Comprehensive Evaluation Study Of Atherosclerotic Plaque In The MCA Using High-Resolution Magnetic Resonance Imaging

Background and purposeRecently,high-resolution magnetic resonance imaging(hrMRI)has been gradually applied for the evaluation of intracranial atherosclerosis.The objectives of present study were to assess the vulnerability and the risk of recurrence of the atherosclerotic plaques in the middle cerebral artery(MCA)based on hrMRI.1)to assess the age-related differences in hrMRI findings of target lesions in patients with MCA stenosis;2)to analyze and compare vascular morphological features and components characteristics qualitatively and quantitatively between patients with symptomatic and asymptomatic atherosclerotic stenosis in MCA;3)to assess the complementary value of hrMRI in identifying symptomatic patients with MCA atherosclerosis who are likely to experience recurrent ischemic cerebrovascular events;4)evaluating the dynamic changes of hrMRI imaging characteristics after standard medicine treatment in patients with MCA atherosclerosis,and exploring their association with future ischemic events.MethodsIn this retrospective cohort study,patients with MCA stenosis attributed to atherosclerosis who underwent hrMRI examination between January 2014 and December 2019 were included.Inner and outer wall and various plaque components i.e.lipid,fibrous tissue,intraplaque hemorrhage,and enhancement were manually delineated and segmented using a custom-developed tool.Plaque characteristics,including morphological features and components features were evaluated qualitatively and quantitatively.All patients were grouped according to an increase of 10 years of age,and the association of age with plaque characteristics were assessed.A univariate/multivariate logistic regression analysis was performed to identify the independent variables related to the culprit plaque.All symptomatic patients were followed clinically up to 6 years and recurrent ischemic cerebrovascular events were recorded.Cox regression analysis and time-dependent ROC were performed to qualify the association between the plaque characteristics and recurrent events.Plaque progression was calculated on images from both examinations.Association of changes of imaging variables and future ischemic events were examined by using Cox regression analysis.ResultsPart 1.The 283 patients(mean age 51.0±11.7,203 males)with MCA stenosis were classified into 4 groups:Group Ⅰ[<40 years(n=52)];Group Ⅱ[40-49 years(n=70)];Group Ⅲ[50-59 years(n=100)];Group Ⅳ[≥60 years(n=61)].Negative remodeling was most common,and eccentricity index,plaque length,and fibrous volume was greatest in Group Ⅳ.In the multiple logistics regression analysis,patient age was an independent predictor of negative remodeling(OR-1.782;P<0.001)and fibrous volume(OR=1.350;P=0.019).Part 2.Plaque characteristics were analyzed and compared in the 283 patients(215 symptomatic,68 asymptomatic)with atherosclerotic stenosis of the MCA.For morphological features,we found that irregular plaque surface,the degree of lumen stenosis,eccentricity index,remodeling index,average of wall thickness and wall volume were significantly greater in the symptomatic group than in the asymptomatic group.Moreover,multivariate logistic regression identified that the discontinuity of the plaque surface(OR=2.204;P=0.019),positive remodeling(OR=2.577;P=0.005),and larger wall volume(OR=1.011;P=0.001)were independent risk factors of symptomatic MCA stenosis.And for componence features,lipid core volume(P<0.001)and enhancement volume(P<0.001)were independent predictors of the culprit plaque after multivariate logistic regression.Part 3.During the follow up,46 patients experienced recurrent ischemic cerebrovascular events.Patients with poor medication persistence and greater lipid volume were more likely to experience recurrent events.After adjustment of covariates,lipid volume(HR=1.033;P=0.023),HbAlc(HR=1.209;P=0.014),and medication persistence(HR=2.657;P=0.001)were independent biomarkers associated with recurrent events.Part 4.48 patients who underwent multiple hrMRI scanning were followed clinically.After the last hrMRI scan,22.4%of patients(N=11)had experienced ipsilateral ischemic events.Multivariable Cox regression indicated that progression of volume of lipid core(HR=1.459;P=0.001)and enhancement(HR=1.060;P=0.001)were independent imaging features for future ischemic events.Conclusion1.Elderly patients have more severe fibrous tissue with negative remodeling,whereas youngers patients have more positive remodeling.2.Patients with symptomatic atherosclerotic stenosis of MCA were more likely to have irregular surface of plaque,positive remodeling,and large wall volume for morphological features.3.Patients with symptomatic atherosclerotic stenosis of MCA were more likely to have large lipid volume and enhancement volume.Additionally,large lipid volume was the significant predictors of stroke recurrence among symptomatic MCA stenosis4.Plaques show significant regression after standard medicine therapy.However,the progression of lipid core and enhancement volume were independently associated with future ischemic events.