What should I expect during cardiac magnetic resonance imaging?

Depending on what the doctor is looking for, a cardiac stress magnetic resonance imaging (MRI) test takes approximately 60 minutes. Here's what happens during the test:

  • Getting on the MRI exam table. During the test, you'll lie on a moveable exam table. Pillows or straps may be used to help you remain in the correct position. The technologist will help you get comfortable. If you want an extra pillow or a blanket under you, tell the technologist.
  • Talking with the technologist. You'll probably be alone in the MRI room during the test, but the technologist will be able to see and hear you. If you have a question or you're uncomfortable, tell the technologist.
  • Medication through the intravenous (IV). You will have medication to simulate stress on your heart.
  • What you may feel: The medication may make you feel like you are exercising. You may also have some minor tingling, light-headedness, headache or nausea.
  • Tell your healthcare provider if you have chest pain, a fluttering heartbeat, trouble breathing or sweating. Your healthcare provider will be in the room when the medication is injected and can make sure you are safe. If necessary, your healthcare provider can give you medication to reverse the symptoms.
  • Lying still. While the machine is recording images, you'll need to lie as still as possible. The technologist will tell you when you can move and when you need to lie still.
  • Holding your breath for a few seconds. You will be asked to hold your breath briefly while a scan is being performed—this helps to produce a clearer image.
  • MRI sounds and sensations. When the MRI machine is working, you will hear thumping, knocking or humming that can sometimes be loud. This is normal, and you will be given earplugs to minimize the noise. You may also feel some warmth in the area being examined by the MRI, but this is normal.

Magnetic resonance imaging (MRI) machines usually are located at hospitals or special medical imaging facilities. A radiologist (ra-de-OL-o-jist) or other doctor who has special training in medical imaging oversees MRI testing. Cardiac MRI usually takes 45 to 90 minutes, depending on how many pictures are needed. The test may take less time with some newer MRI machines. The MRI machine will be located in a specially constructed room. This will prevent radio waves from disrupting the machine. It also will prevent the MRI machine's strong magnetic fields from interfering with other equipment.

Traditional MRI machines look like a long, narrow tunnel. Newer MRI machines, called short-bore systems, are shorter, wider and don't completely surround you. Some of the newer machines are open on all sides. Your doctor will help decide which type of machine is best for you. Cardiac MRI is painless and harmless. You'll lie on your back on a sliding table that goes inside the tunnel-like machine.

You will need to remain very still during the test. Any movement may blur the pictures. If you're unable to lie still, you may be given medicine to help you relax. You may be asked to hold your breath for 10 to 15 seconds at a time while the technician takes pictures of your heart.

A contrast agent, such as gadolinium (gad-oh-LIN-e-um), may be used to highlight your blood vessels or heart in the pictures. Contrast agent usually is injected into a vein in your arm with a needle. You may feel a cool sensation during the injection and discomfort where the needle was inserted. Gadolinium doesn't contain iodine, so it won't cause problems for people who are allergic to iodine.

Your cardiac MRI may include a stress test to detect blockages in your coronary arteries. If so, you'll get other medicines to increase the blood flow in your heart or to increase your heart rate.

This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.