as possible sources of EMI.
Methods
Volunteers with a pacemaker or an
implantable cardioverter-defibrillator
The volunteers in the study were recruited from among pacemaker
patients attending their normal pacemaker follow-up done at the Pacemaker Clinic of the Helsinki University Central Hospital. We included
only clinically stable people at working age and not entirely dependent
on their devices.
Eleven volunteers with a bradycardia pacemaker and 13 with an ICD
were chosen to participate in the study. Seven of the 11 volunteers
with a bradycardia pacemaker were women. The age of the volunteers
averaged 53 years (range 34 – 64). Four of the 13 volunteers with an
ICD were women. The mean age of the ICD volunteers was 46
years (range 23 – 62). The models and operating modes of the pacemakers and ICDs tested are presented in Tables 1 and 2.19,20
Table 1 Manufacturers, models, and modes of the
bradycardia pacemakers tested
Manufacturer
Model
Pacing
mode
Volunteer
number
DDIR
DDD
DDDR
DDIR
VVIR
DDIR
DDD
DDD
AAIR
DDIR
1
2
3
4
5
6
7
8
9
10
DDI
11
................................................................................
Medtronic
Kappa KDR 401/403
Kappa KDR 401/403
Kappa KDR 901
Boston Scientific Altrua 50 S502
Altrua 60 S602
St Jude Medical Accent DR RF 2212
Accent DR RF 2212
Accent DR RF 2212
Identity ADx SR 5180
Identity ADx XL DR
5386
Zephyr XL DR 5826
Table 2 Manufacturers, models, and modes of the ICDs
tested
Manufacturer
Model
Pacing
mode
Volunteer
number
VVI
VVI
VVI
12
13
14
................................................................................
Medtronic
Marquis VR 7230
Marquis VR 7230
Maximo VR 7232
Boston Scientific Teligen 100 F102
St Jude Medical
Atlas + VR V-193
Atlas + VR V-193
Fortify DR 2233-40Q
Fortify DR 2233-40
Fortify DR 2233-40Q
Epic + VR V-196
Epic + DR V-239
Current VR RF
1207-36
Current VR RF
1207-36
VVI
15
VVI
VVI
DDI
DDD
DDD
VVI
DDI
VVI
16
17
18
19
20
21
22
23
VVI
24
The study design was approved by the Coordinating Ethics Committee of the Hospital District of Helsinki and Uusimaa. Each volunteer
gave his/her written, informed consent prior to the study.
Measurement procedure
During the tests a cardiologist specialized in pacemaker treatment
monitored the patient using real-time electrocardiography (ECG) in
order to immediately discover possible EMI in the pacemaker/ICD
and alterations in the patient’s condition. We analysed electrogram
(EGM) recordings of each pacemaker and ICD to find possible
stored effects of EMI.
The sensitivities of the bradycardia pacemakers were programmed
as 1.0 mV for the ventricle and 0.18 – 0.5 mV for the atrium. Ventricular/atrial high rate or mode switch detection rates were programmed
to 175– 190 b.p.m. We tested the pacemakers with two programmed
390
M. Tiikkaja et al.
pacing settings in order to better detect the possible episodes of
undersensing, oversensing, or mode switch. In the first phase, the subjects were exposed to different magnetic fields with the basic rate programmed low enough (30 – 50 b.p.m.) to favour the patient’s intrinsic
rhythm. In the second phase, the tests were repeated with the basic
rate programmed high enough (and atrioventricular delay short
enough in dual-chamber devices) to result in 100% pacing of the
atria and/or ventricles, depending on the device. The basic rates
used ranged from 60 to 90 b.p.m. Bipolar settings were used in all
the tested pacemakers.
One bradycardia pacemaker from each manufacturer was chosen to
also be tested using unipolar sensing. The pacemakers tested with unipolar configurations were those of Volunteers 3, 5, and 8. The two
DDD pacemakers were programmed to an atrial sensitivity of
0.5 mV and atrial/ventricular tachycardia (VT) detection rate of
180 b.p.m. All pacemakers were programmed to a ventricular sensitivity of 1.0 mV. The pacemakers were programmed to pace with a rate
higher than the subject’s intrinsic rhythm (base rates 75, 80, and
90 b.p.m.) operating in modes DDD, VVI, and DDD, respectively.
The sensitivities of the ICDs tested were 0.3 –0.6 mV for the ventricle and 0.2 mV for the atrium.
The basic rates of ICDs were programmed as 30 – 60 b.p.m., VT detection rates were programmed to 120 – 150 bpm, and ventricular fibrillation detection rates to 200 – 300 bpm. The detection of VT was
programmed to monitor tachyarrhythmias and possible shock therapies resulting from false detection of VT were disabled.
All the initial settings of the devices were restored after the tests.
Magnetic field exposure using a Helmholtz
coil
During the tests, the volunteer sat between the two coils of a Helmholtz coil system with his/hers chest in the middle of the coils, perpendicular to the magnetic field. The Helmholtz coil consisted of two
identical coils with 25 turns of copper wire in each and a radius of
54 cm. The distance between the coils was 57 cm. Electric current
was conducted to the Helmholtz coil and the current induced a magnetic field between the two coils. The test set-up used has been
described in detail in our previous reports, in which the perpendicular
direction was found to cause most of the interference.21,22
We tested magnetic field interference detection from the pacemakers/ICDs using three different exposure set-ups with varying waveforms, frequencies, and magnetic field intensities.
We chose the exposure levels of Exposure set-up I (Table 3) in
order to comply with European Norm 50527-1, according to
which magnetic flux density of 100 mT is considered to be the
‘safety level’ for pacemakers and ICDs at 50 Hz.23 The percentages
of occupational and public exposure reference levels relate to the
guidelines given by the International Commission on Non-Ionizing
Radiation Protection (ICNIRP) for sinusoidal magnetic fields.24 The
peak limits for non-sinusoidal waveforms were derived from the corresponding ICNIRP reference levels. We determined the magnetic
field exposure levels and the peak limits using a magnetic field
meter (Narda ELT 400, Narda Safety Test Solutions, Pfullingen,
Germany). The tests were conducted in an electromagnetically
shielded laboratory.
Exposure set-ups II and III (Table 4) were chosen to comply with the
waveforms and frequencies that were found to cause most of the
interference in our previous phantom studies.21,22 The selection of
the exposure set-ups was based on the concern about EMI caused
by electrical appliances such as generators, transformers, and hand
tools emitting various types of magnetic field waveforms and
intensities.
Exposure set-up I was used for exposing volunteers with bipolar
bradycardia pacemakers and ICDs. Volunteers 2, 9 – 11, 17, and 21
were exposed using Exposure set-ups I and II. Volunteers 3, 5, 8,
14 – 16, 18 –21, and 23 – 24 were exposed using Exposure set-ups I
and III. The pacemakers of Volunteers 3, 5, and 8 were also exposed
to set-up III with unipolar sensing settings.
Exposure set-up I was divided into four sessions, each of which
included exposures with one waveform. Exposure set-ups II and III
were conducted without a resting period. In all cases (set-ups I – III),
the duration of an exposure to a specific magnetic field was 10 s, followed by a rest of 10 s after each exposure.
Electromagnetic field exposure using an
electronic article surveillance gate
We tested EMI caused by an EAS gate with the pacemakers and ICDs
using a Sensormatic AMS-1080 acoustomagnetic gate (Sensormatic
Electronics Corporation, Boca Raton, FL, USA), operating at a frequency of 58 kHz (+200 Hz). The root-mean-square (rms) value of
a magnetic flux density was 23 mT and a peak value 210 mT in front
of the gate. At 20 cm from the surface of the gate, the rms value of
the magnetic flux density was 9.6 mT and the peak value 83 mT. The
magnetic fields were measured at a height of 140 cm. The tests
Table 3 Maximum intensities of magnetic fields used in Exposure set-up I
f (Hz)
Sine-wave
...................................
Pulse-wave
...................................
Ramp-wave
...................................
Square-wave
...................................
Brms (mT)
Bocc/Bpub (%)
Brms (mT)
Bocc/Bpub (%)
Brms (mT)
Bocc/Bpub (%)
Brms (mT)
Bocc/Bpub (%)
2
5
110
100
0.22/1.1
1.3/6.3
3.5
1.9
35/170
35/170
100
100
47/230
47/240
100
100
27/140
26/130
10
100
4.0/20
2.5
35/170
100
47/230
100
28/140
25
50
98
95
9.8/49
20/99
3.7
4.8
35/170
35/170
97
95
53/260
61/310
96
95
31/150
38/190
60
95
23/110
5.0
35/170
95
64/320
95
41/200
100
200
94
93
38/19
75/370
5.6
6.1
35/170
35/170
94
67
77/380
79/400
94
94
50/250
75/370
...............................................................................................................................................................................
Brms is the measured root-mean-square value of magnetic flux density.
Bocc/Bpub is the highest percentages of ICNIRP reference levels for occupational and public exposure to sinusoidal magnetic fields, and the highest peak limits for occupational and
public exposure to non-sinusoidal magnetic fields.
Electromagnetic interference with cardiac pacemakers and implantable cardioverter-defibrillators
Table 4 Maximum intensities of magnetic fields used in
Exposure set-ups II and III
f
(Hz)
Waveform
Exposure set-up II
Exposure set-up III
........................ ........................
Brms
(mT)
Bocc/Bpub
(%)
Brms
(mT)
Bocc/Bpub
(%)
................................................................................
25
50
Sine
Sine
170
170
17/85
35/170
300
240
30/150
50/250
60
Sine
170
41/200
220
53/260
100
2
Sine
Ramp
160
160
66/330
74/370
160
160
65/320
74/370
5
Ramp
170
76/380
160
76/380
10
25
Ramp
Ramp
160
140
74/370
74/370
160
130
74/370
74/370
2
Square
180
47/240
290
75/380
5
10
Square
Square
180
180
45/230
47/240
300
280
75/380
76/380
25
Square
170
56/280
230
76/380
50
60
Square
Square
170
170
67/340
72/360
190
170
75/370
75/380
Brms is the measured root-mean-square value of magnetic flux density.
Bocc/Bpub is the highest percentages of ICNIRP reference levels for occupational
and public exposure to sinusoidal magnetic fields, and the highest peak limits for
occupational and public exposure to non-sinusoidal magnetic fields.
were conducted using a simple protocol: the volunteer first walked
past the gate at normal speed four times at a distance of 10 – 20 cm.
He/she then remained standing for 1 min in front of the gate, with
his/her chest almost touching it.
Electromagnetic field exposure using an
induction cooktop
The induction cooktop used was a UPO household cooktop/oven,
model A4200140 (UPO, Lahti, Finland), equipped with four cooking
plates. During the tests, both of the front cooking plates were set to
maximum heating power, with the boost function on. Two pots
filled with water were placed on the cooking plates. During the first
phase of the test, the volunteer stood in front of the cooktop for
1 min. During the second phase, the volunteer held the handles of
one of the pots standing in front of the cooktop for a 1 min. Thirdly,
the volunteer moved one of the pots to a cooking plate at the back
of the cooktop, then stayed in front of the cooktop for 1 min.
During the lifting, most of the volunteers had to lean above the
cooktop, so that their pacemaker/ICD was right above the cooking
plate which still remained at the maximum power for some seconds
after the removal of the pot.
The main operating frequency of the cooktop was 48 kHz. The magnetic flux density measured in front of the induction cooktop was 2 mT
at 40 cm above the cooking plates and 3 mT directly above the plates
at a height of 35 cm while one of the pots was being lifted.
Electromagnetic field exposure using
MIG-welding equipment
The susceptibility of the pacemakers/ICDs to EMI produced by a
welding cable was tested using a Migatronic Automig 250 XE MIGwelding machine (Migatronic, Leicestershire, UK). The volunteer
391
stood close to the welding cable for four continuous welding
periods, each lasting a few seconds. The distance between the volunteer’s pacemaker/ICD and the cable was 40 cm for Volunteers 1, 4, 6,
7, 12, and 13. Magnetic flux densities were measured during each
welding period. The mean value of the magnetic flux density was
30 mT, with a standard deviation of 8 mT, at a distance of 40 cm.
Because of the rather low-flux density at a distance of 40 cm, the
rest of the volunteers were tested with a distance of 20 cm between
their pacemaker/ICD and the welding cable. The mean value of the
magnetic flux density at this distance was 93 mT, with a standard deviation of 29 mT.
The tests with the three (Volunteers 3, 5, and 8) bradycardia pacemakers set in unipolar sensing mode were made at a distance of 20 cm
from the welding cable. The mean value of the magnetic flux density in
these tests was 98 mT, with a standard deviation of 20 mT.
Results
No interference from any of the EMF exposure sources used in
this study was found in any of the bradycardia pacemakers with
bipolar settings, or any of the ICDs tested. Some tests were
repeated for a few volunteers, because minor abnormalities were
observed in ECG. All the abnormalities were, however, interpreted to be caused by the volunteer’s own cardiac activity and
not by interference from the external EMFs with the pacemakers/ICDs.
All of the three unipolarly programmed pacemakers, subjected
to Exposure set-up III using a Helmholtz coil, experienced interference. During the exposures to 25 Hz sine-waves and to ramp- and
square-waves at 2 and 5 Hz, the pacemaker of Volunteer 3 intermittently and completely experienced inappropriate atrial
sensing, resulting in ventricular pacing at the maximum tracking
rate. These malfunctions were observed in the ECG. The pacemaker of Volunteer 5 experienced EMI from 25 and 50 Hz sinewaves, as well as from 2, 5, 10, and 25 Hz ramp-waves and 2, 5,
and 10 Hz square-waves. The interference caused complete and
intermittent loss of pacing due to inappropriate ventricular
sensing. Ventricular tachycardia detections were also found in
the stored EGM recordings. One of these VT detections is presented in Figure 1.
For Volunteer 8, interference was present during the whole of
Exposure set-up III. Complete or intermittent loss of pacing due
to inappropriate ventricular sensing was found in the monitored
ECG during all exposure periods of Exposure set-up III. In
stored EGM, these were seen as inappropriate auto mode switch
(AMS) episodes, reversions to noise mode, and detections of
high ventricular rate. One of the noise mode reversions is
shown in Figure 2.
The pacemaker of Volunteer 8 also experienced interference
with unipolar settings during exposure to the EAS gate. When
the volunteer was walking past the gate, the ECG showed inappropriate atrial sensing of the pacemaker, which resulted in ventricular
pacing at the maximum tracking rate. However, this did not occur
when the volunteer stood close to the gate for 1 min. During exposure to the welding cable, the pacemaker of Volunteer 8 sensed
atrial signals inappropriately, resulting first in ventricular pacing at
maximum rate and later in an AMS episode seen in the stored
EGM. The volunteer also reported a heavy feeling in her chest.
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M. Tiikkaja et al.
Figure 1 Inappropriate ventricular tachycardia detection and complete loss of pacing stored in electrogram due to inappropriate ventricular
sensing during Exposure set-up III with Volunteer 5’s unipolarly programmed pacemaker.
Figure 2 Stored electrogram showing inappropriate atrial and ventricular sensing episode resulting first in loss of pacing and then causing
reversion to noise mode (DOO pacing) and an inappropriate auto mode switch episode during Exposure set-up III with Volunteer 8’s pacemaker programmed to unipolar sensing settings.
Because of the subjective feelings of the volunteer, the exposure to
the welding cable was discontinued after two welding periods. The
maximum magnetic flux densities measured during these two
welding periods were 130 and 100 mT. The pacemakers programmed to unipolar configurations, in Volunteers 3 and 5, did
not experience any interference during the exposures to the
EAS gate, the induction cooktop, or the welding cable. The unipolar pacemaker of Volunteer 8 also functioned correctly during
exposure to the induction cooktop.
Discussion
The findings of this study indicate that, despite the high magnetic
field intensities used, none of the pacemakers was susceptible to
EMI when used in the bipolar sensing mode. Compared with the
previously widely used unipolar settings, pacemakers with bipolar
sensing performed better in rejecting EMI. This finding is consistent
with previous studies that have reported the superior electromagnetic compatibility of bipolar pacemakers.2,25,26 Although bipolar
settings are mainly used today, unipolar settings may still exist in
older pacemaker models and for some specific reasons. Persons
with pacemakers programmed to unipolar sensing need to be cautious regarding the increasing number of EMF-emitting devices in
occupational and residential environments.
The malfunctions observed in unipolar pacemakers were inappropriate atrial and ventricular sensing, i.e. the pacemaker interpreted external signals as intrinsic heartbeats. Atrial oversensing
may lead to inappropriate ventricular tracking. In contrast, inhibition of atrial or ventricular pacing can cause asystole if the
person has no intrinsic rhythm, and thereby posing immediate
danger. These malfunctions can also cause other symptoms such
as palpitations, low blood pressure, and chest pain. Some of the inappropriate sensing incidents during the 10 s exposures were too
short to cause AMS episodes or false tachycardia detections, and
Electromagnetic interference with cardiac pacemakers and implantable cardioverter-defibrillators
these malfunctions were only seen in the monitored ECG, not in
the stored EGMs.
In this study we applied the initial ICNIRP reference levels for
the time-varying magnetic fields.24 For 50 Hz sinusoidal fields,
the reference levels are 100 mT for the general public and
500 mT for occupational exposure. The more recently published
guidelines are 200 mT for public and 1000 mT for occupational exposure.27 We chose to use the former reference levels, as we have
found that pacemakers and ICDs in a phantom experienced interference at these and even lower levels.21,22 In the present study,
we started the Helmholtz coil exposure with settings which corresponded to the reference level of 100 mT. This was quickly found
to cause no interference with the pacemakers/ICDs, and we then
started to use higher magnetic field flux densities up to 300 mT.
Even though we found no pacemaker/ICD malfunctioning in the
relatively high magnetic fields used, we maintain that the new
ICNIRP guideline of 1000 mT for occupational exposure (at
50 Hz) may be too high for workers with a pacemaker/an ICD.
However, an appropriate, individual risk assessment is necessary
before workers can safely resume work in an electromagnetically
hostile environment after implantation of a pacemaker or an ICD.
The testing of only one EAS-gate, induction cooktop, and
welding apparatus can be considered as a limitation of this study.
Another potential limitation is that there was no real time telemetry, so it is possible that some EMI were not recorded by ECG or
EGM, especially with the ICDs. Finally, some of the pacemakers
tested are older models and their sensing features may differ
from newer models.
Conclusions
We found no interference with the bipolar pacemakers or ICDs,
even from quite high magnetic fields. Magnetic field intensities
similar to those used in this study are rare even in industrial
work environments. In most cases, employees can return to
work after an implantation of a bipolar pacemaker or an ICD,
based on an appropriate risk assessment. However, pacemakers
with unipolar settings experienced a great deal of interference in
identical fields. Even the EAS gate and the welding cable caused
interference in one of the pacemakers. These findings support
the contemporary trend to use bipolar settings in new pacemakers.
Unipolar configurations can result in life-threatening situations in
EMF environments for pacemaker-dependent persons, and therefore should be avoided whenever possible.
Acknowledgements
The authors wish to thank the volunteers who participated in this
study. Pacemaker manufacturers Medtronic, St Jude Medical and
WL-Medical (representing Boston Scientific) and other participated companies are gratefully acknowledged for consultation
and equipment resources.
Conflict of interest: none declared.
Funding
This work was supported by the Finnish Work Environment Fund
[grant number 107236].
393
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doi:10.1093/europace/eus175
Online publish-ahead-of-print 22 June 2012
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Fever outperforms flecainide test in the unmasking of type 1 Brugada
syndrome electrocardiogram
Sérgio Barra*, Rui Providência, and José Nascimento
Cardiology Department, Coimbra Hospital Centre and University, Coimbra, Portugal
* Corresponding author. R. António F. Fiandor 112-4 Dto, 4430-017, V. N. Gaia, Portugal. Tel: +00 351 916685716, Email: [email protected]
A thirty-year-old male patient with previous abrupt syncopal episode
and a family history of sudden cardiac death was seen for a type 2
Brugada pattern. Risk stratification was performed through flecainide
test and programmed electrical stimulation, which were negative.
Two weeks later, a new was electrocardiogram (ECG) performed
during a febrile syndrome, with precordial leads at third intercostal
space, unmasked unequivocal type 1 Brugada pattern.
Drug testing with flecainide or ajmaline is recommended in symptomatic patients with non-type 1 Brugada pattern, as symptomatic
patients with drug-induced type 1 ECG carry a worse prognosis than
their counterparts with non-inducible type I pattern.
Although a negative test does not exclude the presence of Brugada
syndrome (BS) and several studies have demonstrated the appropriateness of the flecainide/ajmaline challenges to unmask electrocardiographic patterns of BS, some authors have found disparate responses
of BS patients to these two drugs. A previous study reported a
failure of flecainide in 7 of 22 cases (32%) who had previously had a
positive response to ajmaline testing, explained as resulting from
greater inhibition of Ito by flecainide rendering it less effective.
In our patient, fever outperformed the flecainide test for unmasking
type I BS ECG. Accelerated inactivation of sodium channels under conditions of elevated temperature might be sufficient to obliterate
phase-1 depolarization reserve and shift balance of currents in favour of premature repolarization, revealing BS phenotype. Furthermore, it is not known whether currents other than (INa) may present temperature-dependent changes underlying the ECG phenotype.
This case demonstrates how important it is for symptomatic patients with non-type 1 Brugada pattern to perform an ECG in case of
fever, irrespective of the result of the flecainide drug challenge.
Conflict of interest: R.P. holds a research grant from Medtronic and a training grant from Boston Scientific.
The full-length version of this report can be viewed at: http://www.escardio.org/communities/EHRA/publications/ep-case-reports/
Documents/flecainide-test-fever-brugada-syndrome.pdf
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2012. For permissions please email: [email protected].