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A cardiac MRI image of the heart

An image of a heart attack, which shows up as white against the background of healthy heart tissue, which shows up as black

Cardiac magnetic resonance scan (cardiac MRI)

What is a cardiac MRI Scan?
Magnetic resonance scanning (MRI) uses the combination of radiowaves and magnetic fields to provide images of the human body. Unlike an X-ray, MRI does not involve radiation.

A cardiac MRI scan provides information about the following:

  • The structure of the heart muscle, heart valves and major blood vessels

  • The cause of heart failure, such as heart attacks and cardiomyopathies.

  • The blood supply to the heart

What does it involve?
You lie on a table that moves into a tunnel-shaped scanner, which is open at both ends. You will be asked to lie still . The scan lasts from half an hour to an hour, depending on the complexity. You will be able to hear quite a loud noise whilst the images are being taken, but you will be given earplugs and you can listen to music. In some cases, a dye (contrast agent) will be injected in an arm vein to highlight certain parts of the heart.

The test is non-invasive and pain free. If you are claustrophobic (afraid of being in small spaces), tell us beforehand. In most cases, we can get around this. You could come in beforehand for a 'dummy run'. You won't be able to have a cardiac MRI scan if you have a pacemaker or a defibrillator (ICD). Some of these devices may be more compatible with MRI than others but, as a rule, a cardiac MRI should not be undertaken if you have one. If we suspect you have any metal bodies in your eyes or brain.

An injection of a contrast agent, so-called gadolinium, into a vein is common. This agent is used to light up areas of muscle scarring in the heart (see figure). Sometimes an additional 'stressing' agent, like adenosine or dobutamine, is used to test the blood supply to the heart muscle. These agents can speed up the heart rate and may give rise to chest pain or tightness. These scans are undertaken with a doctor present. Symptoms will dissapear when the infusion is stopped.


If you have a cardiac MRI scan, it is essential that you meet and discuss the findings with a cardiologist.

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