Size Of Embolic Particles Research Articles

Abstract No. 146 Effect of Embolic Particle Size on Outcomes of Uterine Artery Embolization for Mixed Adenomyosis/Fibroids: Are Smaller Particles Needed?

Abstract No. 146 Effect of Embolic Particle Size on Outcomes of Uterine Artery Embolization for Mixed Adenomyosis/Fibroids: Are Smaller Particles Needed?

The relationship of embolic particle size to patient outcomes in prostate artery embolisation for benign prostatic hyperplasia: a systematic review and meta-regression

To explore the relationship of embolic particle size used in prostate artery embolisation (PAE) to patient outcomes. A systematic review of PubMed, EMBASE, and the Cochrane database was undertaken to identify all existing studies using PAE for benign prostatic hyperplasia (BPH). Inclusion criteria included prospective studies reporting baseline and 12-month International Prostate Symptom Score (IPSS) and particle size. Exclusion criteria were overlapping studies, commentaries, abstracts, and letters. Data extraction from eligible studies included the size of embolic particle, particle material, and baseline and 12-month values for the following patient outcomes: IPSS, IPSS quality of life, urinary flow rate (Q-max), prostate volume, prostate specific antigen, and post-void residual volume. A meta-regression analysis was then undertaken to examine the relationship of particle size to patient outcome measures. Six studies with a total of 687 patients were identified. Meta-regression analysis demonstrated particle size as a statistically significant (p<0.001) moderator of 12-month IPSS change following PAE. No statistically significant relationships were identified with other patient outcome measures. Smaller embolic particle size is associated with a greater reduction in IPSS following PAE.

Carotid artery stenting may be performed safely in patients with radiation therapy-associated carotid stenosis without increased restenosis or target lesion revascularization

Neck radiation therapy (XRT) can induce carotid artery stenosis and may increase the technical difficulty of endarterectomy. It is considered a relative indication for carotid angioplasty and carotid artery stenting (CAS). This study sought to evaluate differences in CAS embolic potential and restenosis performed on XRT and non-XRT patients. At three institutions, 366 CAS procedures were performed on 321 patients (XRT, n = 43; non-XRT, n = 323). Mean follow-up was 410 days (median, 282 days; range, 7-1920 days). Patients were observed with duplex ultrasound to assess for restenosis. Additional end points included target lesion revascularization (TLR), myocardial and cerebrovascular events, and perioperative complications. Captured particulate from embolic protection filters was analyzed with photomicroscopy and image analysis software for 27 XRT and 214 non-XRT filters. XRT patients were more likely to be male and had lower rates of hypertension, coronary artery disease, and diabetes mellitus, although the mean age at procedure did not differ. There was no increase in severe internal carotid tortuosity among XRT patients (XRT: 50% vs non-XRT: 34.7%; P = .06). Indication for CAS did not differ between the two groups, including the number of CAS procedures performed for symptomatic carotid stenosis (XRT: 39.7% vs non-XRT: 39.0%; P = NS). Perioperative outcomes, including the composite 30-day stroke, myocardial infarction, and mortality, were not significantly different (XRT: 2.6% vs non-XRT: 3.9%; P = NS.) There were no significant differences in restenosis rate at the 50% (XRT: 9.4% vs non-XRT: 8.6%; P = NS) or 70% (XRT: 3.5% vs non-XRT: 8.6%; P = NS) threshold. Filter particle analysis revealed that filters from XRT patients had more numerous large particles per filter (1.4 vs 0.7; P < .05) and larger mean particle size (464.1 μm vs 320.0 μm; P < .05). TLR did not differ significantly between the groups. In contrast to earlier studies, this analysis reveals that there are significant differences in XRT and non-XRT patients undergoing CAS in terms of medical comorbidities and embolic material captured in embolic protection filters. The decreased incidence of atherosclerotic risk factors was observed in XRT patients probably because XRT was the primary factor responsible for carotid stenosis. Despite increased embolic particle size, CAS can be performed safely with no increased morbidity, TLR, or restenosis in XRT patients.

Predicting embolic potential during carotid angioplasty and stenting: Analysis of captured particulate debris, ultrasound characteristics, and prior carotid endarterectomy

Extracranial carotid stenoses exhibit significant variance in embolic potential, with restenotic lesions having a particularly low propensity for embolization. This study sought to identify characteristics associated with increased generation of embolic debris during carotid angioplasty and stenting (CAS). Captured particulate was available for analysis in 56 consecutive patients. Demographics were mean age, 74 years (range, 60-94 years); mean stenosis, 88% (range, 70%-99%); symptomatic, 27%; prior carotid endarterectomy (CEA), 27%; prior radiotherapy, 7%. Plaque echogenicity, heterogenicity, ulceration, and irregularity were assessed with B-mode duplex ultrasound analysis. Gray scale median (GSM) was calculated from normalized B-mode VHS video recordings. Calcification and degree of stenosis were determined angiographically. Captured particulate debris was evaluated for total number; number >200 microm, >500 microm, >1000 microm; mean and median size. Hematoxylin and eosin, trichrome, and von Kossa stains were used for histologic analysis of captured material. Restenotic carotid stenoses after prior CEA generated minimal embolic debris compared with primary stenoses. Four of 15 patients (27%) with restenotic lesions demonstrated embolic particles; all debris was <500 microm. All 41 patients with primary stenoses had some embolic debris; particulate size was >200 microm in 91%, >500 microm in 72%, and >1000 microm in 43%. In primary lesions, the number and size of captured particulate correlated with GSM and with the combined ultrasound findings of echogenicity, heterogenicity, and luminal irregularity/ulceration (P < .02, 95% confidence interval, 4.5-27.6). None of these ultrasound factors correlated independently with embolic particulate (P = NS). Patients aged >70 years exhibited more total particles (8.1 vs 2.3, P = .008) and increased mean particle size (370 vs 157 mum, P = .02). No significant correlation was observed between the number and size of captured embolic particulate and any other variable (stenosis percentage, prior radiotherapy, preprocedural symptoms, periprocedural symptoms, and calcification). Histologically, the embolic debris consisted of extensive amorphous, acellular proteinaceous material. Calcium debris in the embolic particulate was associated with heavily and moderately calcified lesions. Considerable variation exists in the number and size of embolic particles generated during CAS. Embolic potential is positively correlated with lesion GSM and the combination of lesion echogenicity, heterogenicity, and irregularity. Restenosis after prior CEA is associated with minimal embolic particulate generation, suggesting that embolic protection may not be necessary for CAS of restenotic lesions.

Application of Superselective Artery Embolization in Nasopharyngeal Angiofibroma before Operation

Objective: To evaluate the clinical application of superselective transcatheter arterial embolization (TAE) in nasopharyngeal angiofibroma before operation. Methods: Superselective angiography was done via femoral. TAE with polyvinyl alcohol particles and/or gelfoam (GF) was performed in 12 patients with nasopharyngeal angiofibroma. All patients underwent surgical removal of devascularized tumors in 3 to 7 days after TAE. Results: During digital subtraction angiography, tumor staining was seen in 12 patients. Embolization of maxillary artery was performed in 12 cases and additional embolization of ascending pharyngeal artery in 8 cases. Conclusion: Superselective angiographic diagnosis, embolization and appropriate embolic particle size are important for successful treatment of nasopharyngeal angiofi- broma. TAE is safe and effective in decreasing haemorrhage during surgical operation for nasopharyngeal angiofibroma.

Carotid angioplasty in a pulsatile flow model: Factors affecting embolic potential

Ojectives: carotid endoluminal intervention is an alternative to urgery but carries a risk of embolic stroke even with distal rotection devices. We investigated the clinical features and degree of stenosis related to number and size of emboli during carotid angioplasty. Design: an experimental ex vivo study. Materials: an ex vivo pulsatile flow model was used in which temperature, velocity, flow, pressure and viscosity characteristics were designed to simulate the carotid circulation. Methods: carotid endarterectomy specimens excised as intact cylinders (n = 28) were subjected to a standardised angioplasty procedure using radiological guidance. Emboli collected in filters placed distally were counted and sized using microscopy. Results: median number of emboli during angioplasty was 133 (range 15-1331). Median size of the largest embolus was 700 microns (range 75-2400). Severity of stenosis correlated with increased maximum size (r = 0.55, p = 0.012). Statin therapy >4 weeks pre-operatively was associated with reduced emboli number and size (54 (range 15-748) vs 247 (range 37-1331) [p = 0.023] and 400 μm (range 75-2400) vs 1300 μm (range 600-2200) [p = 0.022]). Conclusions: in this model a wide range of emboli number and size were produced. Number and size of embolic particles were highest in patients with high-grade stenoses not receiving statin therapy.Eur J Vasc Endovasc Surg 26, 22-31 (2003)

Mechanical versus Chemical Thrombolysis: An In Vitro Differentiation of Thrombolytic Mechanisms

To assess differing mechanisms of thrombolysis determining time to reperfusion, completeness of thrombus dissolution, and embolic potential. An in vitro perfusion model designed to mimic arterial flow conditions was created. Bifurcated limbs allowed continuous flow through one channel and the placement of radiolabeled (iodine-125) thrombus housed in a 5-cm segment of polytetrafluoroethylene graft in the other. The three experimental groups consisted of a standard continuous urokinase infusion, a pulsed pressurized injection of saline, and a similar injection with urokinase. A continuous infusion of 5% dextrose served as a control group. Time to reflow (as assessed with ultrasonic flow monitoring), completeness of thrombus dissolution (I-125 liberated into solution), and the number and size of embolic particles produced (detected by a series of graduated filter sizes) were analyzed. Time to reflow was significantly faster for both groups when pressurized injections were used (P < .001). There was no reflow in the control arm at 90 minutes. Completeness of thrombus dissolution was higher when a continuous infusion of urokinase was used in comparison to either of the power injection groups or the control (P < .05). The amount of embolic debris produced was significantly lower with a continuous infusion of urokinase compared with either of the power lysis groups (P < .05), but significantly greater than the control arm (P < .001). The size of the embolic particles in the power pulsed lysis groups was significantly decreased by the addition of urokinase (P < .05). Reflow is more rapidly established by the use of mechanical means. However, a less complete dissolution of thrombus in conjunction with a greater amount of embolic debris is achieved with this approach. The size of the embolic particles produced is reduced by the addition of a thrombolytic agent.

Clinical features and echocardiography of embolism during cemented hip arthroplasty.

In previous studies the degree of embolization detected by transoesophageal echocardiography (TEE) during cemented total hip arthroplasty (THA) did not correlate with changes in haemodynamic variables nor did it result in persistent ventilation-perfusion mismatching. The aim of this study was to record evidence of embolism and to relate the findings to demographic data and the subsequent clinical course of the patients during THA. Forty-eight patients scheduled to undergo elective cemented THA during general anaesthesia were monitored. A TEE probe was inserted with special attention to the right atrium (RA), the right ventricle (RV) Haemodynamic (heart rate, arterial blood pressure, central venous pressure) and blood-gas variables were measured repeatedly during the operative procedure (after induction, placement of the acetabular component, placement of the femoral component, relocation of the hip joint). Grading of venous embolism at these times was based on the size of particles detected by TEE (three-minutes video segments of each periods) and correlated with demographic, haemodynamic and blood-gas data. The TEE monitoring revealed showers of echogenic material traversing the RA and RV in all but one patients during reaming and cementing of the acetabular and femoral components, and during relocation of the hip joint. No correlation was observed between frequency or size of embolic particles and demographic or blood-gas and haemodynamic variables studied at the same times. This study failed to show any clinical impact of TEE detected emboli during cemented THA.