The Carotid Artery Multi-modality Imaging Prognostic (CAMP) Study

Description

BACKGROUND AND RATIONALE

State of the art and preliminary data Stroke is a most relevant health burden, the second most common cause of death and the third cause of disability worldwide. Stroke is a heterogeneous disorder with several disease mechanisms implicated in its pathogenesis. Ischemic stroke accounts for 87% of all stroke cases. The TOAST (Trial of Org 10172 in Acute Stroke Treatment) and the more recent SSS-TOAST (Stop Stroke Study TOAST) classifications currently provide the most widely used schemes of stroke classification for clinicians. Accordingly, pathomechanisms comprise: (a) large artery atherothrombosis (i.e., a major brain artery or branch cortical artery); (b) cardioembolism; (c) small vessel occlusion (lacunar infarcts); (d) other determined etiology (i.e., hypercoagulable states, hematologic disorders); (e) undetermined etiology (cryptogenic embolism; incomplete patient evaluation).

Silent stroke, usually defined as focal T2 hyperintensities >3 mm with correlative T1 hypointensities at magnetic resonance imaging (MRI), has a reported incidence of 10-15% and a relevant significance in terms of cognitive impairment and correlations with clinically overt stroke. Silent stroke is a cerebrovascular ischemic (less frequently haemorrhagic) lesion detected by neuroimaging such as magnetic resonance imaging (MRI) that does not determine acute focal neurological deficits but causes cerebral damage in an unaware way. Typically, silent stroke (SS) affects regions associated with various mental processes, mood regulation and cognitive functions, and therefore is a leading cause of vascular cognitive impairment that impacts about one-third of individuals over the age of 70. Cerebral small vessel disease related to aging (and possibly to age-related arterial stiffness) leading to leucoaraiosis and lacunar infarctions is a main cause of SS, but also microembolic lesions due to atrial fibrillation and carotid stenosis may be involved.

The diagnosis of SS stroke may be challenging. In many cases, subjects are not diagnosed until long after a stroke occurs or in case of progressive cognitive impairment. Occasionally, strategic lesions in cerebral areas related to cognitive function, the hippocampus or the thalamus, and, more frequently, incremental lesion load over time lead to vascular dementia (VD). VD is is the second most common form of dementia after Alzheimer's disease. The prevalence of the illness is about 5% in Western countries. Current epidemiologic research suggests that AF contributes to cognitive decline and dementia independent of a history of stroke. Further work is warranted to elucidate the potential mechanisms underlying this association, and better designed studies are needed to explore the possible cognitive benefits of different therapeutic options in patients with carotid disease. Potential pathophysiological pathways linking carotid disease with cognitive decline are microembolism, systemic inflammation, and cerebral hypoperfusion.

STUDY DESIGN This is a monocenter, prospective, longitudinal, observational study. This is a no-profit study, granted by Regione Toscana - Bando Salute 2018.

Setting Eligible participants (see inclusion and exclusion criteria below) will be selected and recruited in the outpatient setting of the UO Cardiologia 1 - AOUP. Exclusion and inclusion criteria will be evaluated according the previous medical history and imaging tests of the participant. All participants identified as eligible will receive all the necessary information about the study and will sign the informed consent under the supervision of the Principal Investigator. In case of enrollment, a detailed plan will be prepared for each participant to schedule the study evaluations to be integrated with the routine examinations.

STUDY OUTCOMES Variables

Different variables will be assessed and analyzed, in particular:

1. Baseline neurological, psychological and neurocognitive evaluation
2. Baseline brain MRI evaluation
3. Angio-MRI for carotid stenosis assessment and plaque tissue characterization
4. Angio-CT evaluation for carotid stenosis assessment and plaque characterization
5. Multigate Doppler (MGD) Investigation of Carotid Artery Stenosis
6. Carotid stenosis assessment
7. Wall shear rate and flow separation analysis
8. Advanced ultrasound techniques for plaque vulnerability and local mechanical properties assessment a. Ultrasonographic markers of plaque composition b. Validation of 3D US for carotid plaque stenosis severity and morphology assessment c. Radiofrequency data for assessment of fibrous cap thickness, plaque deformation, and local arterial waveform and stiffness
9. Follow-up (2-years) brain MRI evaluation
10. Follow-up (2 years) neurological, psychological and neurocognitive evaluation
11. Baseline neurological, psychological and neurocognitive evaluation

Each participant will be evaluated at baseline and at the 2-year follow-up with a detailed medical history and physical examination. A detailed assessment of cognitive decline/dementia will be performed as below detailed:

• Montreal Cognitive Assessment (MoCA), a brief screening tool wide used and sensitive for mild cognitive impairment. Moreover, performing a subtests analysis of MoCA results will allow to analyse performance visuospatial and executive functions, attention, and recall.
• Adopting a more focus on specific cognitive functions, and following results of two recent studies (The Tromso study - Mathiesen et al., 2004; Cheng et al., 2012) in asymptomatic carotid stenosis, the investigators will also assess:

Working memory: Backward Digit Span

Attention and psychomotor speed: Trail Making Test (Parts A and B)

Motor functioning: Grooved Pegboard Test

Memory: Verbal and Visual Paired Association (immediate and delayed recall - subtest of the Wechsler Memory Scale)

• Complex visuospatial perception: Modified Complex Figure Test (copy and recall)
• Finally, it is also important to evaluate subjective dizziness and changes in cognitive status, proved sensitive to carotid stenosis, using two brief self-report

  questionnaires

The Dizziness Handicap Inventory

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)

• The total assessment time will be around 30 minutes. The Clinical Psychology Unit will be responsible for preliminary tutorship of Centers about questionnaires administration, and subsequent centralized analysis. 2. Baseline brain MRI evaluation Silent brain infarction will be defined as focal T2 hyperintensity >3 mm with correlative T1 hypointensities at MRI. This evaluation will be matched with the similar 2-year follow-up examination, to assess the occurrence of silent strokes. 3. Angio-MRI for carotid stenosis assessment and plaque tissue characterization Angio-MRI of carotid arteries will be performed at baseline and after a two-year follow-up for carotid plaque characterization. 4. Angio-CT evaluation for carotid stenosis assessment and plaque characterization Estimation of lumen stenosis and vessel anatomy with contrast agents. Specific algorithms (quantitative evaluation of calcifications - lipid core - haemorrhage): the two main CT techniques for plaque characterization here used will be multi-detector-row CT and dual-source CT. Multi-detector-row CT will characterize plaque calcification, ulcerations, fibrous plaque thickness, intra- plaque haemorrhage and the presence of lipid-rich necrotic cores, based on voxel Hounsfield units density (HUs). 5. Multigate Doppler (MGD) Investigation of Carotid Artery Stenosis The University of Pisa has a long-standing collaboration with the Microeletronic System Design Lab (MSD-Lab) at the Department of Informational Engineering (DINFO) of Florence University, based upon an ultrasound advanced open platform (UlAOP) providing a detailed representation and quantification of flow velocity profile and wall shear rate by means of multiple spectral Doppler sample volumes (128) aligned perpendicularly through the longitudinal arterial axis.
  1. Carotid stenosis assessment A customized configuration developed in Florence will be used to provide in real time a simplified flow velocity profile in common and internal carotid artery, using 7 Doppler vectors aligned through the vessel transverse axis, before, within and after the plaque. This approach allows to overcome the assumption of a fully parabolic flow velocity profile through the vessel, which is instead variably skewed in the presence of curvatures and stenosis. The correlation of central flow velocity, peak flow velocity and flow velocity distribution with severity and shape of carotid stenosis as assessed by angio-TC will be investigated. The association of flow velocity values and skewness with MES and silent brain ischemic lesions will be also assessed.
  2. Wall shear rate and flow separation analysis By post-processing of MGD datasets, wall shear rate, oscillatory flow velocity patterns and retrograde flows will be estimated using a computational fluid dynamics (CFD) approach. The association of these parameters with MES and baseline and incident silent brain ischemic lesions will be assessed. This evaluation will be performed in a subset of 100 participants recruited in Pisa, no more than 2 months after the angio-TC evaluation
  3. Advanced ultrasound techniques for plaque vulnerability and local mechanical properties assessment After the baseline investigation, in a subset of participants, the ultrasound investigation of carotid arteries and plaques will be repeated by US system providing radiofrequency raw data for post-processing analysis. Conventional 2D US scan as well as acquisition of the RF-data sets will be performed. Two-dimensional images will be exploited for tissue characterization analysis; RF- datasets will be used to determine fibrous cap thickness, local plaque deformation, arterial contour- wave analysis with central pulsatile pressure and excess pressure estimate. This evaluation will be performed at baseline no more than 2 months after the angio-TC evaluation, and then repeated at the two-year follow-up.
     1. Ultrasonographic markers of plaque composition Carotid plaque characterization will be performed on 2D images at Lund University, by means of a customized software recently validated against immunohistochemistry by Nilsson J and Goncalves I within the context of a FP7 collaborative study on diabetes (IMI-SUMMIT project), with the participation of the University of Pisa (Palombo C et al).
     2. Validation of 3D US for carotid plaque stenosis severity and morphology assessment Plaque volume and shape assessment (concentric/eccentric, regular, irregular) will be assessed with a dedicated 3D probe implemented on a Philips cardiovascular US platform in 50 participants. After acquisition of a 3D dataset (Fully Automated Mechanical Transducer), including total plaque volume and maximum area reduction. Total ulcer volume and size will be integrated. Off-line texture analysis will be performed on a dedicated subset of images. Beside conventional 2D ultrasonographic assessment of stenosis severity (including Doppler findings and 2D findings), advanced ultrasonographic examinations will be performed with the aim of quantitative data acquisition on tissue characterization, detection of neovascularity, detection of total plaque burden (volume 3D), plaque deformation and flow profiling. This subproject will be performed only at baseline.
     3. Radiofrequency data for assessment of fibrous cap thickness, plaque deformation, and local arterial waveform and stiffness The RF-dataset provided by the Esaote systems will allow estimate of common carotid distensibility and plaque fibrous cap thickness and deformation thanks to an array of 16 parallel lines crossing the vessel longitudinal axis through 14 mm, with high spatial (10 m) and temporal (660 Hz) resolution. A pressure- calibrated local arterial distension waveform is also obtained, from which indices of local stiffness, pulsatile pressure, including the so-called "excess pressure", and wave reflection can be assessed.
     4. Follow-up (2-years) brain MRI evaluation This examination will be performed at the 2-year follow-up and matched with the baseline examination, to assess new incident events. Silent stroke will be similarly defined as focal T2 hyperintensity >3 mm with correlative T1 hypointensities at MRI. At this visit, MRI will be limited to the brain, without carotid reassessment
     5. Follow-up (2 years) neurological, psychological and neurocognitive evaluation This will be done with a complete physical examination and the use of dedicated scales to perform an evaluation of signs of silent stroke or cerebral involution, as per item 1.

Tools/equipment: questionnaires. Expected results: assessment of possible neuropsychologic and cognitive status changes after two years + correlations between changes in neuropsychologic and cognitive status after follow-up and MES, carotid plaque features, local arterial mechanics, and atherosclerotic risk profile at baseline (longitudinal study) + correlations between changes in neuropsychologic and cognitive status after follow-up and changes in silent brain ischemic lesions (MRI), and in carotid plaque features and local arterial mechanics by ultrasound, conventional and advanced (longitudinal study).

DATA MANAGEMENT Data collection All variables listed above will be safely reported on the case report form, collected and stored, including some self-reported questionnaires, i.e. the Dizziness Handicap Inventory and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).

Data management All data will be managed in compliance with the General Data Protection Regulation (GDPR). A dedicated platform (Data Platform) in full compliance with the GDPR rules and the Italian Legislative Decree no. 196 dated 30/06/2003 will be developed. Digital and paper-based case report forms will be generated to collect participants' data. Data will be then uploaded on the Data Platform for safe storing by using cloud technologies and secured access credentials and protocols (TLS / HTTPS). All necessary measures to ensure full protection of data will be applied.

Pseudonymisation will be guaranteed by a secured alphanumeric code, whose key will be password-protected and available only to the study investigators.

Data storage The principal investigator (Prof. Raffaele De Caterina) will be responsible for data collection, management, storage and pseudonymisation.

Statistical analysis Correlation and regression analysis will be performed in uni- and multivariate manner, after correction for collinearity. Bland-Altman Analysis will assess the predictive power and concordance of each methods for specific plaque features. Logistic regression analysis, Cox regression analysis and survival analysis will be performed according to different predictors, after determination of cut-off values for single continuous variables. Incremental analysis (Chi-square; Net reclassification) will be performed in order to assess the integrated value of combined (multi-imaging; soluble biomarkers; clinical) methods. Finally, an inter- and intra-observer analysis will be performed. A mathematical models combining the features derived from all the techniques used to construct the best model predictive of stroke and the development of neurocognitive decline.

ADMINSITRATIVE ASPECTS Study financial support The study will be financially supported by Regione Toscana, Bando Salute 2018. There will be no interference from Regione Toscana on the scientific management of the study. Three financial tranches will be bestowed as for formal agreements (at the beginning of the study, at 18 months, at 36 months or termination of the study).

Ethical considerations The study will be conducted according to the norms of Good Clinical Practice (ICH/GCP) and to the ethical guidelines of the Declaration of Helsinki. Enrollment will start only after the protocol is approved by the local Ethical Committee. Written informed consent will be obtained from each participant before enrollment.

Informed consent acquisition Each participant will be carefully and thoroughly informed by the investigators involved in the study at the time of enrollment. Written informed consent will be requested only after a comprehensive discussion with the participant.

There are no financial conflict of interest for any of the investigators involved in the study.

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