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. 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 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 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. Methods Device 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. Methods Control 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 Methods Primary Outcomes

125 generators and 255 leads. 157 clinically-indicated 1.5T MRI scans between Jan 2006 and March Length of MRI scan 48.9±20.67 minutes. One patient had a pacemaker and an ICD in place. Results Clinical Experience

Results Baseline Characteristics ControlMRI Patients Gender68% Male76% Male Age77 +/- 10 years76 +/- 12 years Number of generators34125 Number of leads68177 Average time between implant and interrogation 2.3 +/- 2.4 years (range days) 2.6 +/- 2.1 years (range days) Atrial leads28113 RV/LV leads34/6124/18 Pacer Dependent12%22% Pacemakers/ICDs41%/59%67%/33%

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 (%) p Battery Voltage Decrease > 0.04 V0 (0/34)4.2(4/96)0.57 All Pacing Lead Impedance Change > 50 ohms3.2 (2/63)5.8 (12/207)0.53 Shock Lead Impedance Change > 3 ohms15.8 (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 Results Device Parameter Changes

Control (%) MRI (%) Atrial Lead Threshold Increase > 0.5 mV0.0 (0/23)1.2 (1/87) RV Lead Threshold Increase > 0.5 mV0.0 (0/33)4.1 (4/97) LV Lead Threshold Increase > 0.5 mV16.7 (1/6)14.3 (2/14) All Leads Threshold Increase > 0.5 mV1.6 (1/62)3.5 (7/198) Results Device Parameter Changes

Results Dependency 3.6% 0% p= % 4.7% 5.2% 3.4% p=0.43

Results ICD versus Pacemaker 5.0% 2.6% p= % 4.7% 4.5% 3.9% p=1.0

Results Brain Scans 4.7% p=1.0

Results Length of Scans 4.7% 6.1% 5.0% 3.8% 4.7% 3.0%

Results Multiple Scans 4.7% 3.2% 5.4% p=0.33

Results Time Since Implant 4.7% 3.0% 4.8% 0% 1.1% 5.4% 3.1%

Results Leads = 19 Lead Threshold Changes Leads = 33 Average Lead Threshold Change 0.02 ± 0.18 V

Results Lead Threshold Changes Average Lead Threshold Change 0 ± 0.16 V Leads = 8

Results Battery Voltage Changes Generators = 19 Generators = 6 Average Battery Voltage Change ± V

Results Battery Voltage Changes Average Battery Voltage Change 0.00 ± 0.01 V Generators = 5Generators = 3

Results Lead Impedance Changes Average Lead Impedance Change -5.9 ± 25.1 Ω Leads = 129Leads = 54

Results Lead 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 Subjects enrolls in study Device parameters recorded Magnetic resonance imaging 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 months Follow-up Interrogation at 6 months