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

Abstract

The surgical creation of vascular accesses for renal failure patients provides an abnormally high flow rate conduit in the patient’s upper arm vasculature that facilitates the hemodialysis treatment. These vascular accesses, however, are very often associated with complications that lead to access failure and thrombotic incidents, mainly due to excessive neointimal hyperplasia (NH) and subsequently stenosis. Development of a framework to monitor and predict the evolution of the venous system post access creation can greatly contribute to maintaining access patency. Computational fluid dynamics (CFD) has been exploited to inspect the non-homeostatic wall shear stress (WSS) distribution that is speculated to trigger NH in the patient cohort under investigation. Thereafter, CFD in liaison with a gradient-free shape optimization method has been employed to analyze the deformation modes of the venous system enduring non-physiological hemodynamics. It is observed that the optimally evolved shapes and their corresponding hemodynamics strive to restore the homeostatic state of the venous system to a normal, pre-surgery condition. It is concluded that a CFD-shape optimization coupling that seeks to regulate the WSS back to a well-defined physiological WSS target range can accurately predict the mode of patient-specific access failure.

A longitudinal study of the arterio-venous fistula maturation of a single patient over 15 weeks

“…WSS results for this patient show that values are not restored to the pre-creation baseline set point as previously suggested (Javid Mahmoudzadeh Akherat et al 2017), but fluctuate around a new, higher value. This demonstrates a possible control mechanism in which the diameter is adjusted to maintain WSS within a narrow range of the new set point.…”

“…Studies to monitor newly created AVFs have reported elevated WSS in the artery when compared to baseline (precreation) values (Ene-Iordache et al 2003). It would follow that the artery will increase in lumen diameter to lower the WSS back to baseline, which has been a hypothesis of previous AVF studies (Javid Mahmoudzadeh Akherat et al 2017). It is generally accepted that arterial vasculature seeks to maintain constant WSS at a preferred, homeostatic value (Humphrey 2008), with the presence of a control mechanism demonstrated by Le Noble et al (2005).…”

Quantitative hemodynamics of draining veins in brain arteriovenous malformation: a preliminary study based on computational fluid dynamics

“…[22] On the other hand, the variation in vessel wall parameters increases turbulence and introduces ow separation, leading to damage repair and reconstruction of the endothelial cell. [27] Therefore, the hemorrhagic presentation in AVMs may result from the interaction of hemodynamics and speci c angioarchitecture resulting in occlusive congestion within the AVM nidus. [9] There were some limitations in our study.…”

Measuring the palpable pulsatility length as a physical examination test in defining the severity of inflow stenosis for hemodialysis fistulas

“…The hemodynamic characteristics associated with a stenosis in an artery are 1) pre-stenotic pressure buildup and 2) post-stenotic pressure drop [5, 6]. When pressure waves pass through an inflow stenosis, the pressure energy is dissipated by being converted to kinetic energy and is attenuated downstream to the anastomosis along the length of an AVF according to Poiseuille’s law.…”