Randomized clinical trial of open-cell vs closed-cell stents for carotid stenting and effects of stent design on cerebral embolization

Carotid artery stenting: an update

In patients with carotid disease, the purpose of carotid artery revascularization is stroke prevention. For >50 years, carotid endarterectomy has been considered the standard treatment for severe asymptomatic and symptomatic carotid stenoses. Carotid artery stenting (CAS) has emerged in the last 15 years as minimally invasive alternative to surgery. However, the value of the endovascular approach in the management of carotid disease patients remains highly controversial. The aims of this review are to elucidate the current role of CAS, to describe the major technology advancements in the field, and to speculate about the future of this therapy.

Carotid artery stenting

Carotid artery stenting (CAS) has achieved clinical equipoise with carotid endarterectomy (CEA), as evidenced by 2 large U.S. randomized clinical trials, multiple pivotal registry trials, and 2 multispecialty guideline documents endorsed by 14 professional societies. The largest randomized trial conducted in patients at average surgical risk of CEA, CREST (Carotid Revascularization Endarterectomy Versus Stenting Trial) found no difference between CAS and CEA for the combined endpoint of stroke, death, and myocardial infarction (MI) after 4 years of follow-up. The largest randomized trial comparing CAS and CEA in patients at increased surgical risk, SAPPHIRE (Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy), looked at 1-year stroke, death, and MI incidence and found no difference in symptomatic patients, but a significantly better outcome in asymptomatic patients for CAS (9.9% vs. 21.5%; p = 0.02). Given that >70% of carotid revascularization procedures are performed in asymptomatic patients for primary prevention of stroke, it is incumbent upon clinicians to demonstrate that revascularization has an incremental benefit over highly effective modern medical therapy alone.

Carotid artery stenting: current and emerging options

Carotid artery stenting technologies are rapidly evolving. Options for endovascular surgeons and interventionists who treat occlusive carotid disease continue to expand. We here present an update and overview of carotid stenting devices. Evidence supporting carotid stenting includes randomized controlled trials that compare endovascular stenting to open surgical endarterectomy. Carotid technologies addressed include the carotid stents themselves as well as adjunct neuroprotective devices. Aspects of stent technology include bare-metal versus covered stents, stent tapering, and free-cell area. Drug-eluting and cutting balloon indications are described. Embolization protection options and new direct carotid access strategies are reviewed. Adjunct technologies, such as intravascular ultrasound imaging and risk stratification algorithms, are discussed. Bare-metal and covered stents provide unique advantages and disadvantages. Stent tapering may allow for a more fitted contour to the caliber decrement between the common carotid and internal carotid arteries but also introduces new technical challenges. Studies regarding free-cell area are conflicting with respect to benefits and associated risk; clinical relevance of associated adverse effects associated with either type is unclear. Embolization protection strategies include distal filter protection and flow reversal. Though flow reversal was initially met with some skepticism, it has gained wider acceptance and may provide the advantage of not crossing the carotid lesion before protection is established. New direct carotid access techniques address difficult anatomy and incorporate sophisticated flow-reversal embolization protection techniques. Carotid stenting is a new and exciting field with rapidly advancing technologies. Embolization protection, low-risk deployment, and lesion assessment and stratification are active areas of research. Ample room remains for further innovations and developments.

Surgery Versus Stenting in Symptomatic Patients

Symptomatic carotid artery stenosis is an important cause of stroke with significant morbidity and mortality. Revascularization with carotid endarterectomy reduces the recurrence of stroke and until recently was considered the gold standard of therapy. Carotid artery stenting has emerged as an alternative method of revascularization in both high-risk and standard-risk patients. This review appraises the role of surgery versus stenting for patients with symptomatic carotid stenosis.

Patient, Anatomic, and Procedural Characteristics That Increase the Risk of Carotid Interventions

Subjective characteristics for increased risk of carotid artery stenting (CAS) have included thrombus-containing lesions, heavily calcified lesions, very tortuous vessels, and near occlusions. More objective high-risk features include contraindications to dual antiplatelet therapy, a history of bleeding complications, and lack of femoral artery vascular access. Variables that increase the risk of CAS complications are attributed to patient characteristics, anatomic features, or procedural factors. Operator and hospital volume affect the risk of complications occurring with CAS. As the complexity and difficulty of CAS patients increases, the need for more highly skilled operators and teams becomes even more necessary to minimize complications.

[Carotid artery stenting technique]

Over the past 25 years carotid artery stenting (CAS) has emerged as an alternative to carotid endarterectomy (CEA). Most of all younger patients and symptomatic patients with contralateral carotid artery occlusion particularly benefit from CAS. To achieve an optimal result with CAS, patient selection and even more important, knowledge and experience of the interventionist is crucial. The periprocedural complication rate of CAS in large experienced centers is lower (2-3%) than those in randomized trials. Several different devices are now available which allow the procedure to be tailored according to patient anatomy and lesion complexity. Complications like hyperperfusion syndrome and intracerebral bleeding, rupture of side branches of the external or internal carotid artery as well as problems caused by slow flow can be widely avoided by adequate experience.

Incidence of embolism associated with carotid artery stenting: open-cell versus closed-cell stents

Object

Carotid artery stenting (CAS) can be an alternative option for carotid endarterectomy in the prevention of ischemic stroke caused by carotid artery stenosis. The purpose of this study was to evaluate the influence of stent design on the incidence of procedural and postprocedural embolism associated with CAS treatment.

Methods

Ninety-six symptomatic and asymptomatic patients, consisting of 79 males and 17 females, with moderate to severe carotid artery stenosis and a mean age of 69.0 years were treated with CAS. The stent type (48 closed-cell and 48 open-cell stents) was randomly allocated before the procedure. Imaging, procedural, and clinical outcomes were assessed and compared. The symptomatic subgroup (76 patients) was also analyzed to determine the influence of stent design on outcome.

Results

New lesions on postprocedural diffusion-weighted imaging (DWI) were significantly more frequent in the open-cell than in the closed-cell stent group (24 vs 12, respectively; p = 0.020). The 30-day clinical outcome was not different between the 2 stent groups. In the symptomatic patient group, stent design (p = 0.017, OR 4.173) and recent smoking history (p = 0.036, OR 4.755) were strong risk factors for new lesions on postprocedural DWI.

Conclusions

Stent design may have an influence on the risk of new embolism, and selecting the appropriate stent may improve outcome.

Carotid artery stenting: patient, lesion, and procedural characteristics that increase procedural complications

From the earliest experiences with carotid artery stenting (CAS) presumptive high risk features have included thrombus-containing lesions, heavily calcified lesions, very tortuous vessels, and near occlusions. In addition patients have been routinely excluded from CAS trials if they have contra-indications to dual antiplatelet therapy (aspirin and thienopyridines), a history of bleeding complications and severe peripheral arterial disease (PAD) making femoral artery vascular access difficult. Variables that increase the risk of CAS complications can be attributed to patient characteristics, anatomic or lesion features, and procedural factors. Clinical features such as older age (≥80 years), decreased cerebral reserve (dementia, multiple prior strokes, or intracranial microangiopathy) and angiographic characteristics such as excessive tortuosity (more than two 90° bends within 5 cm of the target lesion) and heavy calcification (concentric calcification ≥ 3 mm in width) have been associated with increased CAS complications. Other high risk CAS features include those that prolong catheter or guide wire manipulation in the aortic arch, make crossing a carotid stenosis more difficult, decrease the likelihood of successful deployment or retrieval of an embolic protection device (EPD), or make stent delivery or placement more difficult. Procedure volume for the operator and the catheterization laboratory team are critical elements in reducing the risk of the procedure. In this article, we help CAS operators better understand procedure risk to allow more intelligent case selection, further improving the outcomes of this emerging procedure.

Patterns in neurosurgical adverse events: endovascular neurosurgery

As part of a project to devise evidence-based safety interventions for specialty surgery, the authors sought to review current evidence in endovascular neurosurgery concerning the frequency of adverse events in practice, their patterns, and current methods of reducing the occurrence of these events. This review represents part of a series of papers written to consolidate information about these events and preventive measures as part of an ongoing effort to ascertain the utility of devising system-wide policies and safety tools to improve neurosurgical practice.

Based on a review of the literature, thromboembolic events appeared to be the most common adverse events in endovascular neurosurgery, with a reported incidence ranging from 2% to 61% depending on aneurysm rupture status and mode of detection of the event. Intraprocedural and periprocedural prevention and rescue regimens are advocated to minimize this risk; however, evidence on the optimal use of anticoagulant and antithrombotic agents is limited. Furthermore, it is unknown what proportion of eligible patients receive any prophylactic treatment.

Groin-site hematoma is the most common access-related complication. Data from the cardiac literature indicate an overall incidence of 9% to 32%, but data specific to neuroendovascular therapy are scant. Manual compression, compression adjuncts, and closure devices are used with varying rates of success, but no standardized protocols have been tested on a broad scale. Contrast-induced nephropathy is one of the more common causes of hospital-acquired renal insufficiency, with an incidence of 30% in high-risk patients after contrast administration. Evidence from medical fields supports the use of various preventive strategies.

Intraprocedural vessel rupture is infrequent, with the reported incidence ranging from 1% to 9%, but it is potentially devastating. Improvements in device technology combined with proper endovascular technique play an important role in reducing this risk.

Occasionally, anatomical or technical difficulties preclude treatment of the lesion of interest. Reports of such occurrences are scant, but existing series suggest an incidence of 4% to 6%. Management strategies for radiation-induced effects are also discussed. The incidence rates are unknown, but protective techniques have been demonstrated.

Many of these complications have strategies that appear effective in reducing their risk of occurrence, but development and evaluation of systematic guidelines and protocols have been widely lacking. Furthermore, there has been little monitoring of levels of adherence to potentially effective practices. Protocols and monitoring programs to support integrated implementation may be broadly effective.

Advances in the management of carotid artery disease: focus on recent evidence and guidelines

Recent landmark randomized trials and society guidelines have significantly revised the management of carotid artery disease. Duplex ultrasonography is the recommended initial diagnostic test for the assessment of extracranial carotid artery stenosis. Carotid artery imaging is reasonable in select patients scheduled for coronary artery bypass graft (CABG) surgery. Carotid revascularization can be achieved safely and effectively with carotid endarterectomy or carotid artery stenting. Because each procedure has a different risk/benefit profile, the optimal approach is to match the particular patient to the intervention that maximizes outcome benefit. Carotid revascularization is recommended in patients scheduled for CABG surgery when the carotid artery stenosis is symptomatic and/or bilateral. Further trials are required to guide the management of asymptomatic unilateral carotid artery stenosis in patients undergoing CABG surgery. Aggressive medical therapy remains the gold standard for intracranial carotid artery disease because landmark trials have shown no outcome improvement with vascular bypass or percutaneous angioplasty and stenting. A large recent trial showed that local anesthesia, as compared with general anesthesia, for carotid endarterectomy has no major clinical outcome advantage. Although carotid artery stenting is associated with a reduced risk of myocardial ischemia, it still has important risks of stroke and hemodynamic instability that significantly affect clinical outcome. The timing and choice of carotid revascularization technique ultimately depends on multiple clinical factors.

Comparing the embolic potential of open and closed cell stents during carotid angioplasty and stenting

OBJECTIVE

We sought to determine the effects of open (O) and closed (C) cell stents on the size and number of embolic particles generated during carotid artery stenting (CAS) and assess the impact on outcome.

METHODS

Embolic debris from carotid filters after CAS was analyzed using photomicroscopy and imaging software. Patient comorbidities, preoperative cerebrovascular symptoms, stent type, and outcomes (perioperative major adverse events) were examined.

RESULTS

Carotid filters from 173 consecutive CAS procedures (O, 125 and C, 48) were reviewed. The mean age was 70.9 ± 9.2 years; 58% were men. Mean stenosis was 88.2% ± 8.1%; 36.6% had neurological symptoms preprocedurally. There was no difference in preoperative symptoms between the two groups (O, 38.7% vs C, 31.3%; P = not significant [NS]). However, closed cell stent use was associated with higher degree of stenosis (O, 87.2% ± 8.0% vs C, 90.6% ± 7.8%; P = .01), an older age (O, 70.0 ± 8.6 years vs C, 73.4 ± 10.2 years; P = .03), and peripheral arterial disease (21.1% vs 43.5%; P = .01). A larger mean particle size was observed in patients treated with open cell stents compared to closed cell stents (O, 416.5 ± 335.7 μm vs C, 301.1 ± 251.3 μm; P = .03). There was no significant difference in the total number of particles (O, 13.8 ± 21.5 vs C, 17.6 ± 19.9; P = NS), periprocedural stroke (P = NS), and major adverse events between the two groups (P = NS).

CONCLUSIONS

Open cell stents are associated with a larger mean particle size compared to closed cell stents. No impact on procedural outcomes based on stent type was observed.