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Medical Policy

Policy Num:      06.001.004
Policy Name:    Magnetic Resonance Angiography (MRA) of the Chest (excluding the heart)
Policy ID:          [06.001.004  [Ar / B / M+ P+]  [6.01.17]

Last Review:      July 11, 2023
Next Review:      Policy Archived
 

ARCHIVED

Related Policies: None

Magnetic Resonance Angiography (MRA) of the Chest (excluding the heart)

Summary

Magnetic resonance angiography (MRA) is the general term used to describe magnetic resonance imaging of vascular structures, but when MR is used to image a vein instead of an artery, the term “magnetic resonance venography” (MRV) may be used. The technical capabilities of current MRA make it most suitable for evaluation of large- and medium-sized vessels such as the thoracic aorta and major aortic branch vessels or the larger caliber central veins. MRA of the chest has the potential to replace angiography for some indications, thus eliminating its associated risk. In addition, MRA offers the unique ability to provide cross-sectional and projectional images of the vasculature in predictable orientations and easy-to-understand display formats without the use of contrast materials. This capability can facilitate planning of complex surgical procedures by simultaneously demonstrating the vascular anatomy of interest and displaying the anatomic interrelationships of these structures in three dimensions.

 MRA applications in the thorax can be subdivided into the following categories:

 · Acquired disease of the thoracic aorta;

· Developmental anomaly of the thoracic vasculature;

· Systemic venous thrombosis or occlusion;

· Pulmonary embolism.

Objective

The objective of this evidence review is to evaluate the safety and efficacy of MRA of the chest in evaluating/imaging vascular structures.

Policy Statements

MRA of the chest may be considered medically necessary in patients with the following indications in whom angiography/venography would otherwise be indicated and in whom the result of MRA could obviate the need for angiography/venography:

 Acquired disease of the thoracic aorta (i.e., aortic dissection, aneurysm occlusive disease, and aortitis);

· Developmental anomaly of the thoracic vasculature; or

· Systemic venous thrombosis or occlusion.

MRA of the chest may be considered medically necessary as an alternative to angiography for evaluation of pulmonary embolus in patients who have a contraindication to the use of IV iodinated contrast material (e.g., a history of severe contrast media allergy, such as anaphylactic shock or a cardiac arrest; or high risk of contrast-induced renal failure such as in diabetic patients with moderate renal insufficiency).

Investigational applications of MRA of the chest include, but are not limited to, the following:

 · Evaluation of pulmonary emboli in patients without contraindications to the use of IV iodinated contrast agents.

Policy Guidelines

It should be noted that the above policy indicates that MRA of the chest (CPT code 71555) is considered medically necessary only as an alternative to an angiography. Therefore, MRA should rarely precede or be followed by an angiography/venography as described by the following CPT codes:

75600-75605: thoracic, aortography

75741-75746: pulmonary angiography

75756: internal mammary, angiography

75827: superior vena cava venography

 In the workup of a pulmonary embolism, an MRA is not routinely the first imaging test done. MRA is typically preceded by a ventilation-perfusion scan. The necessity for a subsequent angiogram (or MRA in those who have contraindications for an angiogram) is based on both the results of the ventilation perfusion scan and the clinical suspicion of pulmonary embolus.

Benefit Application

BlueCard/National Account Issues

Benefits are determined by the group contract, member benefit booklet, and/or individual subscriber certificate in effect at the time services were rendered.  Benefit products or negotiated coverages may have all or some of the services discussed in this medical policy excluded from their coverage.

Background

Magnetic resonance angiography (MRA) is an application of magnetic resonance imaging (MRI) that provides visualization of blood flow, as well as images of normal and diseased blood vessels. 

Magnetic resonance angiography is an effective non-invasive technique for establishing a diagnosis and evaluating the extent and severity of nearly all diseases of the thoracic aorta.  Studies have shown that MRA of the chest has a high level of diagnostic accuracy for pre-operative and post-operative evaluation of aortic dissection of aneurysm.  Depending on the clinical presentation, MRA may be used as an alternative to other non-invasive imaging technologies (e.g.,  trans-esophageal echocardiography and CT).

Studies have proven that MRA is considered a reliable diagnostic tool for the pre-operative evaluation of patients who will undergo elective abdominal aortic aneurysm (AAA) repair.  In addition, scientific data has revealed that MRA is considered comparable to conventional angiography in determining the extent of the AAA, as well as evaluation of aorto-illiac occlusion disease and renal artery pathology that may be necessary in the surgical planning for AAA repair.  If pre-operative angiography is not necessary, then patients are not exposed to the risks associated with invasive contrast procedures, namely allergic reactions, end-organ damage or arterial injury.

Current scientific data shows that diagnostic pulmonary MRAs are improving due to recent developments such as faster imaging capabilities and gadolinium-enhancement.  However, these advances in MRA are not significant enough to warrant replacement of pulmonary angiography in the diagnosis of pulmonary embolism for patients who have no contraindication to receiving intravenous iodinated contrast material.

On December 24, 2008, the United States Food and Drug Administration (FDA) approved Vasovist injection (gadofosveset trisodium, now marketed as Ablavar), the first contrast imaging agent for use in patients undergoing MRA.  Gadofosveset reversibly binds to albumin providing extended intravascular enhancement compared with existing extracellular magnetic resonance contrast agents.  Administration of gadofosveset provides a clearer image in patients who are suspected of having blockages or other problems with the blood vessels in their abdomen or extremities.  The safety and effectiveness of Vasovist was established in 2 clinical trials of patients with known or suspected aorto-iliac disease.  In the studies, patients underwent MRA with and without Vasovist and their scans were compared to standard X-ray pictures using contrast.  Magnetic resonance angiography with Vasovist detected more arterial disease than MRA performed without Vasovist and the pictures were of improved technical quality.

Regulatory Status

N/A

Rationale

The above policy is based on a series of 1997 TEC Assessments (1-4), which concluded that, compared to angiography, MRA provides a reliable diagnostic assessment of acquired thoracic aortic diseases, vascular anomalies involving the great thoracic arteries and veins, and evaluation of the thoracic, systemic, and central veins for the diagnosis of thrombo-occlusive disease. However, the evaluation also concluded that diagnostic performance is not sufficiently accurate to allow replacement of pulmonary angiography in the diagnosis of pulmonary embolism (PE) in patients who have no contraindications to receiving IV iodinated contrast material. In this setting, MRA may be an acceptable alternative to angiography in patients who are allergic to or who have other contraindications (e.g., renal insufficiency) for iodinated contrast media. It should be noted that in all applications, MRA is considered an alternative to angiography. A 2003 review did not identify any published articles that addressed the limitations noted in the series of TEC Assessments; therefore, the policy statement is unchanged. Specifically, the appropriateness criteria of the American College of Cardiology (ACR) are consistent with the conclusions of the TEC Assessment. (5) For example, the ACR appropriateness criteria offer the following statement regarding MRA in a patient with suspected pulmonary embolism. “MRA is not indicated in the routine evaluation of patients with suspected pulmonary embolism…currently it is mainly used in certain centers with particular interest and expertise, and in patients in whom contrast administered for helical CT scans or even for pulmonary angiography is thought to be contraindicated.”

2005 Update

The literature was searched for the period of 2003 through November 2004, with a particular focus on MRA of the chest to detect pulmonary emboli. No published studies were identified that would prompt reconsideration of the policy statement, which remains unchanged. Published studies do suggest that spiral CT scanning using multidetector CT has emerged as a noninvasive alternative to diagnostic pulmonary. Spiral CT scanning is widely available, and therefore, as noted in the policy statement, MRA would only be indicated in the subset of patients that have a contraindication to contrast media.

Evidence reviews assess whether a medical test is clinically useful. A useful test provides information to make a clinical management decision that improves the net health outcome. That is, the balance of benefits and harms is better when the test is used to manage the condition than when another test or no test is used to manage the condition.

The first step in assessing a medical test is to formulate the clinical context and purpose of the test. The test must be technically reliable, clinically valid, and clinically useful for that purpose. Evidence reviews assess the evidence on whether a test is clinically valid and clinically useful. Technical reliability is outside the scope of these reviews, and credible information on technical reliability is available from other sources.

Promotion of greater diversity and inclusion in clinical research of historically marginalized groups (e.g., People of Color [African-American, Asian, Black, Latino and Native American]; LGBTQIA (Lesbian, Gay, Bisexual, Transgender, Queer, Intersex, Asexual); Women; and People with Disabilities [Physical and Invisible]) allows policy populations to be more reflective of and findings more applicable to our diverse members. While we also strive to use inclusive language related to these groups in our policies, use of gender-specific nouns (e.g., women, men, sisters, etc.) will continue when reflective of language used in publications describing study populations.
 

Population Reference No. 1 

MRA is an excellent imaging tool for the diagnosis of aneurysm and aortic dissection. Spin echo sequences and other "black blood" techniques, can detect the medio-intimal flap and determine the type and extent of dissection. Gradient echo sequences can differentiate the true lumen (with higher flow and higher signal intensity) from the false lumen (with lower flow and lower signal intensity). Contrast material-enhanced MR angiography is widely used for evaluation of aortic disease as technical capabilities of scanners have improved. In the past, transesophageal echocardiography and MRI have been considered the two methods of choice for diagnosing dissections. However, advances in CT technology and the greater availability of multislice CT have caused this latter modality to assume a primary role in imaging of aortic disease

Population Reference No. 2 

Contrast-enhanced magnetic resonance (MR) angiography using provocative arm positioning can allow excellent imaging to the vessels and can be a useful diagnostic tool.   In many centers, conventional arteriography has been supplanted by CT angiography for the diagnosis of aTOS; however, arteriography may still be needed for patients who have signs and symptoms of acute arterial insufficiency or ischemia, and to plan surgical reconstruction. The advantage of arteriography and venography is the ability to obtain dynamic studies in which the patient performs upper extremity maneuvers during imaging to assist in identifying arterial or venous compression, or to initiate thrombolytic therapy, if indicated. Although contrast venography is not always needed to establish a diagnosis of vTOS, early intervention with catheter-based thrombolytic therapy appears to be associated with improved outcomes. 

Population Reference No. 3 

 A definitive diagnosis of mesenteric venous thrombosis is established with imaging studies that show thrombosis within the mesenteric veins. Mesenteric venous thrombosis is most reliably demonstrated using magnetic resonance (MR) venography, although we recommend computed tomography (CT) with and without oral and intravenous contrast as an initial screening study because of its widespread availability. For patients with a nondiagnostic CT for whom a clinical suspicion for mesenteric venous thrombosis persists (ie, no alternative explanation for symptoms and a known hypercoagulable risk factor or family history of venous thrombosis), we suggest angiography (CT angiography with delayed imaging to capture venous phase, MR angiography, or standard catheter based).

MR angiography is an excellent imaging study for the diagnosis of mesenteric venous thrombosis, but motion artifacts may limit its accuracy. Some studies report 100 percent sensitivity and specificity for the diagnosis of acute or chronic mesenteric venous thrombosis. However, CT angiography of the abdomen is reasonably sensitive and specific for mesenteric venous thrombosis, provided there is adequate portal venous phase contrast, and is preferred over MR because of its lower costs and wide availability. In addition, as an initial study, CT more reliably demonstrates findings of focal or segmental bowel wall ischemia, in addition to ruling out other causes of acute abdominal pain

Population Reference No. 4

MR angiography is able to detect vascular intraluminal filling defects (eg, emboli), but pulmonary emboli are currently better visualized using CT. New MR sequences may further facilitate the visualization of pulmonary emboli [54]. The use of intravenous gadolinium-based contrast material (as a first pass perfusion agent) and arterial spin labeling (endogenous perfusion assessment without injection) may expand the role of MRI in the diagnosis of pulmonary vascular disease.

Supplemental Information

N/A

Practice Guidelines and Position Statements

N/A

Medicare National Coverage

CMS National Coverage Determinations (NCDs)

NCD 220.3 Magnetic Resonance Angiography

References 

1. 1997 TEC Assessment; Tab 8, MRA of the Chest-part I: Acquired Disease of the Thoracic Aorta

2. 1997 TEC Assessment; Tab 9, MRA of the Chest-part II: Developmental Anomalies of the Thoracic Vasculature

3. 1997 TEC Assessment; Tab 10, MRA of the Chest-part III: Systemic Venous Thrombosis of Occlusion 4. 1997 TEC Assessment; Tab 11, MRA of the Chest-part IV: Pulmonary Embolism

5. www.acr.org/dyna/?doc=departments/appropriateness_criteria/toc.html

6. Haddad MC, Clark DC, Sharif HS, et al. MR, CT, and ultrasonography of splanchnic venous thrombosis. Gastrointest Radiol 1992; 17:34.

7. Gehl HB, Bohndorf K, Klose KC, Günther RW. Two-dimensional MR angiography in the evaluation of abdominal veins with gradient refocused sequences. J Comput Assist Tomogr 1990; 14:619.

8.Kreft B, Strunk H, Flacke S, et al. Detection of thrombosis in the portal venous system: comparison of contrast-enhanced MR angiography with intraarterial digital subtraction angiography. Radiology 2000; 216:86.

9. Hagspiel KD, Leung DA, Angle JF, et al. MR angiography of the mesenteric vasculature. Radiol Clin North Am 2002; 40:867.

Codes

Policy History