Dataset Information

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access.

ABSTRACT:

Background

An autogenous arteriovenous fistula is the optimal vascular access for hemodialysis. In the case of brachiocephalic fistula, cephalic arch stenosis commonly develops leading to access failure. We have hypothesized that a contribution to fistula failure is low wall shear stress resulting from post-fistula creation hemodynamic changes that occur in the cephalic arch.

Methods

Twenty-two subjects with advanced renal failure had brachiocephalic fistulae placed. The following procedures were performed at mapping (pre-operative) and at fistula maturation (8-32 weeks post-operative): venogram, Doppler to measure venous blood flow velocity, and whole blood viscosity. Geometric and computational modeling was performed to determine wall shear stress and other geometric parameters. The relationship between hemodynamic parameters and clinical findings was examined using univariate analysis and linear regression.

Results

The percent low wall shear stress was linearly related to the increase in blood flow velocity (p < 0.01). This relationship was more significant in non-diabetic patients (p < 0.01) than diabetic patients. The change in global measures of arch curvature and asymmetry also evolve with time to maturation (p < 0.05).

Conclusions

The curvature and hemodynamic changes during fistula maturation increase the percentage of low wall shear stress regions within the cephalic arch. Low wall shear stress may contribute to subsequent neointimal hyperplasia and resultant cephalic arch stenosis. If this hypothesis remains tenable with further studies, ways of protecting the arch through control of blood flow velocity may need to be developed.

SUBMITTER: Hammes M

PROVIDER: S-EPMC4830603 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access.

Hammes Mary M Boghosian Michael M Cassel Kevin K Watson Sydeaka S Funaki Brian B Doshi Taral T Mahmoudzadeh Akherat S M Javid SM Hines Jane J Coe Fredric F

PloS one 20160413 4

<h4>Background</h4>An autogenous arteriovenous fistula is the optimal vascular access for hemodialysis. In the case of brachiocephalic fistula, cephalic arch stenosis commonly develops leading to access failure. We have hypothesized that a contribution to fistula failure is low wall shear stress resulting from post-fistula creation hemodynamic changes that occur in the cephalic arch.<h4>Methods</h4>Twenty-two subjects with advanced renal failure had brachiocephalic fistulae placed. The following ...[more]

PMID: 27074019

Similar Datasets

Project description:BackgroundThe most common configuration for arteriovenous fistula is brachiocephalic which often develop cephalic arch stenosis leading to the need for numerous procedures to maintain access patency. The hemodynamics that contributes to the development of cephalic arch stenosis is incompletely understood given the inability to accurately determine shear stress in the cephalic arch. In the current investigation our aim was to determine pressure, velocity and wall shear stress profiles in the cephalic arch in 3D using computational modeling as tools to understand stenosis.MethodsFive subjects with brachiocephalic fistula access had protocol labs, Doppler, venogram and intravascular ultrasound imaging performed at 3 and 12 months. 3D reconstructions of the cephalic arch were generated by combining intravascular ultrasounds and venograms. Standard finite element analysis software was used to simulate time dependent blood flow in the cephalic arch with velocity, pressure and wall shear stress profiles generated.ResultsOur models generated from imaging and flow measurements at 3 and 12 months offer snapshots of the patient's cephalic arch at a precise time point, although the remodeling of the vessel downstream of an arteriovenous fistula in patients undergoing regular dialysis is a dynamic process that persists over long periods of time (~ 5 years). The velocity and pressure increase at the cephalic bend cause abnormal hemodynamics most prominent along the inner wall of the terminal cephalic arch. The topology of the cephalic arch is highly variable between subjects and predictive of pathologic stenosis at later time points.ConclusionsLow flow velocity and wall pressure along the inner wall of the bend may provide possible nidus of endothelial activation that leads to stenosis and thrombosis. In addition, 3D modelling of the arch can indicate areas of stenosis that may be missed by venograms alone. Computational modeling reconstructed from 3D radiologic imaging and Doppler flow provides important insights into the hemodynamics of blood flow in arteriovenous fistula. This technique could be used in future studies to determine optimal flow to prevent endothelial damage for patients with arteriovenous fistula access.

Project description:PurposeWall shear stress (WSS) and pulse wave velocity (PWV) are important parameters to characterize blood flow in the vessel wall. Their quantification with flow-sensitive phase-contrast (PC) cardiovascular magnetic resonance (CMR), however, is time-consuming. Furthermore, the measurement of WSS requires high spatial resolution, whereas high temporal resolution is necessary for PWV measurements. For these reasons, PWV and WSS are challenging to measure in one CMR session, making it difficult to directly compare these parameters. By using a retrospective approach with a flexible reconstruction framework, we here aimed to simultaneously assess both PWV and WSS in the murine aortic arch from the same 4D flow measurement.MethodsFlow was measured in the aortic arch of 18-week-old wildtype (n = 5) and ApoE-/- mice (n = 5) with a self-navigated radial 4D-PC-CMR sequence. Retrospective data analysis was used to reconstruct the same dataset either at low spatial and high temporal resolution (PWV analysis) or high spatial and low temporal resolution (WSS analysis). To assess WSS, the aortic lumen was labeled by semi-automatically segmenting the reconstruction with high spatial resolution. WSS was determined from the spatial velocity gradients at the lumen surface. For calculation of the PWV, segmentation data was interpolated along the temporal dimension. Subsequently, PWV was quantified from the through-plane flow data using the multiple-points transit-time method. Reconstructions with varying frame rates and spatial resolutions were performed to investigate the influence of spatiotemporal resolution on the PWV and WSS quantification.Results4D flow measurements were conducted in an acquisition time of only 35 min. Increased peak flow and peak WSS values and lower errors in PWV estimation were observed in the reconstructions with high temporal resolution. Aortic PWV was significantly increased in ApoE-/- mice compared to the control group (1.7 ± 0.2 versus 2.6 ± 0.2 m/s, p < 0.001). Mean WSS magnitude values averaged over the aortic arch were (1.17 ± 0.07) N/m2 in wildtype mice and (1.27 ± 0.10) N/m2 in ApoE-/- mice.ConclusionThe post processing algorithm using the flexible reconstruction framework developed in this study permitted quantification of global PWV and 3D-WSS in a single acquisition. The possibility to assess both parameters in only 35 min will markedly improve the analyses and information content of in vivo measurements.

Project description:BackgroundPrevious studies have not described the relationship between reducing radial artery diameter as well as increasing age and functional maturation of the radio-cephalic arteriovenous fistula (RCAVF) and no data identify these as linear relationship. The objective of this study was to perform trend analysis to assess these aspects.MethodsOur retrospective cohort study enrolled and analyzed 353 follow-up cases that underwent first AVF creation. The artery and vein sizes were measured by ultrasound. We performed follow-up, a minimum of 3 months after surgery. Multivariable logistic regression analysis was used to identify independent risk factors inmaturation. Participant age was categorized into four groups (age ≤ 29, 30-49, 50-69, and 70-90 years). Radial artery diameter was categorized into four groups (≤ 1.9, >1.9 and ≤ 2.1, >2.1 and ≤ 2.4, >2.4 mm) according to median and interquartile ranges. We adjusted for confounders in four logistic models, and primary analyses were based on building ordered category models and tested P values for trends to estimate the relationship of radial artery diameter and each 20-year increase in age with risk of maturation.ResultsThe mature RCAVF group included 301 cases, and the immature group included 52 cases. Radial artery diameter, age, and diabetes were independent risk factors of maturation. Odds ratios (ORs) associated with maturation reduced with increasing age, while ORs increased with increasing radial artery diameter. P values for trends(<0.05) were observed in all four models. A reduction in radial artery diameter and higher age were significantly associated with a higher incidence of immaturity after adjusting the multivariate models. The risks of immaturation were increased by more than 1.54 fold for each 20-year increase and increased by more than 1.34 fold for the smaller radial artery diameter group.ConclusionOur findings suggest that a significantly higher immaturity risk of RCAVF was associated with increasing age and a reduction in radial artery diameter. Our study identified a linear exposure-response relationship of age and radial artery diameter with immaturity incident. A careful selection of patients will be helpful in improving AVF functional maturation.

Dataset Information

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access.

Background

Methods

Results

Conclusions

Publications

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets