Prevalence and clinical significance of stent fracture and deformation following carotid artery stenting

The Evolution of Current Management for Carotid Artery Bifurcation Disease

Options for treatment of symptomatic carotid bifurcation disease include carotid endarterectomy (CEA) and carotid artery stenting (CAS). While over the years CEA has established itself as the gold standard for carotid artery revascularization, results from recent trials have shown CAS to be safe and effective in selected patients. This review details the evolution of carotid artery bifurcation disease by highlighting key clinical trials.

Difficulties in Carotid Artery Stenting Due to Calcified Nodules: A Case Report

The feasibility of carotid artery stenting (CAS) for carotid stenosis with severely calcified plaque remains controversial. Understanding the features associated with CAS difficulty in lesions with severe calcification is crucial. Calcified nodules, one of the morphological patterns of calcified plaques, have not been assessed for their association with the feasibility of CAS, even though they are associated with failure of percutaneous coronary intervention (PCI) in coronary arteries. We present a rare case of carotid stenosis with calcified nodules in whom CAS was unsuccessful and who was subsequently successfully treated by carotid endarterectomy (CEA). A 79-year-old man presented with a transient ischemic attack caused by severe stenosis of the right internal carotid artery and opted for CAS. During the procedure, multiple attempts at balloon angioplasty using a 3.5-mm balloon were made, but effective dilation could not be achieved, resulting in recoil. Subsequently, the patient underwent carotid endarterectomy (CEA), and the excised specimen revealed a calcified nodule, a large nodular calcified plaque protruding into the lumen. The patient was discharged with a modified Rankin Scale score of 0 at 19 days after the CEA. The protrusion of this large calcified nodule into the lumen was deemed responsible for the inadequate stent dilation. Although rarely reported in carotid stenosis, calcified nodules might represent a challenging plaque type for CAS treatment.

Carotid Artery Stenting for Asymptomatic Carotid Stenosis: What We Need to Know for Treatment Decision

A clinical decision on the treatment of asymptomatic carotid stenosis is challenging, unlike symptomatic carotid stenosis. Carotid artery stenting (CAS) has been recommended as an alternative to carotid endarterectomy (CEA) based on the finding that the efficacy and safety of CAS were comparable to CEA in randomized trials. However, in some countries, CAS is often performed more frequently than CEA for asymptomatic carotid stenosis. Moreover, it has been recently reported that CAS is not superior to the best medical treatment in asymptomatic carotid stenosis. Due to these recent changes, the role of CAS in asymptomatic carotid stenosis should be revisited. When determining the treatment for asymptomatic carotid stenosis, one should consider several clinical factors including stenosis degree, patient life expectancy, stroke risk by medical treatment, availability of a vascular surgeon, high risk for CEA or CAS, and insurance coverage. This review aimed to present and pragmatically organize the information that is necessary for a clinical decision on CAS in asymptomatic carotid stenosis. In conclusion, although the traditional benefit of CAS is being revisited recently, it seems too early to conclude that CAS is no longer beneficial under intense and systemic medical treatment. Instead, a treatment strategy with CAS should evolve to select eligible or medically high-risk patients more precisely.

Folding Deformation of Open-Cell Stents in Carotid Artery Stenting: Report of Three Cases and Review of Literature

Objective

We describe 3 cases with folding deformation of a PRECISE (Cordis, Miami, FL, USA) stent in carotid artery stenting (CAS).

Case Presentations

The 3 cases with cervical carotid stenosis consisted of 3 males around 80 years old and included 2 symptomatic lesions. During CAS, distal embolic protection was established using a Mo.Ma (Medtronic, Minneapolis, MN, USA) along with a filter device in 2 cases and an Optimo (Tokai Medical Products, Aichi, Japan) along with a filter device in 1 case. For the filter device, either FilterWire EZ (Boston Scientific, Natick, MA, USA) or Spider FX (Covidien, Irvine, CA, USA) was employed. In all cases, a PRECISE stent was deployed after pre-dilation performed using a percutaneous transluminal angioplasty (PTA) balloon with the diameter of 2.5 to 3 mm. Post-dilation was performed after the stent deployment using a PTA balloon whose diameter was about 80% of that of the normal distal internal carotid artery. In all cases, cone-beam CT taken after the deployment of a stent showed folding deformation of the stent. In 2 cases, heavily calcified plaque hampered self-expansion of the stent, which resulted in the stent deformation. On the other hand, in the remaining 1 case, a distal shaft of the Mo.Ma caused the stent deformation, which was likely accelerated by head rotation and cervical compression that was performed to resolve difficulties for a filter retrieval device to pass through the stent, and post-dilation after the stenting.

Conclusion

Heavily calcified plaque and a distal shaft of a Mo.Ma would result in stent deformation.

Therapeutic strategy of severe circular calcified carotid plaque with hemodynamic impairment: A patient treated by carotid endarterectomy following balloon angioplasty to prevent hyperperfusion

Background:

Cerebral hyperperfusion syndrome (HPS) is a serious complication. Recently, staged angioplasty has been reported as an effective strategy to avoid HPS. Severe calcification has been reported as contraindication of carotid artery stenting (CAS). In these cases, carotid endarterectomy (CEA) might be an alternative second stage treatment. We present a case of severe circular calcified plaque with hemodynamic impairments, treated with CEA following percutaneous transluminal angioplasty (PTA) to prevent HPS.

Case Description:

A 77-year-old woman presented with severe stenosis at the proximal left internal carotid artery. A CT scan of the neck demonstrated circular calcification. ¹²³I-iodoamphetamine single-photon emission computed tomography (¹²³I-IMP SPECT) showed reductions in cerebral blood flow (CBF) and cerebral vascular reserve in the left hemisphere. Staged therapy was subsequently performed as this patient had a high risk of HPS after conventional CAS or CEA. In the first stage, PTA was performed under local anesthesia. Two days after the procedure, ¹²³I-IMP SPECT revealed improvements in CBF. There were no neurological morbidities. CEA was then performed under general anesthesia 7 days later, for the second stage. We found a calcified plaque with a large thrombus at its proximal end. A hematoxylin-eosin stain of the thrombus showed mostly intact and partially lytic blood cells. Postoperative ¹²³I-IMP SPECT revealed CBF was improved, with no hyperperfusion immediately and 2 days after CEA. The patient was discharged with no neurological deficits.

Conclusion:

CEA following PTA for severe circular calcified plaque can be an alternative treatment strategy to prevent HPS. A disadvantage is the formation of thrombi. Early CEA should be considered if thrombus formation is suspected.

Assessing the Suitability of the Carotid Bifurcation for Stenting: Anatomic and Morphologic Considerations

OBJECTIVE

Over the years where stents have been used to treat carotid lesions, a great deal has been learned about which anatomical characteristics lead to adverse outcomes. This review summarizes the anatomic and morphologic characteristics of the carotid vasculature that can help guide patient selection and clinical decision-making.

METHODS

Each of the carotid artery anatomy and lesion characteristics that are relevant to carotid stenting are described in detail. These are accompanied with evidence-based outcomes and results.

RESULTS

Data on the prevalence of carotid artery lesions that are unsuitable for stenting are summarized and the implications of these data for practice are discussed, especially as they pertain to transcarotid artery revascularization.

CONCLUSIONS

CAS can be viable option for carotid revascularization, but the lesion must be acceptable and safe for stent placement. There should be thorough assessment to rule out the presence of severe tortuosity, long-segment disease, severe calcification (circumferential or exophytic), mobile-plaque, swollen ICA sign, and carotid diameters outside the acceptable range. In carefully chosen lesions with the absence of the unfavorable characteristics described-TCAR may offer improved periprocedural success, and CAS may attain better long-term durability.

Prevention of Stroke with Closed-Cell Stent-in-Stent for Carotid Artery Stenosis Due to Stent Fracture

Objective

Stent fracture is a risk factor for stroke. It has not been fully elucidated whether stent-in-stent procedures can effectively treat stent fractures.

Case Presentation

An 80-year-old man underwent carotid artery stenting (CAS) with an open-cell stent to treat asymptomatic right internal carotid artery (ICA) stenosis. Type III stent fracture occurred during CAS. Six months later, in-stent stenosis progressed on DSA. Repeat CAS with a closed-cell stent was performed. CT showed expansion of the narrowed lumen. The patient remained stroke-free and carotid artery restenosis did not occur for 3 years postoperatively.

Conclusion

Repeat CAS with a closed-cell stent is a viable treatment option for stent fracture.

"Whiplash" cervical trauma with fracture and migration of carotid stent fragments

Background:

Angioplasty using a carotid stent is a treatment modality for carotid stenosis, with results similar to those obtained with endarterectomy, as demonstrated by important studies. The increasing use of this procedure has also led to a larger number of reports of complications, stent fractures among those. Stent fracture is a rare manifestation and hence needs further studying so that its actual prevalence can be determined, as well as its associated risk factors and proper clinical management. The current study reports the case of a patient who had previously undergone angioplasty with a carotid stent and, after an automobile accident, presented with a stent fracture and distal embolization of fragments thereof with neurological manifestation.

Case Description:

A male patient, 40 years old, presented with a history of previously stent carotid angioplasty. He had been involved in an automobile accident and suffered a stent fracture with distal fragment migration. As he was an asymptomatic patient (NIHSS 0, Rankin zero), we opted for a conservative treatment with oral anticoagulant.

Conclusion:

Angioplasty is an effective treatment for extracranial atherosclerosis and, albeit rare, stent fractures can result in the migration of fragments thereof. This occurrence should be suspected in patients who have sustained severe neck injuries due to sudden deceleration and may be associated with thromboembolism.

Carotid endarterectomy remains safe in high-risk patients

OBJECTIVE

Carotid endarterectomy (CEA) is a proven intervention for stroke risk reduction in symptomatic and asymptomatic patients. High-risk patients are often offered carotid stenting to minimize the risk and optimize the outcomes. As a referral center for high-risk patients, we evaluated and analyzed our experience with high-risk CEA patients.

METHODS

We retrospectively reviewed consecutive patients who had undergone CEA at a tertiary referral center. The demographics, indications for surgery, physiologic and anatomic risk factors, intraoperative surgical management, perioperative complications, morbidity, and mortality were analyzed. The high-risk physiologic factors identified included an ejection fraction <30%, positive preoperative stress test results, and compromised pulmonary function test results. The high-risk patients included those requiring home oxygen, those with a partial pressure of oxygen of <60 mm Hg, and patients with a forced expiratory volume in 1 second of <30%. The high-risk anatomic factors identified included previous head and/or neck radiation, a history of ipsilateral neck surgery, contralateral nerve palsy, redo CEA, previous ipsilateral stenting, contralateral occlusion, contralateral CEA, nasotracheal intubation, and digastric muscle division. After propensity score matching, patients with and without high-risk physiologic and anatomic factors were compared. The primary outcomes were a composite of stroke, myocardial infarction, and 30-day mortality. The secondary outcomes were cranial injury and surgical site infection.

RESULTS

During a 10-year period, 1347 patients had undergone CEA at the Cleveland Clinic main campus. Of the 1347 patients, 1152 met the criteria for analysis. Propensity score matching found adequate matches for 424 high-risk patients, with 173 patients having at least one physiologic high-risk factor and 293 at least one anatomic high-risk factor. No significant differences were found in the primary composite outcome or any of its components. Overall, the stroke rate for the standard-risk and high-risk patients was 1.9% and 1.4%, respectively. The high-risk patients were significantly more likely to have experienced a cranial nerve injury, although most were temporary. When patients with one or multiple risk factors were analyzed, no significant difference was found in the primary composite outcome or any of its components. Patients with two or more risk factors were significantly more likely to have experienced a cranial nerve injury, with most being temporary.

CONCLUSIONS

In our large series, CEA remained a viable and safe surgical solution for patients with high-risk anatomic and physiologic risk factors, with acceptable stroke, myocardial infarction, and 30-day mortality rates.

Predictors of midterm high-grade restenosis after carotid revascularization in a multicenter national database

BACKGROUND

Restenosis after carotid revascularization is clinically challenging. Several studies have looked into the management of recurrent restenosis; however, studies looking into factors associated with restenosis are limited. This study evaluated the predictors of restenosis after carotid artery stenting (CAS) and carotid endarterectomy (CEA) using a large national database.

METHODS

Patients undergoing CEA or CAS in the Vascular Quality Initiative data set (2003-2016) were analyzed. Patients with no follow-up (33%) and those who had prior ipsilateral CEA or CAS were excluded. Significant restenosis was defined as ≥70% diameter-reducing stenosis, target artery occlusion or peak systolic velocity ≥300 cm/s, or repeated revascularization. Kaplan-Meier survival analysis and bootstrapped Cox regression models with stepwise forward and backward selection were used.

RESULTS

A total of 35,720 procedures were included (CEA, 31,329; CAS, 4391). No significant difference in restenosis rates was seen between CEA and CAS at 2 years (7.7% vs 9.4% [P = .09]; hazard ratio [HR], 0.99; 95% confidence interval [CI], 0.79-1.25; P = .97). However, after adjustment for age, sex, and symptomatic status at the time of the index operation, CAS patients who had postoperative restenosis were more likely to have a symptomatic presentation (odds ratio, 2.2; 95% CI, 1.2-4.0; P = .01) and to undergo repeated revascularization at 2 years (HR, 1.75; 95% CI, 1.3-2.4; P < .001) compared with patients who had restenosis after CEA. Predictors of restenosis after CAS included a common carotid artery lesion (HR, 1.65; 95% CI,1.06-2.57; P = .03), whereas age (HR, 0.91; 95% CI, 0.84-0.99; P = .03) and dilation after stent placement (HR, 0.53; 95% CI, 0.39-0.72; P < .001) were associated with decreased restenosis at 2 years. Predictors of restenosis after CEA included female sex (HR, 1.55; 95% CI, 1.38-1.74; P < .001), prior neck irradiation (HR, 2.35; 95% CI, 1.66-3.30; P < .001), and prior bypass surgery (HR, 1.29; 95% CI, 1.01-1.65; P = .04). On the other hand, factors associated with decreased restenosis after CEA included age (HR, 0.95; 95% CI, 0.92-0.98; P < .001), black race (HR, 0.57; 95% CI, 0.37-0.89; P = .01), patching (HR, 0.61; 95% CI, 0.47-0.79; P < .001), and completion imaging (HR, 0.70; 95% CI, 0.52-0.95; P = .02).

CONCLUSIONS

Our results show no significant difference in restenosis rates at 2 years between CEA and CAS. Restenosis after CAS is more likely to be manifested with symptoms and to undergo repeated revascularization compared with that after CEA. Poststent ballooning after CAS and completion imaging and patching after CEA are associated with decreased hazard of restenosis; however, further research is needed to assess longer term outcomes and to balance the risks vs benefits of certain practices, such as poststent ballooning.

Cervical internal carotid artery tortuosity: A morphologic analysis of patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Cervical internal carotid artery (ICA) tortuosity is thought to impede distal catheterization during attempted mechanical thrombectomy in patients with acute ischemic stroke. This study sought to assess the morphologic characteristics of ICAs and the effects of tortuosity on thrombectomy attempts.

METHODS

A retrospective review was completed of neck CTAs of patients with acute ischemic stroke due to a large vessel occlusion that underwent attempted endovascular recanalization. Significant tortuosity of ICAs was defined as the presence of kink(s) (acute (<90°) angulation), loop(s) (C- or S-shaped curvature with 2+ areas of acute (<90°) angulation), or coil(s) (full 360° turn arterial bend). Findings were statistically compared to procedure time, successful recanalization rate, patient demographics, and co-morbidities.

RESULTS

Of 120 included patients, 47 (39.2%) had some form of tortuosity of one or both ICAs. Twenty-eight patients (23.3%) had a kink of one or both ICAs; this was followed in frequency by loops (n = 20; 16.7%) and coils (n = 8; 6.7%). Kinks were associated with lower rates of successful recanalization (p = 0.02). The presence of any tortuosity (kinks, loops, or coils) was not associated with number of passes during thrombectomy (p = 0.88), successful recanalization (p = 0.11), or total procedure time (p = 0.22). No association was noted between the presence of tortuosity and age (p = 0.96) or prior or current tobacco use (p = 0.75 and p = 0.69, respectively).

CONCLUSION

Among patients referred for urgent revascularization for large vessel occlusion, approximately 40% exhibit some tortuosity. Kinks may portend lower likelihood of recanalization success, although tortuosity as a whole seems to have little effect on endovascular thrombectomy.

A meta-analysis of the effect of stent design on clinical and radiologic outcomes of carotid artery stenting

OBJECTIVE

Procedural characteristics, including stent design, may influence the outcome of carotid artery stenting (CAS). A thorough comparison of the effect of stent design on outcome of CAS is thus warranted to allow for optimal evidence-based clinical decision making. This study sought to evaluate the effect of stent design on clinical and radiologic outcomes of CAS.

METHODS

A systematic search was conducted in MEDLINE, Embase, and Cochrane databases in May 2018. Included were articles reporting on the occurrence of clinical short- and intermediate-term major adverse events (MAEs; any stroke or death) or radiologic adverse events (new ischemic lesions on postprocedural magnetic resonance diffusion-weighted imaging [MR-DWI], restenosis, or stent fracture) in different stent designs used to treat carotid artery stenosis. Random effects models were used to calculate combined overall effect sizes. Metaregression was performed to identify the effect of specific stents on MAE rates.

RESULTS

From 2654 unique identified articles, two randomized, controlled trials and 66 cohort studies were eligible for analysis (including 46,728 procedures). Short-term clinical MAE rates were similar for patients treated with open cell vs closed cell or hybrid stents. Use of an Acculink stent was associated with a higher risk of short-term MAE compared with a Wallstent (risk ratio [RR], 1.51; P = .03), as was true for use of Precise stent vs Xact stent (RR, 1.55; P < .001). Intermediate-term clinical MAE rates were similar for open vs closed cell stents. Use of open cell stents predisposed to a 25% higher chance (RR, 1.25; P = .03) of developing postprocedural new ischemic lesions on MR-DWI. No differences were observed in the incidence of restenosis, stent fracture, or intraprocedural hemodynamic depression with respect to different stent design.

CONCLUSIONS

Stent design is not associated with short- or intermediate-term clinical MAE rates in patients undergoing CAS. Furthermore, the division in open and closed cell stent design might conceal true differences in single stent efficacy. Nevertheless, open cell stenting resulted in a significantly higher number of subclinical postprocedural new ischemic lesions detected on MR-DWI compared with closed cell stenting. An individualized patient data meta-analysis, including future studies with prospective homogenous study design, is required to adequately correct for known risk factors and to provide definite conclusions with respect to carotid stent design for specific subgroups.

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.

Surgical Rescue Retrieval of a Filter Protection Device in Carotid Artery Stenting with Stent Deformation: Case Report and Literature Review

BACKGROUND

Despite the development of neuroendovascular treatment, device-related complications requiring surgical procedures remain. We report a case requiring surgical retrieval of a filter protection device in carotid artery stenting (CAS) with an open-cell stent, due to stent deformation, and review past reports on CAS in which surgical retrieval of devices was required.

CASE DESCRIPTION

An 82-year-old man underwent CAS for symptomatic right internal carotid artery stenosis with severe calcification and tortuosity. Immediately after placement of the open-cell stent, stent deformation was detected and the filter protection device could not be retrieved. All noninvasive device retrieval attempts failed, and the device was ultimately retrieved surgically. After surgery, right cerebral infarction progressed increased, but no permanent deficit was observed.

CONCLUSIONS

As the treatment of cerebrovascular disease shifts from surgical to endovascular approaches, surgeons must be familiar with devices and techniques to manage complications of neuroendovascular treatment.

Relating the mechanical properties of atherosclerotic calcification to radiographic density: A nanoindentation approach

Calcification morphology can determine atherosclerotic plaque stability and is associated with increased failures rates for endovascular interventions. Computational efforts have sought to elucidate the relationship between calcification and plaque rupture in addition to predicting tissue response during aggressive revascularisation techniques. However, calcified material properties are currently estimated and may not reflect real tissue conditions. The objective of this study is to correlate calcification mechanical properties with three radiographic density groups obtained from corresponding Computed Tomography (CT) images. Seventeen human plaques extracted from carotid (n = 10) and peripheral lower limb (n = 7) arteries were examined using micro-computed tomography (µCT), simultaneously locating the calcified deposits within their internal structure and quantifying their densities. Three radiographic density groups were defined based on the sample density distribution: (A) 130-299.99 Hounsfield Units (HU), (B) 300-449.99 HU and (C) >450 HU. Nanoindentation was employed to determine the Elastic Modulus (E) and Hardness (H) values within the three density groups. Results reveal a clear distinction between mechanical properties with respect to radiographic density groups (p < 0.0005). No significant differences exist in the density-specific behaviours observed between carotid and peripheral samples. Previously defined calcification classifications indicate an association with specific radiographic density patterns. Scanning Electron Microscopy (SEM) examination revealed that density group A regions consist of both calcified and non-calcified tissues. Further research is required to define the radiographic thresholds which identify varying degrees of tissue calcification. This study demonstrates that the mechanical properties of fully mineralised atherosclerotic calcification emulate that of bone tissues (17-25 GPa), affording computational models with accurate material parameters. STATEMENT OF SIGNIFICANCE: Global mechanical characterisation techniques disregard the heterogeneous nature of atherosclerotic lesions. Previous nanoindentation results for carotid calcifications have displayed a wide range. This study evaluates calcification properties with respect to radiographic density obtained from Micro-CT images. This is the first work to characterise calcifications from peripheral lower limb arteries using nanoindentation. Results demonstrate a strong positive correlation between radiographic density and calcification mechanical properties. Characterising calcifications using their density values provides clarity on the variation in published properties for calcified tissues. Furthermore, this study confirms the hypothesis that fully calcified plaque tissue behaviour similar to that of bone. Appropriate material parameters for calcified tissues can now be employed in computational simulations.

Sonographic Evaluation of Complications of Extracranial Carotid Artery Interventions

Carotid endarterectomy and carotid artery stenting are among the most common peripheral vascular procedures performed worldwide. Sonography is the initial and often only imaging modality used in the evaluation of iatrogenic carotid arterial injuries. This pictorial essay provides an overview of the clinical and sonographic findings of complications after interventions in the extracranial carotid arteries, including dissection, fluid collections, pseudoaneurysm, thrombosis, thromboembolism, restenosis, and stent deformation. Grayscale, color, and pulsed Doppler imaging findings are reviewed, and correlations with computed tomography, magnetic resonance imaging, and angiography are provided.

Long and short of optimal stent design

The ideal stent must fulfil a broad range of technical requirements. Stents must be securely crimped onto the delivery balloon and, in this form, must have a low profile and be sufficiently flexible to facilitate deliverability to the lesion site without distortion or displacement. Following expansion, stents must exert sufficient radial force on the vessel wall to overcome lesion resistance and elastic recoil. To achieve an optimal lumen diameter, the lesion must be uniformly and adequately scaffolded, with minimal tissue prolapse between struts but without compromising side-branch access. Furthermore, the deployed stent must conform to the vessel curvature to minimise vessel distortion, particularly at the stent edges. Radio-opacity is also important to guide safe positioning, adequate deployment and postdilataion and to permit assessment of optimal stent expansion. Equally though, the stent lumen must also be sufficiently visible to allow radiographic assessment of flow dynamics and restenosis. Efforts to optimise one characteristic of stent design may have detrimental effects on another. Thus, currently available stents all reflect a compromise between competing desirable features and have subtle differences in their performance characteristics. Striving to achieve stents with optimal deliverability, conformability and radial strength led to a reduction in longitudinal strength. The importance of this parameter was highlighted by complications occurring in the real-world setting where percutaneous coronary intervention is often undertaken in challenging anatomy. This review focuses on aspects of stent design relevant to longitudinal strength.

Dynamic Respiratory Tortuosity of the Vertebral Artery Ostium

PURPOSE

To determine the prevalence of dynamic respiratory tortuosity (DRT) of the vertebral artery ostium (VAO) as well as to evaluate its correlation with in-stent restenosis (ISR) and stent fracture.

METHODS

From March 2012 to June 2015, 178 consecutive patients (mean age 65.2±5.8 years; 124 men) with symptoms of atherosclerotic vertebrobasilar ischemia underwent angiography prior to stent implantation in the vertebral, subclavian, and/or carotid arteries. In this cohort, 54 patients (mean age 67.3±5.3 years; 40 men) had VAO stent implantation. Angiography of the vertebral artery was recorded in 2 phases with breath-hold: deep inspiration (DIP) and deep expiration (DEP). Obvious VAO tortuosity was defined as any VAO angle ≤120° in DIP. Obvious VAO-DRT was defined as any VAO angle increasing ≥60° from DIP to DEP. Computed tomography angiography (CTA) or digital subtraction angiography was used in follow-up to detect ISR and stent fracture.

RESULTS

Of the 178 patients in this study, 21 (11.8%) had obvious VAO tortuosity and 8 (4.5%) had obvious VAO-DRT. Two of the 21 patients with obvious VAO tortuosity also had obvious VAO-DRT. Three of the 54 VAO stent patients had VAO-DRT. There were no correlations between VAO-DRT and age, sex, risk factors, body mass index, chronic obstructive pulmonary disease, asthma, or obvious VAO tortuosity (p>0.05). Over a mean follow-up of 28±10 months, there were 4 (7.4%) asymptomatic VAO ISR cases. Two (3.7%) were occlusions at 6 and 12 months, respectively; both were associated with stent fracture in patients with obvious VAO-DRT before stenting. Both stents fractured at the tortuous VAO region. VAO-DRT was correlated with stent fracture (Spearman ρ=0.81, p<0.01) and ISR (Spearman ρ=0.55, p<0.01).

CONCLUSION

VAO-DRT could be a risk factor for stent fracture and restenosis after VAO stent implantation. Angiography in both inspiration and expiration phases, especially the latter, should be considered before VAO stenting. Using a shorter stent to avoid crossing the tortuosity could reduce the occurrence of fracture.

Fatigue of Metallic Stents: From Clinical Evidence to Computational Analysis

The great success of stents in treating cardiovascular disease is actually undermined by their long-term fatigue failure. The high variability of stent failure incidence suggests that it is due to several correlated aspects, such as loading conditions, material properties, component design, surgical procedure, and patient functional anatomy. Numerical and experimental non-clinical assessments are included in the recommendations and requirements of several regulatory bodies and they are thus exploited in the analysis of stent fatigue performance. Optimization-based simulation methodologies have been developed as well, to improve the fatigue endurance of novel designs. This paper presents a review on the fatigue issue in metallic stents, starting from a description of clinical evidence about stent fracture up to the analysis of computational approaches available from the literature. The reported discussion on both the experimental and numerical framework aims at providing a general insight into stent lifetime prediction as well as at understanding the factors which affect stent fatigue performance for the design of novel components.

Delayed carotid wallstent shortening

INTRODUCTION

Carotid angioplasty and stenting (CAS) has been demonstrated to be safe and an acceptable alternative to surgery. Stent malpositioning can occur during the maneuvers of delivering; technical errors can lead to proximal or distal slipping of the stent that needs the placement of additional pieces.

PRESENTATION OF CASE

We describe the case of a postoperative dislocation of a carotid stent that happened 1 year after placement. After the first ultrasound control confirmed the correct position of the Stent the following one, executed 9 months later, showed a severe restenosis due to a proximal dislocation of the stent. The problem was solved with the positioning of a further one more distally.

DISCUSSION

We observe the possibility of Carotid Wallstent shortening during the implant due to an incorrect placement or sizing, but a delayed displacement is a rare complication that, we highlight, can occur after CAS and that needs to be considered at the moment of the preoperative planning.

CONCLUSION

After CAS a closed ultrasound follow up is advisable for a long time in order to detect unexpected complications.

Carotid stent extrusion following carotid blowout

OBJECTIVE

We describe an unusual foreign body, a carotid stent extruded into the upper airway, and discuss the predisposing factors.

METHODS

This is a single patient case report with review of the literature.

RESULTS

Our patient is a 59 year old female treated for T3N2aM0 (stage IVa) left tonsil squamous cell carcinoma who experienced a carotid blowout treated by carotid stent placement with subsequent carotid coiling and vessel takedown. Approximately ten months later, she coughed and expelled approximately 3cm of tubular stent-appearing material into her airway causing acute stridor and dysphagia. CT angiography (CTA) showed the distal and proximal stent in proper position without evidence of extravasation. The stent was extracted transorally showing the distal end of the carotid to be patent and covered by fibrin within its lumen. Review of the literature shows that such stent extrusions, although rare, do occur.

CONCLUSION

Carotid stents are a valuable tool in cases of carotid blowout. However, long-term data on patient prognosis is lacking. The foreign body response triggered by stent placement can cause dislodgement. The potential for stent extrusion is greatest in patients who have preexisting ulceration or who have undergone radiation, both common in head and neck cancer patients.

Delayed cerebral infarction due to stent folding deformation following carotid artery stenting

We report a case of delayed cerebral infarction due to stent longitudinal folding deformation following carotid artery stenting using a self-expandable stent with an open-cell design. The stented segment of the left common carotid artery was divided into two different lumens by this folding deformation, and the separated lumens became restricted with in-stent thrombosis. Although no established method of managing this rare complication exists, a conservative approach was taken with administration of anticoagulant and dual antiplatelet therapy. No neurological symptoms were observed during several months of clinical follow-up after discharge.

Carotid stent deformation: sonographic findings and CT correlation

Carotid artery dissection is a rare but potentially serious complication of endovascular procedures in the carotid arteries. Stent deformation or incomplete expansion may occur following endovascular repair of an iatrogenic carotid artery dissection and may mimic stent fracture. We report an unusual case of deformation of a common carotid artery open cell design stent following endovascular repair of an iatrogenic dissection, which resulted in persistent blood flow between the stent and the wall of the common carotid artery. Sonographic features are described and correlation with intravascular ultrasound and CT is provided.

Stent fracture in the brachiocephalic trunk

Stents are commonly used as a tool for revascularization of different vascular beds in the body. However, many pitfalls have been reported with their use, such as thrombosis, migration, restenosis or fractures. The latter have been strongly correlated to in-stent restenosis with long-term follow-up. We report a rare case of an early stent fracture in the brachiocephalic trunk with in-stent restenosis and recurrence of symptoms. To our knowledge there has been only one case report of a delayed brachiocephalic stent fracture in the English literature. We believe that our case is the first report of an early stent fracture in the brachiocephalic trunk.