Summary Of Evidence

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Analysis of Evidence

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Overview
Non-invasive cerebrovascular studies utilize ultrasonic Doppler and physiologic principles to assess the irregularities in blood flow in arterial and venous systems. Noninvasive vascular studies include the patient care required to perform the studies, supervision of the studies, and interpretation of study results, with copies for patient records of test results and analysis of all data, including bi-directional vascular flow or imaging when provided.

Diagnostic tests must be ordered by the physician who is treating the beneficiary and use the result in the management of the beneficiary’s specific medical problem. Services are deemed medically necessary when all of the following conditions are met:

1. Signs/symptoms of ischemia or altered blood flow are present;
2. The information is necessary for appropriate medical and/or surgical management;
3. The test is not redundant of other diagnostic procedures that must be performed. Although, in some circumstances, non-invasive vascular tests are complimentary, such as MRA and duplex, where the latter may confirm an indeterminate finding or demonstrate the physiologic significance of an anatomic stenosis (especially in the carotids and lower extremity arterial system).

Definitions:
Duplex Scans: Duplex combines Doppler and conventional ultrasound, allowing the structure of blood vessels, how the blood is flowing through the vessels, and whether there is any obstruction in the vessels to be seen. Color Doppler produces a picture of the blood vessel, and a computer converts the Doppler sounds into colors overlaid on the image, representing information about the speed and direction of blood flow. Using spectral Doppler analysis, the duplex scan images provide anatomic and hemodynamic information, identifying the presence of any stenosis or plaque in the arteries. Duplex scans are in real-time.

Transcranial Doppler: Pulsed Doppler ultrasound is used to interrogate the intracranial vasculature of the Circle of Willis. It detects severe stenosis in the major intracranial arteries, assesses patterns and extent of collateral circulation in patients with known regions of severe stenosis or occlusion and evaluating and following patients with vasoconstriction particularly after a subarachnoid hemorrhage.

Cerebrovascular Studies

Extracranial Arteries Studies
Testing methods that include (real-time) duplex scans and Doppler ultrasound waveform with spectral analysis are covered for the following:

Indications:

1. Cervical bruits.
2. Amaurosis fugax (transient monocular blindness).
3. Focal cerebral or ocular transient ischemic attacks.
4. Drop attack or syncope is only covered with vertebrobasilar or bilateral carotid artery disease as suggested by the patient’s history. If an echocardiogram is negative for a cardiac or cardiac valvular cause, it may be medically appropriate to perform extracranial arteries studies for the drop attack or syncope.
5. Subclavian steal syndrome (symptoms usually associated with it are a bruit in the subclavian fossa, unequal radial pulses, arm claudication following minimal exercise, and a difference of 20 mm Hg or more between the systolic blood pressures in the arms).
6. Evaluation of blunt or penetrating neck trauma or injury to the carotid artery.
7. Follow-up after a carotid endarterectomy or carotid stenting.
8. Suspected aneurysm of the carotid artery. Patients with swelling of the neck particularly if occurring post carotid endarterectomy.
9. Re-evaluation of existing carotid stenosis.
10. Evaluation of pulsatile neck mass.
11. Preoperative evaluation of patient scheduled for major cardiovascular surgical procedure when there is evidence of systemic atherosclerosis.
12. Preoperatively validate the degree of carotid stenosis of patients whose previous duplex scan revealed a greater than 60% diameter reduction. The duplex is only covered when the surgeon questions the validity of the previous study and the repeat test is performed in lieu of a carotid arteriogram.
13. Ocular micro embolism (optic nerve/retinal arterial - Hollenhorst plaques/ocular).
14. Evaluation of suspected dissection.
15. Recent stroke (defined as less than six months) for determining the cause of the stroke.
16. Vasculitis involving the extracranial carotid arteries.
17. Diagnosis of carotid disease on medical management and cerebrovascular symptoms are reoccurring.
18. Pulsatile tinnitus with other symptoms involving the cardiovascular system.

Limitations:
Tests may not be considered medically necessary if performed for the following signs and symptoms:

1. Dizziness is not a typical indication unless associated with other localizing neurologic signs or symptoms.
2. Headaches including migraines.
3. Temporarily blurred vision.

Transcranial Doppler Testing

Indications:

1. Detection and evaluation of the hemodynamic effects of severe stenosis or occlusion of extracranial (greater than or equal to 60% diameter reduction) and major basal intracranial arteries (greater than or equal to 50% diameter reduction).
2. Detection and serial evaluation of cerebral vasospasm with spontaneous or traumatic subarachnoid hemorrhage.
3. Evaluation of intracranial hemodynamic abnormalities in patients with suspected brain death. It would be expected that an EEG for cerebral death evaluation would be used to diagnose brain death before a Doppler.
4. Intraoperative and perioperative monitoring of intracranial flow velocity and hemodynamic patterns during carotid endarterectomy or carotid stenting.
5. Evaluation of cerebral embolization.
6. As an alternative to an echocardiogram when detecting residual right to left shunting after repair and/or closure of an intracardiac or intrapulmonary shunt.
7. Detecting arteriovenous malformation and studying their supply arteries and flow pattern.
8. Evaluation of invasive therapeutic interventions for cerebral malformations.
9. Differentiating vertebrobasilar symptoms from carotid symptoms.
10. Assessing tandem lesions (>65% in the major basal intracranial arteries when extra cranial studies fail to identify the problem).
11. Evaluation of the risk for stroke in individuals diagnosed with sickle cell.

Limitations:
It is not medically reasonable and necessary and therefore not covered for:

1. Evaluation of brain tumors.
2. Assessment of familial and degenerative disease of the cerebrum, brainstem, cerebellum, basal ganglia, and motor neurons.
3. Evaluation of infectious and inflammatory conditions.
4. Psychiatric disorders.
5. Epilepsy.
6. Routine evaluation of cerebrovascular symptoms and signs.

The following are considered investigational and not medically necessary:

1. Assessment of migraines or suspected migraines.
2. Evaluation of dilated vasculopathies such as fusiform aneurysms.
3. Assessment of autoregulation, physiologic and pharmacologic responses of cerebral arteries.
4. Monitoring during cardiopulmonary bypass and other cerebrovascular and cardiovascular interventions, and surgical procedures except during a carotid endarterectomy.
5. Evaluation of children with various vasculopathies, such as moyamoya disease and neurofibromatosis.

Credentialing and Accreditation Standards
The accuracy of non-invasive vascular diagnostic studies depends on the knowledge, skill, and experience of the technologist and interpreter. Consequently, the physician performing and/or interpreting the study must be capable of demonstrating documented training and experience. A vascular diagnostic study may be personally performed by a certified technologist, or in a certified vascular testing lab.

Services will be considered medically reasonable and necessary only if performed by appropriately trained providers.

1. All non-invasive vascular diagnostic studies must be performed meeting at least one of the following:
   
   1. performed by a licensed qualified physician, or
   2. performed by a technician who is certified in vascular technology, or
   3. performed in facilities with laboratories accredited in vascular technology.
2. A licensed qualified physician for these services is defined as:
   
   1. Having trained and acquired expertise within the framework of an accredited residency or fellowship program in the applicable specialty/subspecialty in ultrasound (US) or must reflect equivalent education, training, and expertise endorsed by an academic institution in ultrasound or by applicable specialty/subspecialty society in ultrasound, or
   2. Has the Registered Vascular Technologist (RVT), Registered Physician Vascular Interpretation (RPVI), or American Society of Neuroimaging (ASN): Neuroimaging Subspecialty Certification; and
   3. Is able to provide evidence of proficiency in the performance and interpretation of each type of diagnostic procedure performed.
3. Nonphysician personnel performing tests must demonstrate basic qualifications to perform tests and have training and proficiency as evidenced by licensure or certification by an appropriate State health or education department. In the absence of a State licensing board, non-physician personnel must be certified by an appropriate national credentialing body.
   
   Appropriate personnel certifications include the American Registry of Diagnostic Medical Sonographers (ARDMS) Registered Vascular Technologist or (RVT) credential; or Cardiovascular Credentialing International’s Registered Vascular Specialist (RVS).

Laboratories must be certified by one of the following:

• Intersocietal Accreditation Commission (IAC),
• American College of Radiology (ACR),
• Joint Commission (Vascular lab certification would need to be noted under the main certification either under inpatient or ambulatory care depending on where the test is being performed), or
• DNV-GL (specific for hospitals only)

According to which certifying body listed above is selected, that accrediting body’s standards must be followed.