Impact of histological clot composition on preprocedure imaging and mechanical thrombectomy.

INTRODUCTION: We studied the relationship of acute ischemic stroke (AIS) large-vessel occlusion clot composition with vessel recanalization and preprocedure imaging. SUBJECTS AND METHODS: Individual clots from AIS patients who underwent mechanical thrombectomy (MT) between September 2016 and September 2018 were examined. Clot composition was analyzed histologically through a trichrome staining and image segmentation, and the area occupied by red blood cells (RBCs), fibrin, or mixed composition was quantified. RESULTS: Forty-three patients (65.4 ± 12.7 years, 39% of females) who underwent 92 retrieval passes (mean 2.14, range 1-6) were included in this study. Fibrin (44%) occupied the greatest area, followed by mixed composition (34%) and RBCs (22%). A stent retriever was deployed in 81% of cases, 20 patients (47%) achieved first-pass efficacy (FPE) (thrombolysis in cerebral infarction [TICI] 2b-3 after first pass), 41 (95%) achieved successful revascularization (TICI 2b-3), and 21 (49%) had good outcome (modified Rankin Scale [mRS] ≤2) at 90 days. Hyperdense artery sign (HAS) on initial computed tomography was correlated with mixed clot composition (P = 0.01) and lack of fibrin content (P = 0.03). In the univariate analysis, FPE was associated with RBC clot area, atrial fibrillation, and occlusion location but not with fibrin clot area, mixed clot area, stroke etiology, thrombectomy technique, distal emboli, or 90-day mRS. In the multivariate analysis, FPE was significantly correlated with low RBC clot area (odd ratio = 0.96, confidence interval [0.92.99], P = 0.034) but not with atrial fibrillation or location. CONCLUSION: Our results suggest that HAS is correlated with mixed clot composition and lower fibrin content and that lower RBC clot composition is associated with FPE in patients undergoing MT.

Preventing Inadvertent Foreign Body Injection in Angiography.

Background Inadvertent injection of foreign material during angiography, particularly neuroangiography, should be avoided to reduce the risk of embolic complications. Woven gauze and cotton fabrics have been identified as sources of inadvertent foreign body embolization. Purpose To find the source of particles that contaminate injections on an angiography table and to identify measures for their reduction. Materials and Methods The number and size of particles on an angiographic supply table at a tertiary stroke center were analyzed by using the Coulter principle in September 2019. Seven conditions (saline directly drawn from its bag, from a small metal cup, from a small plastic cup, from a large plastic bowl, from a large plastic bowl with a guidewire and its sheath, from a large plastic bowl with a stack of woven gauze, and from a large plastic bowl with a large cotton towel) were tested at different time intervals (0, 30, and 60 minutes). Each container was filled with saline, and particle count was analyzed immediately after unpackaging, after rinsing with saline, and after introduction of foreign material; t tests were used for statistical comparisons. Results Freshly unpacked basins can be contaminated with many submillimetric particles (range, 4.4-25.1 particles per milliliter on average, depending on basin). Cotton towels and woven gauze placed in rinsed basins resulted in a significant increase in particles (from 1.5 particles per milliliter ± 0.4 [standard deviation] to 64.4 particles per milliliter ± 4.1 and 257.1 particles per milliliter ± 11.6, respectively; P < .001). Rinsing basins with saline significantly reduced the number of particles (P ≤ .03). Drawing saline directly from bags through intravenous lines yielded the lowest number of particles (0.1 particles per milliliter). Conclusion To decrease the risk for foreign body embolization, it is best to rinse all basins before use, draw saline and contrast agents directly from the respective bags and bottles through intravenous lines, and avoid cotton towels and woven gauze in basins and on the angiography table altogether whenever possible. © RSNA, 2021 See also the editorial by Nikolic in this issue.

Quantitative Characterization of Recanalization and Distal Emboli with a Novel Thrombectomy Device.

PURPOSE: The first-pass effect during mechanical thrombectomy improves clinical outcomes regardless of first-line treatment approach, but current success rates for complete clot capture with one attempt are still less than 40%. We hypothesize that the ThrombX retriever (ThrombX Medical Inc.) can better engage challenging clot models during retrieval throughout tortuous vasculature in comparison with a standard stent retriever without increasing distal emboli. MATERIALS AND METHODS: Thrombectomy testing with the new retriever as compared to the Solitaire stent retriever was simulated in a vascular replica with hard and soft clot analogs to create a challenging occlusive burden. Parameters included analysis of distal emboli generated per clot type, along with the degree of recanalization (complete, partial or none) by retrieval device verified by angiography. RESULTS: The ThrombX device exhibited significantly higher rates of first-pass efficacy (90%) during hard clot retrieval in comparison with the control device (20%) (p < 0.009), while use of both techniques during soft clot retrieval resulted in equivalent recanalization. The soft clot model generated higher numbers of large emboli (>200 µm) across both device groups (p = 0.0147), and no significant differences in numbers of distal emboli were noted between the ThrombX and Solitaire techniques. CONCLUSIONS: Irrespective of clot composition, use of the ThrombX retriever demonstrated high rates of complete recanalization at first pass in comparison with a state-of-the-art stent retriever and proved to be superior in the hard clot model. Preliminary data suggest that risk of distal embolization associated with the ThrombX system is comparable to that of the control device.

Complete clot ingestion with cyclical ADAPT increases first-pass recanalization and reduces distal embolization.

BACKGROUND: Evidence is mounting that first-pass complete recanalization during mechanical thrombectomy is associated with better clinical outcomes in patients presenting with an emergent large vessel occlusion. We hypothesize that aspiration achieving complete clot ingestion results in higher first-pass successful recanalization with quantitative reduction in distal emboli. METHODS: A patient-specific cerebrovascular replica was connected to a flow loop. Occlusion of the middle cerebral artery was achieved with clot analogs. Independent variables were the diameter of the aspiration catheter (0.054-0.088in) and aspiration pattern (static versus cyclical). Outcome measures were the first-pass rates of complete clot ingestion, the extent of recanalization, and the particle-size distribution of distal emboli. RESULTS: All aspiration catheters were successfully navigated to the occlusion. Complete clot ingestion during aspiration thrombectomy resulted in first-pass complete recanalization in every experiment, only achieved in 21% of experiments with partial ingestion (P<0.0001). Aspiration through the large bore 0.088in device resulted in the highest rates of complete clot ingestion (90%). Cyclical aspiration (18-29 inHg, 0.5 Hz) significantly increased the rate of complete clot ingestion (OR21 [1.6, 266]; P=0.04). In all experiments, complete clot ingestion resulted in fewer and smaller distal emboli. CONCLUSIONS: Complete clot ingestion results in fewer distal emboli and the highest rates of first-pass complete recanalization. The rate of complete ingestion during aspiration thrombectomy is a function of both the inner diameter of the aspiration catheter and use of cyclical aspiration.

Microcatheter navigation through the clot: does size matter?

BACKGROUND: Despite high recanalization rates achieved with endovascular treatment of acute ischemic strokes, around 50% of eligible patients will not achieve a good outcome. Parameters that may determine patient outcomes include: time from puncture to recanalization, the collateral status, the anesthesia regimen, blood pressure management, and distal emboli. Characterization of distal emboli generated during mechanical thrombectomy has been performed in previous studies. OBJECTIVE: To further investigate the risk of distal embolization associated with microcatheter navigation across the clot. METHODS: A contrast-enhanced clot analog was used in an in vitro model that mimicked a middle cerebral artery occlusion within a complete circle of Willis vascular replica. The clot was crossed with one of the following microcatheters: Pro18, XT-27 or 3MAX. The emboli generated during the procedure were collected and measured. RESULTS: The use of Pro18 and XT-27 resulted in a significant reduction of visible particles (size ≥500 µm) as compared with the 3MAX catheter (P<0.003). For the size range between 8 and 200 µm, there was a trend for Pro18 to generate fewer particles (-18%) than XT-27 but without statistical significance (P>0.05). In comparison with previously published data, acquired under the same conditions, it was found that the clot crossing maneuver accounts approximately for 12% of the total number of small emboli (<200 µm) induced during a stent retriever-mediated mechanical thrombectomy procedure via a balloon guide catheter. CONCLUSIONS: The clot crossing maneuver has a significant effect on the total number of small particles induced during mechanical thrombectomy. Smaller microcatheter sizes should be favored when possible.

The occurrence of neointimal hyperplasia after flow-diverter implantation is associated with cardiovascular risks factors and the stent design.

BACKGROUND: Neo-intimal hyperplasia (NIH) is frequently observed after flow-diverter stent (FDS) implantation. Although mostly asymptomatic, this vascular response can sometimes lead to delayed ischemic strokes. This study intended to evaluate the factors potentially influencing the rates of NIH following FDS treatment. MATERIAL AND METHODS: All aneurysm treatments performed with a Pipeline embolization device (PED) or a SILK stent from May 2011 to May 2015 were collected in a prospectively maintained database. Patient demographics, clinical, and angiographic outcomes including both digital subtraction angiography and C-arm cone-beam CT were registered. Two blind reviewers rated the presence of NIH on a binary scale (present/absent). RESULTS: From 148 patients, 63 datasets were available for analysis. Inter-reader agreement was excellent (Kappa=0.88). NIH was positively correlated with smoking, dyslipidemia, and high blood pressure, but not with aneurysm characteristics. At early follow-up (<12 months), NIH was more frequently associated with the use of the SILK stent (68%) rather than the PED (38%): P<0.02. At long-term follow-up, the NIH rate in the total population dropped from 55% to 26% with no more significant difference between the two stents. The complete occlusion rate as seen in early follow-up was higher in the SILK group with 76% vs 65% but without statistical significance (P=0.4). CONCLUSION: NIH is a dual-vessel reaction after FDS implant. When planning a treatment in locations at risk of ischemic complications if severe NIH would occur, then the stent design should be considered. However, minimal NIH might also be needed as it is involved in aneurysm healing. Before treatment patients should be recommended best medical management of their cardiovascular risks factors to prevent an excessive NIH reaction.