Risk stratification of coronary plaques using physiologic characteristics by CCTA: Focus on shear stress.

The identification of factors determining whether a lesion progresses, destabilizes or becomes quiescent remains a challenge. Wall or endothelial shear stress (WSS or ESS, respectively), the frictional force acting on the lumen wall, is strongly associated with changes in the natural history of lesions. Several clinical intravascular imaging studies have shown a clear link between disturbed flow, typically characterized by low WSS, and plaque growth. In support of these studies, in-vitro experiments of shear stress have identified several mechanisms promoting atherosclerosis. More recently, the relationship between WSS and major adverse cardiac events has been explored. Improvements in coronary computed tomography angiography (CCTA) image resolution and quality has allowed for the calculation of WSS from CT. In this review, we provide an introduction to WSS, highlight important human and animal intravascular-based WSS studies, and discuss CT-based WSS studies to date. Finally, we discuss future directions of CCTA and WSS computation.