Magnetic resonance imaging (MRI) is a test that uses a large magnet, radio signals, and a computer to make images of organs and tissue in the body. In this case, the heart is the focus.
The MRI machine is large and tube-shaped. It creates a strong magnetic field around the body. Some MRI machines are more open than others, which may make having the test more comfortable.
The magnetic field lines up the hydrogen protons in your body. The radio waves then knock the protons out of position. As they go back into correct position, they send out radio signals. A computer receives the signals and changes them into images of the body. This image appears on a viewing screen.
MRI of the heart is also called cardiovascular MRI (CMRI). MRI may be used instead of a CT scan when organs or soft tissues are being studied.
MRI of the heart may be done to assess symptoms that may mean you have one of the following:
Atherosclerosis. This is a gradual clogging of the arteries by fatty materials and other substances in the bloodstream. It develops over many years.
Cardiomyopathy. This condition happens when the heart muscle becomes thick and weakened.
Congenital heart disease. These are defects in the heart that happen as the fetus forms. An example is a hole in the wall between the 2 lower chambers of the heart (ventricular septal defect).
Heart failure. This condition means the heart muscle is weak and can’t pump enough blood to the body.
Aneurysm. This is a widening and weakening of a part of the heart muscle or the aorta.
Heart valve disease. When heart valves become damaged, it can result in abnormal blood flow in the heart.
Cardiac tumor. A tumor of the heart may happen on the outside surface or inside the heart.
Your healthcare provider may have other reasons to advise an MRI of the heart.
There is no radiation exposure during MRI.
You can’t have an MRI if you have:
Certain pacemakers or internal defibrillators
Older intracranial aneurysm clips
Implanted medicine infusion pump
Bone growth stimulator
Certain intrauterine birth control devices (IUDs)
Other iron-based metal implants
Bullet or shrapnel
If you have an implanted medical device, be sure to bring your implant ID card to your MRI appointment.
If you are pregnant or think you may be, tell your healthcare provider. MRI is generally safe in pregnancy. But you and your healthcare provider should discuss the risks and benefits of having MRI. If contrast dye is used, there is a risk you could have an allergic reaction to the dye. Tell your provider if you are allergic to or sensitive to medicines. If you have kidney problems, there is a risk of a serious reaction to the dye. Discuss this risk with your healthcare provider before the test.
MRI contrast may affect other conditions. These include allergies, asthma, anemia, low blood pressure, kidney disease, and sickle cell disease.
Nephrogenic systemic fibrosis (NSF) is a very rare but serious complication of MRI when contrast is used. This can happen in people with kidney disease or kidney failure. If you have a history of kidney disease, kidney failure, kidney transplant, liver disease, or dialysis treatment, tell the MRI technologist or radiologist before getting the contrast.
You may have other risks depending on your specific health problem. Talk about any concerns with your healthcare provider before the MRI.
Tell the radiologist, technologist, or your healthcare provider if you:
Have ever had an imaging test such as an MRI or CT with contrast dye
Are allergic to contrast dye, iodine, shellfish, or any medicines
Have a serious health problem, such as diabetes or kidney disease
Are pregnant, may be pregnant, or are breastfeeding
Have any implanted device or metal clips or pins in your body
Recommendations for getting ready include the following:
Your healthcare provider will explain the MRI to you and ask if you have questions.
You will need to sign a consent form if contrast dye is used. Read the form carefully and ask questions if something is not clear. Tell the technologist if you have ever had a reaction to any contrast dye.
Generally, there is no special restriction on diet or activity before an MRI.
Before the test, it is very important that you tell your provider or the technologist if any of these apply to you:
You are anxious about being in a closed space and think that you will be unable to lie still while inside the scanning machine. In this case, you may be given medicine to help you relax (sedative).
You have a pacemaker or have had heart valves replaced.
You have any type of implanted pump, such as an insulin pump.
You have metal plates, pins, metal implants, surgical staples, or aneurysm clips.
You have any metallic pieces anywhere in the body.
You have permanent eye liner or tattoos.
You ever had a bullet wound.
You have ever worked with metal. For example, you are a metal grinder or welder.
You have any body piercing.
You have an intrauterine device (IUD).
Based on your health condition, your healthcare provider may ask you to make other specific preparations.
You may have your MRI as an outpatient or as part of your stay in a hospital.
Generally, an MRI follows this process:
Remove any clothing, jewelry, eyeglasses, hearing aids, hairpins, removable dental work, or other objects that may interfere with the MRI.
If you are asked to remove clothing, you will be given a gown to wear.
If you are to have an MRI done with contrast, a provider will start an IV (intravenous) line in the hand or arm to inject the contrast dye.
You will lie on a scan table that slides into a large circular opening of the scanning machine. You may have pillows or straps to prevent movement during the MRI.
The technologist will be in another room where the scanner controls are located. But you will be in constant sight of the technologist through a window. Speakers inside the scanner will let the technologist talk to and hear you. You will have a call button so that you can let the technologist know if you have any problems during the MRI. The technologist will be watching you at all times and will be in constant communication.
You will be given earplugs or a headset to wear to help block out the noise from the scanner. You may be able to listen to music.
During the scanning process, a clicking noise will sound as the magnetic field is created and pulses of radio waves are sent from the scanner.
It’s important to remain very still during the test. Any movement could affect the quality of the scan.
You may be told to hold your breath, or to not breathe, for a few seconds. You will then be told when you can breathe. You should not have to hold your breath for longer than a few seconds.
If contrast dye is used, you may feel some effects when the dye is injected into the IV line. These include coolness or discomfort at the IV site. They should last for only a few moments.
Tell the technologist if you have any problems breathing, sweating, numbness, or fluttering heartbeats (palpitations).
Once the scan is done, the table will slide out of the scanner and you will be helped off the table.
If an IV line was used to give contrast dye, the line will be removed.
The MRI itself causes no pain. But having to lie still might be uncomfortable. The technologist will use all possible comfort measures and complete the test as quickly as possible to reduce any discomfort or pain.
If you have metal fillings in your teeth, you may feel some slight tingling of the teeth during the test.
Move slowly when getting up from the scanner table to prevent any dizziness or lightheadedness from lying flat during the MRI.
If you had a sedative, you need to rest until the sedative has worn off. You will also need to have someone drive you home.
If contrast dye is used, you may be watched for a period for any side effects or reactions to the contrast dye. These include itching, swelling, rash, or problems breathing.
Tell your healthcare provider if you notice any pain, redness, or swelling at the IV site after you return home. It could mean you have an infection or other type of reaction.
Otherwise, there is no special type of care needed after an MRI scan of the heart. You may go back to your usual diet and activities, unless your healthcare provider tells you differently.
Your healthcare provider may give you other instructions after the MRI, depending on your situation.
Before you agree to the test or the procedure, make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure