Shear stress on the endothelial surface has been implicated in atherosclerosis localization, plaque vulnerability, and remodeling behavior of the arterial wall, as well as in-stent restenosis following percutaneous coronary interventions. The purposes of this chapter are to introduce haemodynamic shear stress, briefly explain the methodology for measuring and imaging shear stress in vivo, present the role of shear stress in the atherosclerotic disease process, and cite the evidence highlighting the effects of stent implantation on local blood flow patterns and linking shear stress at the stent surface to neointimal hyperplasia following coronary artery stenting.
TopIntroduction
Atherosclerotic cardiovascular disease is characterized by chronic inflammation and fibroproliferation of large- and medium-sized arteries, and remains the leading cause of mortality and morbidity in western societies. Despite the systemic nature of risk factors (i.e., dyslipidaemia, diabetes mellitus, hypertension, cigarette smoking, social stress) associated with atherosclerosis, the disease manifestations are focal and eccentric, and evolve in an independent manner. Atherosclerosis is a site-specific disease, which affects primarily the carotid bifurcation, the coronary arteries, the infrarenal aorta and the arteries of the lower limbs having a propensity to involve branch points, bifurcations and highly curved arteries (Asakura & Karino, 1990; Ku et al., 1985). Regional haemodynamic factors that create a unique environment are critical determinants of the behavior of atherosclerosis at focal sites throughout the vasculature in susceptible individuals. Flow-derived shear stress, in particular, exerts its pathobiological effects on the arterial endothelium that are associated with increased atherosclerosis susceptibility and development, and plaque vulnerability (Chatzizisis, Coskun, Jonas, Edelman, Feldman et al., 2007; Davies, 2009).
The advancement of percutaneous coronary interventions during the last three decades has provided efficient non-surgical management of obstructive atherosclerotic lesions. Coronary stenting using bare metal stents or, more recently, drug-eluting stents, has currently dominated as an interventional strategy for restoring arterial blood flow in diseased arteries. However, stenting constitutes an invasive procedure involving the implantation of a foreign metal body, which affects the regional arterial geometry, and consequently, alters the local haemodynamic environment. Stent architecture influences the detailed characteristics of post-stent implantation blood flow patterns (Balossino et al., 2008), which are recognized as major determinants of the vascular response, neointima distribution and deposition of the eluted drugs.