The Correlation Between CT Imaging Features And Clot Composition In Acute Ischemic Stroke And Its Role On Recanalization Outcomes Of Thrombectomy

Background:Mechanical thrombectomy(MT)is widely used for acute ischemic stroke(AIS)caused by large vessel occlusion,and make it possible for histopathologic analysis of intracranial clots.Histological composition of thrombus determines its physical property,and could impact recanalization outcomes of MT.As imaging markers could implicate clot composition,it might also correlate with recanalization outcomes.Purposes:1)To explore the correlation between CT-based imaging markers and clot composition.2)To explore the correlation between CT-based thrombus density and recanalization outcomes based on different thrombectomy technique.3)To explore the correlation between secondary embolism events and clot composition,as well as imaging markers.Methods:AIS patients who underwent endovascular treatments at Beijing Hospital between July 2015 and December 2019 were reviewed.1)Thrombus density was recorded as mean Hounsfield unit(HU)value of clot on non-enhanced CT;and clot perviousness was evaluated as an increase in HU value based from contrast-enhanced CT compared to non-enhanced CT The clots were stained with hematoxylin and eosin,Martius Scarlet Blue,and immunohistochemistry.The proportion of erythrocytes,fibrin and platelets in each clot was quantified using Orbit Imaging Analysis Software.Spearman rank correlations and Mann-Whitney U test were used to detect the correlation between imaging parameters(thrombus density,clot perviousness)and each component(erythrocytes,fibrin,platelets)in clots.2)Among patients with anterior circulation AIS,logistic regression analysis was adopted to compare the recanalization outcomes between stent retriever(SR)(including combined technique)and contact aspiration(CA)technique;and subgroup analysis was performed according to the presence of hyperdense artery sign(HAS).In addition,student t test was used to compare the difference in thrombus density between successful(mTICI 2b-3)and unsuccessful reperfusion(mTICI 0-2a)groups;and subgroup analysis was performed according to frontline thrombectomy technique(SR,CA,combined technique).3)Secondary embolism event was identified when the following situation occurred:after the primary occlusion site was recanalized,a new occlusion appeared downstream or in a new-territory of the primary occluded vessel.Among patients with anterior circulation AIS,logistic regression analysis was used to detect the risk factors of secondary embolism.The prediction models of secondary embolism were built and the corresponding nomograms were drawn.Results:1)Relative thrombus density showed a significantly positive correlation with erythrocyte fractions[dHU(r=0.337,p=0.014),rHU(r=0.365,p=0.007)];thrombus with HAS had more erythrocyte fractions than those without HAS(41.1%vs 20.6%,p=0.007).Clot perviousness showed a significantly negative correlation with the proportion of platelets[δHU(r=-0.577,p<0.001),εHU(r=-0.573,p<0.001)];pervious clots had less platelet fractions than impervious clots(19.0%vs 33.9%,p=0.003).2)There showed no significant difference in recanalization outcomes between SR(including combined technique)and CA technique.Among patients who presented with HAS,SR(including combined technique)showed a relatively higher proportion of successful reperfusion after first-pass of maneuvers(OR 4.43,95%CI 0.91 to 21.45,p=0.065),as well as after frontline strategy(OR 3.73,95%CI 0.78 to 17.76,p=0.099)compared with those who received CA technique.While for patients without HAS,the recanalization outcomes between SR(including combined technique)and CA techniuqe were relatively comparable.Additionally,the difference in thrombus density between successful and unsuccessful recanalization were compared.After first-pass of CA,the thrombus density(aHU)was lower in patients with successful reperfusion than those without successful reperfusion(MD-8.09,95%CI-13.07 to-3.10,p=0.003).After first-pass of SR,the thrombus density(aHU)in patients with successful reperfusion was relative higher than those without successful reperfusion(MD 3.27,95%CI-3.3 to 10.28,p=0.301).3)For patients with anterior circulation AIS,we built a multivariate analysis to detect the correlation between secondary embolism and clot composition,showing that lower clot burden score(OR 0.71,95%CI 0.54 to 0.89,p=0.006)and higher erythrocyte fractions(OR 1.05,95%CI 1.00 to 1.10,p=0.045)were independent risk factors for secondary embolism events.In view of the correlation between thrombus density and erythrocyte fractions,the relative thrombus density(dHU)were included in logistic regression analysis instead of erythrocyte fractions to build a prediction model for secondary embolism events.The parameters of prediction model were as follows:clot burden score(OR 0.78,95%CI 0.66 to 0.92,p=0.004),relative thrombus density(dHU)(OR 1.05,95%CI 0.97 to 1.15,p=0.239),and a history of cerebral infarction or transient ischemic attacks(OR 2.53,95%CI 0.81 to 8.25,p=0.112);the C-index was 0.801 and the area under the receiver operating characteristic curve was 0.801,indicating a moderate predictive ability.Conclusions:To sum up,1)The relative thrombus density was positively correlated with the content of erythrocytes,while clot perviousness was negatively correlated with the proportion of platelets.2)For patients presented HAS,SR(including combined technique)showed a relatively higher proportion of successful reperfusion after first-pass of maneuvers compared with CA technique,though there was no significant statistical difference.After first-pass of CA,the thrombus density in patients with successful reperfusion was lower than those without successful reperfusion,which indicated that CA might be more efficient for lower density thrombus;while an inverse tendency was observed in SR subgroup.3)Lower clot burden score and higher erythrocyte fractions were independent risk factors for secondary embolism events.Our study suggested the correlation between CT-based imaging markers and clot composition,as well as the correlation between thrombus density and recanalization outcomes of MT.However,this study was retrospective with a small sample size,and some results only showed statistical trend without significant difference.Hence,the conclusions should be drawn with caution.