"Carotid Stenting and Emboli Protection"
Embolic Protection Devices Jay S. Yadav, MD Director of Vascular Intervention, The Cleveland Clinic Foundation The incidence of stroke in USA and Europe is about 1 in 500 population per year, with 80% of these due to ischemia. Carotid stenosis is responsible for approximately 50% of the ischemic stroke, and one-third of these are not preceded with any warning symptoms. The role of carotid endarterectomy for symptomatic and asymptomatic patients has been established through a number of clinical trials reported in the past decade (1-5). However, these studies selected only patients who were considered low- risk for surgery, and those whose anatomy was suitable for surgical revascularization. In practice, many of our day-to-day patients are at high-risk, or deemed unsuitable, for surgical revascularization. Carotid artery stenting is now evolving as an alternative to endarterectomy for symptomatic and asymptomatic carotid artery disease (5-12). When compared with surgical revascularization, percutaneous technique has the advantage of not requiring general anesthesia, a shorter recuperative period enabling early discharge, and less peri- procedural complications (cervical hematoma, cervical nerve palsy, or stroke) (5,13,14). In a large world-wide registry of 5,210 carotid stent procedures, the technical success rate of carotid stenting was 98.4%, and the 30-day combined rate of death and stroke was 5.07% (10). In another report of >500 consecutive patients, the 5-year event-free survival after carotid stenting was 92% (6). Numerous multi-centered, comparative studies focus on the comparison between surgical and percutaneous revascularization for patients with various risk profile. Stent and Angioplasty with Protection in Patients at High-Risk for Endarterectomy 1 (SAPPHIRE) has just completed the enrollment phase. Carotid Revascularization Endarterectomy vs Stent Trial (CREST), Carotid Revascularization with Endarterectomy or Stenting System (CARESS), International Carotid Stenting Study (ICSS/CAVATAS 2), Stent-Protected Percutaneous Angioplasty of the Carotid Versus Endarterectomy (SPACE) are designed to compare endarterectomy with carotid stenting, and they are currently in progress. Collectively, these trials will better define the role of carotid stenting and surgery in broad patient population, and will refine the guidelines for the treatment of carotid artery disease. One of the major peri-procedural adverse events of stent implantation in carotid circulation is related to dislodgement of atheroembolic particles and distal embolization. Transcranial Doppler studies (15,16) have documented the prevalence of microembolization during unprotected carotid stenting. In cadaver models, the mean diameter of these particles ranged from 120-1200 m (mean 338 m) (17). The Saphenous Vein Graft Free of Emboli Randomized (SAFER) trial first reported the benefit of a distal protection device in conjunction with stenting lesions in saphenous vein grafts in a randomized clinical trial. Efforts are ongoing to optimize the outcome of carotid stenting by developing strategies that eliminate the risk of embolic events. Several protective devices have been designed and are in various stages of testing. Distal neuro-protection device can be mainly classified into and flow-through filter (eg. AngioGuardTM, ACCUNETTM, EPI FilterWire EXTM) and distal balloon occlusion (eg. PercuSurgeTM). AngioGuardTM is composed of a 300 cm 0.014” medium support (ATW) guidewire with a 3.5 cm flexible distal tip and basket filter (pore size = 100 m, diameters 4-8 mm). It comes with a 5.0 Fr capture sheath and hence is compatible with 2 8.0 Fr guiding catheter. Similarly, the ACCUNETTM System consists of a delivery sheath, a 0.014” guidewire with attached filter basket, an inner recovery sheath, and an outer recovery sheath. The EndoTexTM Interventional Systems together with Boston Scientific EPI has developed a stent and distal protection device system composed of the EndoTex NexStentTM (NexStent) and the Boston Scientific EPI FilterWire EXTM (FilterWire). Distal-balloon protection system has been shown to reduce the frequency of microembolization during carotid stenting (18). The feasibility of cerebral protection with filter devices has also been shown (19). Currently, numerous trials are undergoing to evaluate the safety and efficacy of these devices when combined with carotid stents (eg. CARBENET [NexStentTM and FilterWireTM], MAVERIC [AVE self-expanding stent and PercuSurge GuardWireTM], ARCHeR [ACCULINKTM and ACCUNETTM], SHELTER [Monorail WALLSTENTTM and PercuSurge GuardWireTM]). In conclusion, carotid stenting in conjunction with distal emboli-protection device will be proved to provide a safe and efficacious method for percutaneous carotid revascularization. Within the next few years, numerous devices will be commercially available and this will improve our armamentarium for a safe approach for the treatment of extracranial cerebrovascular disease. 3 References 1. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators. N Engl J Med 1991; 325:445-453. 2. Barnett HJ, Taylor DW, Eliasziw M, et al. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators. N Engl J Med 1998; 339:1415-1425. 3. Hobson RW, 2nd, Weiss DG, Fields WS, et al. Efficacy of carotid endarterectomy for asymptomatic carotid stenosis. 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