Abstract 3: Collaterals, Not Clots! CT Angiography Predictors of Recanalization, Reperfusion and Clinical Outcomes After Thrombectomy in Pooled Analyses of TREVO EU and TREVO2

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
David S Liebeskind ◽  
Nerses Sanossian ◽  
Fabien Scalzo ◽  
Bin Xiang ◽  
Mark S Johnson ◽  
...  
Keyword(s):  
Multivariate Analyses ◽  
Hounsfield Unit ◽  
Systematic Evaluation ◽  
Multivariate Models ◽  
Anterior Circulation ◽  
Predictors Of Response ◽  
Noncontrast Ct ◽  
Clot Burden ◽  
Maximum Intensity Projections ◽  
Underlying Pathophysiology

Background: CTA is often used to define clot location prior to endovascular therapy yet systematic evaluation may reveal many details about underlying pathophysiology. We tested a battery of CTA measures to identify optimal predictors of response to thrombectomy. Methods: CTA datasets of anterior circulation strokes in TREVO EU and TREVO2 with available source images were reconstructed into 3D-curved and 2D-orthogonal maximum-intensity projections by the core lab. Occlusion site, clot length and volume, clot burden score (CBS) and regional leptomeningeal collateral score (rLMC) were scored on CTA. Hyperdense vessels, Hounsfield Unit (HU) indices and location of hyperdensity relative to CTA occlusion site were noted on noncontrast CT. Results: 111 cases (mean age 68.0 ± 13.8 years; 58.6% women; median baseline NIHSS 18 (8-28)) were analyzed. CTA occlusions were 68.5% M1, 22.5% M2, and 9.0% ICA. CTA clot volumes were mean 49.3 ± 36.3 mm 3 with mean CBS 6.7 ± 1.8 and mean rLMC 15.3 ± 4.2. Noncontrast hyperdensity was noted at M1 in 44.1%, M2 in 27.0%, and ICA 8.1%, with ipsilateral:contralateral HU indices of mean 1.3 ± 0.2. Noncontrast CT hyperdensity relative to CTA opacification revealed hyperdensity proximal to occlusions in 2.7%, just past occlusion in 55.0%, and distal to clot end in 6.2%. Only better collaterals on rLMC predicted AOL 2-3 recanalization (OR 1.26, p=0.058) in multivariate analyses and distal hyperdensity (OR 0.11, p=0.037) predicted worse recanalization. Similarly, only rLMC predicted TICI 2b-3 reperfusion (OR 1.27, p=0.004) and distal hyperdensity (OR 0.12, p=0.071) predicted worse reperfusion. Clots (CBS) and collaterals (rLMC) were moderately correlated with each other (0.44 Spearman) in multivariate models of good clinical outcome (mRS 0-2) at day 90, yet clots were significant only when removing collaterals. Conclusions: Collaterals, not clots, are the best CTA predictors of outcomes after thrombectomy. Worse outcomes with hyperdensity distal to clots on CTA likely reflect stasis due to poor retrograde collaterals.

Abstract TP59: Atherosclerosis and Unsuccessful Recanalization in Acute Stroke Patients

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Cynthia Zevallos ◽  
Kiddy Ume ◽  
Matthew Weber ◽  
Abigail Levy ◽  
Andrea Holcombe ◽  
...  
Keyword(s):  
Medical Records ◽  
Regression Models ◽  
Imaging Data ◽  
Inpatient Mortality ◽  
Stroke Patients ◽  
Anterior Circulation ◽  
Logistic Regression Models ◽  
Noncontrast Ct ◽  
Clot Burden

Unsuccessful recanalization rates in acute ischemic stroke patients range between 8-18%. Currently, there are no models to predict thrombectomy reperfusion success with current thrombectomy techniques. We aimed to describe the clinical and radiological features of patients with unsuccessful thrombectomy (UT) and its association with intracranial atherosclerosis (ICAD). A cohort of 413 consecutive, adult, thrombectomy patients admitted to two comprehensive stroke centers were reviewed from 2014 to 2017. Patients with anterior circulation large vessel occlusions (LVOs) and a thrombolysis in cerebral infarction (TICI) score of ≤2a were selected. Demographics, clinical and imaging data were obtained from electronic medical records. Head CT, CT angiography and digital subtraction angiography (DSA) images were reviewed by one independent investigator to evaluate ASPECTS score, vessel calcifications, clot burden score and CTA and DSA collateral score. Proposed causes of UT were categorized based on angiography evaluation by two independent neurointerventionalists. Analysis was performed using descriptive frequency analysis and univariate logistic regression models. A total of 87 low TICI score (≤2a) patients from 413 procedures were included. The median age was 74 years (IQR 58.5-84) and 58% were female. The most common comorbidity was hypertension (73.5%), followed by hyperlipidemia (46%). TICI score of 0 was found in 23% (N=20), 1 in 9.2% (N=8), and 2a in 67.8% (N=59). The inpatient mortality rate was 19.5% (17/87). Out of the remaining 70 patients, 78.5% (N=55) had a 3-month follow up modified Rankin Scale (mRS) of 3-6. The most common proposed cause of poor revascularization in our study was presence of ICAD [29.9% (n=32) of patients]. In our cohort of UT patients with ICAD, 68.8% (N=22) had TICI 2a score with majority (96.8%) having a 3 months mRS of 3-6. Patients with ICAD had 7.3% increased odds of having angiographic collateral score of 5 (p=0.035) and 15.2% increased odds of having an absence of hyperdense MCA in noncontrast CT scan (p=0.003). ICAD is frequently found in patients that undergo UT. Identification of radiological predictors of ICAD may be helpful to consider alternative revascularization strategies for LVOs.

Abstract TP10: Prediction of Thrombolytic Efficacy: Usefulness of Measurement of Enhancement in the Thrombus on Thin-reconstructed Perfusion CT

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Dong Hoon Shin ◽  
Eung Yeop Kim
Keyword(s):  
Collateral Circulation ◽  
Motion Correction ◽  
Hounsfield Unit ◽  
Spiral Ct ◽  
Perfusion Ct ◽  
Vascular Imaging ◽  
Escape Trial ◽  
Tissue Plasminogen ◽  
Noncontrast Ct

Purpose: To directly measure enhancement in acute thrombi using thin-reconstructed perfusion CT images for prediction thrombolytic efficacy. Materials and Methods: Prior to administration of tissue plasminogen activator (tPA), noncontrast CT (NCCT), 60-second 70-kVp adaptive 4D spiral CT (CTP), and CT angiography (CTA) were prospectively obtained and reconstructed at 1-mm thickness. Length and Hounsfield unit ratio (HUr) of thrombus were measured using 1-mm NCCT. Collateral circulation was assessed on dynamic CTA that were reconstructed from 1-mm CTP images. Good collateral circulation was defined as the criteria that were used for ESCAPE trial. After spatial motion correction of 1-mm CTP images, circular regions of interest were drawn in the central portion and each end of thrombus to measure the level of HU increase from baseline on time-attenuation curves (TAC). Recanalization was assessed on follow-up vascular imaging studies that were obtained within 24 hours after tPA. Modified TICI 2b or 3 was considered successful recanalization. Thrombus length, HUr, collaterals, and minimum increase of HU on TAC (HUmin) were compared between the recanalized and non-recanalized groups. Results: Of 57 patients who received tPA therapy, 31 patients (female, 13; mean age, 66.5 years) with occlusions in ICA (n=7), M1 (n=8), M1-M2 (n=6), and M2 (n=10) were only assessed. Thrombus length ranged 3-45 mm (median, 12 mm; IQR, 7). HUr was measured from 1.03 to 1.69 (median, 1.26; IQR, 0.19). Good collaterals were noted in 27 patients. HUmin ranged 3-70 HU (median, 15; IQR, 12), and showed negative correlation with thrombus length (rho=-0.410, P=0.022), but not with HUr. HUmin was significantly higher in the recanalized group (n=19) than the non-recanalized group (mean HUmin 23.79 vs 7.83; P<0.0001) independent of thrombus location. Thrombus length, HUr, or collateral status was not significantly different between the two groups. HUmin > 13 was determined with sensitivity of 89.5%, specificity of 91.7%, and AUC of 0.961 for prediction of recanalization. Conclusion: HUmin of thrombus was significantly higher in patients with successful recanalization after tPA therapy.

Heterogeneity between proximal and distal aspects of occlusive thrombi on pretreatment imaging in acute ischemic stroke

2021 ◽  
pp. 197140092110497
Author(s):  
Tetsuya Hashimoto ◽  
Takenobu Kunieda ◽  
Tristan Honda ◽  
Fabien Scalzo ◽  
Latisha K Sharma ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Ischemic Stroke ◽  
Region Of Interest ◽  
Hounsfield Unit ◽  
Distal Segment ◽  
Large Vessel Occlusion ◽  
Anterior Circulation ◽  
Vessel Occlusion ◽  
The Difference

Background The potential heterogeneity in occlusive thrombi caused by in situ propagation by secondary thrombosis after embolic occlusion could obscure the characteristics of original thrombi, preventing the clarification of a specific thrombus signature for the etiology of ischemic stroke. We aimed to investigate the heterogeneity of occlusive thrombi by pretreatment imaging. Methods Among consecutive stroke patients with acute embolic anterior circulation large vessel occlusion treated with thrombectomy, we retrospectively reviewed 104 patients with visible occlusive thrombi on pretreatment non-contrast computed tomography admitted from January 2015 to December 2018. A region of interest was set on the whole thrombus on non-contrast computed tomography under the guidance of computed tomography angiography. The region of interest was divided equally into the proximal and distal segments and the difference in Hounsfield unit densities between the two segments was calculated. Results Hounsfield unit density in the proximal segment was higher than that in the distal segment (mean difference 4.45; p < 0.001), regardless of stroke subtypes. On multivariate analysis, thrombus length was positively correlated (β = 0.25; p < 0.001) and time from last-known-well to imaging was inversely correlated (β = −0.0041; p = 0.002) with the difference in Hounsfield unit densities between the proximal and distal segments. Conclusions The difference in density between the proximal and distal segments increased as thrombi became longer and decreased as thrombi became older after embolic occlusion. This time/length-dependent thrombus heterogeneity between the two segments is suggestive of secondary thrombosis initially occurring on the proximal side of the occlusion.

Abstract T P10: Hounsfield Unit Value and Clot Length in the Acutely Occlude Vessel and Time Required to Achieve Thrombectomy, Complications and Outcome

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Alejandro Spiotta ◽  
Jan Vargas ◽  
Harris Hawk ◽  
Raymond Turner ◽  
Imran Chaudry ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Acute Ischemic Stroke ◽  
Functional Outcome ◽  
Hounsfield Unit ◽  
Hounsfield Units ◽  
Unit Value ◽  
Procedural Complications ◽  
Noncontrast Ct ◽  
Time Required

Introduction: Intra-arterial therapy for acute ischemic stroke (AIS) now has an established role. We investigated if Hounsfield Units (HU) quantification on noncontrast CT is associated with ease and efficacy of mechanical thrombectomy and outcomes. Methods: We retrospectively studied a prospectively maintained database of cases of acute ischemic stroke that underwent intra-arterial therapy between May 2008 and August 2012. Functional outcome was assessed by ninety-day follow up modified Rankin Scale (mRS). Patients were dichotomized base on time to recanalization. Hounsfield units were calculated on head CT. Thrombus location and length were determined on CT angiography. Simple linear regression was used to analyze the association between clot length, average HU, and other clinical variables. Results: 141 patients were included. There was no difference in clot length or average HU among patients with good recanalization achieved within an hour compared to those in which procedures extended beyond an hour. There was no relationship between clot length or density and recanalization. The thrombus length and density were not significantly different between patients with procedural complications and those without. The presence of post procedure intracranial hemorrhage was not associated with thrombus length or density. Ninety day mRS was not associated with thrombus length or density. Conclusions: We have not found any significant associations between either thrombus length or density and likelihood of recanalization, time to achieve recanalization, intraprocedural complications, postprocedural hemorrhage or functional outcome at ninety days. These results do not support a predictive value for thrombus quantification in the evaluation of AIS.

scholarly journals Visual Partitioning for Multivariate Models: An approach for identifying and visualizing complex multivariate dataset

2021 ◽  
Author(s):  
Dustin Fife
Keyword(s):  
Multivariate Analyses ◽  
Interactive Effects ◽  
Multivariate Models ◽  
Assumption Violations ◽  
Conditional Inferences

Users of statistics quite frequently use multivariate models to make conditional inferences (e.g., stress affects depression, after controlling for gender). These inferences are often done without adequately considering (or understanding) the assumptions one makes when claiming these inferences. A particularly problematic instance of assumption violations is with nonlinear and/or interactive effects. Many of these inferences are not merited because the inference is "contaminated" by the variables and their relationships within the model. In this paper, we highlight when conditional inferences are contaminated by other features of the model and identify the conditions under which variable effects are marginally independent. We then show a strategy for partitioning multivariate effects into uncontaminated blocks using visualizations. This approach simplifies multivariate analyses immensely, without oversimplifying the analysis.

Abstract 193: Preliminary Clot Length Analysis of Anterior Circulation Large Vessel Occlusions:

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Albert Yoo ◽  
Donald Heck ◽  
Donald Frei ◽  
Osama Zaidat ◽  
Mario Aceves ◽  
...  
Keyword(s):  
Ct Scan ◽  
Interim Analysis ◽  
Controlled Trial ◽  
Ct Images ◽  
Large Vessel ◽  
Case Review ◽  
Anterior Circulation ◽  
Clot Burden ◽  
Contrast Ct ◽  
Length Analysis

Purpose: Thin-section (≤ 2.5 mm) non-enhanced CT images may be used to reliably measure clot lengths in acute MCA occlusions, with clots ≥ 8mm long having a low probability of recanalization with IV rtPA alone. However, it is unclear what proportion of large vessel anterior circulation strokes have clot lengths ≥ 8mm and may potentially benefit from a bridging interventional approach. Methods: A multicenter imaging case review (target enrollment= 200 patients at 5 U.S. centers) was initiated to determine the proportion of patients meeting the below study criteria who have clot lengths ≥ 8mm. Study criteria include presentation within 8 hours of onset; imaging evidence of ICA-T, MCA M1, or M2 occlusion; and thin slice (≤ 2.5 mm) admission non-contrast CT images. Results are reported from an interim analysis of the data. Results: At 2 comprehensive stroke centers, all consecutive stroke admissions between August 2011 and July 2012 were reviewed for eligibility. Of these patients, 64 met study criteria (mean age= 72.3 years; 60% female; mean baseline NIHSS= 18). Mean times from symptom onset to presentation and to CT scan were 3.6 and 4.4 hours, respectively. Primary occlusions were located in the ICA-T (26.6%), M1 (64.1%), and M2 MCA (9.4%). Thrombus was visible in 92% (59/64) of cases, with lengths ranging from 3.0 to 64.8mm (mean = 18.6mm). Of these, 83% were ≥ 8mm in length. Clot length was statistically significantly longer in ICA-T occlusions and for those who did not receive IV rtPA prior to CT scan. Conclusion: This interim analysis suggests that the vast majority of anterior circulation large vessel occlusions have extensive (≥ 8mm length) clot burden, and may benefit from an IV-IA bridging approach. This idea will be tested in the ongoing THERAPY randomized controlled trial.

Association of clot burden score with radiographic and clinical outcomes following Solitaire stent retriever thrombectomy: analysis of the SWIFT PRIME trial

2016 ◽  
Vol 9 (10) ◽  
pp. 929-932 ◽  
Author(s):  
Maxim Mokin ◽  
Elad I Levy ◽  
Adnan H Siddiqui ◽  
Mayank Goyal ◽  
Raul G Nogueira ◽  
...  
Keyword(s):  
Clinical Outcome ◽  
Clinical Outcomes ◽  
Stent Retriever ◽  
Study Cohort ◽  
Prime Trial ◽  
Good Clinical Outcome ◽  
Anterior Circulation ◽  
Clot Burden ◽  
Proximal Occlusion ◽  
The Relationship

BackgroundThe clot burden score (CBS) was developed as a tool to evaluate the extent of intracranial thrombus burden in patients with anterior circulation acute ischemic stroke. CBS is based on the presence or absence of contrast opacification on CT angiography (CTA). Its value in predicting radiographic and clinical outcomes in patients given endovascular stroke therapy remains unknown.ObjectiveTo evaluate the relationship between CBS and outcomes after stent retriever thrombectomy in the interventional arm of the SWIFT PRIME trial.MethodsCBS was calculated for the endovascular arm (IV tissue plasminogen activator plus Solitaire stent retriever) of SWIFT PRIME using baseline CTA. The cohort of 69 patients was divided into three groups according to their CBS values: CBS 0–5 (n=14), CBS 6–7 (n=23), and CBS 8–9 (n=32).ResultsThe mean age of the 69 patients who formed the study cohort was 63.2±13.1 years, mean National Institutes of Health Stroke Scale score was 16.8±4.5, and 55% of the patients were male. There was no difference in clinical characteristics among the three groups, except for the baseline Alberta Stroke Program Early CT Score (p=0.049). The site of proximal occlusion varied significantly among the three groups (p<0.001). Rates of successful recanalization (TICI 2b/3), complete recanalization (TICI 3 only) and of good clinical outcome at 3 months were similar among the three groups (p=0.24, p=0.35, and p=0.52, respectively).ConclusionsThe combination of IV thrombolysis and stent retriever thrombectomy with the Solitaire device is highly effective in achieving successful recanalization and a good clinical outcome throughout the entire range of CBS values.

Lower Incidence of Symptomatic Vasospasm after Subarachnoid Hemorrhage owing to Ruptured Vertebrobasilar Aneurysms

Neurosurgery ◽  
2005 ◽  
Vol 57 (6) ◽  
pp. 1110-1116 ◽  
Author(s):  
Yutaka Hirashima ◽  
Masanori Kurimoto ◽  
Emiko Hori ◽  
Hideki Origasa ◽  
Shunro Endo
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Multivariate Analyses ◽  
Multiple Logistic Regression Analysis ◽  
Posterior Circulation ◽  
Anterior Circulation ◽  
Symptomatic Vasospasm ◽  
Group 3 ◽  
The Difference ◽  
First Time ◽  
Vertebrobasilar Aneurysms

Abstract OBJECTIVE: In this study, we evaluated the difference in incidence of symptomatic vasospasm between ruptured aneurysms in the anterior and posterior circulation using multiple logistic regression analysis. METHODS: A total of 145 consecutive patients who underwent surgery for aneurysms within 72 hours after subarachnoid hemorrhage (SAH) were studied. RESULTS: The ruptured aneurysm was in the anterior circulation in 128 patients (88.3%) and in the posterior circulation in 17 patients (11.7%). Forty patients (27.6%) had symptomatic vasospasm and 105 patients (72.4%) did not. Univariate and multivariate analyses were performed to assess relationships among various variables and the occurrence of symptomatic vasospasm after SAH. Finally, Grade III to V (Hunt and Hess grade) and Group 3 (Fisher's classification) on admission were found to be independently positively associated with the occurrence of symptomatic vasospasm while ruptured vertebrobasilar aneurysm were negatively associated. CONCLUSION: Although a poor clinical grade and a severe SAH classification on admission such as Hunt and Hess grade and Fisher's classification are established powerful predictors of symptomatic vasospasm, ruptured vertebrobasilar aneurysm are for the first time reported to be a predictor of symptomatic vasospasm based on results of a recent reliable statistical analysis.

scholarly journals NIH Stroke Scale as a Predictor of Clot Presence, Location, and Persisting Occlusion in Candidates for Thrombolysis

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 324-324
Author(s):  
W Scott Burgin ◽  
Anne W Wojner ◽  
James C Grotta ◽  
Andrei V Alexandrov
Keyword(s):  
Arterial Occlusion ◽  
Vascular Occlusion ◽  
Inclusion Criteria ◽  
Stroke Patients ◽  
Anterior Circulation ◽  
Conventional Dose ◽  
Clot Burden ◽  
Vascular Patency ◽  
Time Of Presentation ◽  
Iv Tpa

46 Background: In acute stroke, few tools are readily available to determine clot presence and location before thrombolysis, nor whether occlusion persists after intravenous TPA. Because the NIH Stroke Scale (NIHSS) is easily obtained in the Emergency Department, we correlated sequential NIHSS scores and arterial occlusion in prospective candidates for IV TPA. Methods: Potential thrombolysis patients evaluated with transcranial Doppler (TCD) ultrasound and the NIHSS at the time of presentation were studied. TCD was performed using previously validated criteria for clot detection, localization, and subsequent degree of recanalization after thrombolysis. In patients treated at <180 minutes with conventional dose TPA (0.9 mg/kg), repeat NIHSS scores and diagnostic TCD were performed at the end of infusion. Results: 119 ischemic stroke patients met inclusion criteria (age 68±15, NIHSS 15±7, median 14, range 2–36), with 83% having occlusion consistent with symptoms. Occlusion was present in all patients with NIHSS ≥22, none with NIHSS <4, and there was a direct relationship between baseline NIHSS and clot presence (p<0.0001). Each additional NIHSS point increased the odds of occlusion by 1.33(95%CI 1.17–1.51). In patients with anterior circulation symptoms (N=80), increasing NIHSS corresponded with increasing M1 MCA and/or ICA occlusion, and decreasing vascular patency or M2 occlusion (p<0.001). In thrombolysed patients with initial vascular occlusion (N=55), end-of-infusion NIHSS was less predictive of persisting occlusion, with 70% of patients with scores ≥6 having persisting occlusion and 20% of patients with scores ≥16 having complete recanalization. The odds of persisting occlusion per end-of-infusion NIHSS point were 1.14 (95%CI 1.06–1.24,p <0.0008). Conclusions: Baseline NIHSS accurately predicts clot presence with increasing scores corresponding to increasing clot burden. However, NIHSS becomes less predictive of clot persistence at the end of TPA infusion and may less accurately identify patients for further revascularization efforts.

Abstract TP73: Heterogeneity of Occlusive Thrombus Investigated on Pretreatment Imaging in Acute Ischemic Stroke

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Tristan Honda ◽  
Fabien Scalzo ◽  
Latisha K Sharma ◽  
Jason D Hinman ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Hounsfield Unit ◽  
Blood Platelet ◽  
Multivariate Regression Analysis ◽  
Distal Segment ◽  
Reperfusion Therapy ◽  
Filling Defect ◽  
Proximal Segment ◽  
Stroke Subtype ◽  
Anterior Circulation

Background and Purpose: Investigation of occlusive thrombus in ischemic stroke is expected to clarify the etiology and mechanism of stroke fueling an optimal treatment strategy. However, in situ propagation due to secondary thrombosis after initial embolic occlusion could obscure the characteristics of initial emboli. Differentiation of the initial embolus and secondary thrombosis using retrieved specimens might be difficult due to fragmentation of whole thrombi. We aimed to investigate the heterogeneity of occlusive thrombi using pretreatment imaging of ischemic stroke. Methods: Among consecutive stroke patients with acute embolic occlusion of the anterior circulation eligible for endovascular reperfusion therapy, we retrospectively reviewed 81 patients who underwent both brain non-contrast CT (NCCT) and CT angiography (CTA) on admission from June 2015 to May 2018. Region of interest (ROI) was set on the whole thrombus on NCCT, which was identified referring to the filling defect on CTA, and the size of thrombus was measured. ROI was then divided equally into proximal and distal segments and Hounsfield Unit (HU) densities of those segments were measured respectively. Difference of HU between proximal and distal segments (ΔHU; HU in proximal segment - HU in distal segment) was calculated and analyzed. Results: HU density on NCCT in proximal segment was higher than in distal segment (mean difference: 3.75, 95% CI: 2.69-4.80, p<0.01). ΔHU was correlated positively with the length of thrombus (ρ=0.32, p<0.01), and correlated inversely with the time from last-known-well (LKW) to imaging (ρ=-0.29, p=0.01) and blood platelet level (ρ=-0.27, p=0.02). Stroke subtype and vascular risk factors had no significant correlation with ΔHU. On multivariate regression analysis, the length of thrombus (β=0.31, p=0.01) and the time from LKW to imaging (β=-0.30, p=0.01) were associated with ΔHU. Conclusions: Density of occlusive thrombi in the proximal segment is higher than in the distal segment. This difference increases as thrombi grow longer and decreases as thrombi get older after embolic occlusion. This time/length-dependent thrombus heterogeneity is suggestive of secondary thrombosis, occurring initially at the proximal side of occlusion.

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