Adaptive regulation of wall shear stress to flow change in the canine carotid artery

Abstract

To study the adaptive response of the vascular wall to blood flow changes, an arteriovenous shunt was constructed between the common carotid artery and the external jugular vein in 12 dogs. Six to eight months postoperatively, the arterial internal radius (r) was determined by angiography and/or the use of pressure-volume relationship. The results showed that r increased with increased flow load (f) and vice versa. Wall shear rate (gamma) was calculated from gamma = 4f/(tau r3), assuming laminar flow. The value of gamma, initially proportional to f, had recovered almost to the control level (within 15%) due to the vessel dilatation or atrophy during the chronic experiment, when f was less than 4 times the control. Transendothelial protein permeability, evaluated at the T-1824-stained surface by a reflectometric method, also showed a close correlation with wall shear (r = 0.934). A local autoregulatory mechanism of wall shear stress involving protein turnover in the vascular wall is suggested.

Right coronary artery becomes stiffer with increase in elastin and collagen in right ventricular hypertrophy

“…The remodeling of blood vessels in response to flow-overload obeys the constant WSS hypothesis (23,39). This principle implies that the volumetric flow rate is proportional to the cube of the vessel radius assuming a laminar, incompressible, Newtonian flow through a rigid cylindrical vessel (24).…”

“…For example, changes in blood flow cause changes in fluid wall shear stress (WSS; the tractive frictional force exerted by flowing blood on the inner layer of the vessel wall) by eliciting a wide range of biochemical and physiological responses in experimental (46) and clinical studies (16,22). Studies have demonstrated that a sudden increase in blood flow initiates an enlargement of the arterial lumen that progresses for months as the WSS tends to a homeostatic or normal level (23,25). A gradual increase in blood flow has been reported by several groups to result in outward hypertrophic remodeling of resistance (4,41,44,45,47) and conductive arteries (25,36,39).…”

Extension of Increased Atherosclerotic Wall Thickness Into High Shear Stress Regions Is Associated With Loss of Compensatory Remodeling

“…Second, the endothelium in controlling lumen size regulates SS in a negative feedback control loop. 18 Therefore, cross-sectional SS increments (induced by wall thickening, Figure 4C) will induce positive vascular remodeling, 6 causing SS to decrease. However, almost any control loop will leave some residue of the initial disturbance.…”

My biorheology research guided by curiosity

“…His lecture was: "Blood vessels change their sizes (vascular diameters) in response to changes in the blood flow, and this vascular remodeling is an adaptive response aimed at keeping the shear stress on the vascular wall (a biomechanical force arising from flow ing blood) constant, enabling maximization of the efficiency of the vascular work from the viewpoint of consumed energy [1]. Since the vascular endothelium is exposed to shear stress, blood flow dependent remodeling of blood vessels probably arises when the vascular endothelium senses shear stress.…”