Study to Monitor Patients With Pacemakers or ICDs Who Undergo MRI Scans

General Approach: This study is a prospective, non-randomized, unblinded case series of
patients with permanent pacemakers or implantable cardioverter-defibrillators (ICDs)
undergoing medically-required MRI scanning, followed for a 12 month period. MRI scanning will
be performed using accepted, standard protocols using FDA-approved equipment.

Methods and Materials: Patients will be enrolled over a 60-month period by the Principal
Investigator (PI) and/or Sub-Investigator (Sub-I), at the Regional Heart Center, located at
St. Mary's Medical Center, Essentia Health, Duluth, MN, during evaluations for
medically-required MRI scanning. Eligible patients includes any person with a permanent
pacemaker or ICD implanted for at least 6 weeks, referred for a medically-required MRI scan
by a physician not participating in the trial. ICD generators must have been market released
after 2001. Both pacemaker dependent and non-dependent patients are eligible. The primary
endpoint is any change greater than 1 V at a pulse width of 0.5 ms in a pacemaker or ICD lead
at any time within 12 months of the MRI scan.

On the day of the MRI scan, the pacemaker or ICD will be interrogated and programmed per
usual practice at Essentia Health for patients undergoing an MRI scan with device in place.
Three separate baseline capture threshold measurements (V) will be obtained at a fixed pulse
width of 0.5 msec. Three separate baseline measurements will also be made of lead pacing
impedances (Ohms) and sensed P- or R-waves (mV) using programmer default methods. Histograms
will be cleared. Leads will be programmed to bipolar modality. If the patient is not device
dependent, the device will be programmed to ODO/OVO/OAO mode (monitor only) if available,
otherwise it will be reprogrammed to DDI or VVI mode with a lower rate of 40 bpm with pacing
outputs programmed to subthreshold levels in all leads. If the participant is device
dependent, the device will be programmed to an asynchronous pacing modality (DOO/VOO) with
maximum pacing output. If the patient has an ICD, therapies will be disabled. The attending
investigator may alter the pacing modality during the course of the scan if he or she deems
it necessary to maximize patient safety or comfort. Rate responsiveness, any rate
enhancements including Ventricular Rate Regulation mode, and magnet mode will be turned off.

During MRI scanning, resuscitation equipment will be available. If the participant is
pacemaker dependent, the study PI or sub-I must be in the MRI suite during the scan. If the
participant is not pacemaker dependent, then a pacemaker nurse will be in the MRI suite to
perform pre- and post-checks, and an electrophysiologist will be available in the building
for questions and troubleshooting. Patients will be asked to report all symptoms including:
palpitations; pain; heat or warmth sensation; device movement; or light-headedness.

Scans will be performed using usual protocols with standard peak Specific Absorption Rate
(SAR) limitations for the scan. The MRI scans will be evaluated for any artifact created by
the pacemaker system. During the scan, continuous electrocardiographic and pulse oxymetry
with waveform monitoring will be performed using usual protocols. Following the scan, repeat
thresholds will be performed for each lead and histograms will be obtained. Three separate
capture threshold measurements (V) will be obtained immediately after the patient leaves the
scanner room at a fixed pulse width of 0.5 msec. Three separate measurements will also be
made immediately following the scan of the lead pacing impedances (Ohms) and sensed P- or
R-waves (mV) using programmer default methods. Participants who are pacemaker dependent will
undergo a one-hour post-scan check using the same threshold protocol. These one-hour post
scan measurements will be performed either in the pacemaker clinic if the patient is an
outpatient or in the hospital if the patient is an inpatient. Any stored events detected on
the device as electromagnetic interference (EMI) artifact during the scan may be retrieved
and stored to diskette for later analysis. The pacemaker or ICD will be reprogrammed to
original settings prior to discharge from the MRI suite unless the attending investigator
deems it necessary to alter device setting to maximize patient safety or comfort. If the
patient has an ICD, the capacitor will be reformed and charge time noted prior to dismissal
from the MRI suite.

Patients will be followed up in the pacemaker clinic at 3 and 12 months from the MRI scan
using usual clinic protocols for device follow-up. If a patient undergoes a second MRI scan,
the follow-up schedule will be set based upon the most recent MRI scan.

Inclusion Criteria:

1. Permanent Pacemaker or ICD implanted for at least 6 weeks

2. Referred for medically-required MRI scan

3. Age greater than or equal to 18 years

Exclusion Criteria:

1. ICD market released before 2001 including GDT Ventak-AV, GDT MINI-II, GDT MINI-IV, GDT
MINI-III, GDT Prizm, GDT Prizm-2 and MDT GEM-I series

2. Epicardial lead or subcutaneous array

3. Device has reached elective replacement indicator (ERI) or end of life (EOL)

4. Other usual contraindications to MRI scanning

5. Known or suspected lead fracture or abandoned lead

6. Pacemaker dependent patients with an ICD that cannot be programmed to asynchronous
pacing (DOO/VOO)

7. Clinical factors that are deemed by the PI or Sub-I to increase the participant's risk
above an acceptable clinical threshold