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

Presenter Disclosure Information

•None of the authors have any disclosures.

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