Filter Debris Research Articles

Impact of Carotid Stent Design on Embolic Filter Debris Load During Carotid Artery Stenting.

The carotid stent design may influence the risk of embolization during carotid artery stenting. The aim of the study was to assess this risk by comparing the quantity of embolized material captured by filters during carotid artery stenting, using different stent designs. We conducted a single-center retrospective study of patients undergoing carotid artery stenting for asymptomatic carotid stenosis >70% (2010-2022) in a tertiary academic hospital (Padua University Hospital, Italy). Carotid stents were classified according to their design as open-cell (OCS), closed-cell (CCS), or micromesh stents (MMS). A distal filter protection was used in all patients, and the amount of captured embolized particles was semiautomatically analyzed using a dedicated software (Image-Pro Plus, Media Cybernetics). Primary end point was embolic filter debris (EFD) load, defined as the ratio of the filter area covered by particulate material to the total filter area. Secondary end points were 30 days major stroke and death. Four-hundred-eighty-one carotid artery stentings were included; 171 (35%) using an OCS, 68 (14%) a CCS, and 242 (50%) a MMS. Thirty-days mortality was 0.2% (n=1) and major stroke rate was 0.2% (P=0.987). Filters of patients receiving MMS were more likely to be free from embolized material (OCS, 30%; CCS, 13%; MMS, 41%; P<0.001) and had a lower EFD load (OCS, 9.1±14.5%; CCS, 7.9±14.0%; MMS, 5.0±9.1%; P<0.001) compared with other stent designs. After stratification by plaque characteristics, MMS had a lower EFD load in cases of hypoechogenic plaque (OCS, 13.4±9.9%; CCS, 10.9±8.7%; MMS, 6.5±13.1%; P<0.001), plaque length>15 mm (OC, 10.2±15.3; CC, 8.6±12.4; MM, 8.2±13.6; P<0.001), and preoperative ipsilateral asymptomatic ischemic cerebral lesion (OCS, 12.9±16.8%; CCS, 8.7±19.5%; MMS, 5.4±9.7%; P<0.001). After multivariate linear regression, use of MMS was associated with lower EFD load (P=0.038). The use of MMS seems to be associated with a lower embolization rate and EFD load, especially in hypoechogenic and long plaques and in patients with a preoperative evidence of asymptomatic ischemic cerebral lesion.

Prediction of postprocedural filter debris after transcarotid revascularization.

Transcarotid revascularization (TCAR) is a technique in which cerebral flow reversal is utilized as embolic protection during carotid stenting. The presence, or absence, of filter debris created during TCAR could potentially be a surrogate to characterize carotid lesions at high risk for embolization and, therefore, explored in this investigation. A retrospective review of TCARs performed within the Indiana University and Memorial Hermann (McGovern Medical School at UTHealth) Health Systems to capture demographics and preoperative variables. A mixed effect multivariate logistic regression model was created to discern the best predictors of intraoperative filter debris. During the study period, from December 2015 to December 2021, we captured filter debris status in 693 of 750 patients containing 323 cases of filter embolization at case completion. With respect to demographics and indications, we found a higher incidence of neck radiation (2.7 vs. 7.1%, p = 0.01) and a more pronounced Charlson Comorbidity Index (CCI; 5.3 ± 0.3 vs 5.7 ± 0.3, p < 0.01) in the filter debris cohort while contralateral carotid occlusion (6.6 vs. 2.9%, p = 0.05) and clopidogrel usage (87.3 vs. 80.1%, p = 0.03) were less common. Longer intraoperative flow reversal (8.0 ± 1.2 vs 10.5 ± 1.2, p < 0.01) and fluoroscopy time (4.0 ± 0.6 vs 5.1 ± 0.6, p < 0.01) were also seen in those with filter debris. These findings remained when a mixed effect univariate logistic regression model was used to account for differences in filter debris reporting between locations. After multivariable modeling, we found that reverse flow time and CCI remained predictive of filter debris while the presence of a contralateral carotid occlusion was still protective. In our combined experience, the creation of visible filter debris after TCAR seems to be independently associated with extended reverse flow time and elevated CCI while a contralateral carotid occlusion was protective.

A Comparative Quantitative Analysis of Embolic Filter Debris Load During Carotid Artery Stenting, Between Open Cell, Closed Cell And Micromesh Stents

Introduction: The design of the stent used in carotid artery stenting (CAS) may influence the amount of embolized material during the procedure, responsible of perioperative neurological complication. The aim of the study was to compare the quantity of embolized material captured by filters during CAS, using different types of stent design (open/closed cell and micromesh). Methods: All patients with carotid stenosis >70% undergoing CAS between 2010 and 2018 were included in a prospective database. Stents were classified according to their design as micromesh (MMS), open-cell (OCS) and closed-cell stents (CCS). A distal filter protection was used in all patients; at the end of the procedure, the filter was fixed in formalin and then analyzed with a stereo-microscope. Morphometric analysis was performed with Image-Pro Plus software (Media Cybernetics). Embolic filter debris load (EFD) load, defined as the ratio of the filter area covered by particulate material to the total area of the filter membrane, was quantified as percentage and compared between different types of stents. Also thirty-days neurological complication, as stroke and transient ischemic attack (TIA), were compared. Results: 275 consecutive CAS were included in the analysis; a MMS was used in 43 cases (15.6%), an OCS in 168 (61.0%), and a CCS in 64 (23.2%). No perioperative deaths were reported. Overall, perioperative stroke was 2.5% (MMS: n=1, 2.3%; OCS: n=4, 2.4%; CCS: n=2, 3.1%; P=.489), while TIA rate was 3.6% (MMS: n=1, 2.3%; OCS: n=7, 4.1%; CCS: n=2, 1%; P=.873), without differences between subgroups. The filters quantitative analysis revealed that any quantity of EFD was present in 70.5% of cases; filters of patients receiving MMS were more likely to be free from embolized material compared to other subgroups (MMS: n=20, 46.5%; OCS/CCS: n=52, 23.3%; P=.003). The overall mean EFD load was 8.9±13.7%, with a significantly lower quantity reported in the MMS subgroup (MMS: 5.8±9.9%, OCS: 8.5±12.9%, CCS: 11.3±17.2%; P=.048). Compared to other types of stents, MMS had a significantly lower EFD load in particular in cases with hypoechogenic plaque (MMS: 7.6±7.0%; OCS/OCC: 20.7±21.6%; P=< .001) and in patients with preoperative ipsilateral asymptomatic ischemic lesion at the cerebral CT (MMS: 7.9±12.1%; OCS/OCC: 13.4±18.7%; P=.015), while there were no significant differences in case of plaque length >15mm (MMS: 8.4±14.7%; OCS/OCC: 9.5±13.0%; P=.598), kinking/coiling (MMS: 10.7±16.2%; OCS/OCC: 9.5±10.0%; P=.621), and carotid restenosis (MMS: 5.9±13.2%; OCS/OCC: 6.8±11.3%; P=.641). Conclusion: The use of MMS seems to be associated to a significantly lower embolization rate and EFD load, especially in cases of hypoechogenic plaque and preoperative evidence of asymptomatic ischemic cerebral lesion; however the use of MMS did not resulted in a reduction of the overall 30-day neurological complication rate. Disclosure: Nothing to disclose

CAR 16. A Comparative Quantitative Analysis of Embolic Filter Debris Load During Carotid Artery Stenting Between Open-Cell, Closed-Cell, and Micromesh Stents

CAR 16. A Comparative Quantitative Analysis of Embolic Filter Debris Load During Carotid Artery Stenting Between Open-Cell, Closed-Cell, and Micromesh Stents

IYSC07. A Comparative Quantitative Analysis of Embolic Filter Debris Load During Carotid Artery Stenting, Between Open Cell, Closed Cell and Micromesh Stents

IYSC07. A Comparative Quantitative Analysis of Embolic Filter Debris Load During Carotid Artery Stenting, Between Open Cell, Closed Cell and Micromesh Stents

Therapeutic mechanism and regularity of “treating angina pectoris from spleen” in Coronary Heart Disease caused by “spleen deficiency and phlegm”

Although Mo.Ma Ultra is an embolic protection device for interrupting the anterograde blood flow to the internal carotid artery, incomplete blood stagnation is often observed. We report the effectiveness of the combined use of a distal filter protection device and Mo.Ma Ultra (Medtronic, Minneapolis, MN).Our case series comprises 10 consecutive patients (11 carotid arteries) who underwent carotid artery stenting (CAS) using Mo.Ma Ultra and FilterWire EZ (Boston Scientific, Natick, MA).The superior thyroid artery originated from the proximal side of the bifurcation of the common carotid artery, except for 1 artery. Although complete blood stagnation was observed in 6 arteries, filter debris was detected in 3 of these 6 arteries. Positive postoperative findings on diffusion-weighted magnetic resonance imaging were observed in 3 cases (3 arteries). Only 1 patient had transient neurological deficits.The combined use of a distal filter protection device and Mo.Ma Ultra could provide a more reliable embolic protection in CAS.

Proteomic characterization of Aspergillus fumigatus isolated from air and surfaces of the International Space Station

The on-going Microbial Observatory Experiments on the International Space Station (ISS) revealed the presence of various microorganisms that may be affected by the distinct environment of the ISS. The low-nutrient environment combined with enhanced irradiation and microgravity may trigger changes in the molecular suite of microorganisms leading to increased virulence and resistance of microbes. Proteomic characterization of two Aspergillus fumigatus strains, ISSFT-021 and IF1SW-F4, isolated from HEPA filter debris and cupola surface of the ISS, respectively, is presented, along with a comparison to well-studied clinical isolates Af293 and CEA10. In-depth analysis highlights variations in the proteome of both ISS-isolated strains when compared to the clinical strains. Proteins that showed increased abundance in ISS isolates were overall involved in stress responses, and carbohydrate and secondary metabolism. Among the most abundant proteins were Pst2 and ArtA involved in oxidative stress response, PdcA and AcuE responsible for ethanol fermentation and glyoxylate cycle, respectively, TpcA, TpcF, and TpcK that are part of trypacidin biosynthetic pathway, and a toxin Asp-hemolysin. This report provides insight into possible molecular adaptation of filamentous fungi to the unique ISS environment.

Quantitative analysis and predictors of embolic filter debris load during carotid artery stenting in asymptomatic patients

ObjectiveThe objective of this study was to perform a quantitative analysis and to identify predictors of embolic filter debris (EFD) load during carotid artery stenting (CAS) in asymptomatic patients. MethodsAll patients with asymptomatic carotid stenosis >70% undergoing CAS between 2008 and 2016 were included in a prospective database. A distal filter protection device was used in all patients. At the end of the procedure, the filter was fixed in formalin and then analyzed with a stereomicroscope. Morphometric analysis was performed with Image-Pro Plus software (Media Cybernetics, Rockville, Md). The total area of the filter membrane and the area covered by particulate material were quantified. The quantity of membrane occupied by debris was expressed as percentage of covered surface area. Anatomic and clinical variables were evaluated for their association with EFD load using multiple logistic regression. ResultsAmong the 278 patients undergoing CAS, an open-cell stent was implanted in 211 patients (76%); 67 patients (24%) received a closed-cell stent. Overall technical success and clinical success were both 99%; no perioperative death was reported. Stroke rate was 1.8% (major, n = 1 [0.4%]; minor, n = 4 [1.4%]); transient ischemic attacks occurred in 5% of cases (n = 14). The quantitative analysis of the filter revealed that EFD was present in 74% of cases (n = 207). The mean EFD load was 10% of the filter surface (median, 1; range, 0-80); it was <10% in 203 patients (73%), between 11% and 20% in 39 patients (14%), between 21% and 30% in 14 patients (5%), and >31% in 22 (8%). Patients with any type of ischemic neurologic event after CAS (stroke and transient ischemic attack) had a significantly higher mean EFD load compared with uneventful cases (26.7% ± 19.0% vs 8.5% ± 13.5%; P < .001). The observational frequency distribution analysis identified the presence of >12.5% EFD load as the optimal cutoff for the association with clinically relevant perioperative ischemic events (sensitivity, 78%; specificity, 77%; area under the curve, 0.81). The multivariate analysis demonstrated that age >75 years (odds ratio [OR], 2.56; P = .003), pre-existing ipsilateral ischemic cerebral lesions (OR, 2.09; P = .047), hypoechogenic plaque on the preoperative duplex ultrasound examination (OR, 6.05; P < .001), and plaque length >15 mm (OR, 1.79; P = .049) were independent predictors of EFD load >12.5%. ConclusionsThe majority of asymptomatic carotid stenoses treated with CAS have detectable embolic debris in the protecting filter. Age >75 years, pre-existing ipsilateral cerebral ischemic lesions, hypoechogenic plaque, and plaque length >15 mm should be taken into consideration as independent predictors of clinically relevant embolic debris during the procedure.

VESS03. Quantitative Analysis and Predictors of Embolic Filter Debris Load During Carotid Artery Stenting in Asymptomatic Patients

This study was conducted to perform a quantitative analysis and to identify predictors of embolic filter debris (EFD) load during carotid artery stenting (CAS) in asymptomatic patients. All patients with asymptomatic carotid stenosis ≥70% undergoing CAS between 2008 and 2016 were included in a prospective database. A distal filter protection was used in all patients. At the end of the procedure, the filter was fixed in formalin and then analyzed with a stereomicroscope. Morphometric analysis was performed with Image-Pro Plus software (Media Cybernetics). The total area of the filter membrane and the area covered by particulate material were quantified. The percentage of membrane occupied by debris was expressed as the percentage of covered surface area. Anatomic and clinical variables were evaluated for their association with EFD load using multiple logistic regression. Among the 278 patients undergoing CAS, an open-cell stent was implanted in 214 patients (78%), and 62 patients (22%) received a closed-cell stent. Overall technical and clinical success were both 99%. No perioperative death was reported. Stroke rate was 1% (major: n = 1 [0.4%]; minor: n = 2 [0.7%]), and transient ischemic attacks (TIA) occurred in 5.7% (n = 16). The quantitative analysis of the filters revealed that EFD was present in 74% (n = 207). The mean EFD load was 10% ± 14% of the filter surface (median, 1%; range, 0%-80%), and was ≤10% in 132 patients (47.5%), between 11% and 20% in 39 (14%), between 21% and 30% in 14 (4%), and ≥31% in 22 (8%). Patients with any type of ischemic neurologic event after CAS (stroke and TIA) had a significantly higher mean EFD load compared with uneventful cases (26.7% ± 19% vs 8.5% ± 13.5%; P < .001). The observational frequency distribution (Fig) identified the presence of >12.5% EFD load as the optimal cutoff for the association with clinically relevant perioperative ischemic events (sensitivity, 78%; specificity, 77%; area under the curve, 0.81). The multivariate analysis demonstrated that age >75 years (odds ratio [OR], 2.56; P = .003), pre-existing ipsilateral ischemic cerebra lesions (OR, 2.09; P = .04), hypoechogenic plaque at the preoperative duplex ultrasound study (OR, 6.05; P < .001), and plaque length >15 mm (OR, 1.79; P = .04) were independent predictors of EFD load >12.5%. Most patients with asymptomatic carotid stenosis treated with CAS have detectable embolic debris in the protecting filter. Age >75 years, pre-existing ipsilateral cerebral ischemic lesions, hypoechogenic plaque, and plaque length >15 mm, should be taken in consideration as independent predictors of clinically relevant embolic debris during the procedure.

Effectiveness of the Combined Use of Distal Filter Protection Device and Mo.Ma Ultra: Technical Note

Although Mo.Ma Ultra is an embolic protection device for interrupting the anterograde blood flow to the internal carotid artery, incomplete blood stagnation is often observed. We report the effectiveness of the combined use of a distal filter protection device and Mo.Ma Ultra (Medtronic, Minneapolis, MN). Our case series comprises 10 consecutive patients (11 carotid arteries) who underwent carotid artery stenting (CAS) using Mo.Ma Ultra and FilterWire EZ (Boston Scientific, Natick, MA). The superior thyroid artery originated from the proximal side of the bifurcation of the common carotid artery, except for 1 artery. Although complete blood stagnation was observed in 6 arteries, filter debris was detected in 3 of these 6 arteries. Positive postoperative findings on diffusion-weighted magnetic resonance imaging were observed in 3 cases (3 arteries). Only 1 patient had transient neurological deficits. The combined use of a distal filter protection device and Mo.Ma Ultra could provide a more reliable embolic protection in CAS.

A Microscopic and Biomarker Evaluation of Embolic Filter Debris Collected During Carotid Artery Stenting

Purpose: To evaluate and characterize debris retrieved from the cerebral embolic protection devices (EPDs) used during carotid artery stenting (CAS) and compare debris size, volume, tissue types, cellular composition, and protein biomarker expression in symptomatic and asymptomatic patients. Methods: Distal protection filters were retrieved from 22 consecutive patients (mean age 71.6 years, range 52–85; 16 men) undergoing elective CAS between July 2012 and February 2014 for >70% internal carotid artery stenosis (mean 85.4%±10.3%). Six patients were symptomatic. The debris within each EPD was visually characterized using stereomicroscopy and then processed for histology and immunohistochemistry. Biomarkers were immunohistochemically measured to evaluate plaque stability [matrix metalloproteinase-9 (MMP-9)], inflammation [glycoprotein CD68 and interleukin-6 (IL-6)], or phenotype [smooth muscle (SM)-actin and type IV collagen]. The immunohistochemical results were measured using semiquantitative grading criteria based on both staining intensity and distribution in the samples. Results: Macroscopic debris was visible in 5/22 EPDs; 3 of the 5 filters came from symptomatic patients. Microscopic debris was detected in all filters and ranged in size from 0.01 to 8.57 mm2. Debris consisted of calcified, fibrous, and necrotic tissue, as well as fibrin and foam cells with no significant difference between the symptomatic and asymptomatic groups. There was no association between the degree or type of embolic material and stenosis severity, carotid tortuosity, calcium grade, soft plaque, or arch type. Symptomatic patients had a larger volume of debris (8.24 vs 0.58 mm3, p<0.01), mean particle size (1.30 vs 0.32 mm2, p<0.001), and expression of biomarkers IL-6 (2.17 vs 0.81, p<0.05), CD68 (2.00 vs 0.38, p<0.01), SM-actin (1.00 vs 0.25, p=0.055), type IV collagen (1.17 vs 0.25,p=0.082), and MMP-9 (1.00 vs 0.06, p<0.05). Conclusion: Histological analysis revealed particulate embolization in all EPDs used during CAS. Symptomatic patients had a larger volume of embolic debris, mean particle size, and the biomarkers associated with inflammation, necrotic core, and diminished fibrous cap.

Bioaccumulation and biological effects of cigarette litter in marine worms.

Marine debris is a global environmental issue. Smoked cigarette filters are the predominant coastal litter item; 4.5 trillion are littered annually, presenting a source of bioplastic microfibres (cellulose acetate) and harmful toxicants to marine environments. Despite the human health risks associated with smoking, little is known of the hazards cigarette filters present to marine life. Here we studied the impacts of smoked cigarette filter toxicants and microfibres on the polychaete worm Hediste diversicolor (ragworm), a widespread inhabitant of coastal sediments. Ragworms exposed to smoked cigarette filter toxicants in seawater at concentrations 60 fold lower than those reported for urban run-off exhibited significantly longer burrowing times, >30% weight loss, and >2-fold increase in DNA damage compared to ragworms maintained in control conditions. In contrast, ragworms exposed to smoked cigarette filter microfibres in marine sediment showed no significant effects. Bioconcentration factors for nicotine were 500 fold higher from seawater than from sediment. Our results illustrate the vulnerability of organisms in the water column to smoking debris and associated toxicants, and highlight the risks posed by smoked cigarette filter debris to aquatic life.

Abstract 502: Smokers Have Significantly Increased Rates of Intraoperative Microembolization Detected on Transcranial Doppler with Carotid Angioplasty/Stenting Compared to Endarterectomy Procedure in Preliminary Study

Background: The benefits of revascularization must be balanced against the risks of peri/post-operative cerebrovascular events in determining the management of carotid stenosis. Higher rates of intra-operative microembolization during elective carotid revascularization are associated with increased risks of clinically detectable cerebrovascular accidents, and the identification of specific patient demographics that predispose to vulnerable plaque formation can be useful in guiding intervention and decreasing embolic potential during procedures. Methods: 150 patients (symptomatic, stenosis&gt;50%; asymptomatic, stenosis&gt;70%) undergoing either CAS or CEA will be enrolled. A pre-operative Mini-mental Status Exam, carotid MRI, and cerebral diffusion-weighted MRI are obtained one week prior to intervention. All MRI are performed with 3T MR system, carotid plaque are classified according to AHA criteria. Intraoperatively, transcranial Doppler is performed to monitor for microembolic signals (MES), detected as high-intensity unidirectional transient signals. Plaque specimen and filter debris are analyzed histologically for high-risk characteristics and correlated with MRI. A post-operative DW-MRI and MMSE are performed within 72 hours to examine for microinfarcts and changes in neurocognitive function. Demographic analysis for cardiovascular risk factors, current and former smokers, was performed retrospectively. Results: Preliminary results with 33 patients demonstrate an average of 46 total MES generated during carotid angioplasty/stenting in 4 nonsmokers, compared to 19.9 total MES in 9 nonsmoking patients undergoing endarterectomy (p = 0.091). In the smoker population, an average of 63.4 total MES was generated in 13 patients undergoing CAS compared to 21 total MES in 7 patients undergoing CEA (p = 0.024). Procedural phases with the highest production of microemboli include dissection phase during CEA (35.5% of total MES) and filter placement in CAS (22.2% of total MES). Conclusions: Preliminary results suggest significantly increased microembolic potential and risk of clinically detectable CVA with carotid angioplasty/stenting compared to endarterectomy in smokers.

International Space Station environmental microbiome — microbial inventories of ISS filter debris

Despite an expanding array of molecular approaches for detecting microorganisms in a given sample, rapid and robust means of assessing the differential viability of the microbial cells, as a function of phylogenetic lineage, remain elusive. A propidium monoazide (PMA) treatment coupled with downstream quantitative polymerase chain reaction (qPCR) and pyrosequencing analyses was carried out to better understand the frequency, diversity, and distribution of viable microorganisms associated with debris collected from the crew quarters of the International Space Station (ISS). The cultured bacterial counts were more in the ISS samples than cultured fungal population. The rapid molecular analyses targeted to estimate viable population exhibited 5-fold increase in bacterial (qPCR-PMA assay) and 25-fold increase in microbial (adenosine triphosphate assay) burden than the cultured bacterial population. The ribosomal nucleic acid-based identification of cultivated strains revealed the presence of only four to eight bacterial species in the ISS samples, however, the viable bacterial diversity detected by the PMA-pyrosequencing method was far more diverse (12 to 23 bacterial taxa) with the majority consisting of members of actinobacterial genera (Propionibacterium, Corynebacterium) and Staphylococcus. Sample fractions not treated with PMA (inclusive of both live and dead cells) yielded a great abundance of highly diverse bacterial (94 to 118 taxa) and fungal lineages (41 taxa). Even though deep sequencing capability of the molecular analysis widened the understanding about the microbial diversity, the cultivation assay also proved to be essential since some of the spore-forming microorganisms were detected only by the culture-based method. Presented here are the findings of the first comprehensive effort to assess the viability of microbial cells associated with ISS surfaces, and correlate differential viability with phylogenetic affiliation.

The role of embolic protection devices during carotid stenting prior to cardiac surgery in asymptomatic patients: Empty filters?

The purpose of this study was to analyze the debris captured in the distal protection filters used during carotid artery stenting (CAS). CAS is an option available to high-risk patients requiring revascularization. Filters are suggested for optimal stroke prevention during CAS. From May 2005 to June 2007, filters from 59 asymptomatic patients who underwent CAS were collected and sent to a specialized laboratory for light-microscope and histological analysis. Peri- and postprocedural outcomes were assessed during 1-year follow-up. On the basis of biomedical imaging of the filter debris, the captured material could not be identified as embolized particles from the carotid plaque. On histological analysis the debris consisted mainly of red blood cell aggregates and/ or platelets, occasionally accompanied by granulocytes. We found no consistent histological evidence of embolized particles originating from atherosclerotic plaques. Post-procedure, three neurological events were reported: two (3.4%) transient ischemic attacks (TIA) and one (1.7%) ipsilateral minor stroke. The filters used during CAS in asymptomatic patients planned for cardiac surgery often remained empty. These findings may be explained by assuming that asymptomatic patients feature a different atherosclerotic plaque composition or stabilization through antiplatelet medication. Larger, randomized trials are clearly warranted, especially in the asymptomatic population.

Distal Protection Device-Induced Slow- or Stop-Flow Phenomenon During Carotid Stenting and the Use of Aspiration to Decrease Periprocedural Events

The phenomenon of slow flow (significant reduction in antegrade flow in the internal carotid artery [ICA]) or stop flow (cessation of antegrade flow in the ICA) during carotid artery stenting (CAS) caused by distal embolic protection devices (EPDs), specifically the Angioguard XP filter, was evaluated in the article by Sorimachi et al. (12) in this issue of WORLD NEUROSURGERY. Although this is not a well-discussed topic in the literature, it could have very important implications with respect to the acceptance of CAS because this acceptance depends on the equivalent effectiveness of CAS when compared to its operative counterpart, carotid endarterectomy, in preventing periprocedural stroke. CAS has been criticized for its higher periprocedural event rates when compared to carotid endarterectomy. These events mainly occur during stent placement and angioplasty, although they have been shown to occur up to 18 hours after the procedure (13). The use of a distal EPD can potentially reduce the incidence of intracranial embolization observed during CAS, decreasing periprocedural event rates. The literature includes multiple studies that show lower stroke rates with distal EPDs as well as studies that show no statistical difference when they are used, such as the Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) trial (5). However, the most recent trial published, the Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST), which was a multicenter randomized North American trial that compared the efficacy of carotid endarterectomy with that of CAS, performed with the aid of an EPD in the prevention of stroke, myocardial infarction, and death in symptomatic and asymptomatic patients, showing a very low 30-day composite rate of stroke and death for symptomatic (6.1%) and asymptomatic (3.8%) CAS patients (3). Other studies have looked at the slow-flow phenomenon during CAS, such as Casserly et al. (4), who used multivariate logistic regression analysis to evaluate 71 CAS procedures. Their analysis showed that increased age, history of transient ischemic attack or stroke within 6 months of the procedure, and large stent diameter were predictive of slow flow during CAS. Slow flow was noted predominantly after balloon dilatation, although 25% of the cases occurred after stent deployment (4). The underlying etiology of slow flow is uncertain, but it is known that once the filter is retrieved, normal flow is restored. This isolates the filter as the problem and, thus, likely the occlusion of the pores of the filter as the reason for the slow-flow state. Histopathologic analysis of the filter debris has shown amorphous material derived from the core of atherosclerotic plaque (1). This correlates with the findings of slow flow being related to stent deployment and balloon angioplasty, as well as symptomatic lesions and increased stent diameter being independent predictors of slow-flow states. Casserly et al. (4) found that the 30-day incidence of stroke and/or death among patients with slow flow was 9.5%, compared to 2.9% in patients with normal flow. All the strokes occurred the same day as the procedure and were noted after retrieval of thefilter. These risk factors of slowflow have also been shown to be general risk factors of neurologic events associated with CAS. The CREST trial showed that patients older than age 79 years had higher 30-day stroke and death rates (11.9%) (8). Both the CREST (3) and the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE)

Using Lubricating Oil Filter Debris Analysis to Monitor Abnormal Wear of Aero-Engine

With the installation of finer oil filters in the lubrication system of aero-engine, the traditional wear analysis techniques such as Rotating Disc Electrode Atomic Emission Spectrometry Analysis (RDE-AES) become less efficient at detecting abnormal wear failure caused by large debris. These filters capture large debris containing large amounts of tribological information about the operation of an aero-engine. Removal and analysis of the filter debris has proved to be an effective tool for aero-engine health management by determining wear modes and observing failure progression providing long lead times for maintenance. An automated aero-engine oil filter debris analysis system was recently developed. This instrument could efficiently complete filter core washing, debris amount and size distribution analysis, and prepare a patch of the debris for further composition analysis.

Filter Debris Analysis for Aircraft Engine and Gearbox Health Management

Oil filters capture a tremendous amount of tribology information about the operation of a machine. Removal and analysis of the filter debris has proved to be an effective tool for engine health management by determining wear modes and observing failure progression providing long lead times for maintenance remediation. The process of manual debris removal and analysis in a laboratory, however, is tedious. An automated filter debris analysis system provides a repeatable process for at-line or laboratory use. The filters are automatically cleaned; the particles are counted and sized utilizing a quantitative oil debris sensor; and the debris is deposited on a patch for automatic analysis by an integral energy dispersive X-ray fluorescence spectrometer. The XRF analysis procedure provides metallurgical analysis and an expert determination of engine condition. The system has been successfully applied to two operational aircraft fleets, the Canadian Forces S-61 Sea King helicopter fleet and the US Navy EA-6B Prowler aircraft fleet. In both applications, significant benefits have been realized.

A study of significant variables and their effects on the analysis of hexavalent chromium

The recent reduction in the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for hexavalent chromium Cr(VI) will most certainly cause employers to perform more exposure determinations. The standard applies to Cr(VI) in both the soluble and insoluble form. The National Institute for Occupational Safety and Health (NIOSH) Method 7600, an analytical technique utilizing visible spectrophotometry, was examined. The new OSHA PEL of 5 micrograms per cubic meter (μg/m 3 ) mandated that the lowest possible method detection limit (MDL) be obtained. Also, the solubilities of the test samples were in most cases unknown. Accordingly, this study focused on the following: (1) removal of filter debris or other turbidity, (2) filter type, storage stability and (3) the alkaline extraction of the samples. Preliminary analysis of blank polyvinyl chloride (PVC) filters resulted in noticeable debris and turbidity. To test turbidity a blank PVC filter was placed in a centrifuge tube and extracted with sulfuric acid. Eight replicates yielded a MDL of 4 micrograms per liter (μg/L). The aliquots were then filtered using a Buchner funnel and yielded 2 μg/L MDL. Finally, the filtrates were centrifuged for 2 minutes further reducing the MDL to 0.7 μg/L. The use of the centrifuge to eliminate turbidity was significant enough to necessitate further investigation. To determine the effect of an alkaline extraction on soluble Cr(VI), a standard addition of 0.5 μg of potassium chromate was performed on a filter, allowed to dry and then extracted with the alkaline solution. Three replicates had a 109.4% recovery. Centrifuging the filters was useful in eliminating the CO 2 interference for the alkaline extraction. Also, the use of an alkaline extraction did not negatively impact the soluble Cr(VI). The positive result of the preliminary extractions resulted in further investigation of an alkaline extraction to incorporate the inclusion of both soluble and insoluble Cr(VI).

Virtual Histology Intravascular Ultrasound Assessment of Carotid Artery Disease: The Carotid Artery Plaque Virtual Histology Evaluation (CAPITAL) Study

To determine the diagnostic accuracy of virtual histology intravascular ultrasound imaging (VH IVUS) of carotid plaque and to assess the feasibility of VH IVUS to identify plaque with embolic potential in patients undergoing carotid artery stenting (CAS). Thirty patients (17 men; mean age 74+/-7 years) were entered nonrandomly into a single-center, prospective, 2-arm study following FDA and Institutional Review Board approval. In one arm, 15 patients underwent VH IVUS examination of carotid plaque with a cerebral protection device immediately followed by carotid endarterectomy (CEA). A comparison of "virtual" with true histology was then performed, classifying plaque type by VH IVUS and histopathology in a blinded study. In the second arm, 15 patients undergoing CAS had a preliminary VH IVUS scan performed with cerebral protection. Debris collected from the filter following stenting was examined histologically and compared with the VH IVUS data. The diagnostic accuracy of VH IVUS to agree with true histology in different carotid plaque types was 99.4% in thin-cap fibroatheroma, 96.1% for calcified thin-cap fibroatheroma, 85.9% in fibroatheroma, 85.5% for fibrocalcific, 83.4% in pathological intimal thickening, and 72.4% for calcified fibroatheroma. Filter debris was captured in 2 patients prior to CEA and in 4 patients undergoing CAS for restenosis; VH IVUS classification of plaque composition was consistent with the histological evaluation of filter fragments. Calcified nodules projecting into the carotid artery lumen were associated with a higher incidence of previous neurological symptoms (66.7% versus 33.3%, p<0.05), while patients on aspirin has significantly less necrotic lipid core plaque detected by VH IVUS than patients not taking aspirin (6.4%+/-4.7% versus 9.7%+/-2.8%, p<0.05). This study showed a strong correlation between VH IVUS plaque characterization and the true histological examination of the plaque following endarterectomy, particularly in "vulnerable" plaque types. The feasibility study to examine VH IVUS data and the filter debris histology in CAS patients supports a larger prospective study.