Magnetic Resonance imaging in people with cardiac implantable electronic devices

Dr Martin Lowe

Consultant Cardiologist

Clinical Director Cardiac Electrophysiology

Barts Heart Centre                                                               July 18

 

Magnetic resonance imaging (MRI) is used increasingly for diagnostic purposes and to assess responses to treatment, and the recognition that many cardiac device (ILR, Pacemaker, and ICD) patients will have a clinical indication for an MRI scan, has led to the development of MRI conditional devices which allow patients to undergo MRI scanning.  In addition, selected patients with non-MR conditional cardiac devices have undergone MRI scanning without deleterious effects on either the patient or on device function.  The presence of a cardiac device is therefore, not a contraindication to an MRI scan.

MRI Scanning in Patients with MRI Conditional Devices

The development of MRI conditional devices has allowed patients with specified implantable cardiac monitors, pacemakers, ICDs & CRT-P/D devices to undergo MRI scanning safely. MRI “safe” activation reprograms the device to OOO for non-pacing dependent patients or VOO pacing for dependent patients, reducing the risk of inappropriate pacing inhibition.

Patients with MRI conditional systems undergoing scans within the indications of device should have the device programmed according to the manufacturer’s instructions and the patient monitored appropriately.  There is little or no risk of significant harm to the patient.  Implantable cardiac monitors (ECG loop recorders) should also be interrogated and the stored data downloaded, as it is likely to be erased by the strong magnetic field. Full details for all manufacturers’ devices are available through the website links below.

See table 1 below for checklist for patients with MRI conditional devices who require MR scanning.

Programming to MRI “Safe” Mode

All MRI conditional devices should be programmed to MR “safe” mode prior to scanning.  It is important to record the lead and/or device parameters prior to scanning.  This should be performed by a cardiac physiologist or cardiologist with specific training in this programming procedure.  Some devices may be rendered MRI “safe” through an activating device or automatically in the presence of a strong magnetic field.

MRI Scanning in Patients with non-MRI Conditional Devices

MRI scans should in general not be performed in patients with non-MRI conditional cardiac devices unless there is no alternative method to obtain important clinical information and the information will change clinical management. For these patients referral to a centre with specific experience in MRI scanning of non-MRI conditional devices is recommended. See table 2 below for checklist for patients with non-MRI conditional devices who require MR scanning.

BHRS standards for CRM devices - centres

As part of the 2018 revised BHRS standards document for CRM devices new guidance mandates that each device implanting centre in the UK must ensure that arrangements are in place that allow their patients access to MRI scanning. For MRI conditional devices ideally this should be performed locally with an agreed standard operating policy or protocol to ensure patients are scanned in a timely manner. Patients should not be denied access to MRI scanning because of lack of these arrangements or resource.

Table 1

Magnetic Resonance Imaging: Checklist for imaging
MRI Conditional Devices

This checklist is in addition to a standard MRI safety questionnaire

 

Before the Scan:

 

Is the scanner 1.5-3T with maximum gradient slew rate ≤200T/m/s?

 

Is the pacemaker or defibrillator documented as MRI conditional?

 

Are the leads all documented to be MRI conditional?

 

Are leads and generator part of a manufacturer-specific ‘pacing system?’ i.e. no mixing of different manufacturer’s devices and leads

 

Have generator and lead parameters been recorded as within acceptable limits as per manufacturers guidance?

 

Date implanted (must be >6 weeks before MRI scan, unless urgent clinical need):

 

Implanted position (must be either right or left pectoral implant)  Specify which:

 

Confirm there no other leads (previously abandoned), adaptors or devices, or lead fractures

 

Are at least two MRI radiographic staff present and are they aware of the evacuation procedure and trained in MR safety?

 

Is there an external defibrillator with external pacing capabilities in the MRI suite, and are trained staff available to use it?

 

Is there a suitably trained cardiac physiologist / cardiologist present on site responsible for programming the device to enable MRI scanning, and download device data that may be erased by the scan (N.B. implantable loop recorders)

 

Is the device programmed to MRI “safe” mode?

 

During the Scan:

 

Are all MRI protocols run in “Normal” mode (SAR ≤2.0W/kg; head SAR ≤3.2W/kg)?

 

The patient is not positioned on his or her side within the scanner.  Confirmed?

 

Local transmit or transmit/receive coils are not placed over the pacing system, when possible.  Confirmed?

 

Is the patient monitored (results should be recorded) by at least one of the following means - pulse oximetry and/or electrocardiography?

 

After the scan:

 

Has the radiologist has confirmed the patient is stable?

 

Has the cardiologist / physiologist checked the device parameters and reprogrammed to normal device mode?

 

 

Table 2

Magnetic Resonance Imaging: Checklist for imaging
non-MRI Conditional Devices

This checklist is in addition to a standard MRI safety questionnaire

Before the scan:

 

Have all alternative imaging modalities been considered?

 

Has the clinician stated in writing that the information will materially change management/outcome/quality of life to outweigh risk?

 

Will device metal significantly interfere with image quality?

 

Are there additional device risk factors for MR scanning?

  • Abdominal system
  • Retained leads/fractures
  • Implanted less than 6 weeks

If so, patient-specific increased risks should be documented

 

Are lead/device parameters within limits and with adequate safety margins?

  • Battery not approaching EOL
  • Lead impedance/capture threshold well within normal limits

 

Underlying rhythm / tachytherapies?

  • If adequate rhythm – switch off advanced modes and program to OVO, ODO
  • If bradycardic (<40 bpm), program to VOO or DOO mode
  • If no underlying rhythm, patient-specific increased risks should be documented
  • Tachycardia therapies should be disabled

 

Has patient consented in writing with the uncertainty of risk communicated?

 

Is cardiologist or cardiac physiologist immediately available?

 

Is crash trolley with external pacing in department and available?

 

During the scan:

 

Is the patient being monitored by at least one of the following means - pulse oximetry, or electrocardiography?

 

After the scan:

 

Have all pacing parameters been checked and programming changes reversed?

 

Have parameters changed?  If so arrange follow-up in the device clinic

 

 

Appendix

Up to date specific manufacturer guidance for performing MRI scans on patients with MRI conditional devices should be obtained from the websites below.  All device models and leads should be checked for MRI compatibility before scanning is performed.

Medtronic

http://www.mrisurescan.com/europe/ and http://www.medtronic.com

Boston Scientific

http://www.bostonscientific.com

St Jude

http://SJMprofessional.com/MRI

Biotronik

http://www.biotronik.com/wps/wcm/connect/en_promri/biotronik/homeand http://www.biotronik.com

Sorin

http://www.sorin.com

Non-manufacturer specific

http://www.mrisafety.com/

For additional guidance please see the paper below;

Lowe et al. Safe use of MRI in people with cardiac implantable electronic devices. Heart: 2015 Dec:101(24)

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