Computed tomography analysis of vulnerable carotid atherosclerotic plaque and relationship to clinical characteristics

Objective The presence of atherosclerotic plaque components such as lipid rich necrotic core and intraplaque haemorrhage is associated with increased plaque vulnerability, and may be used to stratify the risk of future cerebrovascular events. Our aim was to investigate the relationship between selected carotid plaque components imaged with CTA, patient characteristics, and clinical outcomes. Methods Symptomatic patients underwent carotid CTA as part of the BIOVASC study. Images were analysed for plaque volume composition with a semi-automatic Hounsfield Unit (HU)-based algorithm. Plaque components were classified based on their attenuation values: lipids <61 HU, fibrous tissue 61-129 HU and calcium >131 HU. Parametric and non-parametric tests were performed to compare plaque measurements to clinical characteristics and outcomes. Results One-hundred and two symptomatic carotids were analysed (avg. age 69y, 54.9% Male, 29.4% severe stenosis). Mean plaque volume was 480±230 mm3, and the mean LRNC volume was 170±100 mm3. A difference in LRNC volume was identified between moderate and severe stenosis (190–150 mm3, p=0.012). Regression analysis showed that age and gender may predict increased plaque volume (p<0.001). A trend for reduced mean plaque LRNC was identified in patients receiving statins (130-210 mm3, p=0.08). Intra-reader reliability showed good agreement (0.62-0.78, p<0.001) between CTA plaque measurements. Conclusions In-vivo CTA plaque volume composition assessment is feasible with good intra-reader reliability. Our findings suggest that CTA-HU measurements may be used to provide improved mechanistic and diagnostic insights into atherosclerotic disease, and facilitate the quantification of selected plaque components whose presence may be associated with increased plaque vulnerability. Key Points ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was partially supported by the Health Research Board (Ireland). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study has been granted full institutional, ethical approval by the Mater Misericordiae University Hospital Ethics Committee on the 2 April 2014 as part of the larger BIOVASC study (Reference number: 1/378/1131). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors * BIOVASC : Biomarkers Imaging Vulnerable Atherosclerosis in Symptomatic Carotid disease CPR : Curved-planar reformation DSA : Digital subtraction angiography ECST : European Carotid Surgery Trial FC : Fibrous cap ICA : Internal carotid artery ICC : Intraclass correlation IPH : Intraplaque haemorrhage LRNC : Lipid rich necrotic core MRS : Modified Rankin scale NASCET : North American Symptomatic Carotid Endarterectomy Trial TIA : Transient ischaemic attack