William M. Feinberg Lecture: Asymptomatic Carotid Stenosis: Current and Future Considerations.

Asymptomatic high-grade carotid stenosis is an important therapeutic target for stroke prevention. For decades, the ACAS (Asymptomatic Carotid Atherosclerosis Study) and ACST (Asymptomatic Carotid Surgery Trial) trials provided most of the evidence supporting endarterectomy for patients with asymptomatic high-grade stenosis who were otherwise good candidates for surgery. Since then, transfemoral/transradial carotid stenting and transcarotid artery revascularization have emerged as alternatives to endarterectomy for revascularization. Advances in treatments against atherosclerosis have driven down the rates of stroke in patients managed without revascularization. SPACE-2 (Stent-Protected Angioplasty Versus Carotid Endarterectomy-2), a trial that included endarterectomy, stenting, and medical arms, failed to detect significant differences in stroke rates among treatment groups, but the study was stopped well short of its recruitment goal. CREST-2 (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial) will be able to clarify whether revascularization by stenting or endarterectomy remains efficacious under conditions of intensive medical management. Transcarotid artery revascularization has a favorable periprocedural risk profile, but randomized trials comparing it to intensive medical management are lacking. Features like intraplaque hemorrhage on MRI and echolucency on B-mode ultrasonography can identify patients at higher risk of stroke with asymptomatic stenosis. High-grade stenosis with poor collaterals can cause hemispheric hypoperfusion, and unstable plaque can cause microemboli, both of which may be treatable risk factors for cognitive impairment. Evidence that there are patients with carotid stenosis who benefit cognitively from revascularization is presently lacking. New risk factors are emerging, like exposure to microplastics and nanoplastics. Strategies to limit exposure will be important without specific medical therapies.