Use of the Smart Nitinol Stent System for the Treatment of Severe Atherosclerotic Carotid Stenosis: Study Protocol for a Retrospective, Non-randomized, Long-term Parallel Controlled Trial

Atherosclerosis is a leading cause of carotid artery stenosis. The risk of atherosclerosis increases with age, occurring mainly in middle-aged and elderly populations. The morbidity and mortality of stroke caused by atherosclerosis also increase with aging. An epidemiologic study demonstrated that carotid artery intima-media thickness is a marker of atherosclerotic peripheral arterial disease, and found evidence that the likelihood of a clinical diagnosis of atherosclerosis increases two- to threefold from 20 to 90 years of age. The risk of atherosclerosis also increases with age in animals fed atherosclerosis-inducing diets. The close relationship between atherosclerosis and aging shows that atherosclerosis is a chronic and progressive degenerative disease.

Atherosclerotic carotid stenosis is an independent risk factor for ischemic cerebrovascular disease. Vascular stenting of carotid artery stenosis is an increasingly popular technique. It is safe, quick, minimally invasive, can be performed under local anesthesia, and can be used to treat proximal and intracranial lesions. Vascular stenting enables flow to be restored in previously narrowed vessels, restoring blood supply to the brain and preventing plaque rupture. Carotid artery stenosis of 70%-90% is considered the highest risk for stroke, and is a compelling indication for stenting. The Smart stent system (Cordis Corporation, Miami, FL, USA) is a nitinol self-expanding stent that is soft, elastic, has uniform radial tension and is readily endothelialized.

Phatouros et al. treated four patients with carotid artery stenosis >70% using self-expanding Smart stents and <20% residual stenosis was achieved in all cases; no transient ischemic attacks or new strokes occurred during a follow up period of 6 months. Drescher et al. also used self-expanding Smart stents in 13 patients with severe carotid artery stenosis and found no complications during a 6-month follow-up period. Wholey et al. deployed stents to treat carotid artery stenosis in more than 500 patients, and found that the rates of neurologic complications and restenosis were decreased after application of either balloon-mounted or self-expanding stents. Three-year follow-up results have shown that balloon-mounted stents lead to better vessel patency than self-expanding stents, but that balloon-mounted stents are vulnerable to compression. Lownie et al. examined the efficacy of self-expanding Smart stents in 21 patients with severe symptomatic carotid artery stenosis (stenosis >70%) without angioplasty. All patients were followed up for an average period of 19 months. Self-expanding Smart stents improved vascular stenosis and blood flow without the need for balloons or adjunctive protection devices.

Zhao et al. used Smart stents to treat patients with carotid artery stenosis of >65%, and found the treatment safe and effective, while observing no severe complications. Li et al. treated patients with carotid bifurcation and origin stenosis of >50% with self-expanding Smart stents, and found that patients' neurologic function improved to different extents, and that there were no strokes or transient cerebral ischemic attacks during a subsequent period of 13-14 months. Chen et al. used self-expanding Smart stents to treat 48 patients with carotid artery stenosis of 75%-99%, achieving favorable clinical outcomes in 43 (89.6%), with no recurrence of stenosis during a relatively short follow-up period of 1-6 months, and few postoperative complications or sequelae.

In a cohort of 38 patients with extracranial artery (internal carotid artery outer segment, vertebral artery or subclavian artery) stenosis treated with Smart stents and followed up for an average of 18 months, satisfactory clinical outcomes were achieved in 33 (86.8%). These investigators also treated another cohort of 41 patients with carotid artery stenosis with Smart stents, and concluded that vascular Smart stent deployment is an effective and safe method for treating carotid artery stenosis.