Thrombus volume and Hounsfield unit density as a predictor of pulmonary embolism in patients with deep vein thrombosis.

BACKGROUND: There is a lack of studies evaluating the association between thrombus volume and density of deep vein thrombosis (DVT) and pulmonary embolism (PE). PURPOSE: To assess the clinical value of thrombus volume and density for prediction of PE in patients with DVT. MATERIAL AND METHODS: Among the patients with DVT, those without PE were classified as the "DVT-only group" and those with PE were classified as the "DVT-PE group." Thrombus volume and Hounsfield unit (HU) density of DVT was measured by drawing free-hand volume of interests within the thrombus. Multivariate regression and receiver operating characteristic (ROC) analysis was used to evaluate the predictive value of thrombus volume and density for PE. RESULTS: Of the included 145 patients (mean age=41.7 ± 10.3 years), there were 87 patients in the DVT-only group and 58 patients in the DVT-PE group. The DVT-PE group showed a significantly higher DVT density (67.4 ± 8.6 HU vs. 57.3 ± 10.4 HU; P < 0.001) and larger DVT volume (16.4 ± 13.9 cm3 vs. 12.8 ± 10.1 cm3; P = 0.016) than the DVT-only group. On multivariate analysis, thrombus density was the only associated factor for PE. ROC analysis showed that thrombus density ≥61.8 HU was the optimal cutoff for predicting PE with an area under the curve (AUC) of 0.774 and thrombus volume ≥14.0 cm3 was the cutoff with an AUC of 0.638. CONCLUSION: Though the results of our study should be considered within the limitations, DVT density could be a predictor for acute PE. Further studies are needed to clarify the clinical value of quantitative features of DVT including thrombus volume as an imaging biomarker for PE.

Association of thrombus density and endovascular treatment outcomes in patients with acute ischemic stroke due to M1 occlusions.

PURPOSE: We aimed to study the association of non-contrast CT (NCCT) thrombus density with procedural and clinical outcomes in patients with acute ischemic stroke who underwent endovascular treatment (EVT). Since thrombus density is associated with thrombus location, we focused on M1 occlusions only. METHODS: Patients with available thin-slice (< 2.5 mm) NCCT were included from a nationwide registry. Regression models were used to assess the relation between thrombus density (per Hounsfield unit [HU]) and the following outcomes. For reperfusion grade, adjusted common odds ratios (acOR) indicated a 1-step shift towards improved outcome per HU increase in thrombus density. For the binary outcomes of first-pass reperfusion (first-pass extended thrombolysis in cerebral infarction [eTICI] 2C-3, FPR), functional independence [90-day modified Rankin Scale (mRS) score of 0-2] and mortality), aORs were reported. Adjusted ß coefficients (aß) were reported for 24-h NIHSS and procedure duration in minutes. Outcome differences between first-line treatment devices (stent retriever versus aspiration) were assessed with interaction terms. RESULTS: In 566 patients with M1 occlusions, thrombus density was not associated with reperfusion (acOR 1.01, 95% CI 0.99-1.02), FPR (aOR 1.01, 95% CI 0.99-1.03), mortality (aOR 0.98, 95% CI 0.95-1.00), 24-h NIHSS (aß - 0.7%, 95% CI - 1.4-0.2), or procedure duration (aß 0.27, 95% CI - 0.05-0.58). In multivariable analysis, thrombus density was associated with functional independence (aOR 1.02, 95% CI 1.00-1.05). No interaction was found between thrombus density and first-line treatment device for any outcome. CONCLUSION: In patients with M1 occlusions, thrombus density was not clearly associated with procedural and clinical outcomes after EVT.

CT-based Higher Thrombus Density is associated with Secondary Embolism during Mechanical Thrombectomy: A Preliminary Observation.

BACKGROUND: Secondary embolism (SE) during mechanical thrombectomy (MT) for acute ischemic stroke (AIS) is the main reason for incomplete recanalization, while its risk factors are largely unknown. This study addresses a potential relationship between thrombus density on preinterventional computed tomography (CT) and the occurrence of SE. METHODS: We reviewed anterior circulation AIS patients who underwent MT from July 2015 to January 2019 in our center. Thrombus density was measured in Hounsfield Units (HU) on 1-mm and 5-mm preinterventional nonenhanced CT (NECT). Thrombus density, baseline characteristics, procedural, and clinical outcomes were compared between patients with SE and those without SE. Logistic regression was conducted to identified potential risk factors of SE. RESULTS: Sixty-four consecutively patients were included, of whom SE was identified in 16 (25.0%) patients. Compared with those without SE, patients with SE showed a higher thrombus density on both 1-mm (72.85 versus 64.28, P = .005) and 5-mm NECT (60.31 versus 49.71, P < .001), a higher proportion of atrial fibrillation (75.0% versus 45.8%, P = .043), a lower clot burden score (.5 versus 6.0, P = .029), and a higher proportion of front-line contact aspiration strategy (50.0% versus 16.7%, P = .020). Multivariate regression analysis showed that only thrombus density was the independent predictor of SE (for the model including HU values on 1-mm NECT, OR 1.11, 95%CI 1.01-1.23, P = .029; for the model including HU values on 5-mm NECT, OR 1.09, 95%CI 1.02-1.17, P = .018). CONCLUSIONS: Higher thrombus density was the independent predictor for SE. Further studies are needed to investigate its role in the optimization of thrombectomy strategy.

Histological composition behind CT-based thrombus density and perviousness in acute ischemic stroke.

BACKGROUND: Clot composition could impact recanalization outcomes of thrombectomy, and preoperative imaging markers may help know about the histological components of thrombus. METHODS: Consecutive patients who underwent thrombectomy from June 2017 to December 2019 were reviewed. The mean Hounsfield unit (HU) of thrombus (aHU) and contralateral artery (cHU) were recorded based on non-enhanced CT. The relative thrombus density was calculated (dHU=aHU-cHU). Hyperdense artery sign (HAS) was identified if dHU≥ 4HU. The clot perviousness was evaluated via thrombus attenuation increase (δHU) on contrast-enhanced CT compared to non-enhanced CT. Pervious clots were identified when δHU≥ 11HU. Tissue quantification for thrombus was based on Martius Scarlet Blue staining, using the Orbit Imaging Analysis Software. Spearman rank correlations was used to detect the association between imaging markers and clot composition. The differences in clinical characteristics were compared according to the presence of HAS or pervious clots. RESULTS: Fifty-three patients were included. The dHU was positively correlated with erythrocyte fractions (r = 0.337, p = 0.014), while there was no significant association between aHU and erythrocyte components (r = 0.146, p = 0.296). HAS (+) patients showed a comparable proportion of modified Thrombolysis In Cerebral Infarction (mTICI) 2b-3 (94.6% vs. 87.5%, p = 0.740) and modified Rankin Scale score (mRS) 0-2 (35.1% vs. 56.3%, p = 0.152) compared with those HAS (-). Forty-seven cases were available for the analysis of clot perviousness. Clot perviousness was negatively associated with platelet fractions (r = -0.577, p < 0.001). Patients with pervious clots also showed a comparable proportion of mTICI 2b-3 (86.2% vs. 100%, p = 0.283) and mRS 0-2 (37.9% vs. 50.0%, p = 0.416) compared with impervious clots. CONCLUSIONS: This study suggests that relative thrombus density was positively correlated with erythrocyte fractions, while clot perviousness showed a negative relationship with platelet components. Yet, the presence of HAS or pervious clots did not show significant associations with recanalization and clinical outcomes. The conclusions should be drawn with caution.

Post-EVAR Thrombus Density on Late Non-Contrast CT Scans Predicts Successful Aneurysm Exclusion.

PURPOSE: The incidence of type II endoleaks (ELII) after endovascular aneurysm repair (EVAR) ranges from 10-44%. Aneurysm thrombus density after EVAR could predict successful aneurysm exclusion. MATERIALS AND METHODS: Twenty-seven patients with an abdominal aortic aneurysm (AAA) who had a CT scan within the first 45 days (early group) post-surgery or after 7 months (late group) were included. Thrombus density was analyzed on non-contrast enhanced CT scans. RESULTS: A total of 5/13 (38%) patients in the early group had an ELII and 9/14 (64.3%) in the late group had a persistent ELII since surgery. In the early group, thrombus density was similar in patients with or without an ELII (mean: 39.9 ± 4.8 vs. 41.9 ± 3.4, p = 0.7; median: 38.7 ± 4.8 vs. 39.7 ± 3.1, p = 0.8). In patients with an ELII, there was no difference in thrombus density at 45 days and after 7 months (mean: 39.9 ± 4.8 vs. 40.2 ± 2.1, p = 0.9; median: 38.7 ± 4.8 vs. 38 ± 2.6, p = 0.9). In patients without an ELII, thrombus density was significantly higher at 45 days than after 7 months (mean: 41.9 ± 3.44 vs. 25.7 ± 2.0, p = 0.005; median: 39.7 ± 3.11 vs. 24.4 ± 1.5, p = 0.004). In patients with an ELII, thrombus density was significantly higher after 7 months than in patients without an ELII (mean: 40.2 ± 2.1 vs. 25.7 ± 2.0. p = 0.001; median: 38 ± 2.6 vs. 24.4 ± 1.5, p = 0.003). CONCLUSION: Low thrombus density after EVAR on late unenhanced CT scans predicts aneurysm exclusion.

Influence of Onset to Imaging Time on Radiological Thrombus Characteristics in Acute Ischemic Stroke.

Introduction: Radiological thrombus characteristics are associated with patient outcomes and treatment success after acute ischemic stroke. These characteristics could be expected to undergo time-dependent changes due to factors influencing thrombus architecture like blood stasis, clot contraction, and natural thrombolysis. We investigated whether stroke onset-to-imaging time was associated with thrombus length, perviousness, and density in the MR CLEAN Registry population. Methods: We included 245 patients with M1-segment occlusions and thin-slice baseline CT imaging from the MR CLEAN Registry, a nation-wide multicenter registry of patients who underwent endovascular treatment for acute ischemic stroke within 6.5 h of onset in the Netherlands. We used multivariable linear regression to investigate the effect of stroke onset-to-imaging time (per 5 min) on thrombus length (in mm), perviousness and density (both in Hounsfield Units). In the first model, we adjusted for age, sex, intravenous thrombolysis, antiplatelet use, and history of atrial fibrillation. In a second model, we additionally adjusted for observed vs. non-observed stroke onset, CT-angiography collateral score, direct presentation at a thrombectomy-capable center vs. transfer, and stroke etiology. We performed exploratory subgroup analyses for intravenous thrombolysis administration, observed vs. non-observed stroke onset, direct presentation vs. transfer, and stroke etiology. Results: Median stroke onset-to-imaging time was 83 (interquartile range 53-141) min. Onset to imaging time was not associated with thrombus length nor perviousness (ß 0.002; 95% CI -0.004 to 0.007 and ß -0.002; 95% CI -0.015 to 0.011 per 5 min, respectively) and was weakly associated with thrombus density in the fully adjusted model (adjusted ß 0.100; 95% CI 0.005-0.196 HU per 5 min). The subgroup analyses showed no heterogeneity of these findings in any of the subgroups, except for a significantly positive relation between onset-to-imaging time and thrombus density in patients transferred from a primary stroke center (adjusted ß 0.18; 95% CI 0.022-0.35). Conclusion: In our population of acute ischemic stroke patients, we found no clear association between onset-to-imaging time and radiological thrombus characteristics. This suggests that elapsed time from stroke onset plays a limited role in the interpretation of radiological thrombus characteristics and their effect on treatment results, at least in the early time window.

Association Between Thrombus Density and Reperfusion Outcomes Using Different Thrombectomy Strategies: A Single-Center Study and Meta-Analysis.

Background: For patients with acute ischemic stroke (AIS), the thrombus density on non-enhanced CT (NECT) indicates the composition of the thrombus, a characteristic that impacts the efficacy of mechanical thrombectomy (MT). A previous meta-analysis suggested a correlation between higher thrombus density and successful reperfusion, but some new studies have drawn different conclusions. This single-center study and meta-analysis aimed to detect the association between thrombus density and reperfusion outcomes based on various thrombectomy strategies. Methods: We reviewed AIS patients who underwent MT at our center between July 2015 and May 2019. Thrombus density was recorded as mean Hounsfield Unit (HU) value on 1-mm reconstructed NECT, and expanded Thrombolysis In Cerebral Infarction (eTICI) scale was used to evaluate the reperfusion grade. The difference in thrombus density was examined according to reperfusion outcomes. Then, we systematically searched relevant literature on this issue. The random effect model was used to calculate standardized mean difference (SMD), and subgroup analysis was conducted according to MT strategies employed, including stent retriever (SR), contact aspiration (CA), Solumbra (a combination of SR and aspiration), and multiple thrombectomy modalities. Results: Sixty-four patients with anterior circulation AIS were included in our single-center study with 57 (89.1%) achieving successful reperfusion (eTICI2b-3). Retrospective analysis showed no significant difference in thrombus density between eTICI2b-3 and eTICI0-2a reperfusion (65.27 vs. 62.19, p = 0.462). As for systematic review, 11 studies were included in qualitative analysis, among which 6 had data available for meta-analysis. Pooled result showed that a comparable thrombus density between eTICI2b-3 and eTICI0-2a reperfusion (SMD 0.14, 95%CI -0.28 to 0.57, p = 0.50). Interestingly, in the SR subgroup, eTICI2b-3 reperfusion showed a significant higher thrombus density (SMD 0.53, 95%CI 0.10 to 0.96, p = 0.02), while an inverse trend was observed in the CA subgroup (SMD -0.48, 95%CI -0.88 to -0.07, p = 0.02). Conclusions: Although the pooled result of meta-analysis did not show a significant association between thrombus density and successful reperfusion, subgroup analysis implicated that the SR technique might be prone to retrieve high-density thrombus, while the CA subgroup showed an opposite tendency. Further studies are needed to confirm these results and to investigate its role in the optimization of thrombectomy strategy.