An magnetic resonance imaging test (MRI) uses magnets and radio waves to capture images inside your body without making an surgical incision. An MRI allows your doctor to see the soft tissues in your body, along with your bones.
An MRI can be performed on any part of your body. However, a heart or cardiac MRI looks specifically at your heart and the adjacent vessels.
Unlike a CT scan, an MRI does not use radiation. It is considered a safer alternative for pregnant women.
Your doctor might order a heart MRI if he or she believes you are at risk for heart failure or other, less severe heart problems.
According to the National Institutes of Health (NIH), a cardiac MRI is a common test used to assess and diagnose several conditions (NIH , 2012). Some of these include:
- congenital heart defects
- coronary heart disease
- damage from a heart attack
- heart failure
- heart valve defects
- inflammation of the membrane around the heart (pericarditis)
Because MRIs show cross sections of the body, they can also help explain or clarify the results of other tests, such as CT scans and X-rays.
There are no risks for an MRI and few, if any, side effects. The test does not use radiation, and to date, there have been no documented side effects from the radio and magnetic waves. Allergic reactions to the dye are rare.
If you have a pacemaker or any sort of metal implant from previous surgeries or injuries, you may not be able to receive an MRI because of the use of magnets. Be sure to tell your doctor about any implants you have before the test.
If you are claustrophobic or have a hard time in enclosed spaces, you may feel uncomfortable while in the MRI machine. Try to remember that there is nothing to fear. Talk to your doctor about your concerns before the test. He or she may prescribe an anti-anxiety medication to help with your discomfort.
Before the test, tell your doctor if you have a pacemaker. Depending on your type of pacemaker, your doctor may suggest another testing method, such as an abdominal CT scan. However, some pacemaker models can be reprogrammed before an MRI so they are not disrupted during the examination.
Because an MRI uses magnets, it can attract metals. Alert your doctor if you have any type of metal implants from previous surgeries. These may include:
- artificial heart valves
Your doctor may require the use of a special dye to highlight your heart. This dye, called gadolinium is administered through an IV. It is different from the dye used during a CT scan.
Allergic reactions to the dye are rare. However, alert your doctor before the IV is given if you have any concerns or have a history of allergic reactions in the past.
An MRI machine may look intimidating. It is made up of a bench that slowly glides you into a large tube attached to a doughnut-shaped opening. As long you have followed your doctor’s instructions to remove all metal, you will be completely safe.
The technician will ask you to lie back on the bench. You may be given a pillow or blanket if you have trouble lying on the bench. The technician will control the movement of the bench using a remote control from another room. He or she will be able to communicate with you through a microphone.
The machine will make loud whirring and thumping noises as the images are being taken. Many hospitals offer earplugs. Others provide television shows or headphones with music to help pass the time.
The technician will ask you to hold your breath for a few seconds as the pictures are being taken. You won’t feel anything during the test, as the magnets and radio frequencies—similar to FM radios—cannot be felt.
The entire process can take from 30 to 90 minutes.
After the test, you will not have to do anything. You will be able to drive yourself home and go about your day.
If the images are projected onto film, it can take a few hours for the film to develop. It will also take some time for your doctor to review and interpret the images. More modern machines display images on a computer, which allows your doctor to view them instantly.
Reliminary results from a heart MRI may be available within a few days. However, comprehensive results can take up to a week or more. When the results are available, your doctor will review them with you and determine the next steps.