Carotid With Bivalirudin Angioplasty

Inclusion Criteria: * The patient must be at least 18 years of age. * The patient must have a significant diameter reduction of the extracranial or intracranial internal or common carotid artery, defined as ≥50% stenosis for symptomatic patients or ≥80% stenosis for asymptomatic patients determined by carotid duplex ultrasound scan and/or carotid angiography. * Female patients with child bearing potential must have a negative pregnancy test. * The patient and the patient's physician must agree to have the patient return for a 30-day and one-year clinical and ultrasound imaging follow-up evaluations as indicated in the protocol. * Reference vessel diameter ≥ 3.5 mm - ≤ 9.0 mm diameter. Exclusion Criteria: * The patient has had a recent (\<4 weeks) disabling stroke or dementia with major neurologic deficit (stroke scales: Barthel \<60, NIH \>15, or Rankin \>3) at pre-procedure neuro exam. * The patient has had within four weeks of the treatment procedure an intracranial hemorrhage, hemorrhage stroke, major stroke, or any stroke with mass effect demonstrated on MRI or CT. * The patient has a known allergy to heparin, bivalirudin, aspirin or to anti-platelet agents that prevents taking aspirin plus ticlopidine or aspirin plus clopidogrel. * The patient has received fractionated or unfractionated heparin within 8 hours prior to the procedure. * The patient has a history of prior life-threatening radiocontrast reaction that cannot be pre-treated. * The patient has a history of bleeding diathesis or coagulopathy within 3 months. * The patient is currently participating in another study protocol that may influence either procedure results or follow-up evaluations. * Plasma/serum creatinine \> 3.0 mg/dl at time of intervention. * Hemodynamic instability at the time of intervention. * Previous stent placement in the ipsilateral carotid distribution. Angiographic Exclusion Criteria * The patient has an intracranial tumor, or cerebral arterio-venous malformation(s) \> 5mm, aneurysms or severe intracranial stenosis distal to target lesion. * The patient has inaccessible intracranial arterial stenosis greater in severity than the extracranial internal carotid artery lesion. * There is angiographic evidence of significant intra-luminal thrombus burden with presumed increased risk of plaque fragmentation and consequent distal embolization. * There is total occlusion of the ipsilateral carotid artery treatment site with TIMI 0 flow characteristics. * The reference segment diameter (internal carotid artery segment cephalad to the lesion) is less than 3 millimeters by operator visual estimate. * The patient has peripheral vascular, supra-aortic or internal carotid artery tortuosity precluding use of catheter-based techniques required for successful CSSA