Pacemakers, ICDs, Pacing Wires and Loop Recorders

  • Pacemakers/ICDs can be imaged 6 weeks after placement. All studies must be performed at 1.5T (see details below).
  • Temporary epicardial pacing leads can be imaged if cut at the skin.
  • Temporary external transvenous pacing leads are an absolute contraindication to MRI. The same is true for abandoned intracardiac pacing leads.
  • Cardiac Loop Recorders are MRI conditional devices. See below for details.

Pacemakers/ICDs

Cardiac pacemakers and implantable cardioverter-defibrillator (ICDs) were once considered absolute contraindications for MRI due to the following potential issues:

  1. Movement and/or vibration of the pulse generator or leads
  2. Temporary or permanent modification of the function (i.e., damage) of the device
  3. Inappropriate sensing, triggering, or activation of the device
  4. Excessive heating or induced current in leads
  5. Electromagnetic interference

These problems were linked to pacemaker models produced before 1996. Several pilot studies, however, have shown that limited MRI of patients with nondependent pacemakers in a controlled and monitored environment can be performed safely if strict guidelines are followed. Because of these studies and the approval of several MRI conditional systems, pacemakers are now considered a relative contraindication. Note that guidelines from the American Heart Association (AHA) and the Food and Drug Administration (FDA) do not support MRI in pacemaker patients who do not have MRI conditional/approved systems. The following are MRI Conditional Devices:

Medtronic (pacemakers and ICDs):
  • CRT-Ds — Amplia MRI CRT-D SureScan Model DTMB1D4; Amplia MRI Quad CRT-D SureScan Model DTMB1QQ; and Compia MRI Quad CRT-D SureScan Model DTMC1QQ
  • ICDs — Evera MRI™ XT DR SureScan Model DDMB1D4; Evera MRI S SureScan Model DDMC3D4; and Evera MRI XT VR SureScan Model DVMB1D4
  • Pacemakers — Advisa DR MRI™ SureScan Model A2DR01; Advisa SR MRI™ SureScan Model A3SR01; and Revo MRI™ SureScan RVDR01 IPGs
Boston Scientific: ACCOLADE MRI Pacemaker, X4 MRI CRT-D Biventricular Pacemaker.
Biotronik: ProMRI cardiac pacemaker systems, resynchronization systems (CRTs) and implantable cardioverter defibrillator systems (ICDs).
St Jude Medical: Accent MRI Pacemaker. Specifically, models PM1224, PM2224, PM1226, PM2226, PM1124 PM2124
 

Specific guidelines for patients with pacemakers/ICDs

  • The pacemaker/ICD must be in place for more than 6 weeks. The patient must be not at or near Elective Replacement Indicator (ERI).
  • The patient should be alert and responsive. If MRI is requested in an unresponsive patient, 1) attending to attending confirmation of the need for MRI, and not alternative imaging modalities, must be confirmed; and 2) informed consent is required.
  • Patients should be scanned during normal workday hours (8am to 5pm) on 1.5T scanners in the hospital setting. 3T will only be considered for appropriate MRI conditional devices at Parnassus.
  • Expedited approval is possible if 1) an MRI conditional device listed in the previous section is documented; and 2) an established, modified MRI scan protocol appropriate for pacers/ICDs will be used. To facilitate this, the specific device in question and MRI scan protocol should be clearly stated in the MRI requisition. Note that established scan protocols are in place for:
    • Brain
    • Cardiac
    • Abdomen
    • Knee
    • Spine following the manufacturer's guidelines regarding MRI protocol restrictions.
  • The workflow for MRI conditional pacers/ICDs is as follows:
  1. Prior to scheduling, the MRI conditional device should be confirmed (see list in previous section), as should the non-pacemaker dependent status (this should be noted in pacemaker reports).
  2. An electrophysiology (EP) physician, nurse or a manufacturer representative will reprogram the pacer/ICD to the appropriate setting before and after the MRI. This will be done at the MRI scanner. Device interrogators for the four major manufacturers will be stored in the MRI suite.
  3. Monitoring during the MRI scan will be performed by a Radiology nurse. Monitoring will entail pulse oximetry and heart rate, as well as continuous visual and voice contact with the patient.
  4. If any issue arises (i.e., pain, discomfort, significant change in heart rate), the patient will be removed from the MRI scanner and the EP consult fellow will be called at 443-UCEP. If the patient is unresponsive or unstable, a code will be called. An external defibrillator should be easily accessible.
  • If there is not an MRI conditional device, the workflow will be modified as follows:
  1. Approval is needed both from the attending radiologist and electrophysiologist. Risk-benefit analysis should clearly show the benefits of MRI. The study should not be performed if similar clinical information could be obtained with another image modality. Indications for which MRI will be considered without an MRI conditional device include: Brain, Cardiac, or Other indications where the risk-benefit analysis is compelling.
  2. An appointment with the EP clinic should be schedule prior to the MRI date to review the details of the pacer/ICD and leads, and confirm that MRI is appropriate. EP should document in their notes regarding the encounter that a full discussion of risks and benefits of MRI was performed with the patient.
  3. On the day of the exam, an EP physician or nurse will reprogram the pacer/ICD to the appropriate setting before and after the MRI.
  4. Patient must consent to undergoing the MRI.
  5. Monitoring during the MRI scan will be performed by a Radiology nurse. Monitoring will entail pulse oximetry and heart rate, as well as continuous visual and voice contact with the patient.
  6. If any issue arises (i.e., pain, discomfort, significant change in heart rate), the patient will be removed from the MRI scanner and the EP consult fellow will be called at 443-UCEP. If the patient is unresponsive or unstable, a code will be called. An external defibrillator should be easily accessible.
  • Note that the presence of a coronary sinus lead is no longer a contraindication in patients with approved CRT-D devices (listed above).
  • Thoracic MRI presents additional risk that should be considered. Multiple MRI exams should also be avoided, when possible.
  • Appropriate personnel, a crash cart, and defibrillator must be available throughout the procedure to address an adverse event. Visual and voice contact with the patient should be maintained throughout the study. The patient should report any unusual sensations or problems so that, if necessary, the study can be terminated.
  • Appointments will be coordinated to ensure that an MRI physicist and an attending radiologist are involved to tailor the study for minimum SAR while obtaining the essential clinical information.

Cardiac Loop Recorders

Cardiac Loop Recorders typically contain no lead wires or large loops of electrically conductive material. Product details regarding the specific loop recorder in question should be reviewed prior to MRI. The Medtronic Reveal LINQ and Plus 9528 and 9529 Insertable Loop Recorders (ILR) have been deemed MRI conditional 5 (i.e., acceptable if specific guidelines/recommendations are followed) at both 1.5 and 3T.

The main issue to consider with MRI is that data stored on the device may be altered or erased. Data should be downloaded before the time of study, and this issue should be discussed with the cardiologist who manages the loop recorder.

Because loop recorders contain ferromagnetic components, patients may feel slight movement during scanning. While not a safety hazard, patients should be made aware of this before scanning.

 

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