Cardiac (heart) MRI

MRI scans let us see detailed pictures of inside your body. They use strong magnetic fields and radio waves. 

The cardiac MRI scan that you have been referred for looks at your heart. This is a safe and painless test. It does not use radiation and is not harmful.

You can read more about MRI scans on the NHS website.

Before your appointment

Remember to confirm your appointment.

Please tell us immediately if you:

  • have a pacemaker or reveal device (heart monitor)
  • have an artificial heart valve
  • have had surgery to your brain or head
  • have any shrapnel or metal that has gone into your body
  • have a history of metal going into your eyes
  • are pregnant, or might be
  • suffer from claustrophobia (a fear of closed spaces)
  • have asthma or chronic obstructive pulmonary disease (COPD) and use inhalers
  • have any kidney problems
  • weigh more than 102 kg (16 stone)

The MRI scanner is a large tube that is open at both ends. You go through the hole in the middle, which is 60 to 70cm across. For this reason, some people cannot fit in the scanner.

If you weigh more than 102kg (16 stone), please call the booking team. We can then take your height and body size measurements over the phone.

If you call us in advance, this will help to avoid your scan being cancelled and an unnecessary journey to the hospital. 

How to prepare

Do not drink or eat anything that contains caffeine, including tea, coffee, chocolate and cola. Otherwise, you can eat and drink as normal.

Please do not smoke on the day of the scan. Our stop smoking service can help with this. 

Do not use lotions or oil on your chest. This makes it difficult to attach ECG electrodes (sticky pads to monitor your heart rate). If your chest is hairy, you might want to shave it before your appointment. Otherwise, we will shave the area for you.

Please do not come to the hospital if you have flu-like symptoms, are being sick (vomiting) or have diarrhoea.

When you arrive at the department

We ask you to complete some paperwork before we start your scan.

We give you a patient safety questionnaire. This is to make sure that it is safe for you to have your scan. The scanner is a large magnet. This means that we need to know about any metal inside or on your body.

You should also have received information about the research that we do. When you arrive, we ask you if you want to take part in the research. This is your choice and your decision does not affect the results of your test.

What happens during your scan

A member of the clinical team comes to meet you and takes you to the MRI scanner.

Several members of staff are often present. These are all people involved in cardiac MRI scans.

The scan takes 60 to 90 minutes. This depends on the complexity of your test and your heart rate.

Sometimes people need a little extra time and care, so the appointments might be slightly behind. If you would like information about this, please ask one of the MRI team when you arrive in the department.

Using a dye (contrast agent)

We might put a small plastic tube (cannula) into your arm to give you a dye (contrast agent).

The dye allows us to see some structures of your heart more clearly. This stays in place throughout the scan and is removed at the end.

Sometimes, there can be problems inserting a cannula because of difficult veins. If you have had problems before or would like to discuss this, please contact the department. We can ask a more specialist team to help us.

The dye can cause some side effects. The most common (less than 1 in 200 people) are a headache, feeling sick (nausea) and dizziness. The side effects generally do not last long.

Please let us know in advance if you have experienced any allergy problems with contrast agent in the past.

Accessories used within the scanner

  • ECG stickers on your chest monitor your heart rate while you are in the scanner. If you have a hairy chest, we need to shave the area before the scan to make sure the stickers stay in place.
  • An MRI coil is put on your chest to take the pictures.
  • Breathing bellows are like a small pad (about the size of a glasses case). We put them on your tummy to monitor your breathing pattern during the scan. This helps us to get some of the pictures.
  • Headphones are used to communicate with you during your scan. They also help to protect your ears from the noise of the scanner.
  • A blood pressure cuff is used to monitor your blood pressure during the scan.

Sometimes, we may also need to look at the blood flow to your heart during exercise. 

Having an exercise test

We may find that an exercise test is needed when we see some of the first images. We always discuss the procedure with you before any decisions are made.

If we do need to exercise the heart, we will put a second cannula into your arm and inject a medicine called adeonosine. This stimulates the effort of exercise. It raises your heart rate in a steady and controlled way over a short time (up to 4 minutes) while you lie down.

We monitor you to make sure that you are safe at all times during this procedure.

You may get mild side effects, such as shortness of breath or a red (flushed) face, when you have this medicine. The effect wears off shortly after we stop the drip.

There are doctors at the MRI scanner at all times during this injection.


We are an active research department and contribute to improvements in cardiac MRI scans.

We invite you to contribute to the research when you have your scan. You can read more about this with your letter. If you consent, we remove all information that could identify you.

Taking part in the research is voluntary and does not affect your care. Please ask us any questions you may have.

Getting your results

Specialists review the images from the scan and write a report. They send this report within 2 weeks to the specialist who referred you for the scan.

Your GP also gets the report or a summary of it.


Resource number: 4539/VER2
Last reviewed: April 2022
Next review due: April 2025

Trusted Information Creator. Patient Information Forum

Contact us

If you have any questions, or need advice, before or after your scan, please contact us.

Phone: 020 7188 5441 Monday to Friday, 9am to 5pm.

Email: [email protected]

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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