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What is a cardiac MRI?

A cardiac MRI is a test that uses a magnetic field and radiofrequency waves to make detailed pictures of your heart and arteries.

Why do people have cardiac MRIs?

A cardiac MRI is usually requested if someone has more advanced or complex heart conditions. It is often ordered after other tests have been done.

It can be used to look at:

• Blood vessels and how blood flows through them
• How much blood the left ventricle can pump out to the body
• Heart structure and function
• Valve disease or shunts

A cardiac MRI can help your health care team diagnose heart conditions including:

• Tissue damage from a heart attack
• Heart artery blockages that are causing chest pain due to reduce blood flow
• Inflammation in the middle muscular layer of the heart wall
• Problems in the the heart’s main artery, such as a tear, aneurysm or narrowing
• Diseases of the outer lining of the heart muscle, such as constrictive pericarditis
• Heart muscle diseases, such as cardiomyopathies, heart failure and tumors
• Heart valve disorders, such as regurgitation and stenosis
• Congenital heart problems and the success of surgical repair

What are the risks of a cardiac MRI?

A cardiac MRI is a safe and painless test for most people. People with a metal device inside their body shouldn’t have a cardiac MRI unless the device is certified as MRI safe. Such devices may include:

• Pacemakers and implantable cardioverter defibrillators
• Inner ear implants
• Neuromuscular stimulators, such as those used for pain management or muscle rehabilitation.
• Implanted drug infusion pumps
• Some intrauterine devices (IUDs)
• Brain aneurysm clips that are not approved for MRI
• Some dental implants (check with your dentist to make sure they aren’t magnetic)

The MRI staff will ask you to answer questions to help them find out if you have anything in your body that would prevent you from having an MRI. You should avoid cardiac MRI if you have metal fragments in your body. Metal fragments in the eyes can be dangerous because the magnet may move the metal, causing eye damage or blindness.

For some cardiac MRIs, a special contrast dye (without iodine) may be used. This dye is not usually given to people with advanced kidney failure. If you have kidney problems, your health care team will check your kidney function before the test.

Ask your health care team about the safety of a cardiac MRI if you:

• Are pregnant, especially during the first three months
• Are breastfeeding
• Have tattoos or permanent (tattooed) makeup. You might feel some mild discomfort or a burning feeling on your skin from the metal in the darker inks of the tattoo. 
• Have been told you have kidney problems

How do I prepare for a cardiac MRI?

• You may be asked to not eat or drink anything for four to six hours before the MRI.
• It’s very important to remove all objects containing metal or electronics before the test. This includes rings, earrings, hairpins, dentures, watches and hearing aids.
• Don’t bring your credit or debit cards into the MRI room. The machine might erase or damage the magnetic strip on the cards.
• If you have implants or clips in your body, have your health care professional write a note to indicate if they are safe for MRI.

What happens during an MRI?

A radiologist or MRI technologist usually performs the scan. It usually takes place in a hospital, clinic or imaging center.

• You’ll lie on a table that slides into the MRI machine. The machine looks like a long metal tube.
• You’ll need to lie still during the exam. Movement can blur the images.
• Your technologist will watch you from another room. You can speak to them by microphone.
• The MRI machine will create a strong magnetic field around you. Radio waves will be directed at the area of your body to be imaged.
• During the MRI, the magnet produces loud tapping or thumping sounds and other noises. You may be given earplugs, or you may listen to music with headphones to help block the noise.
• You might have an IV line in your hand or arm for injecting dye into your veins. This produces better images of your tissues and blood vessels.
• An MRI usually lasts between 30 and 60 minutes, though it may be longer.

Tell your health care professional if you are uncomfortable in close spaces. They may prescribe a sedative to help you stay calm during the test. Some clinics have machines with shorter magnets or wider openings to make you more comfortable.

What happens after my MRI?

You can usually go back to your normal activities right away.

• If you had a sedative, you’ll stay at the MRI center until the effects wear off. You’ll need someone to drive you home.
• A radiologist will review the images and send your health care team a report so they can discuss the test results with you.