Quantification of Shear Stress and Geometric Risk Factors in Carotid Atherosclerosis: Review and Clinical Evidence

Cardiovascular ischemic diseases, such as myocardial infarction and stroke, are the leading causes of death and disability worldwide. Atherosclerotic plaque is one of the main reasons for such ischemic events. Major systemic atherosclerotic risk factors, such as hypertension, smoking, hyperlipidemia, diabetes mellitus and a sedentary lifestyle, fail to explain the focal nature of atheroma. Local hemodynamic conditions are thought to be closely associated with such a phenomenon. Shear stress has been widely accepted as an important factor in the development of atherosclerosis plaques. Recent advances in medical imaging and computational modeling techniques have enabled patients-specific hemodynamics to be visualized in vivo. Shear stress can be computed using direct flow imaging techniques, such as Doppler ultrasound and phase-contrast magnetic resonance imaging (PC-MRI), or image-based computational fluid dynamics (CFD) simulations. Due to the important role of geometry in determining local flow patterns, it is also relevant to study geometric risk factors, which could potentially be used as a surrogate for hemodynamic conditions, to avoid expensive flow imaging and computations. This patent review focuses on: (1) current approaches of in vivo quantification of patient-specific shear stress conditions, including both direct flow imaging techniques and image-based CFD simulations; and (2) clinical evidence of shear stress conditions and geometric risk factors in the development of atherosclerosis.