Department of Biomedical Engineering, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy.
Diagnostic Radiology, Papa Giovanni XXIII Hospital, Bergamo, Italy.
Int J Artif Organs. 2023 Oct-Nov;46(10-11):547-554. doi: 10.1177/03913988231191960. Epub 2023 Sep 27.
The mechanisms underlying vascular stenosis formation in the arteriovenous fistula (AVF) for hemodialysis (HD) remain mostly unknown. Several computational fluid dynamics (CFD) studies have suggested a potential role for unsteady flow in inducing intimal hyperplasia and AVF stenosis, but the majority of these observations have been limited to a single time point after surgical creation. The aim of the present study was to investigate the relation between hemodynamic conditions and AVF vascular remodeling through a CFD longitudinal study. Non contrast-enhanced MR images and Doppler Ultrasound (US) examinations were acquired at 3 days, 40 days, 6 months, 1 year, and 1.5 years after surgery in a 72-year male referred for native radio-cephalic AVF. Three-dimensional AVF models were generated and high fidelity CFD simulations were performed using pimpleFoam, setting patient-specific boundary conditions derived from US. Morphological and hemodynamic changes over time were then analyzed. Analysis of vessel morphology and hemodynamics during follow-up showed that the AVF had a successful maturation process, characterized by a massive arterial and venous dilatation within the 6 months after surgery, a corresponding increase in blood flow volume and important flow instabilities. Between 6 months and 1 year, a stenosis developed in the juxta-anastomotic vein and caused AVF failure at 1.5 years. The development of stenosis was paralleled by the regularization of blood flow velocity pattern and consequent decrease in the near-wall disturbed flow metrics. These results suggest that development of intimal hyperplasia and vessel stenosis, triggered by unsteady flow, could be the result of vascular inward remodeling toward regularization of turbulent-like flow.
动静脉瘘（AVF）用于血液透析（HD）时血管狭窄形成的机制在很大程度上尚不清楚。几项计算流体动力学（CFD）研究表明，非稳定流在诱导内膜增生和 AVF 狭窄方面可能具有潜在作用，但这些观察结果大多仅限于手术后的单一时间点。本研究旨在通过 CFD 纵向研究探讨血流动力学条件与 AVF 血管重塑之间的关系。对一名 72 岁男性进行了非对比增强磁共振成像（MRI）和多普勒超声（US）检查，该患者因原发性桡尺侧 AVF 而接受治疗，在手术后 3 天、40 天、6 个月、1 年和 1.5 年进行了检查。生成了三维 AVF 模型，并使用 pimpleFoam 基于 US 获得的患者特定边界条件进行了高保真 CFD 模拟。然后分析了随时间的形态和血流动力学变化。对随访期间血管形态和血流动力学的分析表明，AVF 经历了成功的成熟过程，表现为手术后 6 个月内动脉和静脉大量扩张，血流量相应增加以及重要的血流不稳定。在 6 个月至 1 年之间，在吻合口附近的静脉中出现狭窄，并导致 1.5 年后 AVF 失败。狭窄的发展与血流速度模式的规则化以及随之而来的近壁扰流度量的减少平行。这些结果表明，不稳定流引发的内膜增生和血管狭窄的发展可能是血管向内重塑以实现类湍流流动规则化的结果。
