1. Aetna considers magnetic resonance imaging (MRI) of the cardiovascular system medically necessary for the indications listed below, in accordance with guidelines developed by the American College of Radiology (ACR) and the American Heart Association (AHA):

   1. Thoracic aortic disease

      For example: abnormal aortic contour or size on chest X-ray, differentiation of mediastinal mass vs. vascular abnormality, to rule out aortic dissection, aneurysm, leaking thoracic aneurysm, exclude aortic source of peripheral embolization, Valsalva aneurysm, Marfan's syndrome and aorta annular actasia, after therapy of aortic dissection of aortic arch anomalies, coarctation, following aortic angioplasty, periaortic abscess or infection; or

   2. Pericardial disease

      For example: to assess pericardial thickness and detection of metastases, for diagnosing pericarditis and constriction, for diagnosing effusion and tamponade; or

   3. External or internal masses, pathology of lung and pleura

      For example: chest wall and mediastinal tumor invasion of the lung and pleura, lipoma, intracavity tumors, and differentiation of tumor from thrombus, assessment of vascular invasion, hilar assessment, and paracardial/cardiac invasion, pleural diseases; or

   4. Pathology involving surrounding structures

      For example: to evaluate intrinsic abnormalities of the pulmonary arteries, including central thrombi, aneurysms, stenoses, occlusions, dissection, and extravascular disease involving the pulmonary arteries; or

   5. Assessment of ventricular dysplasia; or

   6. Congenital heart disease

      For example: pulmonary atresia, severe obstruction to the right ventricular outflow tract, complex cyanotic heart disease, pulmonary venous anomalies, after surgery for correction of congenital heart disease; or

   7. Cardiac function, morphology, and structure when the following criterion is met:

      • After it has been determined that echocardiogram (ECG) is inconclusive; or

   8. Diseases of the large veins

      For example: acquired and congenital abnormalities of the superior vena cavae, inferior vena cavae, and portal venous system (e.g., vena caval thrombus, differentiation of tumor thrombus and blood clot of the vena cava, superior vena caval syndrome, superior vena caval invasion or encasement by lung or mediastinal tumors, diagnosis of Budd-Chiari syndrome, and diagnosis of caval anomalies); or

   9. Valvular heart disease when the following criterion is met:

      • After it has been determined that ECG and Doppler studies are inconclusive; or

   10. To demonstrate complications of infarction

       For example: formation of an aneurysm, mural thrombus formation, to demonstrate regional wall motion or wall thickening abnormalities of a damaged left ventricle.

2. Aetna considers MRI of the cardiovascular system experimental and investigational as a screening test for cardiovascular disease, and for all other indications (except for the ones listed above).

3. Aetna considers intravascular MRI experimental and investigational for detecting coronary vulnerable plaques.

4. Aetna considers whole-heart coronary MRI experimental and investigational for the non-invasive evaluation of the coronary arteries.

Requests for cardiac MRI for indications that are not listed above are subject to medical review.

Any evidence of duplicative services, such as the use of computerized axial tomography (CT) scan, radionuclide studies, ultrasound, radioisotope scanning, sonograms and MRI, is subject to medical review for an evaluation of the medical necessity of the MRI. There must be a compelling reason for multiple diagnostic procedures; in such situations, the MRI will only be considered medically necessary if the physician documents specific, necessary information to be gained from the additional test(s) that the initial test did not provide. If a claim reveals that MRI was performed to detect a suspected medically necessary indication but instead demonstrated a non-medically necessary indication, the MRI will be considered medically necessary.

Magnetic resonance imaging (MRI) is a noninvasive imaging procedure used primarily for studying intracranial and intraspinal pathology, and for evaluating abnormalities of the musculoskeletal system, the heart, and pelvis.  It is also used to evaluate abdominal visceral problems.

Magnetic resonance imaging uses a pulsed radiofrequency wave in the presence of a high magnetic field to produce high quality images of the body in any plane.  Magnetic resonance imaging may be preferred to a CT scan because of its established capability to depict soft tissue, often without the need for contrast material.

During a MRI examination, the patient is placed inside a very strong hollow magnet.  A fraction of the hydrogen atoms within the patient's body align themselves with the magnetic field.   The body area being examined is exposed to radio waves that are first absorbed and then emitted.  The emitted waves become the MRI signal.  The signal is analyzed by computer and processed into images of the body.  The images are usually in the form of slices through the body.   The slices can be taken in any plane.  Magnetic resonance imaging also has the ability to acquire two-, three- or four-dimensional data.  Images with high signals appear white (e.g., fat) and those with low signals appear black (e.g., air in the lungs).

Magnetic resonance imaging is sometimes performed with the use of contrast agents for specific indications in order to achieve a desired image.   Contrast enhancement agents are approved by the Federal Drug Administration for use with MRI:  Magnevist, (gadopentetate dimeglumine), ProHance, (gadoteritol), Omniscan, (gadodiomode), Ultravist, (iopromide), and Ferumoxsil (feroxide).

Magnetic resonance imaging has been shown to have several technical advantages in comparison to other standard diagnostic testing procedures such as CT scan and X-ray.  Magnetic resonance imaging is a non-invasive technique that uses no ionizing radiation and according to available literature, there are no known clinically significant side effects.  The literature indicates magnetic resonance imaging can be used during the first trimester of pregnancy when it has been shown to offer an advantage over other modalities.  Magnetic resonance imaging does not always require contrast agents in order to achieve a high degree of resolution. The literature indicates there is some increased risk of administering MRI contrast agents to patients with asthma or iodine allergy, but administration of these agents is still performed with caution.  Magnetic resonance imaging soft tissue contrast has been shown to be superior to that of other imaging modalities, and there are no image artifacts from bone.  The literature indicates magnetic resonance imaging has greater inherent contrast between different types of normal body tissues and between pathological tissues and normal tissues.  Magnetic resonance imaging clarity is equal in any view:  axial, sagittal, coronal, or oblique.  Magnetic resonance imaging also has the ability to acquire two dimensional, three-dimensional and four-dimensional data.

Magnetic resonance imaging has been shown to have several disadvantages.  It requires more patient cooperation than other tests.  Imaging time is longer than CT or X-ray.  Exposure time of MRI is between 100 and 1,000 times as long as the time required for a CT slice.  Installation and operation of MRI equipment is costly.  It has limitations in the acute trauma setting due to its incompatibility with various medical and life support devices.  Transient biological effects have been noted, such as cardiac T-wave changes.  Overheating may result from the alternating magnetic transmissions of the radiofrequency coils.  The literature indicates that care should be exercised when using MRI with infants, elderly patients, and hyperpyrexic individuals.  There is a forceful attraction of ferromagnetic objects to the magnet.  Most aneurysm clips, intracranial or intraocular metal, shrapnel, cardiac pacemakers or pacemaker wires and cochlear implants are absolute contraindications for MRI.   Magnetic resonance imaging has somewhat less spatial resolution than CT scan.  According to the literature, incidental anatomic discrepancies, such as nonspecific white matter abnormalities, may be misinterpreted as causing the patient's symptoms. 

Magnetic resonance imaging in the field of cardiology is evolving at a dynamic pace.  However, because of the lack of availability of state of the art MRI technology and expertise, echocardiography, in particular transesophageal echocardiogram (TEE), remains the generally accepted modality for the evaluation of cardiac anatomy and function most of the time by most practitioners. According to the literature, fifty to sixty percent of the population cannot be adequately imaged with echocardiogram.  For these patients, MRI has been shown to be particularly important.  Magnetic resonance imaging has the following important attributes that make it effective for the evaluation of the cardiovascular system:

• It can produce high resolution images of the cardiac chambers and large vessels without the need of contrast agents;
• It is a three dimensional imaging technique;
• It produces images of cardiovascular structures without the interference from adjacent bone or air;
• Fast gradient echo techniques can be used to assess global and regional ventricular contractile function;
• Velocity encoded techniques permit measurement of blood flow;
• It has high tissue contrast;
• It does not have the weakness of geometric assumptions as does angiography and echocardiography in the assessment of ventricular volumes; and
• It does not have difficulties in evaluating right ventricular function.

Since MRI can usually not be brought to the bedside like the TEE, it may not be the first test used in an emergency situation, but may be used to better define the diagnosis.  Under established guidelines, magnetic resonance imaging is used as the diagnostic test for the following indications: diseases of the aorta, diseases of the pericardium, external and internal masses, pathology involving surrounding structures, congenital heart disease, and ventricular dysplasia.  Magnetic resonance imaging is increasingly being used in the assessment of cardiac function, morphology and structure.  When echocardiography does not provide enough information, in these circumstances, the literature suggests MRI may be warranted.

García-García et al (2008) noted that thin-capped fibroatheroma is the morphology that most resembles plaque rupture.  Detection of these vulnerable plaques is essential for studying their natural history and assessing potential therapies and, thus, may have an important impact on the prevention of myocardial infarction and death.  At the present time, conventional grayscale intravascular ultrasound, virtual histology and palpography data are being collected with the same catheter during the same pullback.  A combination of this catheter with either thermography capability or additional imaging, such as optical coherence tomography or spectroscopy, would be an exciting development.  Intravascular MRI also holds much promise.  To date, none of the techniques described above has been sufficiently validated and, most importantly, their predictive value for adverse cardiac events remains elusive.  Very rigorous and well-designed studies are compelling for defining the role of each diagnostic modality.  Until vulnerable plaques can be detected accurately, no specific treatment is warranted.

Hauser and Manning (2008) stated that the non-invasive detection of coronary artery disease has been a major goal of newer cardiac imaging technologies.  In the past 10 years, coronary MRI has undergone significant advances, resulting in excellent sensitivity for detecting coronary artery disease.  The authors noted that whole-heart coronary MRI, a technique that is similar to coronary CT angiography, has emerged as a promising approach for the non-invasive evaluation of the coronary arteries.  This is in agreement with the observation of Schaar et al (2007) who noted that the role of non-invasive imaging in vulnerable plaque detection is currently under investigation.  Several invasive and non-invasive techniques (e.g., MRI and multi-slice spiral computed tomography) are currently under development to evaluate the vulnerable plaque.  However, none has proven its value in an extensive in vivo validation and all have a lack of prospective data.