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MRI scans

Nurse talks to patientMagnetic Resonance Imaging (MRI) is a way of creating detailed images of your internal organs.

MRI scans are not currently available at all hospitals in the UK but they are becoming more readily available.

What is a cardiac MRI Scan?

During a cardiac MRI scan an MRI machine uses magnetic and radio waves to create clear pictures showing the inside of your heart. Unlike an X-ray, an MRI scan does not use radiation.

What can a cardiac MRI show?

A cardiac MRI scan is used to view your heart’s structure and to assess how well it’s pumping. This is useful if you have structural problems with your heart such as congenital heart disease or age-related wear and tear of your heart valves. If you have heart failure, the scan can help your doctor to determine the amount of healthy heart muscle. 

Because MRI scans can also be used to study the blood supply to your heart, they can help your doctor to investigate conditions such as coronary heart disease, and estimate the damage to your heart after a heart attack.

What happens during a cardiac MRI scan?

  • Magnetic Resonance ImagingYou lie on a bed, which then moves inside a tunnel-shaped scanner that is open at both ends.
  • You will be asked to lie still while the scan is taking place.
  • The scan may last for up to an hour, but there’s a buzzer you can press if you need to speak to the radiographer (the person operating the scanner). 
  • The scanner is quite noisy – you’ll be able to hear banging sounds – but you’ll usually be offered earplugs or better still, earphones so you can listen to music and relax
  • Because it’s important to stay still during the scan, babies and young children are often given a general anaesthetic before an MRI scan.
  • For some cardiac MRIs the doctor will use a dye known as contrast agent to enable images of the blood flow to your heart show up more clearly on the scan.  The dye will be injected into a vein in your arm before the scan starts.  Your doctor will give you more information about this if it is required.

The test is pain free, but if you’re claustrophobic (afraid of being in small spaces), tell your doctor before the test.  You may be offered a mild sedative - a drug to help you relax.

What happens after the scan?

You should be able to go back to your normal activities straight away. A cardiac MRI scan is usually an outpatient procedure, which means that you will not have to stay in hospital overnight.

However:

  • If you have been given a sedative you will not be able to drive and will need to be taken home by a friend or relative. You will not be allowed to drink alcohol or operate machinery for 24 hours.
  • If you have been given an injection of a dye (contrast agent), it is a good idea to drink a lot of water for the following 24 hours to help flush the dye out of your body.
  • It is unlikely that the results of your scan will be available immediately. Usually the doctor who arranged the scan will discuss the results with you a couple of weeks after the scan. 
 

Is a cardiac MRI suitable for everyone?

You can’t have an MRI scan if you have a pacemaker or an implantable cardiac defibrillator (ICD), inner ear implants or any type of surgical foreign body such as a metal clip in the brain or eye.  That’s because the scanner uses very strong magnets which could deactivate the pacemaker or defibrillator and cause anything made of metal to move.

If your kidneys aren’t working well, the dye used during the scan could cause further damage. Your doctor will take a blood test before the scan to check your kidney function, and explain the risks and benefits to you.