Policy:
INDICATIONS FOR CHEST MRA
Chest Magnetic Resonance Angiography (MRA) is ordered for evaluation of the intrathoracic blood vessels. Chest MRI and Chest MRA should not be approved at the same time.

Vascular Disease

• Superior vena cava (SVC) syndrome (Friedman, 2017)
• Subclavian Steal Syndrome after positive or inconclusive ultrasound (Osiro, 2012; Potter, 2014)
• Thoracic Outlet Syndrome (ACR, 2014; Chavhan, 2017; Povlsen, 2018)
• Takayasu’s arteritis (Keser, 2014)
• Clinical concern for acute aortic dissection (ACR, 2017; Barman, 2014)
  • Sudden painful ripping sensation in the chest or back and may include
    • New diastolic murmur
    • Cardiac tamponade
    • Distant heart sounds
    • Hypotension or shock
• For MRPA (MR Pulmonary Angiography) in patients with intermediate pretest probability with a positive D-dimer or high pretest probability (but only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated)
  • Risk can be determined by the parameters detailed in Background section

Initial/Screening for Thoracic Aortic Disease
(Erbel, 2014; Hannuksela, 2015; Hiratzka, 2010)

• Echocardiogram or chest x-ray show aneurysm
• Screening of first-degree relatives of individuals with a thoracic aortic aneurysm (defined as > 50% above normal) or dissection
  • Known connective tissue disease or genetic conditions that predispose to aortic aneurysm or dissection (e.g., Marfan syndrome, Ehlers Danlos or Loeys-Dietz syndromes)
• Screening of the thoracic aorta after a diagnosis of a bicuspid aortic valve (dilation of the ascending aorta may not be seen on echocardiogram) (Borger,2018; Verma, 2014)
  • If normal, reimage every three to five years  
• Screening of first-degree relatives of patients with a bicuspid aortic valve
• Turner’s syndrome — Screen for coarctation or aneurysm of the thoracic aorta 
  • If normal results, screen every 5 – 10 years
  • If abnormal, screen annually
• Suspected vascular cause of dysphagia or expiratory wheezing with other imaging is suggestive or inconclusive

Follow-up after established Thoracic Aneurysm
(Erbel, 2014; Hannuksela 2015; Hiratzka, 2010)

• Six months follow-up after initial finding of a dilated thoracic aorta, for assessment of rate of change
  • Aortic Root or Ascending Aorta
    • 3.5 to 4.4 Annual
    • 4.5 to 5.5 or growth rate > 0.5 cm/year - Every 6 months
  • Genetically mediated (Marfans syndrome, Aortic Root or Ascending Aorta) 
    • 3.5 to 4.4 Annual
    • 4.5 to 5.0 or growth rate > 0.5 cm/year Every 6 months
    • Surgery generally recommended over 5.0 cm
  • Descending Aorta (Braverman, 2011)
    • 4.0 to 5.0 Annual
    • 5.0 to 6.0 Every 6 months
• Follow-up post medical treatment of aortic dissection
  • Acute dissection: 1 month, 6 months, then annually
  • Chronic dissection: annually
• Follow-up post either root repair or AVR plus ascending aortic root/arch repair: baseline post-op, then annually
• Re-evaluation of known ascending aortic dilation or history of aortic dissection with a change in clinical status or cardiac exam or when findings may alter management

Congenital Malformations

• Thoracic malformation on other imaging (chest x-ray, echocardiogram, gastrointestinal study, or inconclusive CT) (Ferreira, 2015; Hellinger, 2011; Karaosmanoglu, 2015; Poletto, 2017)
• Congenital heart disease with pulmonary hypertension (Pascall, 2018) or vascular anomalies
• Pulmonary Sequestration (Sancak, 2003)

Pulmonary Hypertension based on other testing
(Ascha, 2017; Rose-Jones, 2015)

• Echocardiogram
• Right heart catheterization

Atrial fibrillation with ablation planned
(Kolandaivelu, 2012)

Pre-operative/procedural evaluation

• Pre-operative evaluation for a planned surgery or procedure

Post-operative/procedural evaluation

• Post-operative complications (Bennet, 2017; Choudhury, 2017)
• Routine post-operative (Lawrence; 2018; Uthof, 2012)
  • Thoracic endovascular or open surgical aneurysm repair
    • 1 month
    • More frequent follow-up/possible intervention if complication detected
    • If stable, annual for 5 years

Chest MRA and Abdomen MRA or Abdomen/Pelvis MRA

• Acute aortic dissection (Barman, 2014)
• Takayasu’s arteritis (Keser, 2014)

Background 
Magnetic resonance angiography (MRA) is a noninvasive technique used to provide cross-sectional and projection images of the thoracic vasculature, including large- and medium-sized vessels, e.g., the thoracic aorta. MRA provides images of both normal and diseased blood vessels, and it quantifies blood flow through these vessels. Successful vascular depiction relies on the proper imaging pulse sequences. MRA may use a contrast agent, gadolinium, which is non-iodine-based, for better visualization. It can be used in patients who have history of contrast allergy and who are at high risk of kidney failure.

OVERVIEW
MRA and Coarctation of the Aorta — One of the most common congenital vascular anomalies is coarctation of the aorta which is characterized by obstruction of the juxtaductal aorta. Clinical symptoms, e.g., murmur, systemic hypertension, difference in blood pressure in upper and lower extremities, absent femoral or pedal pulses, may be present. Gadolinium-enhanced 3D MRA may assist in preoperative planning as it provides angiographic viewing of the aorta, the arch vessels and collateral vessels. It may also assist in the identification of postoperative complications.

MRA and Pulmonary Embolism (PE) — Note: D-Dimer blood test in patients at low risk* for DVT is indicated prior to MRA imaging. Negative D-Dimer suggests alternative diagnosis in these patients.  

Low risk is not approved. Low risk is defined as NO to ALL of the following questions with intermediate and high risk defined based on the number of positive responses (Konstantinides, 2014):

• Evidence of current or prior DVT.
• HR > 100.
• Cancer diagnosis.
• Recent surgery or prolonged immobilization.
• Hemoptysis.
• History of PE.
• Oral hormone use.
• Another diagnosis beside PE is less likely.

Studies show mixed results regarding the value of MRA versus CTA in detecting pulmonary embolism. A systematic review and meta-analysis found MRA to be inferior to CTA in detecting PE. Therefore, MRA should be used only if CTA is not available or contraindicated in a specific patient (Li, 2016).

MRA and Thoracic Aortic Aneurysm — One of the most common indications for thoracic MRA is thoracic aortic aneurysm, most often caused by atherosclerosis. These aneurysms may also be due to aortic valvular disease. Aneurysms are defined by their enlargement and patients with rapidly expanding aortas, or with aortic diameters greater than five or six centimeters, are at high risk of rupture and may require surgery.

MRA and Thoracic Aortic Dissection — The most common clinical symptom of aortic dissection is tearing chest pain and the most common risk factor is hypertension. An intimal tear is the hallmark for aortic dissection and intramural hematoma may also be detected. Unfortunately, patients with aortic dissection may be unstable and not good candidates for routine MR evaluation; MRA may be indicated as a secondary study. 3D MRA is also useful in postoperative evaluation of patients with repaired aortic dissections.

MRA and Central Venous Thrombosis — MRA is useful in the identification of venous thrombi. Venous thrombosis can be evaluated by gadolinium-enhanced 3D MRA as an alternative to CTA, which may not be clinically feasible due to allergy to iodine contrast media or renal insufficiency.

Other MRA Indications — MRA is useful in the assessment for postoperative complications of pulmonary venous stenosis.

MRI and Patent Ductus Arteriosus — Patent ductus arteriosus (PDA) is a congenital heart problem in which the ductus arteriosus does not close after birth. It remains patent allowing oxygen-rich blood from the aorta to mix with oxygen-poor blood from the pulmonary artery. MRI can depict the precise anatomy of a PDA to aid in clinical decisions. It allows imaging in multiple planes without a need for contrast administration. Patients are not exposed to ionizing radiation.

References:

1. American College of Chest Physicians (ACCP). Choosing Wisely^®: Five Things Physicians and Patients Should Question. ACCP. 2013. Retrieved from http://www.choosingwisely.org/clinician-lists/american-college-chest-physicians-american-thoracic-society-chest-ct-angiography-to-evaluate-possibly-pulmonary-embolism/.
2. American College of Radiology (ACR). ACR Appropriateness Criteria^®. Published 2014. Revised 2016. Retrieved from https://acsearch.acr.org/list.
3. American College of Radiology (ACR). ACR Appropriateness Criteria^®. https://acsearch.acr.org/list. Published 2017. Retrieved from March 16, 2018.
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5. Barman M. Acute aortic dissection.E-Journal European Society of Cardiology. 2014;12: N° 25 – 02.
6. Bauer AM, Amin-Hanjani S, Alarj A, et al. Quantitative magnetic resonance angiography in the evaluation of the subclavian steal syndrome: Report of 5 patients. J Neuroimaging. 2009; 19:250-252.
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Coding Section 

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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