Magnetic Resonance Imaging (MRI)
What are the generally accepted indications for magnetic resonance imaging (MRI)? Magnetic resonance imaging is increasingly being used for diagnosis…Read more
Cardiovascular magnetic resonance (CMR) is an advanced form of magnetic resonance imaging utilising electrocardiogram gating to avoid cardiac motion blurring.
Its main use is in assessment of anatomy, function and viability of the heart, but it is also useful in detecting ischaemia and infarction, and in assessing congenital heart disease, the aetiology of heart failure, heart valve dysfunction, masses and the presence of inherited diseases.
Cardiac MRI offers greater soft tissue detail than does echocardiography, and can provide unique information with regard to scarring, viability and masses. Soft tissue detail is also superior to computed tomography (CT) scanning. It might be used to further evaluate pathology identified by each of these imaging modalities. The absence of ionising radiation is also an advantage, particularly in young patients and in those requiring multiple scans to follow their condition.
Access to cardiac MRI can vary depending on geographical health service and patient referral policies. For instance, in Australia, cardiac MRI is currently restricted to specialist referral. This and the limited number of specialised cardiac MRI imaging facilities, especially in rural regions, make MRI more difficult to access than more traditional modalities, such as echocardiography and exercise stress tests.
Cardiac MRI is not currently capable of high-resolution imaging of the coronary arteries and quantification of arterial stenoses, for which catheter angiography and CT angiography are superior. It does have an accepted role in assessment of anomalous coronary arteries.
The following are examples of common indications for cardiac MRI studies:
Recent renal function tests, particularly estimated glomerular filtration rate (eGFR), is of assistance in confirming adequate renal function pre-test, to lessen the chance of NSF related to gadolinium injection. An eGFR below 30 mL/min/1.73 m2 is the recommended threshold where gadolinium should not be administered. If the patient is medically unstable, it is prudent to have an eGFR result that is more recent than 6 weeks before the test, as kidney function might have deteriorated in the meantime. See Gadolinium Contrast Medium (MRI Contrast Agents) for more information about gadolinium and kidney function assessment.
MRI scans have safety implications for metal implants of any type in the body when entering a high-strength magnetic field. Referrers should ensure patients presenting for cardiac MRIs have details of the brand, model number and other identifying data of any implants. This will allow the MRI technician to confirm compatibility and maintain patient safety in the MRI environment.
Additional information for MRI angiogram, RV and LV function MRI and structural assessment – Most often the referral is from a cardiologist or cardiothoracic surgeon, and usually as a follow up to a preceding investigation, such as echocardiography. Cardiac MRI is particularly suited to those with congenital heart disease.
In the absence of contrast medium administration, and following appropriate safety screening, there are no anticipated adverse effects of MRI. Sometimes patients may feel a little warm during the scan but this is of no clinical significance.
Gadolinium injection may be required when Cardiac MRI is performed for the following indications:
The likelihood of adverse events related to the gadolinium injection is very low. Allergic reactions can occur with gadolinium, ranging from mild (e.g. rash) to severe (e.g. anaphylaxis), but this is very uncommon. Any adverse (anaphylactoid or allergic) reaction to gadolinium would be handled within the hospital or imaging department. See Gadolinium Contrast Medium (MRI Contrast Agents) for details about the nature and frequency of anaphylactoid reaction and NSF.
It is more common to experience side effects from the adenosine infusion rather than the gadolinium. These include facial flushing, chest tightness, jaw discomfort, shortness of breath, light headedness and palpitations. These side effects are usually short lived due to the short half-life of adenosine.
Severe side effects are uncommon (incidence approximately 1 in 1500), but include:
The risk of death related to adenosine infusion is approximately 1 in 10,000.
Page last modified on 26/7/2017.
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RANZCR® intends by this statement to exclude liability for any such opinions, advices or information. The content of this publication is not intended as a substitute for medical advice. It is designed to support, not replace, the relationship that exists between a patient and his/her doctor. Some of the tests and procedures included in this publication may not be available at all radiology providers.
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