Cardiac MRI: Benefits, Procedure, and When the Test Is Needed

Being recommended for a cardiac MRI can raise many questions. Why is this test needed after an ECG or echocardiography? Is the process painful? How long will you have to stay inside the machine? Also, is MRI safe if you have a pacemaker or an implant? What if your kidney function is impaired?

Cardiac MRI is an imaging test that uses a magnetic field, radio waves, and a computer to produce detailed images of the heart and the structures around it. This test does not use X-rays or ionizing radiation. In medical practice, this test is also referred to as cardiac MRI or cardiovascular magnetic resonance (CMR).

However, cardiac MRI is not a routine test for everyone who has chest pain, shortness of breath, or palpitations. Doctors usually choose this test when they need specific information that has not been sufficiently obtained through consultation, ECG, echocardiography, CT scan, laboratory tests, or other examinations.

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What Is Cardiac MRI?

Cardiac MRI is a noninvasive imaging test designed to assess the anatomy, movement, function, and tissue characteristics of the heart. The test is performed without any incision and without inserting any instrument into the heart.

MRI stands for Magnetic Resonance Imaging. The MRI machine produces a magnetic field and radio waves, and a computer then processes the signals from body tissues into a series of images.

Unlike MRI of body parts that do not move much, cardiac MRI requires special techniques because the heart beats continuously and shifts as you breathe. For this reason, image acquisition can be synchronized with the heart’s electrical activity using ECG electrodes. You may also be asked to hold your breath for a few seconds.

Cardiac MRI can provide information about:

• The size and shape of the heart chambers.
• The thickness and movement of the heart walls.
• The heart’s ability to pump blood.
• The condition of the heart muscle.
• Scar tissue or certain types of inflammation.
• The valves and certain blood flow patterns.
• The aorta and great vessels.
• Congenital heart defects.

Not all of this information is always obtained in a single session. The doctor will choose a protocol, or a series of image acquisitions, based on the medical question that needs to be answered.

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How Cardiac MRI Works

Cardiac MRI works by capturing how body tissues respond to a magnetic field and radio waves, then processing these responses into images. This process does not use X-rays and does not pass electricity directly into the patient’s body.

Magnetic Field and Radio Waves

Most of the human body contains water. Inside the MRI’s magnetic field, the hydrogen particles in water line up in a certain pattern. Radio waves then temporarily change this alignment.

As the particles return to their original state, body tissues release signals. Because muscle, fluid, fat, and scar tissue produce signals with different characteristics, the computer can build images that clearly show the differences between tissues.

Synchronization With the Heartbeat

Staff usually attach ECG electrodes to your chest. The electrodes help the machine identify the phase of the heartbeat when taking images.

This way, images taken while the heart contracts can be distinguished from images taken while the heart is at rest. The series of images can also show the heart’s motion as a sequence of moving pictures.

A very irregular heart rhythm can reduce image quality with certain techniques. However, this does not always mean that MRI cannot be performed. The imaging team can adjust the imaging sequences to suit the patient’s condition.

Why Do You Need to Hold Your Breath?

The position of your heart changes slightly every time you breathe. This movement can make the images look blurry. For this reason, staff may ask you to breathe in, breathe out, and then hold your breath for a few seconds.

Instructions are given one at a time through an intercom. If you find it difficult to hold your breath, tell the staff. Do not force yourself or change your breathing pattern without informing the imaging team.

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Functions of Cardiac MRI

Cardiac MRI helps doctors combine information about the shape, pumping function, blood flow, and tissue condition of the heart in a single evaluation. Its main strength is not only producing images, but also distinguishing certain tissue characteristics.

Assessing Heart Structure

MRI can help show:

• The size of the atria and ventricles.
• The thickness of the heart walls.
• The shape of the heart muscle.
• The connections between the heart chambers.
• The structures around the heart.
• The connection between the heart and the great vessels.

This anatomical information is important in cardiomyopathy, congenital heart defects, pericardial disease, or when certain structures have not been clearly seen on previous tests.

Assessing Pumping Function

A series of images across different phases of the heartbeat allows doctors to see how the heart walls move. In addition, MRI can help calculate the volume of blood inside the ventricles as well as the ejection fraction, which is the percentage of blood pumped out with each contraction.

However, a single number should not be interpreted in isolation. The doctor still considers which heart chamber is being assessed, the symptoms, medical conditions, and other findings.

Assessing the Heart Muscle

One of the strengths of cardiac MRI is its ability to characterize tissue (tissue characterization). The test not only looks at the shape of the heart muscle, but also helps identify patterns of change in the tissue.

With the appropriate protocol, MRI can help evaluate:

• Inflammation of the heart muscle.
• Scar tissue after a heart attack.
• Tissue changes in cardiomyopathy.
• Myocardial viability, which is heart muscle tissue that is still alive and has the potential to maintain its function.
• Masses inside or around the heart.

Assessing the Valves and Blood Flow

MRI can help show valve movement and measure flow through certain vessels or structures. Even so, echocardiography, or a cardiac ultrasound, is still often the first test used to assess the valves.

MRI usually plays a complementary role when the doctor needs additional measurements, an evaluation of ventricular function, or a broader view of the structures.

Assessing the Aorta and Great Vessels

MRI can show the shape and size of the aorta and its connection to the heart. This test can also be used to monitor several conditions of the great vessels.

However, in acute situations, for example a suspected aortic dissection, doctors may choose a CT scan because it is generally faster.

Assessing Congenital Heart Defects

In both children and adults with congenital heart disease, MRI can help depict complex connections between the heart chambers and blood vessels. The test can also support procedure planning and monitoring after surgery.

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Conditions That Can Be Evaluated

Cardiac MRI can help evaluate several cardiovascular conditions, especially when the doctor needs detailed information about the heart muscle or anatomy. However, having one of the following conditions does not automatically mean you need to undergo an MRI.

Cardiomyopathy

Cardiomyopathy is a group of diseases that affect the heart muscle. The muscle may become too thick, enlarged, stiff, or undergo other changes that interfere with the heart’s ability to pump blood.

MRI can help the doctor assess:

• The shape and thickness of the muscle.
• The size of the heart chambers.
• Wall movement.
• Right and left ventricular function.
• Scar tissue patterns.
• Other tissue characteristics.

The MRI results are then correlated with the ECG, echocardiography, family history, and other tests.

Myocarditis

Myocarditis is inflammation of the heart muscle. Symptoms may include chest pain, shortness of breath, tiring easily, or palpitations.

MRI can help show patterns of tissue swelling, injury, and changes that support a suspected diagnosis of myocarditis. However, the diagnosis is not made based on MRI alone. The doctor also considers how the symptoms have developed, the ECG, blood biomarkers, echocardiography, and the patient’s clinical condition.

Damage After a Heart Attack

After a heart attack, part of the heart muscle may be injured and form scar tissue. MRI with specific techniques can help map the location and extent of these changes.

This information can be used to assess:

• The affected part of the muscle.
• Its effect on wall movement.
• The heart’s pumping function.
• The condition of tissue that can still maintain its function.
• The need for further monitoring or treatment.

MRI is not the first test when an acute heart attack is in progress. In that situation, rapid treatment, an ECG, cardiac biomarkers, and emergency evaluation must take priority.

Pericardial Disease

The pericardium is the membrane that surrounds the heart. Disease in this area can cause inflammation, thickening, or fluid buildup.

MRI can help evaluate:

• The thickness of the pericardium.
• Fluid around the heart.
• Signs of inflammation.
• Its effect on the filling of the heart.
• Masses in or near the pericardium.

Heart Valve Disorders

When a valve narrows or leaks, MRI can help assess the anatomy, blood flow, and the effect on the function of the heart chambers.

Even so, echocardiography still plays the main role in many cases of valve disease. MRI is usually used as a complementary test according to clinical need.

Aortic Disease

MRI can assess the size and anatomy of the aorta and help monitor vessel enlargement in certain conditions.

However, if the patient is unstable or the doctor needs results quickly, a CT scan may be more appropriate. The choice of test depends not only on image detail, but also on the level of urgency.

Aortic Disease

MRI can assess the size and anatomy of the aorta and help monitor vessel enlargement in certain conditions.

However, if the patient is unstable or the doctor needs results quickly, a CT scan may be more appropriate. The choice of test depends not only on image detail, but also on the level of urgency.

Congenital Heart Disease

In congenital heart disease, MRI can help assess:

• The connections between the heart chambers.
• The vessels entering and leaving the heart.
• Flow through abnormal connections.
• The function of the heart chambers.
• Changes after surgery or intervention.

In children, doctors usually consider age, the ability to stay still, and the possible need for sedation.

Masses in the Heart

Masses inside or around the heart may be blood clots, benign tumors, malignant tumors, or other changes.

MRI can help estimate the location, size, involvement of surrounding structures, and tissue characteristics. However, additional tests or tissue analysis may still be needed to determine the diagnosis.

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When Is Cardiac MRI Needed?

Doctors usually consider cardiac MRI when initial tests have not answered all the questions about the structure, function, or tissue of the heart. Cardiac MRI is often used after other tests in more complex heart conditions.

This test may be considered to:

• Clarify ECG or echocardiography results.
• Assess the characteristics of the heart muscle.
• View structures that are difficult to assess with other tests.
• Evaluate congenital heart disease.
• Help plan procedures.
• Assess the condition after treatment or surgery.
• Monitor changes over time.
• Look for the cause of unexplained heart dysfunction.

Does Chest Pain Always Require an MRI?

No. Chest pain has many possible causes, ranging from the muscles, digestive tract, and lungs to the heart.

Doctors decide on tests based on:

• The nature and location of the pain.
• How long the symptoms have lasted.
• Their relationship to physical activity.
• Cardiovascular risk factors.
• The physical examination.
• Whether there are signs of an emergency.

Initial tests may include an ECG, cardiac biomarkers, echocardiography, CT angiography, a stress test, or invasive angiography.

MRI may be used when the doctor needs to assess inflammation, scar tissue, the impact of limited blood flow, or the condition of the heart muscle.

Do Shortness of Breath or Palpitations Require an MRI?

Shortness of breath and palpitations also do not automatically require an MRI.

The doctor may first choose:

• An ECG to record the heart’s electrical activity.
• Holter monitoring to record the heart rhythm over a longer period.
• Echocardiography to assess structure and function.
• Laboratory tests.
• An exercise test or other tests.

Cardiac MRI is considered when these symptoms are suspected to be related to structural or tissue abnormalities that have not been seen on initial tests.

Do People Without Symptoms Need an MRI?

Cardiac MRI is not a routine screening test for all healthy people.

Heart health screening should start with an assessment of:

• Blood pressure.
• Blood sugar levels.
• Blood lipid profile.
• Smoking habits.
• Physical activity.
• Body weight.
• Family history.
• Symptoms and clinical examination results.

MRI is indeed an advanced technology. However, a more complex test is not necessarily more beneficial if there is no clear medical indication.

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Differences Between Cardiac MRI, Cardiac CT Scan, and Echocardiography

Cardiac MRI, cardiac CT scan, and echocardiography use different technologies and provide different information. For this reason, no single test is always better than the others for every patient.

Why Is Echocardiography Often Done First?

Echocardiography is easy to use for viewing the heart’s motion directly. It can evaluate the heart chambers, pumping strength, valves, fluid around the heart, and several of the great vessels.

For many patients, echocardiography results can already answer the initial clinical question. MRI is only considered when the doctor needs tissue detail, additional anatomical coverage, or specific measurements.

When Is a CT Scan More Appropriate?

A CT scan is generally faster. It is very useful for showing the anatomy of the coronary arteries, calcification, the aorta, and certain structures.

In addition, CT is more practical when the patient cannot lie down for long or needs an urgent evaluation. MRI offers better tissue detail for certain conditions, whereas imaging of the coronary arteries is more often done with CT angiography or catheter angiography.

Is MRI More Accurate?

Accuracy depends on the question that needs to be answered.

MRI can provide superior information about the heart muscle, scar tissue, inflammation, and ventricular function. On the other hand, CT may be more appropriate for the coronary arteries, while echocardiography is very useful for the valves and for viewing heart movement directly.

So, the better question is not “which one is the most accurate?” but “which test is the most appropriate for this condition?”

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Preparation Before a Cardiac MRI

Preparing for a cardiac MRI includes safety screening, gathering previous test results, and following the facility’s instructions on eating and medications. Instructions may differ depending on the protocol and the use of contrast agents.

Documents to Bring

Prepare:

• Your ID and insurance or guarantor documents.
• A test request or referral letter, if any.
• ECG results.
• Echocardiography results.
• Previous CT scan or MRI results.
• Requested laboratory results.
• A list of your medications and their doses.
• Your pacemaker, ICD, or implant card.
• Surgical records, if available.

Previous results can help the doctor compare changes over time and determine the appropriate protocol.

Information You Should Share

Tell the medical team if you:

• Have a pacemaker or ICD.
• Have an artificial valve or a stent.
• Have vascular clips, a cochlear implant, or a drug pump.
• Have had surgery in which metal was implanted.
• Have ever had metal fragments enter or remain in your body, especially around the eyes.
• Have impaired kidney function.
• Are pregnant or may be pregnant.
• Have had a reaction to contrast agents.
• Feel uncomfortable in confined spaces.
• Have difficulty lying down or holding your breath.
• Take medications regularly.

Do not withhold information out of worry that the test will be canceled. Complete information actually allows the team to plan the test more safely.

Do You Need to Fast?

There is no fasting rule that applies to all MRI scans. Instructions may differ based on the protocol, the use of contrast, the need for sedation, and the facility’s policy.

Therefore:

• Follow the instructions given when your test is scheduled.
• Do not use other patients’ experiences as a reference.
• Do not stop your regular medications without your doctor’s guidance.
• Ask specifically about diabetes, blood pressure, and heart medications.

Items You Must Remove

Before entering the MRI room, you will be asked to remove metal objects and electronic devices, such as:

• Jewelry.
• Watches.
• Mobile phones.
• Cards with magnetic strips.
• Hearing aids.
• Eyeglasses.
• Hair accessories.
• Removable dentures.
• Clothing with metal components.

The MRI magnetic field is always on. Magnetic objects can be pulled toward the machine, while electronic items can be damaged or interfere with the test.

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The Cardiac MRI Procedure

The cardiac MRI procedure begins with safety screening, followed by placement of monitoring equipment, acquisition of several image series, and a check of image quality before the patient goes home.

1. Registration and Screening

Staff will verify your identity, the type of test, and the medical reason for it. You will also be asked questions about surgery, implants, kidney problems, pregnancy, allergies, and any previous MRI experience.

If a device in your body has not been identified, the test may need to be postponed until its documentation is available.

2. Preparation in the Examination Room

Staff may:

• Ask you to change your clothes.
• Insert an IV line if contrast is needed.
• Attach ECG electrodes.
• Attach a pulse monitor.
• Fit a breathing monitor belt.
• Place a signal receiver coil (coil) over the chest area.
• Provide ear protection.

Some chest hair may need to be shaved so the electrodes stick properly.

3. Positioning Inside the Machine

You will lie on your back on a table that moves into the center of the machine. Supports may be used to keep your body comfortable and stable.

The staff are in the control room, but they can see, hear, and talk to you through an intercom.

4. Image Acquisition

The machine takes several series of images. During the process, you may be asked to:

• Stay still.
• Breathe in or breathe out.
• Hold your breath for a few seconds.
• Maintain your position between series.

If contrast is used, some images may be taken before the injection and others afterward.

5. After the Test

Once the series are complete, staff check whether the image quality is adequate. The IV line and monitoring equipment are then removed.

If no sedation was used, you can generally return to your usual activities. On the other hand, if sedation was used, you will need time to recover and someone to accompany you home.

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Duration of a Cardiac MRI

A cardiac MRI generally takes about 30 to 90 minutes, but the duration may vary from patient to patient. This time does not necessarily include registration, screening, and preparation.

The duration is affected by:

1. The condition being assessed.
2. The number of image series.
3. The use of contrast.
4. The speed and regularity of the heartbeat.
5. The ability to stay still.
6. The ability to hold your breath.
7. The need to repeat images.
8. Protocols for congenital heart disease.
9. The use of sedation or special monitoring.

The test often lasts 30 to 60 minutes or longer, while RadiologyInfo states that the entire imaging process is usually completed in 90 minutes or less. Because protocols differ, confirm the estimated time with the facility before you arrive.

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Use of Contrast in MRI

Not every cardiac MRI requires a contrast agent. Its use is determined by the type of information the doctor wants to obtain, especially when an assessment of scar tissue, inflammation, or certain blood flow is needed.

What Contrast Agents Do

MRI contrast agents are generally gadolinium-based. After being given through a blood vessel, the agent can help make tissue patterns clearer.

Contrast can be used to assess:

1. Scar tissue.
2. Inflammation.
3. Blood flow to the heart muscle.
4. The characteristics of a mass.
5. Other patterns of tissue change.

MRI without contrast can still provide important information about shape, function, movement, and flow. So, MRI with contrast is not automatically better.

Contrast and Kidney Function

Most gadolinium contrast agents are removed from the body through the kidneys. For this reason, the doctor may request a kidney function test before the injection, especially if you have kidney disease or certain risk factors.

Nephrogenic systemic fibrosis (nephrogenic systemic fibrosis, or NSF) is a very rare complication, especially with modern contrast agents, and its risk is mainly linked to severe kidney impairment. The American College of Radiology updated its guidance on contrast agents and this risk in 2025.

Reactions to Contrast

Reactions to contrast agents can occur, although severe allergic reactions are rare. Mild symptoms may include:

• Nausea.
• Headache.
• Discomfort at the injection site.
• A temporary metallic taste in the mouth.

Tell the staff right away if you develop itching, hives, swelling, shortness of breath, severe dizziness, or other symptoms after the injection.

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Safety of Cardiac MRI

Cardiac MRI does not use ionizing radiation, but it still requires strict safety procedures. The magnetic field, radiofrequency energy, changing magnetic fields, noise, contrast agents, and medical devices each carry different risks.

The FDA explains that magnetic objects can be pulled toward the machine, radiofrequency energy can cause heating, and the magnetic field can interfere with the function of certain electronic devices.

Does an MRI Hurt?

The scan itself generally does not cause pain. However, you may feel uncomfortable because of:

• Lying down for quite a long time.
• Keeping your position still.
• Holding your breath repeatedly.
• The noise of the machine.
• A space that feels confined.
• The IV insertion.
• A warm sensation in certain parts of the body.

Tell the staff if warmth, pain, or discomfort starts to bother you.

Why Is the MRI Machine Noisy?

The knocking or thumping sounds come from changes in the magnetic field during image acquisition. These sounds are a normal part of the process.

Staff should provide earplugs or headphones. Hearing protection is important because the machine can be quite loud.

What If You Are Afraid of Confined Spaces?

Feeling anxious in confined spaces is quite common. Mention this before the day of the test so the team can prepare a suitable approach.

Some steps that may help include:

1. Asking for an explanation of how the test will go.
2. Practicing the breathing instructions.
3. Listening to music, if available.
4. Asking whether an MRI machine with a wider opening is available, if it suits the needs of the test.
5. Discussing the possibility of sedation with your doctor.

Do not take sedatives on your own initiative. If sedation is used, you will need monitoring and someone to accompany you home.

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MRI for People With Pacemakers and Implants

Having a pacemaker or an implant does not always mean that MRI is not allowed. However, the type of device and its conditions of use must be confirmed before the test.

Some medical devices or metal objects can move, heat up, malfunction, or reduce image quality in the MRI environment. For this reason, the FDA advises patients to bring their implant card and to tell the MRI team about all devices or metal objects in their body.

MRI Safety Categories

• MR Safe: poses no known risks in the MRI environment.
• MR Conditional: safe to use in the MRI environment only if all of the specified requirements are met.
• MR Unsafe: must not be in the MRI environment because it poses unacceptable risks.

Patients with a device whose safety status is unknown should not undergo the test until the type of device and its requirements have been verified.

Devices You Need to Report

Let the team know if you have:

• A pacemaker.
• An implantable cardioverter-defibrillator (ICD).
• An artificial heart valve.
• A stent.
• Vascular clips.
• A cochlear implant.
• A neurostimulator.
• A drug pump.
• An orthopedic implant.
• Metal fragments.
• Other electronic medical devices.

Device Documents to Bring

Bring:

• Your device card.
• The manufacturer’s name.
• The brand and model.
• The date of implantation.
• Surgical records.
• Contact details of the facility that implanted the device.
• Device check results, if requested.

For an MR Conditional pacemaker or ICD, the facility may need to coordinate before, during, and after the scan. So, mention your device when the test is being scheduled, not only once you are already in the MRI room.

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Cardiac MRI in Children

Cardiac MRI can be performed in children when there is a medical indication. However, preparation needs to be adjusted to the child’s age, development, health condition, and ability to stay still.

Why Might a Child Need an MRI?

Doctors may consider an MRI to:

• Clarify congenital heart disease.
• Assess the connections between the heart chambers and blood vessels.
• Measure heart function.
• Evaluate blood flow.
• Plan surgery or an intervention.
• Monitor the results of previous procedures.
• Complement echocardiography results.

Readers who want to understand cardiovascular conditions in children can also read the Heartology article on Kawasaki disease and its risks to children’s hearts.

Preparing Your Child

Parents can help by:

1. Explaining that the machine will “take pictures of the heart.”
2. Introducing the sounds the machine makes.
3. Practicing lying still.
4. Practicing short breath-holds, if appropriate for the child’s age.
5. Following the instructions on eating and drinking.
6. Bringing previous test results.
7. Letting the team know about the child’s sensory or developmental needs.

Explain the test to your child honestly and in a way that suits their age. Let them know that someone will be with them and that they can tell the staff if they feel uncomfortable.

Does a Child Need Sedation?

Not all children need sedation or anesthesia. The considerations include:

• Age.
• Developmental stage.
• Ability to stay still.
• Duration of the test.
• Level of anxiety.
• Complexity of the protocol.
• Medical condition.

If sedation is needed, the test must be supported by competent staff and appropriate monitoring.

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Cardiac MRI Results

Cardiac MRI results are not just a single image, but many image series and measurements that need to be reviewed systematically. For this reason, the report cannot always be given immediately after the patient leaves the machine.

Who Reads the MRI Results?

In general, a doctor who is competent in MRI interpretation will analyze the images and prepare a report. The report is then passed on to the referring or treating doctor so it can be related to the patient’s clinical condition.

Is the Report the Same as a Diagnosis?

Not always. An MRI report describes the imaging findings, whereas the final diagnosis may take into account:

• Symptoms.
• Medical history.
• Physical examination.
• ECG.
• Echocardiography.
• Laboratory tests.
• CT scan or angiography.
• Family history.
• Changes in condition over time.

So, do not interpret a single term in the report on its own through internet searches.

Questions You Can Ask

When discussing the results, you can ask:

• What are the main findings of the MRI?
• Do the results explain my symptoms?
• How do the results compare with previous tests?
• How is my heart’s pumping function?
• Are there any changes in my heart muscle?
• Do I need additional tests?
• Does my condition need to be monitored?
• Do the results affect my treatment plan?
• When do I need to come back for a follow-up visit?

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When Should You Seek Immediate Care?

Cardiac MRI is not the first test in an emergency. Seek medical help immediately if you have severe chest pain or a feeling of pressure in the chest that comes on suddenly, especially if it is accompanied by:

• Pain spreading to the arm, back, neck, jaw, or stomach.
• Shortness of breath.
• Cold sweats.
• Nausea or vomiting.
• Severe dizziness.
• Fainting or nearly fainting.
• Sudden weakness.

Some heart attacks start slowly with discomfort that seems mild. So, do not wait for an MRI appointment or a routine consultation if your symptoms point to an emergency.

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Conclusion

Cardiac MRI can provide detailed information about the structure, function, blood flow, and tissue characteristics of the heart. The test does not use X-rays, but it still requires safety screening, especially if you have a pacemaker or an implant, have kidney problems, are pregnant, or need sedation.

However, a more advanced test is not necessarily the most appropriate test for everyone. Your doctor will consider your symptoms, risk factors, ECG results, echocardiography, laboratory tests, and other tests before recommending an MRI.

By understanding the purpose, procedure, benefits, and limitations of cardiac MRI, you can prepare more calmly and have a more focused discussion with your doctor about the appropriate evaluation steps.