This clinical trial is being done to help evaluate a new investigational device to treat narrowing of the carotid arteries in the neck. The device is called the CGUARD Prime Carotid Stent System.

Patients with narrowing of the carotid arteries in the neck are at high risk of stroke. This problem is traditionally treated with a surgical procedure called endarterectomy. Patients that are at an increased risk of complications for surgical endarterectomy due to a medical condition are often treated with carotid artery stenting instead.

This is the first time the CGUARD Prime Carotid Stent System will be used in the United States. The purpose of this study is to see whether the CGUARD Prime Carotid Stent System is safe for patients and to make sure it is effective in opening the narrowing in the carotid artery to improve blood flow to the brain.

A minimum of 280 patients and a maximum of 315 patients are expected to take part in the research trial at up to 40 hospitals in the US and Europe. Patients'participation will last approximately 3 years after their procedure. The entire study duration (the expected time for all the patients to complete the study) is expected to be about 4 years.

General Inclusion Criteria:

1. Subject is ≥ 19 years and ≤ 80 years of age.
2. Subject is willing and able to provide appropriate study-specific informed consent, follow protocol procedures, and comply with follow-up visit requirements.
3. Subject is willing and able to take dual antiplatelet therapy for a minimum of 30 days.
4. Life expectancy ≥ 24 months from the date of the index procedure.
5. Females who are not pregnant or lactating and not planning to become pregnant for the duration of the study.
6. Subject has a modified Rank Score of ≤ 2at the time of informed consent.
7. Subject is diagnosed with carotid artery disease treatable with carotid artery stenting and is considered high risk for carotid endarterectomy (CEA) as evidenced by:
8. Symptomatic carotid stenosis ≥ 50%.  Symptomatic is defined as amaurosis fugax, transient ischemia attack (TIA) or stroke within the last 6 months ipsilateral to the side of the stenosis. 

   Or

9. Asymptomatic carotid stenosis ≥ 80%

Co-Morbidity High Risk Conditions for CEA, i.e., meets one or more of the following criteria:

1. Age ≥ 70 (maximum 80 years)
2.  CCS angina class 3-4 or unstable angina
3. Congestive Heart Failure (CHF) NYHA class III-IV
4. Left ventricular ejection fraction (LVEF) ≤ 35%
5. MI ≥ 72 hours and < 6 weeks pre-procedure
6. Multi-vessel CAD (≥ 2 vessels >70% stenosis) and history of angina
7. Chronic Obstructive Pulmonary Disease (COPD) with FEV1<50
8. Permanent contralateral cranial nerve injury/paralysis
9. Restenosis from previous carotid endarterectomy (CEA)
10. Planned coronary artery bypass grafting (CABG) or valve replacement surgery between 31-60 days after CAS
11. Abdominal aortic aneurysm surgical repair or endovascular repair is planned between 31 to 60 days after CAS.

OR

High Anatomical Risk for CEA, i.e., meets one or more of the following criteria:

1. Occlusion of the contralateral CCA or ICA.
2. Prior radiation treatment to the neck or a radical neck dissection.
3. Severe bilateral ICA stenosis requiring treatment.
4. Target lesion at or above the level of the jaw (C2) or below the clavicle.
5. Severe tandem lesions
6. Inability to extend the neck due to cervical disorders.
7. Laryngeal palsy or laryngectomy.
8. Prior head and neck surgery in the region of the carotid artery.
9. Tracheostomy or tracheostoma.
10. Spinal immobility of the neck.
11. Hostile neck or surgically inaccessible lesion.

Angiographic General Inclusion Criteria, i.e., meets all of the following criteria:

1. Target lesion location at the carotid bifurcation and/or proximal internal carotid artery (ICA)
2. Vessel distal to target lesion can accommodate embolic protection device (EPD) with either the NAV6 Emboshield distal protection device OR the Mo.Ma proximal embolic protection device
3. Target vessel reference diameter at stent landing zone is 4.8 mm to 9.0 mm.
4. Target lesion length ≤ 36 mm, that can be covered by a single CGuard Prime™ stent.

Exclusion Criteria

Patients are not eligible for the study if they have any of the following exclusion criteria.

1. Planned interventional procedure or surgery of the carotid, coronary or peripheral arteries within 30 days before or after the index carotid procedure.
2. Severe vascular anatomy that would preclude safe sheath insertion, deliverability of stent or embolic protection devices.
3. Type III aortic arch.
4. Total occlusion of the target vessel.
5. In-tandem lesions with ³ 50% or ³ 80% diameter stenosis for symptomatic or asymptomatic patients, respectively, which cannot be covered by a single CGuard Prime™ stent.
6. Presence of “string sign” of the target lesion.
7. History of bleeding diatheses or coagulopathy.
8. Bilateral carotid stenosis requiring treatment on both sides within 30 days prior to or following planned index procedure.
9. Subject is on renal replacement therapy or has Stage 4 or 5 CKD.
10. Known reason for potential stroke other than carotid artery stenosis, including history of atrial fibrillation or other sources of thromboemboli within the past 12 months.
11. History of thrombophilia.
12. Known sensitivity or allergy to nitinol or titanium.
13. Sensitivity to Contrast media or allergy that cannot be adequately pre-treated
14. Sensitivity to both forms of protocol-acceptable anticoagulation strategies (i.e., both heparin AND Bivalirudin
15. Sensitivity to an antiplatelet agent AND all protocol acceptable alternative antiplatelet options.
16. Previous stent placement in the target vessel.
17. Evolving stroke or intracranial hemorrhage, or history of previous intracranial hemorrhage or brain surgery within the past 12 months.
18. Major neurologic deficit with NIHSS of ≥ 15.
19. Dementia or other neurologic condition confounding the neurologic assessment.
20. Clinical condition that, in the opinion of the investigator, makes endovascular therapy impossible or hazardous.
21. Subject previously enrolled in this clinical trial.
22. Possible / probable non-compliance of subject with protocol required follow up or medication.
23. Subject is currently participating in another clinical trial that has not completed its primary endpoint assessment or would confound this C-GUARDIANS Pivotal IDE Clinical Study.