Common Cervical and Cerebral Vascular Variants.

Successful open and endovascular carotid artery intervention depends on a thorough foundational knowledge of cervical and intracranial vascular anatomy. It is essential for the carotid interventionist to be familiar with the common and rare variants of the cervical and intracranial vasculature, and to understand the implications of these variants for the performance of carotid intervention with protection of the distal circulation. This article provides interventionists with a basic description of the normal and relevant variant vascular anatomy from the aortic arch to the circle of Willis, and outlines the potential difficulties that specific variants may present for endovascular therapy.

Carotid artery stenting update.

Stroke is the third leading cause of death and the most common cause of long-term disability in the USA. Approximately 25% of strokes are due to carotid artery disease. The mechanisms of stroke include thrombotic occlusion, thrombus embolism, atheroembolism and dissection or subintimal hematoma. Today, endarterectomy is the standard of care for management of significant carotid artery disease. The SAPPHIRE trial has proved the noninferiority of carotid artery stenting versus carotid endarterectomy in 'high-risk' patients, which led to the US FDA approval of carotid stent for high-risk patients. The CREST trial is the largest randomized trial comparing stenting versus endarterectomy and showed no significant difference in death, stroke or myocardial infarction. Over the last 15 years, the accumulation of experience, the improvement of stent platforms and embolic protection devices, and the strong demand from patients for a less invasive alternative to carotid endarterectomy has made carotid artery stenting an equally efficient and safe procedure for the prevention of stroke.

Assessing the impact of distal protection filter design characteristics on 30-day outcomes of carotid artery stenting procedures.

OBJECTIVE: This study aims to review retrospectively the records of patients treated with carotid artery stenting (CAS) to investigate the potential correlations between clinical variables, distal protection filter (DPF) type and characteristics, and 30-day peri-/postprocedural outcomes. METHODS: This is a multicenter, single-arm, nonrandomized retrospective study of patients who underwent filter-protected CAS in the Pittsburgh, Pennsylvania, region between July 2000 and May 2011. Analysis of peri-/postprocedural complications included myocardial infarction, transient ischemic attacks (TIA), stroke, death, and a composition of all adverse events (AEs). Filter characteristics for Accunet (Abbott Vascular, Santa Clara, Calif; n = 429 [58.8%]), Angioguard (Cordis Endovascular, Miami Lakes, Fla; n = 114 [15.6%]), FilterWire (Boston Scientific, Natick, Mass; n = 113 [15.5%]), Spider (ev3 Endovascular, Plymouth, Minn; n = 45 [6.2%]), and Emboshield (Abbott Vascular; n = 24 [3.3%]) were previously determined in vitro and were used to find correlations with CAS procedural outcomes. Both univariate and multivariate analyses were performed, as well as goodness-of-fit tests to find multivariate correlations with procedural outcomes. RESULTS: In total, 731 CAS procedures using six different DPFs were analyzed. Peri-/postprocedural AEs included 19 TIAs (2.6%), 38 strokes (5.2%), one myocardial infarction (0.1%), 19 deaths (3.6%), and a total of 61 patients with complications (8.3%). Univariate analysis for filter design characteristics showed that the composite of AE was negatively associated with both vascular resistance (P = .01) and eccentricity (P = .02) and was positively associated with porosity (P = .0007), number of pores (P = .005), and pore density (P = .001). Multivariate analysis and the goodness-of-fit test revealed that patients with a history of congestive heart failure, stroke, and TIA (each with odds ratio >1) led to a good-fit model P value of .72 for peri-/postprocedural AEs. Multivariate analysis was inconclusive for all filter design characteristics. CONCLUSIONS: The following filter design characteristics are independently significant for minimizing peri-/postprocedural AEs: higher vascular resistance, concentric in shape, greater capture efficiency, lower porosity, lower number of pores, and lower pore density. Lower porosity and smaller wall apposition were also found to be independently significant for minimization of peri-/postprocedural TIAs. This information can be used when considering the desirable design characteristics of future DPFs.).

A comparative analysis of bench-top performance assessment of distal protection filters in transient flow conditions.

PURPOSE: To compare the performance in vitro of 6 distal protection filters (DPFs) on the basis of filtration ability and effects on pressure gradient and vascular impedance in a flow model of the internal carotid artery (ICA). METHODS: Six DPFs (Accunet, Angioguard, FilterWire, Gore Embolic Filter, NAV6, and SpiderFX) were evaluated in a physiologically realistic flow loop. A blood analog was heated to body temperature and circulated by a pulsatile pump outputting a time-varying flow rate representative of the ICA. The ICA flow model was a highly curved tube representing a challenging site for filter deployment. The DPFs were deployed at the apex of the curved segment, and 2 sizes of microspheres (143 and 200 µm) were injected to simulate embolization. The capture efficiency, pressure gradient, normalized pressure gradient, and vascular impedance were calculated. RESULTS: The Gore filter had high capture efficiency (143 µm: 99.97%; 200 µm: 100.00%) with relatively small increases in pressure gradient (143 µm: +27%; 200 µm: +20%) and vascular impedance (143 µm: +23.4%; 200 µm: +6.1%) after particles were injected. Spider had the lowest capture efficiency (143 µm: 1.50%; 200 µm: 19.34%, p<0.0005), while NAV6 (143 µm: +916%, p<0.0005) and Accunet (200 µm: +179%, p<0.0005) yielded the largest pressure gradient increases. CONCLUSION: A bench-top flow apparatus exhibiting physiologically realistic conditions was developed by combining pulsatile flow and a body temperature blood analog. Using microspheres larger than the pore size of most of the DPFs, the device-wall apposition has an important effect on the overall filter performance and the global fluid dynamics in the flow model.

Reproducibility of IVUS border detection for carotid atherosclerotic plaque assessment.

Plaque composition is a potentially important diagnostic feature for carotid artery stenting (CAS). The purpose of this investigation is to evaluate the reproducibility of manual border correction in intravascular ultrasound with virtual histology (VH IVUS) images. Three images each were obtained from 51 CAS datasets on which automatic border detection was corrected manually by two trained observers. Plaque was classified using the definitions from the CAPITAL (Carotid Artery Plaque Virtual Histology Evaluation) study, listed in order from least to most pathological: no plaque, pathological intimal thickening, fibroatheroma, fibrocalcific, calcified fibroatheroma, thin-cap fibroatheroma, and calcified thin-cap fibroatheroma. Inter-observer variability was quantified using both weighted and unweighted Kappa statistics. Bland-Altman analysis was used to compare the cross-sectional areas of the vessel and lumen. Agreement using necrotic core percentage as the criterion was evaluated using the unweighted Kappa statistic. Agreement between classifications of plaque type was evaluated using the weighted Kappa statistic. There was substantial agreement between the observers based on necrotic core percentage (κ=0.63), while the agreement was moderate (κ(quadratic)=0.60) based on plaque classification. Due to the time-consuming nature of manual border detection, an improved automatic border detection algorithm is necessary for using VH IVUS as a diagnostic tool for assessing the suitability of patients with carotid artery occlusive disease for CAS.

Stroke intervention: catheter-based therapy for acute ischemic stroke.

The majority (>80%) of the three-quarters of a million strokes that will occur in the United States this year are ischemic in nature. The treatment of acute ischemic stroke is very similar to acute myocardial infarction, which requires timely reperfusion therapy for optimal results. The majority of patients with acute ischemic stroke do not receive any form of reperfusion therapy, unlike patients with acute myocardial infarction. Improving outcomes for acute stroke will require patient education to encourage early presentation, an aggressive expansion of qualified hospitals, and willing providers and early imaging strategies to match patients with their best options for reperfusion therapy to minimize complications.

Costs and cost-effectiveness of carotid stenting versus endarterectomy for patients at increased surgical risk: results from the SAPPHIRE trial.

OBJECTIVES: To evaluate the cost-effectiveness of carotid stenting vs. carotid endarterectomy using data from the SAPPHIRE trial. BACKGROUND: Carotid stenting with embolic protection has been introduced as an alternative to carotid endarterectomy for prevention of cerebrovascular and cardiovascular events among patients at increased surgical risk. METHODS: Between August 2000 and July 2002, 310 patients with an accepted indication for carotid endarterectomy but at high risk of complications were randomized to and subsequently underwent either carotid stenting (n = 159) or endarterectomy (n = 151). Clinical outcomes, resource use, costs, and quality of life were assessed prospectively for all patients over a 1-year period. Life expectancy, quality-adjusted life expectancy, and health care costs beyond the follow-up period were estimated for patients alive at 1 year, based on observed clinical events during the first year of follow-up. RESULTS: Although initial procedural costs were significantly higher for stenting than for endarterectomy (mean difference: $4,081/patient; 95% CI, $3,849-$4,355), mean post-procedure length of stay was shorter for stenting (1.9 vs. 2.9 days; P < 0.001) with significant associated cost offsets. As a result, initial hospital costs were just $559/patient higher with stenting (95% CI, $3,470 less to $2,289 more). Neither follow-up costs after discharge nor total 1-year costs differed significantly. The incremental cost-effectiveness ratio for stenting compared with endarterectomy was $6,555 per quality-adjusted life year (QALY) gained, with over 98 percent of bootstrap estimates < $50,000/QALY gained. CONCLUSIONS: Although carotid stenting with embolic protection is more costly than carotid endarterectomy, by commonly accepted standards, stenting is an economically attractive alternative to endarterectomy for patients at high surgical risk.

In vitro performance assessment of distal protection filters: pulsatile flow conditions.

PURPOSE: To evaluate in vitro the capture efficiency of a distal protection filter (DPF) used during carotid artery stenting and examine the longitudinal vascular impedance in the presence of a DPF. METHODS: Four approved DPFs (Spider RX, FilterWire EZ, RX Accunet, and FiberNet) were evaluated in a physiologically realistic in vitro setup. A pulsatile programmable piston pump circulated a blood analog at a time-varying flow rate representative of the human common carotid artery. A silicone carotid bifurcation having average human dimensions was used for the carotid flow model. Microspheres ranging from 40 to 900 microm were injected to simulate embolization. The longitudinal vascular impedance was calculated as the ratio of the time-varying pressure gradient across the DPF to the time-varying flow rate in the internal carotid artery. RESULTS: RX Accunet had the highest capture efficiency (99.4%) and Spider RX the lowest (78.1%). Spider RX increased the longitudinal vascular impedance the least after deployment (+23%), while FilterWire EZ increased the longitudinal vascular impedance the least after particles were injected (+29%). FiberNet increased longitudinal vascular impedance the most (+84%). CONCLUSION: This investigation, unique for examining the effects of physiologically realistic pulsatile flow on DPF performance, can aid in the development of future generations of novel DPFs.

Clinical significance and technical assessment of stent cell geometry in carotid artery stenting.

Carotid artery stenting has gained popularity due to its minimally invasive approach. However, several design concerns preclude the successful use of carotid stents. Technical issues, such as open versus closed cells, scaffolding, trackability, foreshortening, and changes in local geometry and hemodynamics, affect stent performance. Previous clinical and experimental studies have evaluated current stent models while proposing and testing novel stent designs. This review focuses on the technical aspects of carotid stent design and the clinical significance of key design parameters identified via computational and experimental modeling.

Vascular resistance in the carotid artery: an in vitro investigation of embolic protection filters.

PURPOSE: To assess in vitro performance of four embolic protection filters (EPFs) with a varying mass of injected particles. Evaluation is based on capture efficiency, pressure gradient, flow rate, and vascular resistance. MATERIALS AND METHODS: A bench-top flow apparatus was used for in vitro testing of four devices (Spider RX, FilterWire EZ, RX Accunet, and Emboshield). A silicone phantom with average human carotid artery dimensions and a 70% symmetric internal carotid artery (ICA) stenosis was used to model the carotid bifurcation. A blood-mimicking solution (glycerol/deionized water) was circulated at the time-averaged mean peak velocity for the common carotid artery. Five and 10 mg of 200- or 300-mum-diameter microspheres were injected into the ICA to evaluate the capture efficiency of the devices. The normalized pressure gradient, flow rate, and vascular resistance in the ICA were calculated from measured values of pressure and flow rate. RESULTS: The Spider RX captured the most particles (99.9% for 5 mg, 98.4% for 10 mg) and was associated with the slightest increase in pressure gradient (+8%, +15%) for both masses of microspheres injected. The Spider RX and FilterWire EZ were associated with the slightest decreases in flow rate (Spider RX, -1.9% and -12.1%; FilterWire EZ, -3.5% and -8.2%) and the slightest increases in vascular resistance (Spider RX, +10.1% and +33.0%; FilterWire EZ, +20.5% and +32.7%). The device-specific porosity was calculated, and the Spider RX was found to have the greatest at 50.4%; the Emboshield had the lowest at 2.2%. CONCLUSIONS: The Spider RX and FilterWire EZ had the best overall performances. Design features such as porosity and pore density are important parameters for improving the effectiveness of EPFs. Vascular resistance in the ICA is a flow-derived variable indicative of device performance and affected by the filter design features.

Treatment of asymptomatic carotid disease with stenting: pro.

The assumptions upon which the decisions to treat asymptomatic patients are founded on landmark studies, such as the Asymptomatic Carotid Atherosclerotic Study (ACAS), the Veterans Affairs Cooperative Study (VA), and the Asymptomatic Carotid Surgical Trial (ACST). In total, these trials randomized more than 5,000 patients to surgical vs. medical therapy. These trials were based on 60% stenosis and basically "no-risk" entry criteria. The carotid stent trials and registries, however, were based on 80% stenosis and all high-risk entry criteria. With a wide range of operator experience, and patient enrollment based on surgical risk criteria, Carotid ACCULINK/ACCUNET Post Approval Trial to Uncover Rare Events II (CAPTURE) II, Emboshield and Xact Post Approval Carotid Stent Trial (EXACT), and the Carotid Artery Revascularization Using the Boston Scientific EPI FilterWire EX/EZ and the EndoTex NexStent (CABERNET) trials were able to meet the American Heart Association guidelines of 3% procedural events in the asymptomatic subset. Carotid stenting is presently in the first and second generation of devices, and as the technology improves, procedural event rates should also improve. An understanding of the plaque composition and presence or absence of plaque vulnerability will separate those patients best suited for stenting versus endarterectomy. Asymptomatic patients cannot be grouped, but rather require individualization. Those patients with anatomical risks, preocclusive stenosis, and an incomplete Circle of Willis with a poorly collateralized hemisphere, are best managed with stenting versus endarterectomy or best medical management. Those patients, however, with

Wall apposition assessment and performance comparison of distal protection filters.

PURPOSE: To assess the wall apposition of 3 distal protection filters used in carotid artery stenting (CAS) for cerebral protection and quantify the effect on the in vitro capture efficiency of the filters under simulated physiological flow conditions. METHODS: The 3 distal protection filters (Angioguard XP, FilterWire EZ, and RX Accunet) were deployed in silicone flow models of 5.0-, 5.5-, and 6.0-mm inner diameter and were tested at a mean flow rate characteristic of the human internal carotid artery while injecting polydispersed microspheres simulating plaque emboli. The injected microspheres had a diameter larger than the pore size of the devices tested, so it was conjectured that any microspheres missed by the device traveled between the device basket and the vessel wall. Varying the diameter of the vessel phantom within the recommended vessel diameter treatment range for each device simulated the variability of vessel diameter in vivo, allowing the quantification of device wall apposition. RESULTS: None of the devices tested completely prevented distal embolization in the flow model. The RX Accunet device has the best overall wall apposition, yielding gaps of 0.075% of the vessel cross-sectional area. The FilterWire EZ device had the best overall average filtration rate, failing to capture only 0.8% of plaque particles. There were no statistically significant differences in the wall apposition assessment or the capture efficiency of the RX Accunet and FilterWire EZ devices. CONCLUSION: Several complications related to apposition of the filter basket on the vessel wall and device retrieval were detected in all the devices. It is inferred that the adaptability of the filter basket to conform to the vessel cross section at the site of deployment is the primary design variable responsible for distal embolization during CAS with cerebral protection.

Carotid artery revascularization in high-surgical-risk patients using the Carotid WALLSTENT and FilterWire EX/EZ: 1-year outcomes in the BEACH Pivotal Group.

OBJECTIVES: The multicenter, single-arm BEACH (Boston Scientific EPI: A Carotid Stenting Trial for High-Risk Surgical Patients) evaluated outcomes in high-surgical-risk patients with carotid artery stenosis treated with the Carotid WALLSTENT plus FilterWire EX/EZ Emboli Protection System (Boston Scientific, Natick, Massachusetts). BACKGROUND: Carotid artery stent (CAS) placement offers a less invasive alternative for high-risk surgical carotid endarterectomy (CEA) patients. METHODS: The trial enrolled 480 pivotal patients who were candidates for carotid revascularization but considered high surgical risk due to pre-specified anatomic criteria and/or medical comorbidities. The primary end point (all stroke, death, or Q-wave myocardial infarction [MI] through 30 days; non-Q-wave MI through 24 h; and ipsilateral stroke or neurologic death through 1 year) was compared with a proportionally weighted objective performance criterion (OPC) of 12.6% for published surgical endarterectomy results in similar patients, plus a pre-specified noninferiority margin of 4%. RESULTS: Among pivotal patients, 41.2% were at high surgical risk due to comorbid risk factors, and 58.8% due to anatomic risk factors; 76.7% were asymptomatic with flow-limiting carotid stenosis >80%. At 1 year, the composite primary end point occurred in 8.9% (40 of 447), with a repeat revascularization rate of 4.7%. With an upper 95% confidence limit of 11.5% for the primary composite end point, the BEACH trial results met the pre-specified criteria for noninferiority relative to the calculated OPC plus noninferiority margin (16.6%) for historical surgical CEA outcomes in similar patients (p < 0.0001 for noninferiority). CONCLUSIONS: The BEACH trial results demonstrate that CAS with the WALLSTENT plus FilterWire embolic protection is non-inferior (equivalent or better than) to CEA at 1-year in high-surgical-risk patients.

Angiographic lesion characteristics can predict adverse outcomes after carotid artery stenting.

BACKGROUND: Carotid artery angioplasty and stenting (CAS) is an evolving and increasingly common endovascular treatment for carotid artery stenosis. Risk factors associated with an increased incidence of adverse periprocedural neurologic outcomes are being recognized. The goal of this study was to determine if certain angiographic lesion characteristics were predictive of higher risks of adverse outcomes. METHODS: A total of 421 patients who underwent 429 carotid artery stenting procedures between June 1996 and June 2005 for symptomatic or asymptomatic carotid stenosis, and in whom preoperative carotid angiograms and follow-up records were available for review, were selected from a prospectively maintained database. Demographic data and procedural variables were recorded, including the presence or absence of the use of a cerebral protection device. Angiograms were reviewed for the following carotid lesion characteristics: length of lesion, percentage of stenosis, ostial involvement, lesion ulceration, calcification, and presence of contralateral carotid occlusion. Periprocedural stroke and 30-day adverse event rates (stroke, myocardial infarction, and death) were recorded for each patient. RESULTS: The periprocedural all-stroke rate was 3.7%. Octogenarians had a higher incidence of 30-day adverse events at 10.0% vs 3.8% (P = .029). The incidence of periprocedural stroke was increased in lesions > or =15 mm long, at 17.0% (8 of 47) vs 2.1% (8 of 382; P < .001), and in ostial centered lesions, 7.1% (11 of 154) vs 1.8% (5 of 275; P = .007). Multivariate regression also identified these two variables as independently associated with 30-day stroke rate: lesion length > or =15 mm (odds ratio [OR], 6.38; 95% confidence interval [CI], 35 to 17.29) or ostial involvement (OR, 3.12; 95% CI, 3.12 to 8.36). Other variables, including lesion calcification, ulceration, degree of stenosis, or presence of contralateral occlusion, were not associated with adverse outcomes. When studied separately, the use of cerebral protection devices in 241 patients (56%) did not change our observed correlations between angiographic characteristics and adverse procedural events. CONCLUSIONS: Certain lesion characteristics on angiography, such as length and ostial location, can predict adverse outcomes. The indication for CAS should be carefully evaluated in these cases.

Use of AngioJet mechanical thrombectomy for acute peripheral ischemia associated with stent fracture.

Stent fracture has been an uncommonly described etiology in the development of acute peripheral ischemia. We describe the utilization of a rheolytic thrombectomy catheter with thrombolytics for the rapid treatment of superficial femoral artery thrombosis after recanalization and subsequent stent fracture. The implications of stent fracture and the therapeutic maneuvers associated with their treatment in peripheral applications are discussed.

In vitro performance assessment of distal protection devices for carotid artery stenting: effect of physiological anatomy on vascular resistance.

PURPOSE: To assess in vitro the performance of 5 distal protection devices (DPDs) by evaluating the capture efficiency, pressure gradient, volume flow rate, and vascular resistance in the internal carotid artery (ICA). METHODS: The time-averaged mean peak velocity in the common carotid artery and a blood-mimicking solution were used to simulate physiologICAl conditions in a silicone carotid phantom representing average human carotid artery geometry with a 70% symmetrICAl ICA stenosis. Five milligrams of dyed 200-microm nominal diameter polymer microspheres (larger than the pore size of the devices, except Spider RX, which was tested with 300-microm-diameter particles) were injected into the ICA. The percentages of particles missed after injection and lost during device retrieval were measured for the 5 devices (Spider RX, FilterWire EZ, RX Accunet, Angioguard XP, and Emboshield). The normalized pressure gradient, fraction of the volume flow rate, and vascular resistance in the ICA were calculated. RESULTS: Spider RX captured the most particles (missing 0.06%, p<0.05) and yielded the smallest normalized pressure gradient increase (4.2%), the largest volume flow rate fraction (0.40), and the smallest vascular resistance in the ICA (272 mmHg/L x min(-1), a 5.4% increase with respect to initial conditions). Angioguard XP captured the fewest particles (missing 36.3%, p<0.05 except Emboshield) and resulted in the largest normalized pressure gradient increase (37%) in the ICA. RX Accunet produced the smallest volume flow rate fraction in the ICA (0.30) and the largest vascular resistance in the ICA (470 mmHg/ L x min(-1), an 82.2% increase). Emboshield migrated approximately 6 cm distal to the original position after particle injection. FilterWire EZ lost the fewest particles during retrieval (0.45%, p<0.05 except Accunet RX and Spider RX) and had the best overall performance with 200-microm emboli (p<0.05 except Accunet RX). CONCLUSION: None of the devices tested completely prevented embolization. Overall, Spider RX had the best performance and is conjectured to have the best wall apposition of the devices tested. Vascular resistance should be considered a key filter design parameter for performance testing since it represents a quantitative estimation of the "slow-flow phenomenon." Our findings should be extrapolated cautiously to help interventionists choose the best device.