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 imaged.
The MRI machine is large and tube-shaped. It creates a strong magnetic field around the body. Some MRI machines are more open.
The magnetic field lines up the hydrogen protons in your body. The radio waves then knock the protons out of position. As they realign back into proper position, they send out radio signals. A computer receives the signals and converts them into images of the body. This image appears on a viewing monitor.
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 signs or symptoms that may suggest:
- Atherosclerosis. This is a gradual clogging of the arteries by fatty materials and other substances in the blood stream. It develops over many years.
- Cardiomyopathy. This 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 two 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 block blood flow in the heart.
- Cardiac tumor. A tumor of the heart may happen on the outside surface or inside the heart.
There may be other reasons for your healthcare provider to recommend an MRI of the heart.
There is no radiation exposure during MRI.
You can’t have an MRI if you have a:
- Older intracranial aneurysm clips
- Cochlear implants
- Certain prosthetic devices (such as artificial joint)
- Implanted medicine infusion pump
- Bone growth stimulator
- Certain intrauterine contraceptives (IUDs)
- Other iron-based metal implants
- Bullet or shrapnel
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. If you are allergic to or sensitive to medicines, tell your healthcare provider. If you have kidney problems, there is a risk of a serious reaction to the dye. Discuss this risk with your healthcare provider prior to the test.
MRI contrast may have an effect on other conditions, such as 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 contrast use in people with kidney disease or kidney failure. If you have a history of kidney disease, kidney failure, kidney transplant, liver disease or are on dialysis, inform the MRI technologist or radiologist prior to receiving contrast.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your healthcare provider prior to the MRI.Recommendations for preparation 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 prior to an MRI.
- Tell the technologist if you are pregnant or think you may be.
- Before the exam, it is very important that you inform the technologist if any of the following apply to you:
- You may be 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 a 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 fragments 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, a metal grinder or welder)
- You have any body piercing
- You have an intrauterine device (IUD)
- Your healthcare provider may give you a sedative if you have anxiety that would make it difficult for you to stay still during the MRI.
- Based on your medical condition, your healthcare provider may request other specific preparation.
You may have your MRI an outpatient basis 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 a MRI done with contrast, a nurse will start an intravenous (IV) 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. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to 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, and should only last for a few moments.
- You should tell the technologist if you feel any breathing difficulties, sweating, numbness, or heart 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 inserted to give contrast dye, the line will be removed.
The MRI itself causes no pain. But, having to lie still for 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 avoid any dizziness or lightheadedness from lying flat for the length of the MRI.
If you had a sedative, you need to rest until the sedatives have worn off. You will also need to avoid driving.
If contrast dye is used, you may be watched for a period for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.
If you notice any pain, redness, and/or swelling at the IV site after you return home, tell your healthcare provider. It could mean you have an infection or other type of reaction.
Otherwise, there is no special type of care required after a MRI scan of the heart. You may go back your usual diet and activities, unless your healthcare provider advises 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 will you get the results
- Who to call after the test or procedure if you have questions or problems
- How much will you have to pay for the test or procedure
January 16, 2018
Grossman, Neil, MD,Fraser, Marianne, MSN, RN