Can I Have an MRI Scan with a Pacemaker or ICD? Understanding the Risks, Safety and What Really Happens

heartsync

Oct 28

9 min read

For many people living with a pacemaker or implantable cardioverter defibrillator (ICD), being told they need an MRI scan can cause considerable anxiety.

It is perfectly understandable. An MRI scanner uses a powerful magnet, and most people with pacemakers have been warned at some point to be careful around strong magnetic fields.

Two questions are particularly common:

“Could the MRI damage my pacemaker?” and

“Will my pacemaker settings be permanently changed?”

For some patients, the second question is especially worrying.

Finding the right pacemaker settings is not always straightforward. Some people spend months attending appointments, having small adjustments made and working closely with their cardiac physiologist to find settings that make them feel comfortable.

These adjustments can make an enormous difference to everyday life, improving energy levels, reducing breathlessness or helping someone feel more like themselves again.

Understandably, the thought of having those carefully adjusted settings changed, even temporarily, can be unsettling. Nobody wants to lose months of progress or return to feeling unwell.

The reassuring news is that the programming changes made for an MRI scan are designed to be temporary. Your normal settings are preserved and restored after the scan.

Furthermore, extensive clinical research has shown that MRI scans can be performed very safely in appropriately selected patients with pacemakers and ICDs, provided the correct precautions are followed.

Why do pacemakers need special precautions during an MRI?

An MRI scanner uses a powerful magnetic field and radio waves to produce detailed images of the inside of the body.

These can potentially interfere with the electronics inside a pacemaker or ICD. They may also affect the leads, which are the thin insulated wires connecting the device to the heart.

Historically, patients with pacemakers were often told that MRI scans were impossible.

Fortunately, technology and medical understanding have advanced considerably.

Many modern pacemakers are specifically designed to undergo MRI scans under approved conditions. Even some older devices, which were never officially labelled as suitable for MRI, can now be scanned safely in specialist centres.

The key is making sure the correct safety checks are carried out before the scan.

Will having an MRI change my carefully adjusted pacemaker settings?

This is one of the most important concerns to address.

The temporary changes made to a pacemaker for an MRI are not intended to replace or permanently alter its usual programming.

Before the scan, a cardiac physiologist uses a programmer to place the device into a setting commonly called MRI mode.

MRI mode temporarily changes how the pacemaker operates so that it is less vulnerable to interference from the scanner.

Think of it as putting your device into a temporary protective mode.

Your usual settings, including those carefully adjusted over many months, can be recorded and retained.

Once the scan is finished, MRI mode is switched off, and the pacemaker is returned to its previous settings.

This is a routine part of the process and, in most cases, takes only a few minutes.

For those who have spent considerable time finding the right settings, this is particularly important.

Your physiologist does not need to start adjusting everything again from scratch.

The aim is simply to return your pacemaker to exactly how it was programmed before the scan.

Some pacemakers can even restore their original settings automatically

Technology has advanced further still.

Certain newer pacemakers have special MRI safety features that allow the device to recognise the MRI environment and automatically enter its protective mode.

After leaving the MRI environment, these devices can automatically return to their usual settings following the manufacturer's programmed process.

This means that, with compatible devices, the temporary MRI programming can be managed automatically.

Not every device has this feature, but it is another example of how manufacturers have worked to make MRI scanning safer and more straightforward for pacemaker patients.

“I felt unwell when my pacemaker was tested. Will the MRI feel the same?”

Some patients remember feeling dizzy, breathless, uncomfortable or noticing an unusual heartbeat during a previous pacemaker check.

This can make the prospect of having their device reprogrammed understandably worrying.

However, there is an important difference between routine pacemaker testing and preparing a device for MRI.

During a pacemaker clinic appointment, the physiologist may deliberately change certain settings to assess how the pacemaker and its leads are functioning.

For example, the pacing rate may be briefly reduced to assess the patient's own underlying heart rhythm, or the amount of electrical energy delivered to the heart may be adjusted to measure how reliably the heart responds.

These tests are important but can occasionally produce uncomfortable sensations, particularly in patients who rely heavily on their pacemaker.

Programming a pacemaker for MRI is different.

The pacemaker is generally tested as in the pacing clinic to determine that the device readings are normal. The device is then placed into a predetermined setting intended to keep it operating safely while the scan takes place.

Patients who depend upon their pacemaker may have it programmed to maintain a regular, fixed heartbeat throughout the examination.

Other patients, whose hearts can maintain a reliable rhythm independently, may have different temporary settings.

Some people may notice a slightly different heartbeat while MRI mode is active, but many notice very little.

Feeling uncomfortable during a previous pacemaker test does not mean the same thing will happen during MRI.

It is always worth mentioning any previous unpleasant experiences to the cardiac physiologist beforehand. This allows the team to explain the chosen settings and provide appropriate reassurance.

How safe is an MRI scan with a pacemaker?

The evidence is extremely reassuring.

One of the largest studies, known as the MagnaSafe Registry, examined 1,500 MRI scans performed in patients with older pacemakers and ICDs.

These devices were not originally approved for MRI scanning.

The researchers found no deaths, lead failures, loss of pacemaker capture or dangerous ventricular arrhythmias during scans conducted according to the study's safety procedures.

Another major study involving 2,103 MRI examinations in 1,509 patients with older devices similarly found no long term clinically significant adverse events.

Although rare device problems can occur, serious complications are uncommon when the correct precautions are followed.

This is why the British Heart Rhythm Society (BHRS), European Heart Rhythm Association (EHRA) and American heart rhythm specialists support MRI scanning in appropriately assessed patients with cardiac devices.

The important message is not that MRI is completely without risk.

Rather, it is that the risks are generally very low when patients are carefully assessed, their devices are programmed appropriately, and established safety procedures are followed.

What happens on the day of your MRI?

The process is usually much simpler than patients expect.

When you arrive, the MRI team will explain what to expect and make sure you are comfortable with the arrangements.

Before your scan, you will meet the cardiac physiologist responsible for checking your pacemaker or ICD.

They will check that your device is working properly and confirm the settings that are currently programmed.

This is also an opportunity to mention any concerns, particularly if you have previously felt unwell when your pacemaker settings were changed.

The physiologist will then put your device into its temporary MRI setting. This is done using a wireless programming system placed over or near your device. There are no injections or surgical procedures involved.

Once everything is ready, you can have your MRI scan.

The scanner itself can be quite noisy, and some people find the enclosed space a little uncomfortable. However, you will be able to communicate with the MRI team, who will explain how to attract their attention if you need anything.

Your heart rhythm and general condition will be monitored throughout the scan, with trained staff and appropriate emergency equipment available should they be needed.

Afterwards, the cardiac physiologist will check your device again and, where necessary, switch it out of MRI mode.

Your usual settings will be restored, and the device will be checked to ensure it is working as expected.

For most patients, that is all there is to it.

The whole process is designed to be calm, straightforward and, above all, safe.

What if my pacemaker and leads are made by different manufacturers?

This is another area that can cause confusion, particularly when one hospital agrees to perform an MRI scan but another declines.

A pacemaker system consists of two main components: the pacemaker itself, which usually sits beneath the skin near the collarbone, and the leads connecting it to the heart.

Sometimes these components are made by different manufacturers.

For example, someone might have leads manufactured by Medtronic, but a pacemaker manufactured by Boston Scientific.

This can happen when an older pacemaker is replaced but the original leads are left in place.

Although both components may individually be suitable for MRI scanning, the combination may not have been formally approved by either manufacturer.

This is referred to as a mixed manufacturer or MR non-conditional system.

Importantly, this does not automatically mean that having an MRI is dangerous.

It means that the combination of pacemaker and leads has not received formal MRI safety approval as a complete system.

Why do some hospitals refuse to scan mixed systems?

Hospitals operate under their own MRI safety policies.

Some will only perform MRI scans when the pacemaker and leads meet all the manufacturer's published MRI conditions.

These hospitals may decline scans involving mixed manufacturer systems because they fall outside the manufacturer's formal safety approval.

There are also important questions concerning manufacturer responsibility, liability and the hospital's own clinical governance arrangements.

Other hospitals, particularly specialist cardiac centres, have developed protocols that allow them to scan patients with these systems following additional assessments.

Neither approach necessarily means that one hospital is right and another is wrong. They may simply have different facilities, experience and safety policies.

What does the research tell us?

A particularly important study involving researchers at Barts Heart Centre in London provides considerable reassurance.

Published in the European Heart Journal in 2022, the study examined 1,148 MRI examinations performed in 970 patients with pacemakers and defibrillators.

This included patients with older devices and systems that did not meet formal MRI approval conditions.

Among them were patients with pacemakers and leads from different manufacturers.

The researchers found no lead-related adverse clinical events, and there was no evidence that mixed manufacturer systems experienced greater changes in device function compared with systems that met formal MRI conditions.

The findings support the growing evidence that appropriately selected patients with mixed manufacturer systems can undergo MRI safely when specialist protocols are followed.

This does not mean every mixed system is suitable for MRI, but it does mean that being refused a scan at one hospital should not automatically be considered the end of the matter.

A specialist centre may be able to offer further assessment.

Can an MRI permanently damage a pacemaker?

Although the risk is very small, it is important to recognise that MRI scanning is not completely without risk.

In rare circumstances, interference from the scanner can cause a pacemaker to behave unexpectedly, reset certain functions or experience changes in how it operates.

These are not the same as the deliberate, temporary programming changes made before the scan.

In large studies, such complications have been uncommon, and most patients have undergone MRI without clinically significant problems.

This is precisely why pacemakers are checked before and after scanning, why the correct MRI settings are selected, and why trained professionals are involved.

The purpose of these precautions is to make an already low-risk procedure as safe as reasonably possible.

A final word of reassurance

Having a pacemaker or ICD should not automatically prevent you from receiving an MRI scan when one is medically necessary.

The technology has improved; our understanding has developed and there is now a substantial body of research supporting the safety of MRI scanning in patients with cardiac devices.

For those who have spent months getting their pacemaker settings just right, there is a particularly important message:

The temporary programming used for MRI is designed to protect your device during the scan, not to undo the careful adjustments that have been made to help you feel well.

Your normal settings are intended to be restored afterwards, and your pacemaker will be checked to ensure it continues working as expected.

If you have previously felt unwell during pacemaker testing, tell your cardiac physiologist. If your pacemaker and leads are made by different manufacturers, ask whether an assessment at a specialist MRI centre may be possible.

Above all, do not be afraid to ask questions.

Understanding what happens, why it happens and how your device is protected can make an enormous difference to how you feel about having the scan.

An MRI with a pacemaker is no longer the obstacle it once was. With the right expertise, careful preparation and appropriate safety precautions, most eligible patients can undergo their scan with confidence.

Clinical sources and further reading

This article draws on the Joint British Society recommendations, supported by BHRS, the EHRA international consensus (developed with the Heart Rhythm Society and other heart rhythm organisations), and published clinical research. IBHRE provides professional certification rather than a separate MRI safety guideline.