Cardiac MRI Information for Our Referring Physicians
Common Indications for Cardiac MRI
- Quantifying left and right ventricular function
- Heart failure
- Arrythmogenic right ventricular dysplasia (ARVD)
- Pulmonary hypertension
- Defining cardiac anatomy
- Constrictive pericarditis
- Cardiac neoplasm or thrombus
- Congenital heart disease
- Demonstrating the presence of a patent foramen ovale (PFO)
- Myocardial Perfusion: for suspected ischemic heart disease (e.g. angina) Quantifying blood flow
- Valvular disease (e.g. aortic regurgitation, mitral regurgitation, aortic stenosis, etc.)
- Shunts: ASD, VSD, PAPVR, and PDA Assessing myocardial scar / viability
- Identifying hibernating myocardium before revascularization
- Differentiating cardiomyopathy from old myocarditis
Coronary Artery MRA: For Anomalous Coronary Arteries
- Special consideration should be made for patients:
- That are poor echo candidates (e.g. bad echo windows)
- That are poor nuclear candidates (e.g. obesity, large breasts, small size / women).
- Where quantification is important
- Who want to avoid a more invasive test (e.g. TEE, cardiac catheterization)
- Who want one comprehensive test rather than multiple tests
Why would I want to order a perfusion cardiac MRI on my patient instead of a nuclear perfusion (SPECT) study?
- There are many possible reasons. These include:
- Higher spatial resolution
- Shorter exam time
- Absence of soft tissue attenuation artifacts
- No radiation
- The ability to assess other aspects of the heart better and more quantitatively, such as myocardial viability and ventricular and valvular function.
Is perfusion cardiac MRI more accurate than nuclear perfusion (SPECT) imaging?
We don't know yet. There are no published studies that compare the two techniques head-to-head in the same patient population. However, the studies that have been published to date show perfusion cardiac MRI is a safe and accurate test for assessing for the presence of obstructive coronary artery disease. Certainly, the absence of radiation and soft tissue attenuation artifacts make it an attractive alternative. In addition, the higher spatial resolution of MRI allows visualization of perfusion within the myocardial wall. This may give MRI a unique advantage over SPECT for assessing balanced ischemia.
Why would I want to order a cardiac MRI on my patient with valvular disease if they've already had an echocardiogram?
There are many reasons. Most relate to the fact that MRI is a much more quantitative test. In patients with valvular regurgitation, MRI can better quantify how leaky the valve is. This is especially important for patients with mitral regurgitation when the regurgitant jet is eccentric. In patients with calcific valvular stenosis, it can better visualize the valve and directly assess how well it opens. In addition to assessing the valves themselves, MRI is also better at quantifying the effect of the valvular disease on the cardiac chambers. The difference between echocardiography and MRI can sometimes be startling. For example, MRI has demonstrated mild mitral regurgitation in some patients who were thought to have severe, eccentric mitral regurgitation based echocardiograms from nationally and internationally recognized centers. For more information on the value of cardiac MRI in assessing patients with mitral regurgitation, click here.
Should everyone with valvular disease get a cardiac MRI?
No. However, MRI is of great benefit to those patients whose valvular disease is thought to be significant enough to warrant serial follow-up studies as well as for those patients in whom one is trying to determine the timing of surgical intervention. It is also of great benefit when the degree of valvular disease is uncertain, because it can spare the patient a transesophageal echo.
How can cardiac MRI help me take care of my patients with heart failure?
Cardiac MRI can be extremely helpful in assessing patients with heart failure. Cardiac MRI is the standard of reference for determining ejection fraction; and, ejection fraction is often the key determinant for deciding whether a patient will benefit from an implantable cardioverter defibrillator (ICD). Also, cardiac MRI can be helpful in determining the cause of the heart failure, such as in those patients with myocardial scar (i.e. myocarditis), iron overload (i.e., hemochromatosis), and infiltration (i.e.amyloid).
Isn't the cost of cardiac MRI prohibitive?
No. Most physicians are surprised to learn that the reimbursement for cardiac MRI is similar to that of echocardiography, and significantly less than that for nuclear (SPECT) perfusion imaging.