Heart test
Cardiac MRI
A cardiac MRI uses a powerful magnet and radio waves to produce detailed moving images of the heart, showing its structure, function and any damage.
Quick answer
Cardiac MRI: what it is and what the results mean
Cardiac magnetic resonance (CMR) imaging uses an MRI scanner to create detailed still and moving pictures of the heart muscle, chambers, valves and major vessels, without X-rays. A contrast dye is sometimes used to highlight scarring or inflammation.
- Why it is done: It is used to assess the cause of heart failure, damage after a heart attack, heart muscle diseases (cardiomyopathies), inflammation (myocarditis), congenital heart conditions, and to measure how well the heart is pumping.
- Understanding results: A cardiologist or radiologist reviews the images and reports the size and pumping function of the heart, any scarring, inflammation or structural problems, which guides diagnosis and treatment.
What it is
Cardiac magnetic resonance (CMR) imaging uses an MRI scanner to create detailed still and moving pictures of the heart muscle, chambers, valves and major vessels, without X-rays. A contrast dye is sometimes used to highlight scarring or inflammation.
Why it is done
It is used to assess the cause of heart failure, damage after a heart attack, heart muscle diseases (cardiomyopathies), inflammation (myocarditis), congenital heart conditions, and to measure how well the heart is pumping.
What to expect
You lie on a table that slides into the scanner, which is noisy, and wear ear protection. You follow breath-holding instructions and stay still; a contrast injection may be given through a cannula. The scan usually takes 30–60 minutes.
Understanding the results
A cardiologist or radiologist reviews the images and reports the size and pumping function of the heart, any scarring, inflammation or structural problems, which guides diagnosis and treatment.
Good to know
Risks and limitations
It uses no X-rays, but the strong magnet means it may be unsuitable for some metal implants or devices — you are screened first. Gadolinium contrast is used cautiously in poor kidney function. Claustrophobia can be managed with support or sedation.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Cardiac MRI: frequently asked questions
Is a cardiac MRI better than an echocardiogram?
They complement each other. An echo is quick and widely available, while cardiac MRI gives more detailed pictures of the heart muscle and can show scarring and inflammation. Your cardiologist chooses based on the question.
Can I have a cardiac MRI with a pacemaker?
Many modern pacemakers and defibrillators are MRI-conditional and can be scanned with precautions, but older devices may not be safe. The team checks your device details carefully beforehand.
Related tests
Other heart test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- British Cardiovascular Society / relevant professional body
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