MR Safety and the Reveal Plus Insertable Loop Recorder

The 9526 Reveal Plus Insertable Loop Recorder (ILR, Medtronic, Minneapolis) is an implantable single-use programmable device containing two surface electrodes for continuous recording of the patient's subcutaneous electrocardiogram.

This device is indicated for patients who experience transient symptoms that may suggest a cardiac arrhythmia and for patients with clinical syndromes or situations that put them at increased risk of cardiac arrhythmias. Implanting the ILR takes about 15 to 20 minutes and can be done under local anesthetic in an outpatient setting. The physician makes an incision about 2 cm in length, creating a pocket the same size and shape as the ILR device. Once the device is inserted in the subcutaneous pocket, it is programmed to record the ECG. Because the ILR is capable of recording an ECG during an actual fainting episode, physicians are able to confirm or rule out an abnormal heart rhythm more definitively. Since this device may be used continuously for up to 14 months, the likelihood of capturing heart rhythm information during an infrequent fainting episode is excellent.

MR Safety and the Reveal Plus Insertable Loop Recorder

The Reveal Plus ILR contains no lead wires or large loops of electrically conductive material. The electromagnetic fields produced during MR imaging may adversely affect the data stored by the ILR, however. Before permitting a patient with this device into the MR environment, consideration must be given to interrogating the ILR in order to save the data that could become corrupted or erased as a result of undergoing an MR imaging procedure. Careful planning in conjunction with the physician responsible for the patient's ILR is necessary.

Also, since the ILR contains ferromagnetic components, strong magnetic fields associated with the MR system will exhibit mechanical force on the ILR. The patient may feel slight movement of the ILR. While this does not represent a safety hazard, the patient must be informed of this possibility to avoid undue concern. Additional MRI-related information may be found in the "Reveal Plus 9526 Insertable Loop Recorder System Product Information Manual":

• For information on how to interrogate and save data prior to MRI procedures, see "How to interrogate the ILR" and "How to save to disk," both in chapter 3.
• For resetting collection data/parameters following MRI procedures, see "Clearing memory without changing gain and sensitivity settings" in chapter 2.
• For testing patient-triggered storage integrity following MRI procedures, see "Storing an event in a clinical setting" in chapter 2.

Information provided with permission, Medtronic, Minneapolis, http://www.medtronic.com/reveal/rpmri.html. Dr. Shellock is an adjunct clinical professor of radiology at Keck School of Medicine, University of Southern California, and Institute for Magnetic Resonance Safety, Education, and Research.

References

Krahn A, Klein G, Yee R, Norris C. Final results from a pilot study with an implantable loop recorder to determine the etiology of syncope in patients with negative non-invasive and invasive testing. Am J Cardiol 1998;82:117-119. Reveal Syncope Validation Project (RSVP) Clinical Summary. Medtronic data on file. Shellock FG, Tkach JA, Ruggieri PM, Masaryk TJ. Cardiac pacemakers, ICDs, and loop recorder: evaluation of translational attraction using conventional ("long-bore") and "short-bore" MR systems at 1.5- and 3-Tesla. J Cardiovasc Magn Reson 2003;5:387-397.