Covered Versus Bare Self-Expanding Stents for Endovascular Treatment of Carotid Artery Stenosis:A Stopped Randomized Trial

The Evolution of Endovascular Management of Extracranial Carotid Artery Aneurysms and Pseudoaneurysms

Introduction:

Extracranial carotid artery aneurysms and pseudoaneurysms (ECCAs) are rare pathologies with various etiologies, presentations, and management strategies. Historically, open aneurysm resection and arterial repair have been the gold standard management of ECCAs. Our study examines the evolving experience with endovascular management of ECCAs.

Methods:

We performed a literature review of multiple studies on endovascular and open management of carotid artery aneurysms and pseudoaneurysms.

Conclusions:

Endovascular stenting is technically feasible and clinically effective for the treatment of carotid artery aneurysms and pseudoaneurysms. Further follow-up is required regarding long-term safety and efficacy.

Highly-calcific carotid lesions endovascular management in symptomatic and increased-stroke-risk asymptomatic patients using the CGuard™ dual-layer carotid stent system: Analysis from the PARADIGM study

OBJECTIVES

To assess feasibility, safety, angiographic, and clinical outcome of highly-calcific carotid stenosis (HCCS) endovascular management using CGuard™ dual-layer carotid stents.

BACKGROUND

HCCS has been a challenge to carotid artery stenting (CAS) using conventional stents. CGuard combines a high-radial-force open-cell frame conformability with MicroNet sealing properties.

METHODS

The PARADIGM study is prospectively assessing routine CGuard use in all-comer carotid revascularization patients; the focus of the present analysis is HCCS versus non-HCCS lesions. Angiographic HCCS (core laboratory evaluation) required calcific segment length to lesion length ≥2/3, minimal calcification thickness ≥3 mm, circularity (≥3 quadrants), and calcification severity grade ≥3 (carotid calcification severity scoring system [CCSS]; G0-G4).

RESULTS

One hundred and one consecutive patients (51-86 years, 54.4% symptomatic; 106 lesions) received CAS (16 HCCS and 90 non-HCCS); eight others (two HCCS) were treated surgically. CCSS evaluation was reproducible, with weighted kappa (95% CI) of 0.73 (0.58-0.88) and 0.83 (0.71-0.94) for inter- and intra-observer reproducibility respectively. HCCS postdilatation pressures were higher than those in non-HCCS; 22 (20-24) versus 20 (18-24) atm, p = .028; median (Q1-Q3). Angiography-optimized HCCS-CAS was feasible and free of contrast extravasation or clinical complications. Overall residual diameter stenosis was single-digit but it was higher in HCCS; 9 (4-17) versus 3 (1-7) %, p = .002. At 30 days and 12 months HCCS in-stent velocities were normal and there were no adverse clinical events.

CONCLUSION

CGuard HCCS endovascular management was feasible and safe. A novel algorithm to grade carotid artery calcification severity was reproducible and applicable in clinical study setting. Larger HCCS series and longer-term follow-up are warranted.

Carotid artery stenting: Current state of evidence and future directions

Both carotid endarterectomy (CEA) and carotid artery stenting (CAS) are common treatments for carotid artery stenosis. Several randomized controlled trials (RCTs) have compared CEA to CAS in the treatment of carotid artery stenosis. These studies have suggested that CAS is more strongly associated with periprocedural stroke; however, CEA is more strongly associated with myocardial infarction. Published long-term outcomes report that CAS and CEA are similar. A reduction in complications associated with CAS has also been demonstrated over time. The symptomatic status of the patient and history of previous CEA or cervical radiotherapy are significant factors when deciding between CEA or CAS. Numerous carotid artery stents are available, varying in material, shape and design but with minimal evidence comparing stent types. The role of cerebral protection devices is unclear. Dual antiplatelet therapy is typically prescribed to prevent in-stent thrombosis, and however, evidence comparing periprocedural and postprocedural antiplatelet therapy is scarce, resulting in inconsistent guidelines. Several RCTs are underway that will aim to clarify some of these uncertainties. In this review, we summarize the development of varying techniques of CAS and studies comparing CAS to CEA as treatment options for carotid artery stenosis.

Silent brain infarcts on diffusion-weighted imaging after carotid revascularisation: A surrogate outcome measure for procedural stroke? A systematic review and meta-analysis

Aim

To investigate whether lesions on diffusion-weighted imaging (DWI+) after carotid artery stenting (CAS) or endarterectomy (CEA) might provide a surrogate outcome measure for procedural stroke.

Materials and Methods

Systematic MedLine® database search with selection of all studies published up to the end of 2016 in which DWI scans were obtained before and within seven days after CAS or CEA. The correlation between the underlying log odds of stroke and of DWI+ across all treatment groups (i.e. CAS or CEA groups) from included studies was estimated using a bivariate random effects logistic regression model. Relative risks of DWI+ and stroke in studies comparing CAS vs. CEA were estimated using fixed-effect Mantel-Haenszel models.

Results

We included data of 4871 CAS and 2099 CEA procedures (85 studies). Across all treatment groups (CAS and CEA), the log odds for DWI+ was significantly associated with the log odds for clinically manifest stroke (correlation coefficient 0.61 (95% CI 0.27 to 0.87), p = 0.0012). Across all carotid artery stenting groups, the correlation coefficient was 0.19 (p = 0.074). There were too few CEA groups to reliably estimate a correlation coefficient in this subset alone. In 19 studies comparing CAS vs. CEA, the relative risks (95% confidence intervals) of DWI+ and stroke were 3.83 (3.17-4.63, p < 0.00001) and 2.38 (1.44-3.94, p = 0.0007), respectively.

Discussion

This systematic meta-analysis demonstrates a correlation between the occurrence of silent brain infarcts on diffusion-weighted imaging and the risk of clinically manifest stroke in carotid revascularisation procedures.

Conclusion

Our findings strengthen the evidence base for the use of DWI as a surrogate outcome measure for procedural stroke in carotid revascularisation procedures. Further randomised studies comparing treatment effects on DWI lesions and clinical stroke are needed to fully establish surrogacy.

Bare metal stents for treatment of extracranial internal carotid artery aneurysms: long-term results

PURPOSE

To examine the long-term outcomes of bare metal stent placement for exclusion of extracranial internal carotid artery (ICA) aneurysms.

METHODS

From 2006 to 2011, 7 consecutive symptomatic patients (4 men; mean age 52 years) with surgically inaccessible extracranial ICA aneurysms were treated with a bare stent at a single center. Patients received clopidogrel for 3 months after the procedure and aspirin for life. Clinical follow-up with duplex ultrasound and/or computed tomographic angiography was performed at 3, 6, and 12 months and yearly thereafter.

RESULTS

All procedures were technically successful; no neurological complications occurred. After 6 months, there was complete thrombosis of the aneurysm in all except one case. In this asymptomatic patient, the residual active flow was successfully obliterated by additional coil embolization. Over a mean follow-up of 57 ± 22 months, all patients were alive and free of local or central neurological symptoms. All stents were patent, and thrombosis of the aneurysms was complete.

CONCLUSION

In this small series, treatment of extracranial ICA aneurysms with a bare stent seems technically feasible and safe. All treated extracranial ICA aneurysms were excluded by primary intervention or secondary coil embolization.

A New Concept for Carotid Artery Stenting: Coating the Atherosclerotic Plaque by Covered Stent before Bare Stent Implantation

In carotid artery stenting (CAS) procedures, distal embolism, periprocedural stent thrombosis, and 30-day stroke due to the plaque fragmentation and protrusion caused by stent implantation and balloon dilation are frequent complications. In this technical case report, a case is presented of extracranial carotid artery stenosis treated with a covered stent and subsequent implantation of a bare stent. In addition, the possibility is discussed that this new technique prevents the distal microembolic complications, periprocedural stent thrombosis, and 30-day stroke of extracranial CAS.

Efficacy of a Self-Expandable Porous Stent as the Sole Curative Treatment for Extracranial Carotid Pseudoaneurysms

OBJECTIVE

Extracranial carotid pseudoaneurysms are uncommon vascular lesions. Even with conservative management complications can happen, such as delayed cerebral embolization or symptoms due to flow limitation. Although endovascular therapy can be curative, literature demonstrating a preferred technique is scant. Our goal was to evaluate the use of 1 technique only-the deployment of overlapping self-expandable porous stents-to treat a series of extracranial carotid pseudoaneurysms.

METHODS

From 2008 to 2014, 14 consecutive cases of symptomatic extracranial carotid pseudoaneurysms were managed with single or multilayer porous stents at our institution. Each patient underwent a standardized angiographic follow-up at 6 months. Twelve patients also received a follow-up computed tomography angiogram at 12 months, and yearly thereafter (median radiographic follow-up, 38 months). The total clinical follow-up period ranged between 6 and 69 months (median, 46 months).

RESULTS

In our series, each of the extracranial carotid pseudoaneurysms appeared to be the result of carotid artery dissection with associated carotid stenosis at the origin of every pseudoaneurysm. Endovascular treatment consisted of 1-3 layers of self-expandable porous stents placed without balloon angioplasty. Immediately after stenting angiographic images were notable for stagnant opacification of the pseudoaneurysm through the stent(s). All pseudoaneurysms were completely obliterated by the 6-month follow-up angiogram and remained so throughout the radiographic follow-up period. Complications were minimal, consisting of 1 patient developing a mild Horner's syndrome after treatment that resolved during clinical follow-up.

CONCLUSIONS

Extracranial carotid pseudoaneurysms can be successfully obliterated with the use of porous, self-expandable stents.

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.

Carotid artery stenting - current status of the procedure

Surgical carotid endarterectomy (CEA) was long considered the standard approach for the treatment of atherosclerotic carotid artery disease. This was based on results of several randomized trials demonstrating its effectiveness over the best medical therapy. In the past two decades, patients identified high-risk for surgery were offered carotid artery stenting (CAS) as a less invasive option. Despite its initial limitations, CAS has evolved into an elaborate method currently considered to be equivalent and in selected patients even preferable to CEA. However, outcomes of both procedures are highly operator dependent and a simple stratifying method to prioritize CAS, CEA or medical therapy only has not yet been proposed. In addition, recently published randomized trials highlighted the importance of proper patient selection and rigorous training contributing to low absolute rates of (procedural) adverse events. This review discusses the history and evidence for carotid revascularization and briefly presents technical aspects and innovations in CAS.

Covered stents may provide extra protection during carotid artery stenting in high risk patients with an excessive thrombus burden

Carotid artery disease is an important cause of mortality and morbidity related to atherosclerosis. Recently, percutaneous intervention procedures have been widely used to treat atherosclerotic carotid artery disease. We report the case of a 57-year-old male patient with a history of acute amaurosis fugax. Carotid angiography was performed as blood pressure differed between his left and right arms and there was a pan-systolic murmur on the left common carotid artery. Total occlusion of the proximal right brachiocephalic artery and a thrombus occluding 90-99% of the left internal carotid artery were detected by carotid angiogram. A self-expanding graft-covered stent was successfully implanted and there were no complications. This case shows that graft-covered stents may be a good alternative technique in special situations.

A novel carotid covered stent design: in vitro evaluation of performance and influence on the blood flow regime at the carotid artery bifurcation

In the present study, a novel carotid covered stent design has been developed. Prototypes of different geometrical design parameters have been fabricated and their performance has been evaluated in vitro under physiological pulsatile flow condition, utilizing flow visualization (dye injection), and particle image velocimetry techniques. These evaluations include the assessment of emboli prevention capability, side-branch flow preservation, and influence on the branch flow pattern and velocity field. The novel covered stents demonstrated significantly higher emboli prevention capability than the corresponding bare metal stent, while preserving more than 83% of the original flow of the external carotid artery (ECA). Flow in the ECA through these covered stents was uniform without evidence of undesirable flow recirculation and reversed flow that might predispose the vessel wall to post-stenting intimal thickening and atherosclerotic plaque formation. This study demonstrated the potential of these novel covered stent designs for the treatment of carotid atherosclerotic stenosis. However, further computational and in vivo investigations of hemodynamics, biological effects, and mechanical performance of this covered stent design is warranted.

Predictors of in-stent stenosis and occlusion after endovascular treatment of intracranial vascular disease with the Willis covered stent

Covered stent placement has emerged as a promising therapeutic option for intracranial vascular lesions. However, in-stent stenosis and occlusion continue to be important concerns with the use of a covered stent, which is more thrombogenic than other types of stents. The purpose of this study was to determine predictors of in-stent stenosis and occlusion for covered stents used in the treatment of intracranial vascular diseases. Clinical, procedural and angiographic data of 46 patients with 49 intracranial vascular lesions treated with the Willis covered stent (Micro-Port, Shanghai, China) between April 2005 and October 2010 were collected and analyzed retrospectively. Univariate analysis and multivariate logistic regression analysis were performed to determine the factors predictive of in-stent stenosis and/or occlusion of the stents. In-stent stenosis and/or occlusion were documented at angiography in six patients with six lesions, and no stenoses or occlusions were seen at angiography in the remaining 40 patients with 43 lesions. Univariate analysis revealed that hypertension, post-procedure irregular antiplatelet therapy and cerebrovascular arteriosclerosis were associated with in-stent stenosis and/or occlusion. By multivariate logistic regression analysis, post-procedure irregular antiplatelet therapy (odds ratio [OR]=15; 95% confidence interval [CI], 1.172-192.004; p=0.037) and cerebrovascular arteriosclerosis (OR=19; 95% CI, 1.374-262.659; p=0.028) were independent predictors of in-stent stenosis and/or occlusion. Thus, post-procedure irregular antiplatelet therapy and coexistent cerebrovascular arteriosclerosis appear to increase the risk of in-stent stenosis and/or occlusion of covered stents in the treatment of intracranial vascular disease.

A Study on the Effects of Covered Stents on Tissue Prolapse

Polyvinyl alcohol (PVA) cryogel covered stents may reduce complications from thrombosis and restenosis by decreasing tissue prolapse. Finite element analysis was employed to evaluate the effects of PVA cryogel layers of varying thickness on tissue prolapse and artery wall stress for two common stent geometries and two vessel diameters. Additionally, several PVA cryogel covered stents were fabricated and imaged with an environmental scanning electron microscope. Finite element results showed that covered stents reduced tissue prolapse up to 13% and artery wall stress up to 29% with the size of the reduction depending on the stent geometry, vessel diameter, and PVA cryogel layer thickness. Environmental scanning electron microscope images of expanded covered stents showed the PVA cryogel to completely cover the area between struts without gaps or tears. Overall, this work provides both computational and experimental evidence for the use of PVA cryogels in covered stents.

Reconstructive endovascular treatment of intracranial aneurysms with the Willis covered stent: medium-term clinical and angiographic follow-up

Object

Placement of covered stents has emerged as a promising therapeutic option for cerebrovascular diseases. However, the medium- and long-term efficacy and safety of covered stents in the treatment of these diseases remain unclear. The purpose of this study was to evaluate the medium-term clinical and angiographic outcomes of covered stent placement for the treatment of intracranial aneurysms.

Methods

The authors' institutional review board approved the study. Thirty-four patients (13 females and 21 males; mean age 41.9 years) with 38 intracranial aneurysms were treated with the Willis covered stent. Clinical and angiographic follow-up were performed at 3 months, at 6–12 months, and annually thereafter. The initial procedural and follow-up outcomes were collected and analyzed retrospectively.

Results

Forty-two covered stents were successfully implanted into the target artery in 33 patients with 37 aneurysms, and 1 covered stent navigation failed in 1 patient. A complete aneurysm exclusion was initially achieved in 24 patients with 28 aneurysms, and a minor endoleak occurred in 9 patients with 9 aneurysms. Postoperatively, 2 patients died of complications related to the procedure. Angiographic and clinical follow-up data are available in 30 patients. The angiographic follow-up (17.5 ± 9.4 months [mean ± SD]) exhibited complete occlusion in 28 patients with 31 aneurysms, and incomplete occlusion in 2 aneurysms, with an asymptomatic in-stent stenosis in 3 patients (10%). The clinical follow-up (26.7 ± 13 months [mean ± SD]) demonstrated that 16 patients (53.3%) experienced a full recovery, and 14 patients (46.7%) improved. No aneurysm rupture, thromboembolic events, or neurological deficits resulting from closure of a perforating vessel by covered stent placement occurred.

Conclusions

Endovascular reconstruction with the Willis covered stent represents a safe, durable, and curative treatment option for selected intracranial aneurysms, yielding an excellent medium-term patency of the parent artery and excellent clinical outcomes.

The use of covered stents for the endovascular treatment of extracranial internal carotid artery stenosis: a prospective study with a 5-year follow-up

OBJECTIVES

To evaluate the safety and feasibility of the use of covered stents for the treatment of extracranial carotid artery stenosis caused by highly embologenic plaques, and to study the long-term outcome of patients receiving such covered stents.

METHODS

Between 2002 and 2007, 46 patients (63% symptomatic, 78.3% male, 67 +/- 8.6 years old) with internal carotid artery stenosis caused by embologenic plaques or restenosis were treated with self-expanding covered stents (Symbiot, Boston Scientific). Pre-dilatation or protecting devices were not used. Post-dilatation was applied in every patient. Each patient was followed long-term. The outcome measures were the occurrence of neurological events, and the development of in-stent restenosis, as detected by clinical examination and duplex ultrasound.

RESULTS

The technical success rate of stenting was 100%. There were no neurological complications in the peri-procedural period. The mean follow-up period was 34.3 +/- 27.7 months (the rate of patients lost to follow-up was 15.2%) during which no stroke or stroke-related deaths occurred. Restenosis was detected in 3 patients (6.5%).

CONCLUSION

Covered stents provide efficient peri- and post-procedural protection against neurological complications due to embolisation from high-risk plaques during carotid artery stenting. Restenosis of covered stents appears to be infrequent during long-term follow-up.

Stent-grafts in the treatment of emergent or urgent carotid artery disease: review of 25 cases

PURPOSE

To report the authors' initial experience with carotid artery stent-grafts in a comparatively large patient series for the treatment of acute bleeding and impending rupture or the prevention of distal embolization.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review boards and performed according to HIPPA standards. Twenty-five patients were treated with 27 carotid artery stent-grafts (Gore Viabahn, n = 10; Bard Fluency, n = 9; polytetrafluoroethylene-covered Palmaz, n = 5; and Wallgraft, n = 3). Thirteen stent-grafts were placed in patients with carotid blow-out syndrome (including three patients with carotid-airway fistula), 12 in patients with either pseudoaneurysm (n = 9) or true aneurysm (n = 3), and two in patients with intractable high-grade bare stent restenosis.

RESULTS

The technical success rate was 100% (27 of 27 cases). No acute procedural transient ischemic attacks or strokes occurred. Procedural dissections occurred in two of the 27 cases (7.4%). Short-term complications occurred in three of the 27 cases (11%) (repeat hemorrhage, n = 2; common carotid artery occlusion, n = 1). The overall patient mortality rate was 36% (nine of 25 patients, all with carotid blow-out syndrome). Six-month follow-up in 15 of the 16 living patients demonstrated widely patent stent-grafts. Two patients with pseudoaneurysm also demonstrated patent stents at 18- and 33-month follow-up.

CONCLUSIONS

Stent-grafts may be useful in the treatment of carotid artery bleeding syndrome, aneurysm, and stenosis, with a high procedural success rate in selected cases. The results of mid-term follow-up are encouraging, but results of long-term follow-up must be evaluated in future studies.

Exclusion of Atherosclerotic Plaque from the Circulation Using Stent-Grafts: Alternative to Carotid Stenting with a Protection Device?

PURPOSE

To retrospectively assess the feasibility, safety, and clinical mid-term outcome of patients undergoing carotid artery stenting with stent-grafts.

METHODS

Over a 4 year period stent-grafts were used in the endovascular treatment of symptomatic internal carotid artery stenosis in 12 patients (2 women, 10 men, aged 47-83 (mean 64) years). Protection devices were not used. Possible microembolic complications were evaluated by magnetic resonance imaging (MRI) examinations of the brain before and the day after the procedure in all patients. Mean follow-up was 22 months (range 1-42 months), by Doppler ultrasonography and conventional angiography as well as clinical examination.

RESULTS

The technical success rate was 100%. A total of 13 coronary stent-grafts were used. The mean stenosis rate (in terms of diameter) was 85% and the mean length of stent-grafts used was 20.9 mm. The mean diameter to which the stent-grafts were dilated was 4.66 mm. In-hospital complications occurred in 1 patient who suffered a minor femoral access hematoma that did not require transfusion or surgical decompression. Post-stenting diffusion-weighted MRI revealed several ipsilateral silent microemboli in only 1 case, which was completely asymptomatic. Two patients had a major stroke after 2 years of follow-up. Restenosis was found in 2 patients who underwent successful balloon dilatation followed by placement of a self-expandable bare stent within the stent-grafts.

CONCLUSIONS

Stent-grafts may prevent microembolic complications during stenting of atherosclerotic carotid lesions in selected cases, offering immediate exclusion of the atherosclerotic lesion from the circulation by pressing the plaque against the vessel wall. Comparative, randomized studies in larger series of patients are needed with carotid-dedicated stent-graft designs.