My patient has a pacemaker and needs an MRI scan - a review of the guidance and regional survey of referring orthopaedic surgeons

James Dundas, Andrew Brown, Iain Matthews, Thomas Green, Craig Runnett, David P Ripley and Honey Thomas

James Dundas is a final year Cardiology registrar, training in the North East and subspecialising in advanced cardiac imaging. He is Level 3 accredited in Cardiac MRI by the European Association of Cardiovascular Imaging, and in Transthoracic Echo by the British Society of Echocardiography.

Andrew Brown is an Internal Medicine Trainee, Northumbria Healthcare NHS Foundation Trust.

Iain Matthews is a Consultant Cardiologist, Northumbria Healthcare NHS Foundation Trust.

Thomas Green is a Consultant Cardiologist, Northumbria Healthcare NHS Foundation Trust.

Craig Runnett is a Consultant Cardiologist, Northumbria Healthcare NHS Foundation Trust.

David P Ripley is a Consultant Cardiologist, Northumbria Healthcare NHS Foundation Trust.

Honey Thomas is a Consultant Cardiologist and has worked for 11 years within the Northumbria Healthcare NHS Foundation Trust. She has a subspecialty interest in heart failure and advanced rhythm management/complex device implantation. Honey introduced and jointly lead the service within her Trust for implantation and follow-up of complex cardiac devices and lead the local multidisciplinary heart failure service. She is lead author for the national guidance for management of cardiac devices around the time of surgery.

Background

The prevalence of patients with cardiac implantable electronic devices (CIEDs) continues to increase, with approximately 57,000 [1] implanted in 2018/2019 in the United Kingdom. These devices include permanent pacemakers (PPM) for the treatment of bradycardia; implantable cardioverter-defibrillators (ICD) for the treatment of life-threatening ventricular arrhythmia; cardiac resynchronisation therapy (CRT) pacemakers for certain patients with severe heart failure; and lastly implantable loop recorders (ILR) used for diagnosis of intermittent arrhythmia. Some devices can perform multiple functions (e.g. CRT-defibrillators).

Historically, the presence of a CIED was considered an absolute contra-indication to MRI examination due to perceived risk of device malfunction, inappropriate device therapy (including inhibition of required pacing, inappropriate pacing and inappropriate ICD shocks), and direct tissue effects such as heating. This has resulted in patients having to undergo alternative imaging modalities, which can be inferior to MRI, particularly where definition of soft tissues is required for diagnosis.

More recently, the majority of CIEDs implanted are designated as MRI conditional – meaning that they have been demonstrated to pose no known hazards, in a specified MRI environment under certain conditions (for example, magnetic field strength and the scan protocol chosen). All of the major device manufacturers market MRI conditional CIEDs, and MRI scanning for patients with these devices is robustly supported by UK and international guidelines [2,3] . Many centres have developed straightforward standard operating procedures (SOP) whereby the devices are reprogrammed by cardiac physiologists to MRI-safe modes before the study, and then otherwise scanned in the usual fashion.

Loop recorders (ILR) and non-electronic cardiac implants (e.g. coronary stents, prosthetic heart valves) do not pose a safety risk to the patient, although it may be prudent to arrange for ILRs to be interrogated prior to scanning to acquire any useful ECG data stored. Most guidelines [2,3] consider scanning redundant pacing leads (i.e. leads, or parts thereof, left behind after device upgrade or extraction) to be contraindicated, along with scanning within the first six weeks after device implant. However, experienced centres report undertaking scans in both situations [4,5] . The only absolute contraindication to scanning is a ventricular assist device (VAD). Figure 1 illustrates which devices can usually be safely scanned.

Figure 1: Which CIEDs are safe to scan?

Image quality is generally only modestly affected by CIEDs, with magnetic susceptibility artefacts commonly seen around the generator device (usually implanted in the left prepectoral position), and to a lesser extent the pacing leads (Figure 2). Even where the device overlaps with the region of interest (e.g. in cardiac MRI examinations) the images are usually of diagnostic quality. Where the region of interest is distant to the device, (e.g. spinal, limb, or joint MRI away from the left pectoral region) then image quality is usually unaffected. MRI sequences can be specifically chosen and optimised to ameliorate susceptibility artefact.

Figure 2: Cardiac MRI images demonstrating magnetic susceptibility artefact around a pacemaker generator (bold arrow) on localisers (Image A), and the associated pacing leads in the right atrium and right ventricle (dashed arrows) on balanced steady state free precession cine imaging (Image B). The images remain of diagnostic quality.

MRI conditional CIEDs come at an increased cost, but most cardiologists implant them, recognising the potential future benefit if the patient requires MRI. Nevertheless, choosing to implant an MRI-conditional CIED is of no benefit to a patient, if healthcare professionals in different specialties remain unaware that they can request an MRI for them. We sought to gauge the awareness of this issue amongst orthopaedic colleagues. A nine-question survey (Appendix 1) was sent to orthopaedic surgeons both within our trust, and across the regional orthopaedic network.

Results

A total of 53 orthopaedic surgeons responded to the survey, of which 16 (30%) were Consultants, 34 (64%) specialty trainees, and 3 (6%) SAS grades. Six NHS trusts across the North East of England were represented, with 46 respondents (87%) working in four district general hospitals and 7 (13%) between the two regional tertiary referral centres. Regionally, one DGH trust and both tertiary centres have well-established programs for scanning CIEDs, but many of the other hospitals do not.

No surgeon thought it was ‘Always’ possible to undertake MRI in a patient with a pacemaker, whilst 41 (81%) thought it was ‘Sometimes’ possible and 10 (19%) wrongly thought it was ‘Never’ possible.

When the same question was applied to ICDs, again no surgeons thought it was always possible, and the percentage who incorrectly thought it was never possible increased to 27 (51%). For patients with an ILR, the results were 2 (4%) for always, 35 (66%) sometimes, and 15 (28%) never.

Only 4 (7.5%) surgeons reported having requested an MRI for a patient with a CIED and having the examination carried out. 26 (49%) had tried but the scan was not performed, and 21 (40%) had never attempted to request a scan for a CIED patient. Greater than half (57%) of surgeons felt that they would not know whom to contact to arrange a scan for these patients. Lastly, almost all surgeons, (50/53, 94%) felt that clinical outcomes might be improved if patients with CIED could be offered MRI scanning.

Discussion

Misunderstanding regarding the suitability for CIED patients to undergo MRI scans was common among our regional cohort of orthopaedic surgeons. A majority were aware that it could be possible, at least for simple PPMs, but this proportion fell when more advanced devices were considered. Interestingly even ILRs (which are considered no hazard at all to the patient) were wrongly thought to be a barrier to MRI. Over half the surgeons were unaware of whom to contact to arrange a scan, implying that better knowledge amongst referrers could lead to wider access to scanning for CIED patients.

The problem may not only be confined to referring clinicians. Half of surgeons reported having appropriately requested an MRI for a device patient but not having it completed, with our assumption being that these scans were declined by the radiology department. In 2017, half of UK MRI departments reported being unable to scan CIED patients, with the reasons frequently cited including lack of training, concerns regarding safety, lack of support from cardiology, and logistical difficulties [6] . Even within departments who undertake scans in patients with CIED, the referral process can often be cumbersome and scans may be inappropriately declined or delayed.

Nationally, there remains a ten-fold under provision of MRI for patients with CIEDs, despite improvement over the previous four years [7] . Where individual trusts do not offer a service to carry out MRI scans in CIED patients, clinicians and radiology departments may initially seek to refer to other centres with experience in this area. However, given the increasing prevalence of device patients, this is not a sustainable solution and setting up a service requires optimal collaboration between radiologists, cardiologists, MR radiographers, and cardiac device physiologists. Figure 3 is an example of a one-stop MRI service for CIED patients, developed by colleagues at Bart’s Heart Centre (London, UK) [8] . Scanning CIED patients requires multidisciplinary engagement and adequate staffing, and this can limit the capacity for these scans. However, there is a strong argument that encouraging referrals may help drive investment and service development.

Figure 3: A ‘one-stop’ service model for MRI-conditional CIED imaging – kindly adapted from Bhuva et al. BMJ Quality & Safety 2019;28:853-8.

There is also growing recognition that, where the clinical indication is strong and appropriate precautions are taken, even non-MR conditional devices can often be scanned with a very low incidence of adverse events [9,10]. Patients should however be counselled regarding the risks and benefits as this lies outside the manufacturers’ recommendations. This discussion should be individualised to a patient’s circumstances – for example, a patient who is pacing-dependent (without underlying intrinsic cardiac rhythm), would be at much higher risk of death from asystole (in the unlikely event of pacing being inhibited during the scan), when compared with a patient with good underlying rhythm and only intermittent bradycardia. Studies in these patients therefore require a robust clinical indication from the referrer, identification of the device by a physiologist, a suitability and risk assessment by a cardiologist prior to scheduling, and usually medically-led supervision of the scan. In our institution this is undertaken by a cardiologist specialising in cardiac MRI, but in other centres this role is carried out by cardiologists specialising in CIEDs and/or electrophysiology.

It is our suggestion that centres considering starting to scan CIED patients, initially restrict this to patients with confirmed MRI-conditional devices. This pathway is more straightforward, requiring less additional consultant time, and once it is established can be led by device physiologists and MRI radiographers. With increasing experience consideration can be given to supporting the more complex requirements for scanning patients with non-MRI conditional CIEDs. Information for patients and referring clinicians, as well as international guidelines and device MRI SOPs from established centres, can be found at www.mrimypacemaker.com.

Conclusion

There was an overwhelming consensus from orthopaedic specialists that their patients with CIEDs could benefit from MRI scanning, so there is a clear impetus to improve practice in this area. It is important that all MRI scanning sites develop this capability to avoid device patients continuing to be disadvantaged for no valid clinical reason. Education and information provision to relevant medical specialties is also crucial. It is the authors’ view that change in behaviour amongst referrers, to actively refer CIED patients for MRI, is required to stimulate service development and appropriately expand CIED MRI services that already exist. We would encourage orthopaedic colleagues to request MRI scans for their patients with CIEDs, whenever they believe that such imaging will benefit them by altering clinical management.

References and Appendices

References and Appendix 1 can be found online at: www.boa.ac.uk/publications/JTO.