Cardiac MRI

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What is a cardiac MRI?

Also known as Cardiac Magnetic Resonance (CMR), a Cardiac MRI is a type of Cardiac imaging test used to diagnose various heart diseases. It involves the use of a Magnetic Resonance Imaging (MRI) machine. The machine utilises very powerful magnets and radiofrequency pulses to visualise your heart tissues at a high resolution — allowing the cardiologist to evaluate the heart’s anatomy and function and to detect Cardiac diseases.

Some Cardiac MRI tests require the use of a gadolinium-based contrast dye injected into the bloodstream. These are used to accurately localise areas in the heart muscle which are damaged.

What is a cardiac MRI for?

A Cardiac MRI is used to assess your heart’s size, shape, chambers, valves and function. A Cardiac MRI also helps to:

  • Monitor the progression and severity of heart diseases
  • Diagnose certain conditions such as inflammation, blood clots or tumours
  • Examine the extent of damage from a previous heart attack
  • Assess the effectiveness of treatments or procedures
Who would need a cardiac MRI?

A Cardiac MRI is recommended for patients with the following:

  • Heart failure
  • Cardiomyopathy (diseases related to the heart muscles)
  • Coronary artery diseases (caused by narrowed heart arteries)
  • Heart valve diseases
  • Congenital heart disorders (heart conditions that are present from birth)
  • Heart tumour
How accurate is a cardiac MRI?

A Cardiac MRI produces high-resolution images and provides very accurate measurements of your heart. A gadolinium contrast dye is often used during a Cardiac MRI. This contrast dye greatly improves the visualisation between different tissue layers of your heart as compared to other non-invasive Cardiac tests.

Because of that, in certain Cardiac conditions, a Cardiac MRI may allow your cardiologist to see the patterns of abnormalities in your heart that would otherwise require invasive biopsies to diagnose. A Cardiac MRI is thus an important imaging test that complements other Cardiac assessments such as echocardiography.

How safe is a cardiac MRI?

One advantage of a Cardiac MRI is that there is no ionising radiation involved in the procedure and the magnetic field is not harmful. The test is also pain-free but may be uncomfortable as you need to lie down on the MRI machine table for about an hour.

As there is no risk of radiation, an MRI can also be done for pregnant patients. However, do inform your doctor as the contrast, rather than the MRI itself could also be a risk for the baby. Additionally, some patients may be allergic to the contrast.

Prior to the test, it is important to let your doctor know of any prior health problems you may have had, surgeries you’ve done and if you are pregnant. You may also want to let your cardiologist know if you suffer from claustrophobia or anxiety.

Who cannot take a cardiac MRI test?

A Cardiac MRI may not be suitable for the following:

  • Have metal-based implants, including certain models of:
    • Pacemakers
    • Implantable cardioverter-defibrillators
    • Implantable medicine infusion pumps
    • Ear implants
    • Vessel coils, stents, or clips
    • Intrauterine contraceptives (IUDs)
    • Neurostimulator
    • Bone growth stimulator
  • Are claustrophobic or have anxiety
    • The test will require you to lie down in a tube-like machine for up to an hour. However, if the patient is willing, the doctor may prescribe a mild sedative prior to the exam.
  • Extremely obese patients who are not able to fit inside the MRI scanner

The good news is that most medical implants are now MRI-compatible. It is important to check with your doctor to ensure that you do not encounter complications during your test. Some of these implants, while not dangerous to you, may affect the scan quality so your doctor needs to take that into account.

As the contrast material is often used during the procedure, do also remember to let your doctor know if you:

  • Are pregnant, breastfeeding or have a possibility of being pregnant
  • Have kidney-related and/or liver-related diseases
  • Are undergoing dialysis
  • Are allergic to the gadolinium-based contrast

If it is not possible for you to go through with a Cardiac MRI, your cardiologist will recommend alternative methods of testing.

How do I prepare for a cardiac MRI?

There are a few things you should take note of before proceeding with the Cardiac MRI. It may differ depending on your medical history, current condition, and the range of tests you are taking but the general guidelines are as follows:


Food & drinks ● No restrictions
Clothing ● You will be asked to change into a patient gown

● Remove all glasses, belts, piercings & jewellery

● Inform your doctor if you have permanent eyeliner or tattoos


Allergy ● Tell your doctor if you are allergic to the contrast

● You may be asked to consume some medicine to prepare for the test


Claustrophobia ● Inform your doctor if you are claustrophobic

● If a Cardiac MRI is the only test that would suffice, your doctor may prescribe anti-anxiety medication

● In such cases, you must have someone take you home

Medical history Inform your doctor if you:

● Have kidney or liver-related conditions

● Unable to lie down for 1 hour

● Have metal-based implants

● Pregnant or breast-feeding


Medication, vitamin, and supplements ● No restrictions
What can I expect from a cardiac MRI?

The procedure for a Cardiac MRI is as follows:

  • You will be asked to change into a patient gown and remove all metal-based objects.
  • If you are doing the MRI with a contrast material, a nurse will inject the contrast dye through an IV line. You may feel minor discomfort at the injection site which should subside quickly.
  • You will be asked to lie on the MRI scan table. It is important to stay still and you may be comfortably secured to the table to prevent movement during the scan. Movement may affect the quality of the scan.
  • A staff will be outside of the room, visible through a glass wall. You will be provided with a call button to contact the technician if you face any discomfort during the scan. IDo inform if you ever felt any breathing difficulties, excessive sweating, numbness, or heart palpitations.
  • You will be given a headset to block out the noise from the scanner and to hear instructions from the staff.
  • During the scan, you may hear some clicking, tapping, and humming noises as radiofrequency waves are sent from the machine. This is perfectly normal and not a cause for alarm.
  • In some cases, you will be asked to hold your breath for short periods of time (at most 10 seconds).
  • Once the scan is complete, the table will be slid out of the machine and the IV line will be removed.
How long does a cardiac MRI take?

Depending on the symptoms you present and what your doctor is trying to find out, the test Cardiac MRI scan can take between 15 – 60 minutes.

What happens after an MRI scan?

In most cases, there is no special care required after a Cardiac MRI scan. Unless your doctor tells you otherwise, you should be able to return to your normal diet and daily activities. Be sure to ask your doctor if there is anything else you need to be aware of as it will differ depending on each person’s condition.

If sedatives or anti-anxiety medicine were used during the scan, you may be asked to rest for a while before proceeding home. In this case, you must have someone take you home as you might still feel drowsy.

How long does it take to get my cardiac MRI results?

Your cardiologist will discuss your results with you during your next consultation. The follow-up appointment may also include:

  • Other tests to further monitor/diagnose your condition
  • Required changes to your diet or lifestyle to maintain your health
  • Possible treatments for the heart condition

A Cardiac MRI is a highly accurate imaging test that is used to diagnose various complex heart conditions. It is non-invasive, painless, and also suitable for a large range of patients. A Cardiac MRI can be done as a stand-alone test, but more often done in combination with other tests to ensure a proper diagnosis. Always remember to communicate both your concerns and needs with your cardiologist so that they may work with you in creating a treatment plan best suited to you.

How can we help you?

We offer consultation for a comprehensive range of cardiac diagnostic tests and treatment plans.

Dr Joshua Loh

Senior Consultant Interventional Cardiologist

Medical Director at Capital Heart Centre, Dr Joshua Loh has more than 15 years of experience in the field of cardiology.

He has extensive experience in the treatment of complex coronary and interventional procedures.