A Cardiac MRI (Magnetic Resonance Imaging of the heart) is a specialized test that uses a powerful magnetic field and radio waves to create highly detailed, moving 3D images of your heart beating in real-time.
Doctors request this scan to evaluate the structure and function of the heart muscle, assess damage after a heart attack, or investigate unexplained chest pain.
Unlike standard X-rays or CT scans, a Cardiac MRI involves zero radiation and can characterize the actual tissue of the heart, identifying areas of scarring or inflammation that other tests cannot see.
Why would my doctor ask for a Cardiac MRI?
Your doctor may recommend a Cardiac MRI to look closely at your heart, especially if you have:
- Heart failure or unexplained breathlessness.
- A recent heart attack (to measure exactly how much of the heart muscle was damaged).
- Suspected inflammation or infection of the heart muscle (myocarditis or pericarditis).
- Abnormal heart rhythms or inconclusive results from an echocardiogram (ultrasound of the heart).
- Congenital heart defects (heart problems present from birth).
What can a Cardiac MRI detect?
A Cardiac MRI helps doctors visualize:
- The pumping function of the heart chambers.
- The thickness of the heart muscle and the health of the heart valves.
- Blood flow through the major arteries and veins.
It is particularly useful for identifying:
- Scar tissue or fibrosis within the heart muscle.
- Cardiomyopathy (diseases of the heart muscle).
- Tumors within the heart.
Do I need any special preparation for a Cardiac MRI?
Yes. You may be asked to fast (no food or drink) for 4 to 6 hours before the test.
It is extremely important to remove all jewelry, watches, hearing aids, and clothing containing metal zippers or snaps. You must inform your Radiographer if you have any implanted medical devices, especially a pacemaker or defibrillator, as these require specific safety checks before entering an MRI room.
Will I be injected with dye for this scan?
Usually, yes. A contrast dye called gadolinium is often injected through an IV line in your arm. This dye travels to the heart and brightly highlights areas of healthy blood flow versus areas of permanent scar tissue. Tell your doctor if you have severe kidney problems before receiving contrast.
What does a Cardiac MRI feel like?
The scan itself is painless. You will lie flat on a padded table. The Radiographer will place sticky EKG patches on your chest to monitor your heartbeat during the scan, which allows the MRI machine to sync its picture-taking with your pulse.
The scanner is a large, tube-shaped machine, and you will hear loud tapping and humming noises. To get clear images of your moving heart without the blur of your lungs moving, the Radiographer will repeatedly ask you to hold your breath for 10 to 15 seconds at a time through a speaker system.
Is it safe for pregnant women or children?
Yes. MRI is generally safe as it does not use radiation. However, pregnant women should consult their doctors, and contrast dye is usually avoided during pregnancy unless absolutely necessary.
How long does the Cardiac MRI take?
A standard Cardiac MRI typically takes between 45 and 60 minutes.
When will I get my results?
After the scan, a specialized Radiologist or Cardiologist will review the images and prepare a report. Your doctor will use these findings to discuss your diagnosis and treatment plan.
What is a "Stress" Cardiac MRI?
If your doctor wants to see how your heart handles exercise but you cannot run on a treadmill inside the scanner, they will order a "Stress Cardiac MRI". During this scan, a medication called adenosine (or a similar varient) is given through your IV. This drug safely mimics the effects of exercise by making your heart beat faster and widening your blood vessels. For a few minutes, you may feel flushed, breathless, or have a tight, heavy feeling in your chest. These sensations are normal, completely expected, and will stop just seconds after the medication is turned off.
When should I seek urgent help?
Seek emergency care for severe or persistent chest pain, severe breathlessness, fainting, or symptoms of a heart attack. If symptoms occur during a stress MRI, tell the team immediately.
Sources and further reading
- RadiologyInfo: Cardiac MRI
- ACR Manual on Contrast Media
- FDA: Gadolinium retention safety communication
Conclusion
Cardiac MRI provides detailed information about heart structure, function, tissue, and blood flow without ionising radiation. Your cardiology team interprets it alongside symptoms, ECG, echocardiography, blood tests, and other relevant investigations.