The Role of Shear Stress in Arteriovenous Fistula Maturation and Failure: A Systematic Review

Abstract

IntroductionNon-maturation and post-maturation venous stenosis are the primary causes of failure within arteriovenous fistulae (AVFs). Although the exact mechanisms triggering failure remain unclear, abnormal hemodynamic profiles are thought to mediate vascular remodelling and can adversely impact on fistula patency.AimThe review aims to clarify the role of shear stress on outward remodelling during maturation and evaluate the evidence supporting theories related to the localisation and development of intimal hyperplasia within AVFs.MethodsA systematic review of studies comparing remodelling data with hemodynamic data obtained from computational fluid dynamics of AVFs during and after maturation was conducted.ResultsOutward remodelling occurred to reduce or normalise the level of shear stress over time in fistulae with a large radius of curvature (curved) whereas shear stress was found to augment over time in fistulae with a small radius of curvature (straight) coinciding with minimal to no increases in lumen area. Although this review highlighted that there is a growing body of evidence suggesting low and oscillating shear stress may stimulate the initiation and development of intimal medial thickening within AVFs. Further lines of evidence are needed to support the disturbed flow theory and outward remodelling findings before surgical configurations and treatment strategies are optimised to conform to them. This review highlighted that variation between the time of analysis, classification of IH, resolution of simulations, data processing techniques and omission of various shear stress metrics prevented forming pooling of data amongst studies.ConclusionStandardised measurements and data processing techniques are needed to comprehensively evaluate the relationship between shear stress and intimal medial thickening. Advances in image acquisition and flow quantifications coupled with the increasing prevalence of longitudinal studies commencing from fistula creation offer viable techniques and strategies to robustly evaluate the relationship between shear stress and remodelling during maturation and thereafter.

Future research directions to improve fistula maturation and reduce access failure

“…The increased hemodynamics of arterial flow that increases vessel wall shear stress (WSS) is likely to be a critical event after AVF creation that promotes AVF adaptation [104–106]. In a patient-specific side-to-end fistula, image-based computational fluid dynamics studies showed laminar flow within the arterial limbs and a complex multidirectional and reciprocating flow field on the inner side of the swing segment in the proximal venous limb [106].…”

“…In a patient-specific side-to-end fistula, image-based computational fluid dynamics studies showed laminar flow within the arterial limbs and a complex multidirectional and reciprocating flow field on the inner side of the swing segment in the proximal venous limb [106]. NIH is predisposed to occur in the inner wall of the venous segment near the anastomosis, and has a strong inverse correlation with magnitudes of shear stress, but is also related to flow patterns [107].…”

A predictive framework to elucidate venous stenosis: CFD & shape optimization

“…Low WSS has adverse effects on endothelial cells, including increased cell turnover, oxidative stress, and triggers a series of inflammatory genes that create neointimal hyperplasia (NH) [7,8] . NH is a process that leads to formation of a thickened arterial/venous intimal layer followed by occlusion of the vessel (see, for instance, figure 1b).…”

Mitochondrial Ca 2+ transport in the endothelium: regulation by ions, redox signalling and mechanical forces

“…Fluid [117][118][119][120][121][122]. Atherosclerotic vascular disease continues to be the major cause of death in developed nations [25].…”