The purpose of this Long-Term Observational Extension of Participants in the CREST-2 Randomized Clinical Trial (C2LOE - ClinicalTrials.gov Identifier: NCT02089217) study is to study is to assess post-procedural efficacy of carotid endarterectomy and carotid stenting.

Atherosclerotic plaque in the carotid arteries is responsible for 10 to 15% of all ischemic strokes. The ongoing NINDS-funded CREST-2 multicenter randomized clinical trial is testing whether in the short term (up to 4 years after study entry) procedural revascularization improves stroke prevention above and beyond what can be achieved with intensive medical management of vascular risk factors, especially hypertension and hyperlipidemia. Our proposal is for an observational extension of the CREST-2 clinical trial to test whether revascularization improves stroke prevention in the clinically relevant long term (up to 8 to 10 years). The current application proposes to use a site-less, centralized telephone approach to extend the follow-up of CREST-2 trial participants for assessing the primary study outcome (stroke) for up to 10 years. The average follow-up will increase from between 2-3 years (clinic-based randomized trial) to 7-8 years (observational extension). Each patient will be contacted by telephone at 6-month intervals, and queried regarding all hospitalizations since the last contact. Suspected stroke events will be adjudicated by an expert clinical events committee based on medical record review.

Inclusion Criteria:

• Currently active or graduated participants in the CREST-2 randomized trial
• Able to provide written informed consent by self
• Fluent in English or Spanish

Exclusion Criteria:

• Unable to provide written informed consent
• Inability to follow study procedures

Patients with asymptomatic carotid stenosis previously randomized in the CREST-2 trial.