CEID, Pacemakers, ICDs, Pacing Wires and Loop Recorders

1. There are some manufacturers that do not require a 6 week waiting period. Referencing current manufacturer's website is recommended.
2. There are limited studies showing successful MRI completion in patients without a waiting period, assessment by a MD is required, along with careful attention to limiting patient body/arm movement during positioning for the MRI.
3. Pacing leads are electrically conductive, radiofrequency pulses experienced in MRI imaging can induce currents that may result in thermal injuries and severe patient harm.
4. Lead heating can be very difficult to predict, as it depends on many factors:

• configuration/orientation
• polarity
• position in the patient AND in the transmit coil
• composition/structure
• shielding/sheathing
• length (resonant heating), resulting in arrythmias
• size and position of patient within the magnet bore

• Temporary epicardial pacing leads - IF cut at the skin, may undergo MRI of any body part at 1.5T or 3T.
  • To clarify: these are used temporary epicardial pacing in the setting of cardiac surgery.  If the leads cannot be extracted at the end of the procedure, they are left in place and cut at the skin. 
• Temporary external transvenous pacing leads - are an absolute contraindication to MRI due to increased heating risk (20°C/68°F) and increased risk of current induction.
• Fractured Leads - may be considered according to the non-conditional CEID protocol @ 1.5T, radiologist assessment for indication, risk vs benefit discussion with patient and signed consent.
• Abandoned, in situ, permanent intracardiac pacing leads - may be considered MR Conditional @ 1.5T,  using the Non-MRI-Conditional CEID. Radiologist assessment for indication, risk vs benefit discussion with patient and signed consent.
• Abandoned, in situ, epicardial leads - seen infrequently in adults but are common in pediatrics are treated the same as intracardial leads that are abandoned
• Image artifacts - are a risk when the lead is within imaging area.
• CEID images with lead types:

Pacemaker with transvenous leads

 

 

 

 

 

 

 

 

 

 

 

 

Pacemaker with epicardial leads

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Defibrillator lead

 

 

 

 

 

 

 

 

 

 

 

 

Subcutaneous defibrillator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cut epicardial wires (often hard to see)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abandoned leads

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abandon leads plus generator

 

 

 

 

 

 

 

 

 

 

 

Temporary transvenous lead

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Leadless pacemaker

 

 

 

 

 

 

 

 

 

At UCSF, we perform CMR in patients with abandoned pacing leads according to our institutional non-MRI-conditional protocol following safety protocols as patients with leads attached to generators.  This includes static field strength of 1.5T and normal operating mode - ex: SAR (≤1.5 or ≤ 2 W/kg) and dB/dt limitations (<200T/m/s).  Patients with abandoned leads/fragments but without a generator in place do not require involvement by electrophysiology. Radiologist assessment for indication, risk vs benefit discussion with patient and signed consent.

Newly implanted pacemakers and implanted cardioverter/defibrillators are considered MR conditional.  However there are approximately 6 million patients with legacy devices, and >50% of these patients will have a clinical indication for MRI during the lifetime of the device.

Potential risks of MR imaging in patients with implanted cardiac devices include movement and/or vibration of the generator and leads, temporary or permanent malfunction of the device, and excessive heating or induced currents in the leads.  However, a large body of evidence has demonstrated a low overall rate of complications.  Currently there is broad international agreement that both MR conditional and non-MRI-conditional cardiac electronic implanted devices can be safety imaged, including statements from the following groups:

• Heart Rhythm Society
• American Heart Association
• American College of Radiology
• Canadian Heart Rhythm Society
• German Cardiac Society
• British Cardiovascular Society

The CEID/pacemaker/ICD in place for minimum of 6 weeks is strongly preferred.  The patient’s system must not be at or near Elective Replacement Indicator (ERI).

Monitoring

Patient monitoring will be performed by a provider with advanced cardiac life support (ACLS) training and MRI safety training for all CEIDs/pacemakers/ICDs. 

Continuous visual and voice contact must be maintained with the patient. 

In the event that a patient is unresponsive or MRI is requested with anesthesia, radiology attending approval/assessment is required and the exam will only be performed in patients with MR conditional devices.

Exam scheduling

Patients should be scanned during normal workday hours (8am to 5pm) on select 1.5T scanners. 3T will only be considered for appropriate MRI conditional devices.

Device vetting

The device will enter the implant queue for identification and vetting.  Verify that documentation of model, manufacturer, lead information is accurate and list most current system components, including revisions, generator replacement.

Expedited approval is sometimes possible if:

1. an MRI conditional device is documented in the EMR; 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.

MRI conditional versus non-MRI-conditional status

MRI conditional versus non-MRI-conditional status of the generator, leads, and combination thereof should be determined by UCSF Implant vetting team, principal/senior MR Technologist, MR Technologist Supervisor or MRI MD.

• If the entire CEID system is deemed MR conditional:
• The manufacturer MRI safety labelling will be followed including:
  • Static field strength (1.5T vs. 3T)
  • Maximum spatial field gradient
  • Slew rate
  • Specific absorption rate (SAR) limits (most commonly ≤2 W/kg)
  • Anatomic location of isocenter
  • Scan duration
  • Coil restrictions
  • Normal operating mode versus first-level controlled mode

Workflow for MRI conditional pacers/ICDs

1. Prior to scheduling, device and leads identified and assessed for conditional/non-MRI-conditional status by any of these roles: UCSF Implant vetting team, principal/senior MR Technologist, MR Technologist Supervisor or MRI MD.
2. No radiology MD approval is required if scanned per manufacturer recommendations
3. Device rep (remote or in person) will interrogate and manage device at the time of scan
4. Monitoring will be performed by a trained radiology nurse for both pacemaker dependent and nondependent patients
5. Device rep (remote or in person) verifies pacemaker fuction following completion of the exam

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 the system is non-MRI-conditional, the following safety limitations will be implemented:

• MD radiologist approval for appropriateness to proceed
• Risk vs Benefit discussion with signed consent
• Minimum number of MRI sequences performed to answer the diagnostic question
• Depending on patient clinical scenario, low SAR protocols may be performed
• 1.5T static field strength
• Normal Operating Mode with SAR (≤1.5 or ≤ 2 W/kg) and dB/dt limitations (<200T/m/s)
• Coil limitations
  • Body coil can be used for RF transmission
  • Local transmit/receive coils if not positioned directly over the device

Workflow for non-MRI-conditional pacers/ICDs

1. Prior to scheduling, device and leads identified and assessed for conditional/non-MRI-conditional status by any one of these roles: UCSF Implant vetting team, principal/senior MR Technologist, MR Technologist Supervisor or MRI MD.
2. MD radiologist approval (QC fellow or section MRI safety representative) re: appropriateness to proceed – study indicated, presence of reasonable non-MRI alternative
3. Dependency/nondependency is evaluated per EP recommendations from pre-scan visit
4. Consent is obtained by radiology MD
5. EP NP/MD must interrogate and manage device at the time of scan
6. Monitoring for pacemaker dependent patients is performed by an EP nurse.  Monitoring for pacemaker nondependent patient is performed by a trained radiology nurse.
7. EP NP/MD verifies pacemaker function following completion of the exam

For non-MRI-conditional devices, 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.

Assessment by EP (either inpatient consult or 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.

Device programming

Cardiac implanted electronic devices should be interrogated both before and after CMR, with involvement of either electrophysiology providers or device representatives depending on the conditional/non-MRI-conditional status of the device.  The device should be reprogrammed for the MRI including setting in either non-pacing or asynchronous pacing mode.  Defibrillator therapies will be turned off, and magnet mode will be disabled.  The device will be reprogrammed at the end of the exam. 

Cardiac Loop Recorders are MRI conditional devices.  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 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.