Magnetic Resonance Imaging of Carotid Atherosclerosis

__Abstract__ Worldwide, about 17 million people die from cardiovascular disease (CVD) each year, chiefly from ischemic heart disease and stroke.(1) Amongst those, stroke, the most common manifestation of cerebrovascular disease, has been the leading cause of serious, long-term disability in adults worldwide (1990-2010) (2) There are two main types of stroke — ischemic and hemorrhagic. Ischemic stroke is more common and caused by an obstruction in the cerebral vasculature. The causes of ischemic strokes are heterogeneous, including atherosclerosis in the large arteries such as the carotid arteries (see fig 1.), lacunar infarctions and cardiogenic embolism. In this thesis, I will focus on carotid atherosclerosis as it is the most prominent to identify patients with a high risk of ischemic stroke. Atherosclerotic plaques can rupture which will lead to thrombo-embolization into the intracranial circulation or to acute occlusion of the carotid artery. Despite major advances in treatment strategies, ischemic stroke due to carotid atherosclerotic remains a serious public health problem. Current screening and diagnostic methods are insufficient to identify the plaques that have a high rupture risk and thus to select the individual before he is confronted with an ischemic stroke. One of the strategies to better face the challenges of cerebrovascular disease and improve well being of the population and of the individual includes early recognition of the vulnerable high-risk atherosclerotic plaque

High shear stress relates to intraplaque haemorrhage in asymptomatic carotid plaques

Background and aims Carotid artery plaques with vulnerable plaque components are related to a higher risk of cerebrovascular accidents. It is unknown which factors drive vulnerable plaque development. Shear stress, the frictional force of blood at the vessel wall, is known to influence plaque formation. We evaluated the association between shear stress and plaque components (intraplaque haemorrhage (IPH), lipid rich necrotic core (LRNC) and/or calcifications) in relatively small carotid artery plaques in asymptomatic persons. Methods Participants (n = 74) from the population-based

Atherosclerotic Carotid Plaque Composition and Incident Stroke and Coronary Events

Background: Increasing evidence suggests that atherosclerotic plaque composition rather than plaque size is linked to ischemic cardiovascular events, yet largescale population-based data in asymptomatic individuals remain scarce. Objectives: This study sought to investigate carotid plaque composition in relation to incident stroke and coronary heart disease (CHD) in a population-based setting. Methods: Between 2007 and 2012, 1,349 persons (mean age 72 years, 49.5% women) from the population-based Rotterdam Study who were free from a history of stroke or CHD, in whom carotid ultrasonography showed subclinical atherosclerosis, and who underwent high-resolution magnetic resonance imaging of the carotid arteries to assess plaque characteristics. These included the presence of specific plaque components (intraplaque hemorrhage [IPH], lipid-rich necrotic core, and calcification), and measures of plaque size (maximum plaque thickness and presence of stenosis of more than 30%). Individuals were continuously followed for the occurrence of stroke or CHD until January 1, 2015. The authors used Cox regression models to assess the association of the plaque characteristics with the incidence of stroke and CHD, with adjustments for age, sex, and cardiovascular risk factors. Results: During a median of 5.1 years’ follow-up for stroke and 4.8 years for CHD, 51 individuals had a stroke and 83 developed CHD. Independent of maximum plaque thickness and cardiovascular risk factors, the presence of IPH was associated with incident stroke and CHD (fully adjusted hazard ratio: 2.42 [95% confidence interval: 1.30 to 4.50], and 1.95 [95% confidence interval: 1.20 to 3.14]). Presence of a lipid-rich necrotic core and calcification were not associated with stroke or CHD. Conclusions: The presence of IPH in the carotid atherosclerotic plaque is an independent risk factor for stroke and CHD. These findings indicate the promise of IPH as a marker of plaque vulnerability in healthy persons with subclinical atherosclerosis.</p

Carotid wall volume quantification from magnetic resonance images using deformable model fitting and learning-based correction of systematic errors

Cardiovascular Aspects of Radiolog

High shear stress relates to intraplaque haemorrhage in asymptomatic carotid plaques

AbstractBackground and aimsCarotid artery plaques with vulnerable plaque components are related to a higher risk of cerebrovascular accidents. It is unknown which factors drive vulnerable plaque development. Shear stress, the frictional force of blood at the vessel wall, is known to influence plaque formation. We evaluated the association between shear stress and plaque components (intraplaque haemorrhage (IPH), lipid rich necrotic core (LRNC) and/or calcifications) in relatively small carotid artery plaques in asymptomatic persons.MethodsParticipants (n = 74) from the population-based Rotterdam Study, all with carotid atherosclerosis assessed on ultrasound, underwent carotid MRI. Multiple MRI sequences were used to evaluate the presence of IPH, LRNC and/or calcifications in plaques in the carotid arteries. Images were automatically segmented for lumen and outer wall to obtain a 3D reconstruction of the carotid bifurcation. These reconstructions were used to calculate minimum, mean and maximum shear stresses by applying computational fluid dynamics with subject-specific inflow conditions. Associations between shear stress measures and plaque composition were studied using generalized estimating equations analysis, adjusting for age, sex and carotid wall thickness.ResultsThe study group consisted of 93 atherosclerotic carotid arteries of 74 participants. In plaques with higher maximum shear stresses, IPH was more often present (OR per unit increase in maximum shear stress (log transformed) = 12.14; p = 0.001). Higher maximum shear stress was also significantly associated with the presence of calcifications (OR = 4.28; p = 0.015).ConclusionsHigher maximum shear stress is associated with intraplaque haemorrhage and calcifications