- Email: [email protected]
Patients With Cardiac Rhythm Management Devices
JACC: CLINICAL ELECTROPHYSIOLOGY
VOL.
ª 2017 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
-, NO. -, 2017
ISSN 2405-500X/$36.00
PUBLISHED BY ELSEVIER
http://dx.doi.org/10.1016/j.jacep.2017.06.013
EDITORIAL COMMENT
Patients With Cardiac Rhythm Management Devices How True Is the Need for Magnetic Resonance Imaging?* Theofanie Mela, MD
I
maging has become the cornerstone of everyday
the Conformité Européenne in Europe and the Food
diagnostics. Magnetic resonance imaging (MRI)
and Drug Administration in the United States,
and its many applications are the preferred test
respectively, approved the first MRI-conditional
modalities because of their diagnostic capabilities
pacemaker system. Since then a plethora of brady-
and their lack of radiation exposure.
cardia and tachycardia devices have been released
For years, the ability to have an MRI scan was at
under the label of MRI-conditional devices. As a
the top of the wish list of patients with cardiac
result of this revolution, whole-body MRI scans can
rhythm management (CRM) devices and their physi-
now be performed in recipients of these newer CRM
cians. Patients with long-standing back pain who
systems without any significant safety concerns for
were unable to have an MRI scan because of their
these patients. As a matter of fact, 20% of patients
CRM devices had to undergo painful myelograms to
who received a Medtronic SureScan system (Med-
obtain a diagnosis and appropriate therapy. The
tronic, Minneapolis, Minnesota) had undergone an
American Heart Association and the American College
MRI scan within the first 2 years of having the system
of Cardiology suggested as recently as 2007 that “MR
(2), and it is estimated that up to 75% of CRM device
examination of non-pacemaker dependent patients is
recipients will require a clinically indicated MRI scan
discouraged and should only be considered in cases
during their lifetime (3).
where there is a strong clinical indication and in which the benefits clearly outweigh the risk” (1). Since the late 1990s, there had been a simultaneous
Even before the evolution to MRI-conditional devices, there was a whole other effort to define the safety
limits
within
which
non–MRI-conditional
research effort by both industry and academia to
devices could be scanned. Some centers in Europe
advance knowledge about the effect of the magnetic
and the United States had started scanning these
field on implantable devices and to design devices
patients years before the first MRI-conditional system
and leads that would withstand the impact of the
was released. The Johns Hopkins database (4) and the
magnetic field and mitigate the potential harmful
more
effect on the patient. During that time, the majority of
confirmed that on exposure to 1.5-T scanners, CRM
radiologists considered the presence of CRM devices
devices made by all the different manufacturers can
to be an absolute contraindication to MRI scanning.
be safely scanned. Absolute prerequisites, however,
Finally, the unmet technological need was reached in
are appropriate evaluation of the device before the
2008 in Europe and in 2011 in the United States when
scan and careful consideration of the programmed
recently
reported
MagnaSafe
registry
(5)
mode for the scan. The exclusion criteria for these studies included the presence of abandoned leads and epicardial leads. Newer data, however, from a *Editorials published in JACC: Clinical Electrophysiology reflect the views of the author and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology. From the Pacemaker and ICD Clinic, Cardia Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts. Dr. Mela has
small but significant registry including 57 patients with 63 abandoned leads from the Mayo Clinic in Rochester, Minnesota (6), were presented at the Heart Rhythm Society Scientific Sessions in 2017 and sug-
reported receiving speaker’s honoraria from Biotronik, Medtronic, and
gested that even in the presence of abandoned leads,
St. Jude Medical.
an MRI scan can be performed safely, with no
2
Mela
JACC: CLINICAL ELECTROPHYSIOLOGY VOL.
-, NO. -, 2017 - 2017:-–-
Patients With Cardiac Rhythm Management Devices
evidence of device malfunction, arrhythmias, or
in each case. In 75% of the neurological patients and in
myocardial injury.
90% of the cardiovascular patients, the MRI scan
An integral part of the safety of the procedure is
added substantial value to the management of the
that, both for MRI-conditional and non–MRI-condi-
patient. The patient population was representative of
tional devices, significant preparation involving both
a “real-life” practice and included patients with
the radiology team and the cardiology team is
complete heart block, which had been excluded by
required before the scan. The radiology team needs to
other registries, and patients with abandoned leads or
confirm the eligibility of the device-bearing patient
recently implanted leads (less than 6 weeks from
for an MRI scan by searching the device data and
implant) when the indication for the study was very
obtaining a chest radiograph to confirm the lack of
strong. There were no negative sequelae of these MRI
abandoned or epicardial leads. Subsequently, the
scans; however, Samar et al. (7) emphasize the sig-
device needs to be interrogated, the implantable
nificance of having these studies performed by expert
cardioverter-defibrillator needs to have the therapies
personnel and under the supervision of an expert
turned off, and the pacing must be programmed
member of the cardiology team.
according to the patient’s underlying conduction
The finding that these studies occurred at a time
disease. Therefore, a technician needs to be readily
when scant data on the safety of performing MRI
available for the device to be programmed and
scans in patients with non–MRI-conditional devices
reprogrammed before and after the MRI scan. For
existed suggests that these patients had very strong
non–MRI-conditional devices, a cardiologist or a
indications for MRI and a high pre-test probability of
cardiology nurse must be present to supervise the
benefiting from the scan. Therefore, the majority
patient during the scan. After the scan, the device
of the tests had a high diagnostic yield. As the use of
needs to be interrogated again and programmed back
MRI in such patients is constantly expanding, this
to its original mode.
strategy should continue to be applicable because the
All this effort raises a number of questions: Is it
risk for a serious complication from an MRI scan of a
really necessary for the patient to have an MRI scan?
non–MRI-conditional device is not negligible (8). This
Are we exaggerating in our quest for MRI-safe device
is especially true given that groups of patients who
technology or safe MRI protocols so that we can scan
have not been studied extensively before (pace-
patients with non–MRI-conditional devices? Is the
maker-dependent patients were mostly excluded
extra effort rewarded? Are these studies even covered
from previous registries, and patients with aban-
by the patient’s insurance? Should these patients
doned or epicardial leads have been studied in only
have alternative tests, as in previous decades?
very small numbers) are involved.
The paper by Samar et al. (7) in this issue of JACC:
Although the ability to perform MRI has benefited
Clinical Electrophysiology answers some of these
patients with challenging neurological and cardio-
questions as it examines the clinical significance of
vascular conditions who have non–MRI-conditional
MRI for patients with non–MRI-conditional CRM
devices, limitations still exist. Published studies have
devices when there is either no alternative test or
used only 1.5-T MRI. The risk of 3-T MRI, which offers
there is clinical uncertainty after other diagnostic
much a better quality of imaging, for these devices is
tests have been performed.
likely higher, and this technique is therefore avoided.
The 136 patients in this study had already under-
Image quality may also be a limitation. The study by
gone other diagnostic studies (computed tomography
Samar et al. (7) reported that in 2 patients whose
imaging or myelography for neurological or orthope-
implantable cardioverter-defibrillator was inside the
dic cases, transthoracic echocardiography, trans-
thoracic field of view, the device caused severe image
esophageal echocardiography, nuclear examination,
distortion and field degradation. In addition, the
or computed tomography angiography for cardiac
quality of the image may be distorted by the presence
cases), and either the diagnosis had remained unre-
of the leads in the heart and the proximity of the
solved or the patients could not tolerate studies such
device. In 1 patient only partial data were obtained,
as myelography. The scans took place between 2005
and in another patient the data were uninterpretable
and 2015, but mostly after 2009. The MRI protocol
for viability. There is increasing expertise, however,
was similar to that followed by the MagnaSafe regis-
in improving image quality, and this limitation is
try and involved only 1.5-T scans.
becoming much less relevant (9). Finally, at this time,
MRI of the brain or the spinal cord was performed in
the Centers for Medicare and Medicaid Services are
73% of patients, and a cardiovascular examination was
not reimbursing providers for MRI studies performed
performed in 22% of these patients, thus suggesting
in patients with non–MRI-conditional devices, except
that a serious indication for the MRI study was present
under a research protocol (10).
JACC: CLINICAL ELECTROPHYSIOLOGY VOL.
-, NO. -, 2017
Mela
- 2017:-–-
Today,
Patients With Cardiac Rhythm Management Devices
MRI-
The CRM device wish list has become shorter over
conditional CRM devices. The use of these devices is
the past 10 years, but the future seems to be even
financial
more exciting. The newly released leadless pace-
gradually
all
the
manufacturers
expanding,
despite
produce
certain
considerations. It is evident that the financial burden
maker
of performing multiple diagnostic tests that are infe-
subcutaneous implantable cardioverter-defibrillator.
rior to MRI and the effort and expertise necessary to
Future expectations include that MRI-conditional
perform MRI examinations in non–MRI-conditional
technology should have no price difference and
devices exceed the financial concerns about the use
that complete automatization of the MRI process will
of MRI-conditional technology.
exist so that the intervention by the cardiologist is
is
already
MRI
conditional,
as
is
the
The future therefore appears to trend toward the
not required. The cardiologist will continue to
increased use of MRI-conditional technology. The next
supervise non–MRI-conditional devices closely to
step will include automatization of these devices so
offer patients the safest way to undergo valuable
that when they are exposed to a magnetic field, they
MRI scans.
will be reprogrammed automatically to an MRI mode. A newly released feature by Biotronik (Lake Oswego,
ADDRESS FOR CORRESPONDENCE: Dr. Theofanie
Oregon) enables the device to be programmed to
Mela, Pacemaker and ICD Clinic, Cardiac Arrhythmia
an MRI mode 2 weeks before a scheduled MRI scan so
Service, Massachusetts General Hospital, 75 Fruit
that the device will automatically convert to the pre-
Street, Boston, Massachusetts 02114. E-mail: tmela@
selected mode once it enters the magnetic field.
mgh.harvard.edu.
REFERENCES 1. Levine GN, Gomes AS, Arai AE, et al. Safety of magnetic resonance imaging in patients with cardiovascular devices: an American Heart Association scientific statement from the Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology, and the Council on Cardiovascular Radiology and Intervention: endorsed by the American College of Cardiology Foundation, the North American Society for Cardiac Imaging, and the Society for Cardiovascular Magnetic Resonance. Circulation 2007;116:2878–91. 2. Ramza B, Zhong Y, Pouliot E, Compton SJ. Are there cumulative effects of multiple MRI on MRIconditional pacemakers? Poster PO06-24. Presented at: Heart Rhythm Society Scientific
4. Nazarian S, Hansford R, Roguin A, et al. A prospective evaluation of a protocol for magnetic resonance imaging of patients with implanted cardiac devices. Ann Intern Med 2011;155: 415–24. 5. Russo RJ, Costa HS, Silva PD, et al. Assessing the risks associated with MRI in patients with a pacemaker or defibrillator. N Engl J Med 2017;376: 755–64. 6. Padmanabhan D, Kella DK, Mehta R, et al. Safety of magnetic resonance imaging in patients with legacy pacemakers and defibrillators and
Sessions; May 7–10 2014; San Francisco, California.
abandoned leads. Abstract C-PO01-27. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 10–13, 2017; Chicago.
3. Taruya A, Tanaka A, Nishiguchi T, et al. Necessity of magnetic resonance imaging examinations after permanent pacemaker implantation. Int J Cardiol 2015;184:497–8.
7. Samar H, Yamrozik JA, Williams RB, et al. Diagnostic value of MRI in patients with implanted pacemakers and ICDs across a cross population. J Am Coll Cardiol EP 2017;3:xxx–x.
8. Higgins JV, Sheldon SH, Watson RE, et al. “Power-on resets” in cardiac implantable electronic devices during magnetic resonance imaging. Heart Rhythm 2015;12:540–4. 9. Stevens SM, Tung R, Rashid S, et al. Device artifact reduction for magnetic resonance imaging of patients with implantable cardioverterdefibrillators and ventricular tachycardia: late gadolinium enhancement correlation with electroanatomic mapping. Heart Rhythm 2014;11:289–98. 10. Bailey WM, Rosenthal L, Fananapazir L, et al. Clinical safety of the ProMRI pacemaker system in patients subjected to head and lower lumbar 1.5-T magnetic resonance imaging scanning conditions. Heart Rhythm 2015;12:1183–91.
KEY WORDS implantable cardioverterdefibrillator, magnetic resonance imaging, pacemakers
3
VOL.
ª 2017 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
-, NO. -, 2017
ISSN 2405-500X/$36.00
PUBLISHED BY ELSEVIER
http://dx.doi.org/10.1016/j.jacep.2017.06.013
EDITORIAL COMMENT
Patients With Cardiac Rhythm Management Devices How True Is the Need for Magnetic Resonance Imaging?* Theofanie Mela, MD
I
maging has become the cornerstone of everyday
the Conformité Européenne in Europe and the Food
diagnostics. Magnetic resonance imaging (MRI)
and Drug Administration in the United States,
and its many applications are the preferred test
respectively, approved the first MRI-conditional
modalities because of their diagnostic capabilities
pacemaker system. Since then a plethora of brady-
and their lack of radiation exposure.
cardia and tachycardia devices have been released
For years, the ability to have an MRI scan was at
under the label of MRI-conditional devices. As a
the top of the wish list of patients with cardiac
result of this revolution, whole-body MRI scans can
rhythm management (CRM) devices and their physi-
now be performed in recipients of these newer CRM
cians. Patients with long-standing back pain who
systems without any significant safety concerns for
were unable to have an MRI scan because of their
these patients. As a matter of fact, 20% of patients
CRM devices had to undergo painful myelograms to
who received a Medtronic SureScan system (Med-
obtain a diagnosis and appropriate therapy. The
tronic, Minneapolis, Minnesota) had undergone an
American Heart Association and the American College
MRI scan within the first 2 years of having the system
of Cardiology suggested as recently as 2007 that “MR
(2), and it is estimated that up to 75% of CRM device
examination of non-pacemaker dependent patients is
recipients will require a clinically indicated MRI scan
discouraged and should only be considered in cases
during their lifetime (3).
where there is a strong clinical indication and in which the benefits clearly outweigh the risk” (1). Since the late 1990s, there had been a simultaneous
Even before the evolution to MRI-conditional devices, there was a whole other effort to define the safety
limits
within
which
non–MRI-conditional
research effort by both industry and academia to
devices could be scanned. Some centers in Europe
advance knowledge about the effect of the magnetic
and the United States had started scanning these
field on implantable devices and to design devices
patients years before the first MRI-conditional system
and leads that would withstand the impact of the
was released. The Johns Hopkins database (4) and the
magnetic field and mitigate the potential harmful
more
effect on the patient. During that time, the majority of
confirmed that on exposure to 1.5-T scanners, CRM
radiologists considered the presence of CRM devices
devices made by all the different manufacturers can
to be an absolute contraindication to MRI scanning.
be safely scanned. Absolute prerequisites, however,
Finally, the unmet technological need was reached in
are appropriate evaluation of the device before the
2008 in Europe and in 2011 in the United States when
scan and careful consideration of the programmed
recently
reported
MagnaSafe
registry
(5)
mode for the scan. The exclusion criteria for these studies included the presence of abandoned leads and epicardial leads. Newer data, however, from a *Editorials published in JACC: Clinical Electrophysiology reflect the views of the author and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology. From the Pacemaker and ICD Clinic, Cardia Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts. Dr. Mela has
small but significant registry including 57 patients with 63 abandoned leads from the Mayo Clinic in Rochester, Minnesota (6), were presented at the Heart Rhythm Society Scientific Sessions in 2017 and sug-
reported receiving speaker’s honoraria from Biotronik, Medtronic, and
gested that even in the presence of abandoned leads,
St. Jude Medical.
an MRI scan can be performed safely, with no
2
Mela
JACC: CLINICAL ELECTROPHYSIOLOGY VOL.
-, NO. -, 2017 - 2017:-–-
Patients With Cardiac Rhythm Management Devices
evidence of device malfunction, arrhythmias, or
in each case. In 75% of the neurological patients and in
myocardial injury.
90% of the cardiovascular patients, the MRI scan
An integral part of the safety of the procedure is
added substantial value to the management of the
that, both for MRI-conditional and non–MRI-condi-
patient. The patient population was representative of
tional devices, significant preparation involving both
a “real-life” practice and included patients with
the radiology team and the cardiology team is
complete heart block, which had been excluded by
required before the scan. The radiology team needs to
other registries, and patients with abandoned leads or
confirm the eligibility of the device-bearing patient
recently implanted leads (less than 6 weeks from
for an MRI scan by searching the device data and
implant) when the indication for the study was very
obtaining a chest radiograph to confirm the lack of
strong. There were no negative sequelae of these MRI
abandoned or epicardial leads. Subsequently, the
scans; however, Samar et al. (7) emphasize the sig-
device needs to be interrogated, the implantable
nificance of having these studies performed by expert
cardioverter-defibrillator needs to have the therapies
personnel and under the supervision of an expert
turned off, and the pacing must be programmed
member of the cardiology team.
according to the patient’s underlying conduction
The finding that these studies occurred at a time
disease. Therefore, a technician needs to be readily
when scant data on the safety of performing MRI
available for the device to be programmed and
scans in patients with non–MRI-conditional devices
reprogrammed before and after the MRI scan. For
existed suggests that these patients had very strong
non–MRI-conditional devices, a cardiologist or a
indications for MRI and a high pre-test probability of
cardiology nurse must be present to supervise the
benefiting from the scan. Therefore, the majority
patient during the scan. After the scan, the device
of the tests had a high diagnostic yield. As the use of
needs to be interrogated again and programmed back
MRI in such patients is constantly expanding, this
to its original mode.
strategy should continue to be applicable because the
All this effort raises a number of questions: Is it
risk for a serious complication from an MRI scan of a
really necessary for the patient to have an MRI scan?
non–MRI-conditional device is not negligible (8). This
Are we exaggerating in our quest for MRI-safe device
is especially true given that groups of patients who
technology or safe MRI protocols so that we can scan
have not been studied extensively before (pace-
patients with non–MRI-conditional devices? Is the
maker-dependent patients were mostly excluded
extra effort rewarded? Are these studies even covered
from previous registries, and patients with aban-
by the patient’s insurance? Should these patients
doned or epicardial leads have been studied in only
have alternative tests, as in previous decades?
very small numbers) are involved.
The paper by Samar et al. (7) in this issue of JACC:
Although the ability to perform MRI has benefited
Clinical Electrophysiology answers some of these
patients with challenging neurological and cardio-
questions as it examines the clinical significance of
vascular conditions who have non–MRI-conditional
MRI for patients with non–MRI-conditional CRM
devices, limitations still exist. Published studies have
devices when there is either no alternative test or
used only 1.5-T MRI. The risk of 3-T MRI, which offers
there is clinical uncertainty after other diagnostic
much a better quality of imaging, for these devices is
tests have been performed.
likely higher, and this technique is therefore avoided.
The 136 patients in this study had already under-
Image quality may also be a limitation. The study by
gone other diagnostic studies (computed tomography
Samar et al. (7) reported that in 2 patients whose
imaging or myelography for neurological or orthope-
implantable cardioverter-defibrillator was inside the
dic cases, transthoracic echocardiography, trans-
thoracic field of view, the device caused severe image
esophageal echocardiography, nuclear examination,
distortion and field degradation. In addition, the
or computed tomography angiography for cardiac
quality of the image may be distorted by the presence
cases), and either the diagnosis had remained unre-
of the leads in the heart and the proximity of the
solved or the patients could not tolerate studies such
device. In 1 patient only partial data were obtained,
as myelography. The scans took place between 2005
and in another patient the data were uninterpretable
and 2015, but mostly after 2009. The MRI protocol
for viability. There is increasing expertise, however,
was similar to that followed by the MagnaSafe regis-
in improving image quality, and this limitation is
try and involved only 1.5-T scans.
becoming much less relevant (9). Finally, at this time,
MRI of the brain or the spinal cord was performed in
the Centers for Medicare and Medicaid Services are
73% of patients, and a cardiovascular examination was
not reimbursing providers for MRI studies performed
performed in 22% of these patients, thus suggesting
in patients with non–MRI-conditional devices, except
that a serious indication for the MRI study was present
under a research protocol (10).
JACC: CLINICAL ELECTROPHYSIOLOGY VOL.
-, NO. -, 2017
Mela
- 2017:-–-
Today,
Patients With Cardiac Rhythm Management Devices
MRI-
The CRM device wish list has become shorter over
conditional CRM devices. The use of these devices is
the past 10 years, but the future seems to be even
financial
more exciting. The newly released leadless pace-
gradually
all
the
manufacturers
expanding,
despite
produce
certain
considerations. It is evident that the financial burden
maker
of performing multiple diagnostic tests that are infe-
subcutaneous implantable cardioverter-defibrillator.
rior to MRI and the effort and expertise necessary to
Future expectations include that MRI-conditional
perform MRI examinations in non–MRI-conditional
technology should have no price difference and
devices exceed the financial concerns about the use
that complete automatization of the MRI process will
of MRI-conditional technology.
exist so that the intervention by the cardiologist is
is
already
MRI
conditional,
as
is
the
The future therefore appears to trend toward the
not required. The cardiologist will continue to
increased use of MRI-conditional technology. The next
supervise non–MRI-conditional devices closely to
step will include automatization of these devices so
offer patients the safest way to undergo valuable
that when they are exposed to a magnetic field, they
MRI scans.
will be reprogrammed automatically to an MRI mode. A newly released feature by Biotronik (Lake Oswego,
ADDRESS FOR CORRESPONDENCE: Dr. Theofanie
Oregon) enables the device to be programmed to
Mela, Pacemaker and ICD Clinic, Cardiac Arrhythmia
an MRI mode 2 weeks before a scheduled MRI scan so
Service, Massachusetts General Hospital, 75 Fruit
that the device will automatically convert to the pre-
Street, Boston, Massachusetts 02114. E-mail: tmela@
selected mode once it enters the magnetic field.
mgh.harvard.edu.
REFERENCES 1. Levine GN, Gomes AS, Arai AE, et al. Safety of magnetic resonance imaging in patients with cardiovascular devices: an American Heart Association scientific statement from the Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology, and the Council on Cardiovascular Radiology and Intervention: endorsed by the American College of Cardiology Foundation, the North American Society for Cardiac Imaging, and the Society for Cardiovascular Magnetic Resonance. Circulation 2007;116:2878–91. 2. Ramza B, Zhong Y, Pouliot E, Compton SJ. Are there cumulative effects of multiple MRI on MRIconditional pacemakers? Poster PO06-24. Presented at: Heart Rhythm Society Scientific
4. Nazarian S, Hansford R, Roguin A, et al. A prospective evaluation of a protocol for magnetic resonance imaging of patients with implanted cardiac devices. Ann Intern Med 2011;155: 415–24. 5. Russo RJ, Costa HS, Silva PD, et al. Assessing the risks associated with MRI in patients with a pacemaker or defibrillator. N Engl J Med 2017;376: 755–64. 6. Padmanabhan D, Kella DK, Mehta R, et al. Safety of magnetic resonance imaging in patients with legacy pacemakers and defibrillators and
Sessions; May 7–10 2014; San Francisco, California.
abandoned leads. Abstract C-PO01-27. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 10–13, 2017; Chicago.
3. Taruya A, Tanaka A, Nishiguchi T, et al. Necessity of magnetic resonance imaging examinations after permanent pacemaker implantation. Int J Cardiol 2015;184:497–8.
7. Samar H, Yamrozik JA, Williams RB, et al. Diagnostic value of MRI in patients with implanted pacemakers and ICDs across a cross population. J Am Coll Cardiol EP 2017;3:xxx–x.
8. Higgins JV, Sheldon SH, Watson RE, et al. “Power-on resets” in cardiac implantable electronic devices during magnetic resonance imaging. Heart Rhythm 2015;12:540–4. 9. Stevens SM, Tung R, Rashid S, et al. Device artifact reduction for magnetic resonance imaging of patients with implantable cardioverterdefibrillators and ventricular tachycardia: late gadolinium enhancement correlation with electroanatomic mapping. Heart Rhythm 2014;11:289–98. 10. Bailey WM, Rosenthal L, Fananapazir L, et al. Clinical safety of the ProMRI pacemaker system in patients subjected to head and lower lumbar 1.5-T magnetic resonance imaging scanning conditions. Heart Rhythm 2015;12:1183–91.
KEY WORDS implantable cardioverterdefibrillator, magnetic resonance imaging, pacemakers
3