Cardiac MRI
A detailed scan of the heart using a strong magnet and radio waves, with no X-ray radiation, to show the heart's structure, pumping and muscle, sometimes with a contrast injection.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- A detailed heart scan using a magnet and radio waves, with no X-ray radiation, that shows the heart's structure, pumping and muscle.
- It is especially good at assessing the heart muscle, scarring, inflammation and heart function, and a stress version can show areas short of blood.
- Many scans use a gadolinium contrast injection; serious reactions are very rare, but kidney function and any pacemaker or metal implant must be checked first.
- It is not the usual test for looking directly inside the coronary arteries; the result needs a specialist to interpret it alongside your other tests.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your radiologist will give you advice for your situation.
Gives very detailed information about the heart's structure, pumping function and muscle.
Some implanted devices or metal that are unsafe in the magnet; every implant must be checked first.
You lie still in the scanner, hold your breath when asked, and can speak to the radiographer between sequences. Tell them at once if you feel unwell.
Careful safety screening before the scan and clear advice if contrast is used.
You lie still in the scanner, hold your breath when asked, and can speak to the radiographer between sequences...
Brief flushing, breathlessness or chest tightness can occur and settles within minutes; you are monitored until it...
The cannula is removed. Without sedation, you can usually eat, drink, drive and return to normal activity straight...
Drinking normally helps clear the contrast. Any cannula-site bruising settles over a few days.
What is a cardiac MRI?
A cardiac MRI, also called cardiovascular magnetic resonance, uses a strong magnet and radio waves, rather than X-rays, to build detailed pictures of your heart. It shows the size and shape of the heart chambers, how strongly the heart is pumping, the heart muscle itself, the valves and the large blood vessels, and blood flow through them.
It is used to look into many heart conditions, such as problems with the heart muscle (cardiomyopathies), scarring after a heart attack, inflammation of the heart, heart failure, congenital (from birth) heart conditions, and some valve and blood-vessel problems. A stress perfusion MRI, which uses a medicine to make the heart work harder, can show whether parts of the heart muscle are short of blood.
Many cardiac MRIs use a contrast injection, usually a gadolinium-based agent, to highlight scar tissue, inflammation and blood flow. Because it uses no X-ray radiation, it can be repeated when needed. What it mainly tells you is about the heart's structure and function and the state of the muscle; it is not the main test for looking directly inside the coronary arteries, which is usually done with a CT or invasive angiogram.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Cardiac MRI versus CT coronary angiogram
| Feature | Cardiac MRI | CT coronary angiogram |
|---|---|---|
| Main strength | Heart muscle, function, scar | The coronary arteries |
| X-ray radiation | None | Yes (a low dose) |
| Contrast | Often gadolinium | Iodine-based dye |
| Scan time | Longer (30 to 90 min) | Shorter |
The two scans answer different questions and are sometimes used together. Your cardiologist chooses based on what needs to be assessed.
Preparing for your scan
- Complete the MRI safety questionnaire carefully; tell the team about any pacemaker, defibrillator, metal implants, clips, stents or fragments.
- Mention any kidney problems, as a recent blood test may be needed before contrast is given.
- Tell the team if you are or might be pregnant or are breastfeeding.
- Mention claustrophobia in advance, as it can often be managed and sedation is occasionally arranged.
- For a stress perfusion scan, you may be asked to avoid caffeine for around 24 hours, as it can interfere with the stress medicine.
- Ask whether to take or hold any medicines on the day.
- Remove all metal items, jewellery and some clothing, and expect to wear a gown.
- Allow extra time, as cardiac MRI usually takes longer than other scans.
What happens
You lie on a couch that slides into the scanner, which is a tunnel open at both ends. A radiographer positions a soft frame over your chest and attaches ECG electrodes so the scanner can time its pictures to your heartbeat. You are given headphones or earplugs, because the scanner is loud, and a buzzer to call for attention.
If contrast is needed, a small cannula is placed in a vein, usually in the arm, and the gadolinium is injected during the scan. For a stress perfusion scan, a medicine such as adenosine is given through the cannula to make the heart work harder for a few minutes; this can briefly cause flushing, breathlessness or chest tightness that wears off quickly.
During the scan you need to lie still, and you will be asked to hold your breath for short periods so the pictures are sharp. The whole scan usually takes between 30 and 90 minutes. Afterwards the cannula is removed and, if you have had no sedation, you can normally go home straight away.
Is this scan right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Some implanted devices or metal that are unsafe in the magnet; every implant must be checked first.
- People who cannot lie still or hold their breath enough for diagnostic images, unless sedation is arranged.
- When the main question is the inside of the coronary arteries, a CT or invasive angiogram is usually the better test.
- Severe kidney impairment may make gadolinium contrast unsuitable, though a contrast-free scan is often still useful.
Delay or rearrange if…
- Kidney function needs checking before contrast can be given.
- There is uncertainty about whether an implant or device is MRI-safe.
- You are acutely unwell or have unstable symptoms that need urgent assessment first.
- Pregnancy, where contrast in particular is usually avoided unless essential.
- Recent caffeine intake before a stress perfusion scan that could interfere with the stress medicine.
Alternatives to discuss
- An echocardiogram for many questions about structure and function, with no radiation or magnet issues.
- A CT coronary angiogram to look directly at the coronary arteries.
- A myocardial perfusion scan as an alternative way to assess blood flow to the muscle.
- An invasive coronary angiogram where treatment of blockages is likely.
- No imaging, if the clinical question can be answered another way.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Comfort, sedation or contrast choices
If local anaesthetic, sedation, contrast or pain relief is used, ask what is planned, why, and what it means afterwards.
Benefits
- Gives very detailed information about the heart's structure, pumping function and muscle.
- Can show scarring, inflammation or infiltration of the heart muscle that other tests may miss.
- A stress version can reveal areas of heart muscle that are short of blood.
- Uses no X-ray radiation, so it can be repeated when needed.
- Helps diagnose and monitor cardiomyopathies, heart failure and congenital heart conditions.
- Can guide treatment decisions and assess how the heart responds over time.
Risks & complications
- Feeling enclosed or claustrophobic in the scanner.
- Finding the loud knocking noise and the need to lie still and hold your breath tiring.
- A brief cold feeling, flushing or odd taste when contrast is injected.
- Short-lived flushing, breathlessness or chest tightness from the stress medicine, which wears off quickly.
- Bruising or discomfort where the cannula was placed.
- A mild allergic-type reaction to the gadolinium contrast, such as a rash or nausea.
- An incidental finding, unrelated to the original question, that needs further tests.
- A severe allergic reaction to the contrast; the team is trained to treat this.
- In people with severe kidney impairment, a rare scarring condition linked to some older gadolinium agents.
- A safety incident if an unrecognised metal implant or device interacts with the magnet, which screening is designed to prevent.
Cardiac MRI is a low-risk test, and its lack of X-ray radiation is a real advantage. The main safety points are the magnet itself, which is why metal implants and devices must be declared, and the gadolinium contrast, which very rarely causes a serious reaction and needs care in people with poor kidney function. Incidental findings, picked up by chance, can also lead to further tests and worry. Ask whether you need contrast, whether your kidney function has been checked, and whether your device is MRI-safe.
Published figures to discuss
Cardiac MRI is low-risk, and the most useful figures concern the contrast rather than the scan itself. Large registry data give a sense of how rare reactions are, but exact rates vary with the agent used and the population. Incidental findings and the limits of what MRI can see (especially the coronary arteries) are practical uncertainties to weigh up.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Acute reaction to gadolinium contrast | Around 0.1% (about 1 in 1,000) overall in a large cardiac MRI registry, most reactions mild | From the EuroCMR registry of 37,788 patients; most reactions were mild and severe reactions were very rare. | EuroCMR registry — acute reactions to gadolinium contrast in cardiac MRI (PMC)pmc.ncbi.nlm.nih.govPublished figure |
| Severe (anaphylactic) reaction to gadolinium contrast | Very rare; about 0.01% (roughly 1 in 10,000) in the same registry | Imaging teams are trained and equipped to treat severe reactions promptly. | EuroCMR registry — acute reactions to gadolinium contrast in cardiac MRI (PMC)pmc.ncbi.nlm.nih.govPublished figure |
| Claustrophobia or inability to complete the scan | Recognised | Breath-holding, scanner noise and lying still can be difficult; sedation or an alternative test may be needed for some patients. | Guide sourcesClinical context |
| Device or implant incompatibility | Screening-dependent | Pacemakers, defibrillators, older clips, retained metal and some implants need explicit MRI safety checks before booking. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is usually no physical recovery from a cardiac MRI. Most people go home and return to normal activities straight away. The wait that matters is for a specialist to report the images and for your cardiologist to explain what they show.
- Feeling a little tired after lying still and holding your breath.
- Mild bruising where the cannula was placed.
- A short-lived flushed feeling if you had contrast or the stress medicine.
- No lasting effects and a normal return to daily life.
- A wait of days to weeks for the detailed report.
Aftercare
- Drink fluids normally, which helps clear the contrast if you had it.
- Resume normal activity, eating and driving unless you were given sedation.
- Restart any medicines that were paused, as advised.
- Look after the cannula site and keep it clean if it is sore.
- Note any delayed reaction, such as a rash, and report it.
- Make sure you know when and how you will get your results.
- Contact the department if you feel unwell after contrast or the stress medicine.
- MRI safety questionnaire completed honestly
- Recent kidney blood test arranged if contrast is planned
- Caffeine avoided beforehand if a stress scan is booked
- Claustrophobia mentioned in advance if relevant
- Metal items, jewellery and relevant clothing removed
- Way to get home arranged, especially if sedation is used
- Clear plan for how results will reach you
⚠ Get urgent help if…
- Difficulty breathing, throat tightness, widespread rash or swelling after contrast; this needs emergency care.
- Chest pain that does not settle after the stress part of the scan.
- Feeling faint, with a very fast or irregular heartbeat, afterwards.
- A delayed rash, itching or swelling in the hours after a contrast injection.
- Increasing pain, swelling or redness at the cannula site.
- Any sudden weakness, facial droop or slurred speech; call 999.
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your radiologist gives you.
Results & realistic expectations
A normal cardiac MRI is reassuring about the heart's structure, pumping and muscle, but it answers the specific question it was arranged for and does not rule out every heart problem, especially disease inside the coronary arteries, which is better seen on other tests. An abnormal scan may show a weakened or thickened heart muscle, scarring, inflammation, a valve or blood-vessel problem, or areas short of blood on a stress scan, each of which guides diagnosis and treatment.
The images are detailed and need a specialist to interpret them alongside your symptoms and other tests. Results take time, because the scan produces a large amount of information that must be carefully analysed and reported.
A cardiac MRI captures your heart at one point in time. Because it uses no X-ray radiation, it can be repeated to monitor a condition or see how it responds to treatment. How long the result remains useful depends on your condition; your cardiologist will advise whether and when a repeat scan is worthwhile.
Related tests, treatments or support
Cardiac MRI is often used alongside an echocardiogram, ECG, blood tests and, where the arteries are the question, a CT or invasive coronary angiogram. The different tests answer different questions, and your cardiologist puts them together to reach a diagnosis and plan.
Follow-up & long-term care
After the scan a specialist reports the images and sends the findings to your cardiologist, who explains what they mean and whether any further test or treatment is needed, usually at a follow-up appointment. Ask before you leave how and when you will get the result and who to contact with questions.
- Attend any repeat scans arranged to monitor a known heart condition.
- Tell future clinicians and imaging teams about any implant or device before further MRI.
- Keep records of previous scans so changes over time can be compared.
- Have kidney function rechecked before future contrast scans if advised.
Repeat, follow-on and what comes next
- Because there is no X-ray radiation, scans can be repeated to monitor a condition over time.
- An incidental or unclear finding may lead to further tests rather than a final answer.
- A non-diagnostic scan, for example from movement or breath-hold difficulty, may need repeating.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- Careful safety screening before the scan and clear advice if contrast is used.
- A specialist report interpreted alongside your other tests and symptoms.
- A named contact route for delayed reactions or questions.
- A clear plan for any incidental finding, rather than vague reassurance.
- A written result and report shared with you and your GP.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The type and length of the scan, including whether a stress study is needed.
- Whether a contrast injection is used.
- The specialist reporting by a radiologist or cardiologist.
- Whether sedation is needed, for example for severe claustrophobia.
- Any consultation before and after to discuss the result.
- Whether the scan is part of a wider set of heart tests.
- The scan fee and whether contrast is included.
- The specialist reporting of the images.
- Sedation costs if these apply.
- Any consultation to discuss the result.
- What happens, and what it costs, if an incidental finding needs further tests.
- How and when the result and report will be provided.
On the NHS? Cardiac MRI is available on the NHS at specialist centres when detailed heart imaging is clinically needed; private scans are sometimes chosen for speed or convenience.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Not declaring or checking an implant or device before the scan.
- Giving contrast without checking kidney function where that matters.
- Not being told the scan is not the main test for the coronary arteries.
- No discussion of what happens if an incidental finding is picked up.
- Assuming a normal scan rules out all heart disease.
Marketing red flags
- Promoting a heart MRI as a scan that catches every heart problem.
- Offering whole-body or heart MRI screening to people with no symptoms without explaining incidental findings.
- Downplaying the need to check implants and kidney function.
- Implying the scan replaces a coronary angiogram for assessing artery blockages.
Choosing a specialist safely
- Check the radiologist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the radiologist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good radiologist will welcome every one of these.
- What is this scan looking for in my case, and why MRI rather than another test?
- Will I need a contrast injection, and has my kidney function been checked?
- Is my pacemaker, defibrillator or implant safe in the scanner?
- Will this be a stress scan, and what should I expect from the medicine used?
- What will the result change about my diagnosis or treatment?
- How and when will I get the result, and who explains it to me?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the radiologist who carries out my scan, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this scan not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Does a cardiac MRI use radiation?
Will I be enclosed, and what if I am claustrophobic?
Is the contrast injection safe?
Can I have a cardiac MRI with a pacemaker or metal implant?
Why does the scan take so long?
Is it available on the NHS?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — MRI scan British Heart Foundation — Tests for heart conditions EuroCMR registry — acute reactions to gadolinium contrast in cardiac MRI (PMC) NICE — Chronic heart failure in adults (NG106)
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
Related guides: MRI scan · Echocardiogram (heart ultrasound) · CT coronary angiogram · Myocardial perfusion scan (nuclear cardiology) · Coronary angiogram (cardiac catheterisation)