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Jennifer Cohen, MD, Heather Costa, PhD, Robert Russo, MD, PhD, Division of Cardiovascular
Diseases, Scripps Clinic, La Jolla, CA
The MagnaSafe Registry:
Pacemaker and Implantable Cardioverter
Defibrillator Safety for Patients Undergoing Magnetic Resonance
Imaging
Background• The number of patients with
permanent pacemakers or implantable cardioverter-defibrillators (ICD) in the U.S. is increasing dramatically.
0
50,000
100,000
150,000
200,000
250,000
300,000
Pacemaker
AICD
0
50,000
100,000
150,000
200,000
250,000
300,000
Pacemaker
AICD
National estimates of cardiac device implantation
National estimates of cardiac device implantation
• Between 1990 and 2005, an estimated 2.8 million pacemakers and 690,000 ICDs were implanted*.*Zhan, et al, 2008 J Gen Int Med 23 Supp 1:13
• MRI is the diagnostic modality of choice without acceptable alternative for many disease states.
• At Scripps Green Hospital: 8,000 MRI’s performed per year.
• In the Scripps Health System: 18,000 MRI’s performed in 2007.
• There is a 50-75% estimated probability that a patient with a PM or ICD will need an MRI.
Background
MRI Safety Studies• Small number of published studies at
1.5T with a total of approximately 350 patients.
• Varying effects including impedance changes, battery depletion and an increase in pacing thresholds.
• No serious adverse events have been reported.
• No comparison to a control group.
The MagnaSafe Registry
•Data used to design the prospective, multi-center MagnaSafe Registry.
•Establish expected event rates.
•Sample size calculations.
•Design the interrogation protocol.
A retrospective, single site experience
The MagnaSafe Registry• Prospective, multi-center registry to begin
enrollment in April 2009.
• Expected enrollment:
•1000 patients with permanent pacemakers
•500 patients with ICDs
• Clinically-indicated, non-research, non-thoracic MRI deemed medically necessary by the ordering physician.
• Performed under a conditional IDE with the guidance of the FDA .
The MagnaSafe Registry• Prospectively document the incidence of
adverse events or changes in device parameters associated with undergoing an MRI.
• Will provide physicians the risk-assessment data needed to discuss the use of MRI with their patients as a diagnostic tool when no alternative test is available.
• Ultimately, the goal is to amend the guidelines for performing MRI in patients with implanted cardiac devices.
Hypothesis
•Magnetic resonance imaging at 1.5T can be performed safely in selected patients with permanent pacemakers and implantable cardioverter-defibrillators using an optimized device programming protocol and screening process.
Methods• Patients presented for a MRI that was deemed
medically necessary by the ordering physician without acceptable alternative examination.
• Clinical informed consent was obtained by a cardiologist who was present during the scan.
• No scans were excluded.
• No SAR limits placed.
• Technicians were permitted to deviate from normal operating mode.
• Performance of a diagnostic exam was a priority.
Methods
• Device interrogation was performed before and immediately following the scan.
• Non-invasive monitoring performed.
• IRB approval was obtained for retrospective analysis of data previously obtained during clinically-indicated (non-research) MRI.
• Pacemaker-dependent patients were reprogrammed to asynchronous mode (VOO or DOO). Magnet response was disabled.
• Non-dependent patients were programmed to no pacing.
• For ICDs, tachycardia-therapy was turned off.
• Pre and post-MRI interrogations were identical:
•Measurement of intrinsic P/R waves, all lead impedances, shock lead impedances, all lead thresholds measured at a fixed pulse width.
MethodsDevice Interrogation
• A control group was studied to determine the variability of device parameters without MRI.
• 34 patients with pacemakers and ICDs underwent 2 device interrogations 1 hour apart to determine variation (without MRI).
• Recruitment for the Control Group is ongoing.
MethodsControl Group
• Decrease in battery voltage ≥ 0.04 V
• Change in lead impedance:
•Change in pacing lead impedance by ≥ 50 Ω
•Change in shock lead impedance by ≥ 3 Ω
• Change in lead threshold
•Increase in lead threshold ≥ 0.50 V at 0.4 ms
• Change in P/R wave amplitude
•Decrease in P wave amplitude ≥ 50%
•Decrease in R wave amplitude ≥ 25%
• Loss of capture during scan, induced arrhythmia, device failure requiring generator or lead replacement
MethodsPrimary Outcomes
• 125 generators and 255 leads.
• 157 clinically-indicated 1.5T MRI scans between Jan 2006 and March 2009.
• Length of MRI scan 48.9±20.67 minutes.
• One patient had a pacemaker and an ICD in place.
ResultsClinical Experience
ResultsBaseline Characteristics
ControlMRI
PatientsGender 68% Male 76% Male
Age 77 +/- 10 years 76 +/- 12 years
Number of generators 34 125
Number of leads 68 177
Average time between implant and interrogation
2.3 +/- 2.4 years (range 1- 3251 days)
2.6 +/- 2.1 years (range 4-3886 days)
Atrial leads 28 113
RV/LV leads 34/6 124/18
Pacer Dependent 12% 22%
Pacemakers/ICDs 41%/59% 67%/33%
ResultsTypes of Devices
4%
17%
3%
13% 2%
61%
Dual chamberpacemaker
Single chamberpacemaker
Dual chamber ICD
Single chamberICD
Bi-ventricular ICD
Bi-ventricularpacemaker
Results
Scans from Retrospective Data
8%
4%
7%
3%
2%
3%
31%
42%
Brain
Spine
Joint
Cardiac
Abdomen/Pelvis
Orbit
Neck
Other
Predicted Breakdown of Scans for MagnaSafe
8%
8%3% 4%
37%
40%
Brain MRI/MRA
Spine
Joint
Abdomen/Pelvis
Orbit
Other MRI
Results
• No arrhythmias: atrial or ventricular• No loss of capture• No electrical reset-to-on• No generator or lead replacements• No syncope• No deaths• All scans were performed except for
one due to severe claustrophobia
Control
(%)MRI Patients
(%) pBattery Voltage Decrease > 0.04 V 0 (0/34) 4.2(4/96) 0.57
All Pacing Lead Impedance Change > 50 ohms 3.2 (2/63) 5.8 (12/207) 0.53
Shock Lead Impedance Change > 3 ohms
15.8 (3/19) 30.4 (7/23) 0.31
P Wave Decrease > 50% 0 (0/23) 1.5 (1/65) 1.0
R Wave Decrease > 25% 3.3 (1/30) 2.7 (2/75) 0.48
ResultsDevice Parameter
Changes
Control
(%) MRI (%)
Atrial Lead Threshold Increase > 0.5 mV 0.0 (0/23) 1.2 (1/87)
RV Lead Threshold Increase > 0.5 mV 0.0 (0/33) 4.1 (4/97)
LV Lead Threshold Increase > 0.5 mV 16.7 (1/6) 14.3 (2/14)
All Leads Threshold Increase > 0.5 mV 1.6 (1/62) 3.5 (7/198)
ResultsDevice Parameter
Changes
02468
101214161820
All Patients Dependent NotDependent
% MRI Patients
Controls
ResultsDependency
3.6% 0%
p=1.03.0
%
4.7%
5.2% 3.4
%
p=0.43
0
2
4
6
8
10
12
14
16
18
20
All Patients ICD Pacemaker
% MRI Patients
Controls
ResultsICD versus Pacemaker
5.0% 2.6
%
p=0.3
3.0%
4.7%
4.5% 3.9
%
p=1.0
ResultsBrain Scans
0
2
4
6
8
10
12
14
16
18
20
All MRI Scans Brain Only Scans Other Scans
%
4.7% 4.7% 4.7%
p=1.0
0
2
4
6
8
10
12
14
16
18
20
0 min(Controls)
1-30 min 31-60 min 61-90 min >90 min All MRIPatients
%
ResultsLength of Scans
4.7%
6.1% 5.0
%3.8%
4.7%3.0
%
ResultsMultiple Scans
0
2
4
6
8
10
12
14
16
18
20
All MRI Patients Multiple Scans Single Scan
%
4.7% 3.2
%
5.4%
p=0.33
ResultsTime Since Implant
02468
101214161820
AllPatients
0-30 days 31-180days
>180days
% MRI Patients
Controls4.7% 3.0
%
4.8%
0% 0%
1.1%
5.4% 3.1
%
ResultsMRI Patients
0
20
40
60
80
100
120
140
160
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
Change in V at 0.4 ms
Freq
uenc
y
Leads = 19
Lead Threshold Changes
Leads = 33
Average Lead Threshold Change 0.02 ± 0.18 V
Results
Controls
0
5
10
15
20
25
30
35
40
45
50
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
Change in V at 0.4 ms
Freq
uen
cyLead Threshold Changes
Average Lead Threshold Change 0 ± 0.16 V
Leads = 8
Leads = 8
ResultsMRI Patients
0
10
20
30
40
50
60
70
80
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
Change in Battery Voltage (V)
Freq
uen
cyBattery Voltage Changes
Generators = 19
Generators = 6
Average Battery Voltage Change -0.004 ± 0.016 V
Results
Controls
0
5
10
15
20
25
30
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
Change in Battery Voltage (V)
Freq
uenc
yBattery Voltage Changes
Average Battery Voltage Change 0.00 ± 0.01 V
Generators = 5
Generators = 3
Results
MRI Patients
0
20
40
60
80
100
120
-175
-150
-125
-100 -7
5-5
0-2
5 0 25 50 75 100
125
150
175
Change in Lead Impedance (ohms)
Freq
uenc
yLead Impedance Changes
Average Lead Impedance Change -5.9 ± 25.1 Ω
Leads = 129 Leads = 54
ResultsControls
0
5
10
15
20
25
30
-175
-150
-125
-100 -7
5-5
0-2
5 0 25 50 75 100
125
150
175
Change in Lead Impedance (ohms)
Freq
uenc
yLead Impedance Changes
Average Lead Impedance Change 6.2 ± 22.5 Ω
Leads = 19 Leads = 34
Conclusions
•A very low incidence of device parameter change was noted after MRI at 1.5T.
•No patient experienced device failure or a permanent change in lead threshold.
•Based on these findings, we anticipate <5% rate of device failure, <5% rate of permanent reprogramming, <10% rate of temporary reprogramming for the prospective MagnaSafe Registry.
MagnaSafe
Research
Clinical care
Research
Clinical Care
Patient with cardiac device and MRI clinically
indicated
Patient with cardiac device and MRI clinically
indicated
Subjects enrolls in studySubjects enrolls in study
Device parameters recorded
Device parameters recorded
Magnetic resonance imaging
Magnetic resonance imaging
Parameter Change? Parameter Change?
Follow-up interrogation within 7 days
Follow-up interrogation within 7 days
Yes
Device parameters recorded
Restore or Adjust settings
Device parameters recorded
Restore or Adjust settings
No
Follow-up interrogation at 3-6
months when clinically indicated
Follow-up interrogation at 3-6
months when clinically indicated
Follow-up Interrogation at 3
months
Follow-up Interrogation at 3
months
Follow-up Interrogation at 6
months
Follow-up Interrogation at 6
months
MagnaSafeRegistry
MagnaSafeRegistry