MRI scan

MRI scan 1

Magnetic Resonance Imaging (MRI) is a way of creating detailed images of your internal organs, such as your heart and blood vessels.

As MRI machines are not currently available at all hospitals in the UK, you may be referred to a different hospital if you require an MRI scan.

What is a cardiac MRI scan?

A cardiac MRI scan is a non-invasive test that uses an MRI machine to create magnetic and radio waves to show detailed pictures of the inside of your heart. 

What can a cardiac MRI show?

A cardiac MRI scan is a non-invasive test that uses an MRI machine to create magnetic and radio waves to show detailed pictures of the inside of your heart. 

Cardiac MRI scans also look at the blood supply to your heart. They can help your doctor to investigate conditions such as: 

What happens during a cardiac MRI scan?

  • MRI scan 2You will be asked to lie on a bed, which moves inside a tunnel-shaped scanner. The scanner is open at both ends.
  • You’ll 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 earphones so you can listen to music.
  • For some cardiac MRIs the doctor will use a dye known as contrast agent so that the images of blood flow to your heart show up more clearly on the scan. The dye will be injected into a vein in your arm. Your doctor will give you more information about this if it’s required.

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 a cardiac MRI?

Most people that have a cardiac MRI scan will not have to stay in hospital overnight. You should be able to go back to your normal activities straight away. Some exceptions to this are:

  • If you’ve been given a sedative, you won’t be able to drive and will need to be taken home by a friend or relative. You will be advised not to drink alcohol or operate machinery for 24 hours.
  • If you’ve been given an injection of a dye (contrast agent), it’s a good idea to drink plenty of water for the following 24 hours to help flush the dye out of your body.

Usually the doctor who arranged the scan will discuss the results with you when they become available. 

Is a cardiac MRI suitable for everyone?

If you have a pacemaker or an implantable cardiac defibrillator (ICD) you should speak to medical staff before having an MRI scan. Most modern devices can withstand MRI scanning but it's always important that the make and model number is checked beforehand. An MRI can also affect the settings of your device, as each one is programmed specifically for your heart.

You can’t have an MRI scan if you have:

  • inner ear implants or
  • any type of surgical foreign body such as a metal clip in the brain or eye.

This is because the scanner uses very strong magnets that could 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 and soon after the scan to check your kidney function, and explain the risks and benefits to you. You may need some fluids through an intravenous ‘drip’ in your arm before the MRI scan if you have kidney problems.

How can I prepare for a cardiac MRI?

  • Talk to your doctor if you have any medical implants (such as a pacemaker), coronary stents or are pregnant before the test.
  • Unless you have been told otherwise, you can eat and drink normally and continue taking any medication before the test.
  • Remove all electronic devices and credit/debit cards from your pocket. The magnets used in the machine can damage these items.
  • Take off all metal objects such as jewellery, watches and hearing aids.

You'll have to run through a checklist before the test, so don’t worry about forgetting to do any of these things. 

Want to find out more?

Tests booklet

Tests for heart conditions booklet

This booklet describes the special tests that are commonly used to help diagnose heart diseases.

Some of the tests are also used to assess the current condition of people who have already been diagnosed with heart disease.