Cardiac Magnetic Resonance Imaging (MRI)
What is a cardiac MRI?
A cardiac MRI is a noninvasive test that uses a magnetic field and radiofrequency waves to create 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. They are often referred after initial first-line testing, such as transthoracic echocardiography.
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 and measure heart function.
A cardiac MRI can help your health care team diagnose many different heart conditions, such as:
- Tissue damage from a heart attack.
- Reduced blood flow in the heart muscle to help determine whether heart artery blockages (ischemia) are the cause of your chest pain (angina).
- Inflammation in the myocardium, or middle muscular layer of the heart wall.
- Problems in the aorta — the heart’s main artery — such as a tear, aneurysm (bulge) or narrowing.
- Diseases of the pericardium (outer lining of the heart muscle) such as constrictive pericarditis.
- Heart muscle diseases, such as cardiomyopathies, heart failure and cardiac 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 any type of 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 (cochlear) 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 complete a detailed questionnaire to help them determine 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 especially 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 contrast dye is not usually given to people with advanced kidney failure. If you have kidney problems, your health care team will measure your kidney function before the test.
Check with your health care team about the safety of a cardiac MRI if you:
- Have a stent or artificial heart valve, or if you have had open-heart surgery recently.
- Are pregnant, especially during the first three months.
- 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?
- Before your cardiac MRI, eat normally and take your usual medicines unless your health care professional tells you not to.
- It’s very important to remove all objects that may contain metal or electronics before the test, such as rings or 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 back of the cards.
- If you have any 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 in a hospital, clinic or imaging center using special equipment.
- You’ll lie down 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 because 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, and 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 intravenous line in your hand or arm for injecting a contrast agent into your veins (for magnetic resonance angiography). This produces better images of your tissues and blood vessels.
- An MRI usually lasts between 30 and 90 minutes.
If you aren’t comfortable in close spaces, tell your health care professional before the test. They may prescribe a sedative to help you stay calm. 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 also need someone to drive you home.
- The radiologist will review the images and send your health care team a copy of the report so they can discuss the test results with you.