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Background and Purpose— Mechanical thrombectomy may involve multiple attempts to retrieve the occluding thrombus. This study examined the composition of thrombus fragments retrieved with each pass of a device during the thrombectomy procedure. Second, the per-pass composition was compared with procedural and clinical data including angiographic outcome and stroke etiology. Methods— Thrombi were retrieved from 60 patients with acute ischemic stroke, where thrombus fragments retrieved in each pass were segregated as individual samples and maintained throughout the histological analysis as independent samples. All samples were stained with hematoxylin and eosin and Martius Scarlet Blue. The relative composition of red blood cells, fibrin, and white blood cells in thrombus fragments from each pass was quantified. Results— Over the 60 cases, thrombus material was retrieved in 106 of 138 passes. The number of passes required to complete the cases ranged from 1 to 6 passes. The analysis of thrombus fragments retrieved in each pass provided a greater insight into the thrombectomy procedure progression than the overall thrombus composition; the red blood cell content of thrombus fragments retrieved in passes 1 and 2 was significantly higher than that retrieved in passes 3 to 6. The removal of thrombus material in a total of 1, 2, or 3 passes was associated with the highest percentage of final modified Thrombolysis in Cerebral Infarction score of 2c-3. There was no association between modified Thrombolysis in Cerebral Infarction score and per-pass thrombus composition. Conclusions— The differentiation achieved through the per-pass analysis of acute ischemic stroke thrombi provides a greater insight into the thrombectomy procedure progression than the combined per-case thrombus analysis. Insights gained may be a useful consideration in determining the treatment strategy as a case evolves and may be useful for the development of new devices to increase rates of 1-pass recanalization.

BackgroundMechanical thrombectomy is the standard of care for acute ischemic strokes with proximal intracranial occlusion. Arterial access is commonly achieved with femoral artery puncture, although this is not always possible. In this case series, we describe 11 cases of anterior circulation stroke where direct carotid puncture was used to obtain vascular access.Methods and materialsA review of a prospectively maintained thrombectomy database over a 2-year period (August 2016 – August 2018) was undertaken to identify cases where direct carotid access was performed. CT and angiographic imaging were reviewed. Indications for carotid access, techniques used, technical success of procedure, recanalization rates, procedure-related complications, and patient outcomes were assessed.ResultsEleven patients out of 498 overall thrombectomy procedures (2.2% thrombectomies) underwent direct carotid access. Median National Institutes of Health Stroke Scale was 20. Seventy three percent of patients received intravenous thrombolysis. The direct carotid approach was performed following the failed femoral approach due to unfavorable aortic arch anatomy, vessel tortuosity, and severe atherosclerotic disease. Direct carotid puncture was successful in 10 patients, and unsuccessful in one. Successful recanalization (TICI 2b–3) was achieved in eight patients. One patient had spontaneously recanalized on angiography. There was failed recanalization in one patient with tandem ICA and M1 occlusion. Carotid access complications included one patient with both neck hematoma and asymptomatic ICA dissection, and one of delayed central retinal artery occlusion.ConclusionThis case series highlights direct carotid puncture as a successful alternative when the femoral approach is not possible, allowing thrombectomy in patients who would otherwise be unsuitable.

Background and aimsPlatelets and von Willebrand factor (vWF) are key factors in thrombosis and thus are likely key components of acute ischemic stroke (AIS) emboli. We aimed to characterize platelet and vWF levels in AIS emboli and to assess associations between their expression levels and clinical and procedural information.Materials and methodHistopathological and immunohistochemical analysis of emboli collected as part of the multi-institutional RESTORE registry was performed. The composition of the emboli was quantified using Orbit Image Analysis machine learning software. Correlations between clot components and clinical and procedural information were assessed using the χ2 test.ResultsNinety-one emboli samples retrieved from 63 patients were analyzed in the study. The mean platelet (CD42b) content of the clots was 33.9% and the mean vWF content of the clots was 29.8%. There was a positive correlation between platelet and vWF levels (ρ=0.564, p<0.001*, n=91). There was an inverse correlation between both platelets and vWF levels and percentage of red blood cells (RBCs) in the emboli (CD42b vs RBC: ρ=−0.535, p<0.001*, n=91; vWF vs RBC: ρ=−0.366, p<0.001*, n=91). Eighty-one percent of patients in the low platelet group had a good revascularization outcome (Thrombolysis in Cerebral Infarction 2c/3) compared with 58% in the high platelet group (χ2=5.856, p=0.016).ConclusionPlatelet and vWF levels in AIS emboli correlate with each other and both have an inverse relationship with RBC composition. Patients with platelet-rich clots have poorer revascularization outcomes.

BackgroundInitial studies investigating correlations between stroke etiology and clot composition are conflicting and do not account for clot size as determined by area. Radiological studies have shown that cardioembolic strokes are associated with shorter clot lengths and lower clot burden than non-cardioembolic clots.ObjectiveTo report the relationship between stroke etiology, extracted clot area, and histological composition at each procedural pass.MethodsAs part of the multi-institutional RESTORE Registry, the Martius Scarlett Blue stained histological composition and extracted clot area of 612 per-pass clots retrieved from 441 patients during mechanical thrombectomy procedures were quantified. Correlations with clinical and procedural details were investigated.ResultsClot composition varied significantly with procedural passes; clots retrieved in earlier passes had higher red blood cell content (H4=11.644, p=0.020) and larger extracted clot area (H4=10.730, p=0.030). Later passes were associated with significantly higher fibrin (H4=12.935, p=0.012) and platelets/other (H4=15.977, p=0.003) content and smaller extracted clot area. Large artery atherosclerotic (LAA) clots were significantly larger in the extracted clot area and more red blood cell-rich than other etiologies in passes 1–3. Cardioembolic and cryptogenic clots had similar histological composition and extracted clot area across all procedural passes.ConclusionLAA clots are larger and associated with a large red blood cell-rich extracted clot area, suggesting soft thrombus material. Cardioembolic clots are smaller in the extracted clot area, consistent in composition and area across passes, and have higher fibrin and platelets/other content than LAA clots, making them stiffer clots. The per-pass histological composition and extracted clot area of cryptogenic clots are similar to those of cardioembolic clots, suggesting similar formation mechanisms.