2.1 | Patients
One hundred and fifteen cases, including 76 males and 39 females, with acute stroke, hospitalized in the Department of Neurology, Gaozhou People's Hospital between January 2020 and March 2021 were included in the study. The age of the study population ranged from 47 to 91 years, with a mean age of 70.0±10.1 years. In all the patients, computed tomography (CT) or magnetic resonance imaging (MRI) was used to arrive at the diagnosis of atherosclerotic cerebral infarcts. In a calm state, the systolic (SBP) and diastolic (DBP) blood pressure of brachial artery were assessed thrice and the mean values were calculated. In the morning, fasting state venous blood sample (3ml) was collected to evaluate the fasting blood glucose, and lipid profile.
The cases belonging to an age group of 18 years or more, with an initial stroke involving carotid artery territory confirmed by MRI or CT, an ultrasonography demonstrating plaques in carotid artery with a size of 2 mm or more, and those willing to follow-up for 15 months were included in the study. While, cases allergic to sulfur hexafluoride, and with contraindication to CEUS were excluded [8, 9]. Moreover, to exclude the influence of stenosis, patients with severe stenosis (70% or more, according to NASCET) of carotid artery were not included. The present study focused on the vulnerability of carotid plaques and the recurrence of cerebral infarct was the end point of the study.
The study protocol was reviewed and approved by the Ethics Review Committee, Gaozhou People's Hospital. As per the requirements of the National Legislation and Institutions, the written informed consent from the patients was not required.
2.2 Instruments and Methods
2.2.1 Instruments CEUS of the carotid plaque was performed with Esaote MyLab Class C scanner (MyLabClassC Advanced, Esaote, Genova, Italy), equipped with a 12-18 MHz linear transducer.
2.2.2 Ultrasonographic examination The common carotid, internal carotid, external carotid, and vertebral arteries were examined by 2D USG. The stenosis of carotid artery, and the number and distribution of carotid plaques were noted. The thickest carotid plaque was identified and evaluated. The same plaque was studied by both 2D USG and CEUS. The CEUS examination was performed following a bolus injection of SonoVue (Bracco, Milan, Italy). Dynamic images were continuously collected for further offline analysis.
2.2.3 Grading of plaques The plaque echogenicity was interpreted by visual analysis on 2D USG and classified into following 5 types: Type 1 (Uniformly anechoic plaque), Type 2 (Predominantly hypoechoic or anechoic plaque), Type 3 (Predominantly echoic or isoechoic plaque), Type 4 (Uniformly isoechoic or uniformly hyperechoic), and Type 5 (Unclassified calcified plaque) [8, 10]. Obvious hyperechoic (part of Type 4) and calcified plaques (Type 5) which didn`t show contrast were excluded from the present study.
CEUS was used to grade the neovascularization of carotid artery plaques and included four grades as follows: Grade 0 (no enhancement of plaques, denoting absence of plaque neovascularization), Grade 1 (Several punctate enhancements within adventitia or tissue surrounding the plaque suggesting limited presence of plaque neovascularization), Grade 2 (Adventitia or shoulder of the plaque was enhanced, suggesting moderate neovascularization, less neovascularization than Grade 3 but more than Grade 1), and Grade 3 (Diffuse enhancement within the plaque suggesting the presence of a pulsatile artery within the plaque) [11].
2.3 Statistical analysis
The continuous data with normal distribution was represented in terms of as mean ± standard deviation (SD), while categorical data was represented in terms of frequency (percentage). The continuous and categorical data were compared with Student's t-test and Chi-Square or Fisher’s exact test, respectively. Univariate and multivariate logistic regression analysis was used to determine the independent risk factors of recurrent cerebral infarcts. Presence or absence of recurrent cerebral infarct was used as a binary dependent variable. The receiver operating characteristic (ROC) curve was used to evaluate the sensitivity and specificity of independent risk factors in predicting the recurrent cerebral infarcts. The data was analysed with SPSS (IBM, Armonk, NY, USA) version 23.0 for windows. A probability (P) of less than 0.05 was considered as statistically significant.