Stability of Carotid Artery Under Steady-State and Pulsatile Blood Flow: A Fluid–Structure Interaction Study

Abstract

It has been shown that arteries may buckle into tortuous shapes under lumen pressure, which in turn could alter blood flow. However, the mechanisms of artery instability under pulsatile flow have not been fully understood. The objective of this study was to simulate the buckling and post-buckling behaviors of the carotid artery under pulsatile flow using a fully coupled fluid-structure interaction (FSI) method. The artery wall was modeled as a nonlinear material with a two-fiber strain-energy function. FSI simulations were performed under steady-state flow and pulsatile flow conditions with a prescribed flow velocity profile at the inlet and different pressures at the outlet to determine the critical buckling pressure. Simulations were performed for normal (160 ml/min) and high (350 ml/min) flow rates and normal (1.5) and reduced (1.3) axial stretch ratios to determine the effects of flow rate and axial tension on stability. The results showed that an artery buckled when the lumen pressure exceeded a critical value. The critical mean buckling pressure at pulsatile flow was 17-23% smaller than at steady-state flow. For both steady-state and pulsatile flow, the high flow rate had very little effect (<5%) on the critical buckling pressure. The fluid and wall stresses were drastically altered at the location with maximum deflection. The maximum lumen shear stress occurred at the inner side of the bend and maximum tensile wall stresses occurred at the outer side. These findings improve our understanding of artery instability in vivo.

Buckling Reduces eNOS Production and Stimulates Extracellular Matrix Remodeling in Arteries in Organ Culture

“…The decrease in collagen IV in the buckled arteries could be due to both the increases in lumen shear stress and wall stresses, 5,15,28 though we could not distinguish which stress component led to the difference between the inner and outer curves. Shear stress was found higher at the inner curve of buckled arteries, 27 which is most likely the mechanism that led to increased MMP-2 expression, as suggested by Sho et al 36 Buckling-induced changes in hemodynamics, mechanical stress, endothelial cell function, and ECM remodeling could be a possible mechanism for the high occurrence of atherosclerosis in tortuous carotid arteries. 8,29 …”

“…Furthermore, flow and shear stress of different conditions (laminar and perturbed, unidirectional/oscillatory) can differentially regulate eNOS expression. 37,44 Our previous computational analysis demonstrated that flow in the buckled arteries was laminar and unidirectional, 27 similar as in straight control vessels. However, the shear stress magnitude and its spatial distribution are different in buckled and straight vessels.…”

“…27 These stress changes could be the biomechanical mechanism in the observed endothelial dysfunction and ECM remodeling in buckled arteries. The reduction in eNOS could be due to the disturbed lumen shear stress as it acted directly on the endothelium.…”

“…It alters the distributions of fluid shear stress and yields uneven wall stress in arteries. 21,27,40,43 The changes in wall shear stress in the curved regions are known to be pro-inflammatory and pro-atherogenic. 6,26,29,38 One of the mechanobiological mechanisms is that lumen shear stress affects endothelial nitric oxide synthase (eNOS) and NO production in endothelial cells that plays a critical role in modulating artery function.…”

A Piv Comparison of the Flow Field and Wall Shear Stress in Rigid and Compliant Models of Healthy Carotid Arteries

“…Computational methods, in which equations are coupled governing the flow and the elastic walls are maturing. [15][16][17][18] There is a lack of experimental data in compliant arterial systems to validate the numerical predictions with only a few publications available. [19][20][21] Early work with healthy arterial geometries by Perktold et al 22 numerically investigated the effect of compliance on a geometry representing the human common carotid artery (CCA) bifurcation experiencing a physiologically realistic waveform making observations of both the WSS and vessel compliance.…”