1. Carotid duplex ultrasound in an accredited vascular laboratory is the initial diagnostic imaging of choice for evaluating the severity of stenosis in both symptomatic and asymptomatic patients. Under these conditions unequivocal identification of stenosis of 50% to 99% in neurologically symptomatic patients or 70% to 99% in asymptomatic patients is sufficient to make a decision regarding intervention (Grade 1, Level A).
2. Carotid duplex ultrasound (CDUS) in an accredited vascular laboratory is the imaging modality of choice to screen asymptomatic populations at high risk (Grade 1, Level B).
3. When CDUS is nondiagnostic, or suggests stenosis of intermediate severity (50%-69%) in an asymptomatic patient, additional imaging with magnetic resonance angiography (MRA), computed tomographic angiography (CTA), or digital subtraction angiography (DSA) is required prior to embarking on any intervention (Grade 1, Level B).
4. When evaluation of the vessels proximal or distal to the cervical carotid arteries is needed for diagnosis or to plan therapy, imaging in addition to CDUS (either CTA, MRA, or catheter angiography) is indicated. CTA is preferable to magnetic resonance imaging/MRA for delineating calcium. When there is discordance between two minimally invasive imaging studies (CDUS, MRA, CTA), DSA is indicated to resolve conflicting results. DSA is generally reserved for situations where there is inconclusive evidence of stenosis on less invasive studies or when CAS is planned (Grade 1, Level B).
5. A postoperative duplex ultrasound, within 30 days, is recommended to assess the status of the endarterectomized vessel. In patients with 50% or greater stenosis on this study, further follow-up imaging to assess progression or resolution is indicated. In patients with a normal duplex and primary closure of the endarterectomy site, ongoing imaging is recommended to identify recurrent stenosis. In patients with a normal duplex ultrasound after patch or eversion endarterectomy, further imaging of the endarterectomized vessel may be indicated if the patient has multiple risk factors for progression of atherosclerosis. There are insufficient data to make recommendations on imaging after CAS (Grade 2, Level C). While the data in this area are not robust concerning intervals for follow-up imaging, the committee was unanimous in this recommendation, recognizing that follow-up duplex ultrasound carries little risk.
6. Imaging after CAS or CEA is indicated to follow contralateral disease progression in patients with contralateral stenosis ≥ 50%. In patients with multiple risk factors for vascular disease, follow-up duplex may be indicated with lesser degrees of stenosis. The likelihood of disease progression is related to the initial severity of stenosis (Grade 2, Level C). While the data in this area are not robust concerning intervals for follow-up imaging, the committee was unanimous in this recommendation, recognizing that follow up duplex ultrasound carries little risk.