Participants
This study was approved by the Institutional Review Board of Changhai Hospital of Shanghai (No.CHEC2018-092) and Zhongshan Hospital (No.B2022-112R), and written informed consent was obtained from all patients. This prospective study was an observational cohort study19, which included patients admitting to Changhai Hospital of Shanghai from January 2019 to March 2021 and Zhongshan hospital from March 2022 to January 2023 for acute ischemic stroke due to ICAS. And all the patients underwent a 3D head&neck hr-VW-MRI prior to admission and had intensive medical management within 90 days (dual antiplatelet therapy [clopidogrel at an initial dose of 300 mg, followed by 75 mg/d for 90 days, plus aspirin at a dosage of 100 mg/d] and high-intensity statins [40 mg daily]) according to previous studies20,21 and guidelines22,23.
The inclusion criteria were as follows: 1) acute ischemic stroke (having acute ischemic symptoms and diffusion weighted imaging [DWI] positive for no more than 2 weeks), 2) intracranial arterial focal wall thickness > 1mm on hr-VW-MRI24, and 3) more than one atherosclerotic risk factor, including hypertension, diabetes mellitus, hypercholesterolemia, or cigarette smoking.
Patients with the following conditions were excluded: 1) subacute stroke or transient ischemic attack (TIA); 2) underwent head or neck arterial stenting after a period of in-hospital intensive treatment; 3) hr-VW-MRI revealed significant stenosis of the extracranial carotid arteries (stenosis ≥ 50%) and/or the presence of vulnerable carotid plaques including a lipid-rich necrotic core on T1-weighted fat-suppressed images, intraplaque hemorrhage (IPH) and obvious enhancement;25 4) presence of ascending aortic arch atheroma as identified on MRA (defined as plaque thickness > 4 mm);26 5) nonatherosclerotic intracranial arterial disease including aneurysms with intervention therapy, vasculitis, moyamoya disease, dissection, reversible cerebral vasoconstriction syndrome, and intracranial dolichoectasia; 6) suspected cardiogenic thrombosis as assessed on cardiac Doppler ultrasound or cardiac CTA; 7) known coagulopathy; 8) heart failure or respiratory failure; 9) renal dysfunction (serum creatinine > 133 µmol/liter); 10) serious disturbance of consciousness; 11) intracranial hemorrhage; and 12) clinical contraindications to MRI, such as patients with pacemakers, certain types of metallic implants, or severe claustrophobia.
Clinical Data Collection
The demographic and clinical characteristics, including age, sex, body mass index, hypertension, hyperlipidemia, diabetes mellitus, smoking, and medication usage, were collected from the clinical record. According to these clinical features, ABCD2 scale were be calculated.27 All patients underwent NIHSS, Glasgow Coma Scale, and Modified Rankin Scale assessment upon admission and post-treatment at follow-up.28
Lab examinations of blood samples, which are highly related to atherosclerosis, were collected at admission as follows: fasting blood glucose, glycated hemoglobin, hemoglobin, cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein, apolipoprotein A1, apolipoprotein B, homocysteine, serum uric acid, erythrocyte sedimentation rate, lipoprotein(a), and C-reactive protein.
Follow-up Data Collection
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Evaluation of exercise: Post-discharge physical activities were assessed referring to the 2015 standards by the American College of Sports Medicine.29 Those who consistently engaged in physical activities more than 3 days a week were considered to take exercise. By inquiring, it was documented.
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High-risk control: Patients with hypertension and diabetes were further grouped according to the following management types before admission: 1) no management, if the patient did not receive any treatment or had irregular treatment/monitoring; and 2) strict control, when the patient received treatment and monitoring regularly for more than 5 days per week.
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Definition of ischemic recurrence: Recurrent ischemic events referred to the incidence of subsequent ischemic stroke (evidenced by hyperintense signals on DWI images) in the ipsilateral responsible vascular territory. Such recurrence of ischemic stroke was designated as the endpoint event for the current research. The assessment and collection of follow-up information were conducted by a neurologist by clinical visit or telephone interview, who was blind to the patients' MRI results.
MRI Acquisitions
Patients in Changhai Hospital underwent MRI scan on 3.0-T whole-body MR systems (MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany) using a 20-channel head coil combined with an 8-channel neck coil. And the MRI data from Zhongshan Hospital were acquired on a 3.0-T MRI scanner (uMR 790, United Imaging Healthcare, Shanghai, China) with a 24-channel receiver head coil combined with an 8-channel neck coil. Both acquisitions were kept for the head and neck joint scanning. The MRI protocol included T1-weighted imaging, post-contrast T1-weighted imaging, fluid-attenuated inversion recovery (FLAIR), DWI and time-of-flight MRA with more protocol details in the Table-S1. Post-contrast T1-weighted images were acquired using a dose of 0.2 mmol/kg Gd-DTPA injected by power injector at a rate of 2 mL/seconds followed by 15 mL of physiological saline.
Imaging Analysis
All the MR images were analyzed by two experienced radiologists in vessel wall imaging (one with 8 years’ experience, and one with 12 years’ experience). The culprit vessel was defined as the artery arising on the ipsilateral side to a fresh infarction on the DWI images with accompanying clinical symptoms. Any disagreement was resolved by consensus.
The VesselMass software (Leiden University Medical Center, The Netherlands) was employed for semi-automatic delineation of plaques and automatic alignment of hr-VW-MRI scans encompassing T1-weighted imaging, post-contrast T1-weighted imaging and T2-weighted imaging. Manual correction was performed on all thickened vessel wall slices to obtain the inner and outer boundary at the proximal and distal non-stenotic slices of the lesion. Various metrics related to the plaque were calculated, primarily comprising quantitative metrics such as, minimum luminal area (MLA) stenosis rate (SR), plaque volume (PV), enhancement ratio (ER), plaque burden (PB), remodeling ratio (RR), eccentricity index (EI), and qualitative metrics including intraplaque hemorrhage (IPH). (The definitions of these features shown in Supplementary file)
The histogram features of plaques were quantified using methods from our previous study.18 The mean, standard deviation (SD), minimum, maximum, medians, coefficient of variation (CV) and entropy values of each plaque region were calculated.
Reproducibility
To evaluate the reproducibility of the imaging measurements, inter-reader agreement in measuring quantitative plaque morphology was evaluated on baseline images selected at random from 60 patients in the study population. And images were reviewed by one reader with one with 8 years’ experience twice with an interval of 12 weeks to avoid bias. The same MR images were independently reviewed by another reader with 12 years’ experience for testing the inter-observer agreement during the first time measured by the first reader.
Statistical Analysis
1) The calculation of sample size was shown in Supplementary file.
2) All statistical analysis was undertaken using SPSS (version 24.0, IBM, Chicago, IL). The mean and SD were recorded for continuous variables, and the frequency and percentage were recorded for categorical variables. Univariable analysis was first performed. Two-sample t-test, chi-square test or Mann-Whitney U-test was applied to evaluate group differences according to requirement. A Kaplan-Meier survival analysis was performed to estimate the cumulative event-free rates. Univariable and multivariable Cox regression analyses were used to calculate the hazard ratio (HR) and corresponding 95% confidence interval (CI) of the plaque features in discriminating between patients with and without recurrent events. Variables with P < 0.10 in univariable analysis were selected as inputs for the multivariable model and then underwent sequential backward elimination to a P value < 0.05. The diagnostic performance was described using receiver operating characteristic (ROC) curves and area under curve (AUC) values. ROC curves were compared using the method developed by DeLong et al30. The inter-reader reproducibility of continuous variables was evaluated using the intra-class coefficient (ICC) with a two-way random-effects model with absolute measurements, while the Kappa value was determined for the categorical variables. All tests were two-sided and a P value < 0.05 was considered significant.