Magnetic Resonance Imaging of the Heart
Cardiac magnetic resonance imaging (MRI) uses a strong magnetic field combined with radiofrequency waves to create highly detailed, cross-sectional images of the heart and surrounding structures; these scans are examined for abnormalities. For certain cardiac studies, an MRI contrast dye such as gadolinium may be injected to provide better definition of soft tissues and blood vessels and thus enhance the images.
Purpose of the Cardiac MRI
- To detect and evaluate heart diseases and conditions, including coronary artery disease, heart failure, heart valve problems, cardiac tumors, cardiomyopathy, pericardial disease, and masses in or around the heart
- To identify forms of congenital heart disease, such as atrial or ventricular septal defects
- To evaluate the extent of a heart attack and identify possible complications, such as formation of a ventricular aneurysm or thinning of the ventricular wall
- To identify vascular disease in the chest cavity, such as an aneurysm (abnormal outpouching) or a dissection (leakage of blood between layers of the blood vessel wall) in the aorta
Who Performs Cardiac MRI
- A radiologist or a qualified technician
Special Concerns about Cardiac MRI
- People who experience claustrophobia may find it difficult to undergo an MRI, which takes place in a narrow, tunnel-like structure. In some cases, an open MRIa larger unit that is open on several sidesmay be used as an alternative.
- This test may not be possible for severely overweight individuals (over 300 lbs). Some open MRIs can accommodate larger patients.
- Because the MRI generates a strong magnetic field, it cannot be performed on people who have certain types of internally placed metallic devices, including pacemakers, inner ear implants, or intracranial aneurysm clips.
- The test should not be done in pregnant women because the long-term effects of MRI on the fetus are unknown.
Before the Cardiac MRI
- Tell your doctor if you suffer from claustrophobia. He or she may administer a sedative to help you tolerate the procedure.
- Empty your bladder before the test.
- Remove any magnetic cards or metallic objects, including watches, hair clips, belts, credit cards, body piercings, removable dental work and jewelry. You may be asked to disrobe and put on a hospital gown.
- Your doctor may advise you not to eat for 6 hours before the medicine is administered on the day of the test.
- Tell your doctor if you are pregnant or may be pregnant.
- In some cases, you may be required to swallow contrast material or receive an injection of contrast into the bloodstream before your cardiac MRI.
- Tell your doctor about any health concerns or if you have had recent surgery. If you have a history of kidney disease, a blood test may be performed to evaluate kidney function. Severe kidney disease may prevent you from being given contrast material for an MRI.
What You Experience during Cardiac MRI
- You will lie down on a narrow padded bed that slides into a large, enclosed cylinder containing the MRI magnets.
- You must remain still throughout the scanning procedure because any motion can distort the images.
- In some cases, you will receive an injection of contrast dye before or during the procedure.
- There is a microphone inside the imaging machine, and you may talk to the technician performing the scan at any time during the procedure.
- You will hear loud thumping sounds during the scanning process. To block out the noise, you can request earplugs or listen to music on earphones.
- The procedure can take up to 90 minutes.
Risks and Complications
- If contrast material is injected, there is a slight risk of allergic reaction. Allergic reactions to contrast material are usually mild and easily controlled by medication.
- Nephrogenic systemic fibrosis is a rare complication of MRI that may result from high doses of gadolinium contrast material in patients with very poor kidney function.
- MRI does not involve exposure to ionizing radiation and is not associated with any risks or complications.
After the Cardiac MRI
- Most patients can go home right after the scan and resume their normal activities.
- Sedated patients may be monitored for a short period until the effects of the sedative have worn off.
- Blood may collect and clot under the skin (hematoma) at the dye injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
Cardiac MRI Results
- The MRI scans are displayed on a viewing monitor and then recorded on film. The doctor will examine them for any evidence of heart disease or other abnormalities.
- If the doctor can make a definitive diagnosis, appropriate treatment will begin.
- In some cases, additional tests, such as cardiac catheterization, may be required to establish the diagnosis and determine the extent of the problem.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media