UNASSIGNED: Oscillatory wall shear stress and related metrics have been identified as potential predictors of dialysis access outcomes; however, the absence of a simple non-invasive method for measuring these haemodynamic forces has been prohibitive to their adoption into routine clinical practice. We present a computationally enhanced, single patient case study, offering a unique insight into the haemodynamic environment surrounding the development of flow limiting neointimal hyperplasia within the efferent vein of a previously functional arteriovenous fistula (AVF).
UNASSIGNED: Computational fluid dynamics (CFD) simulations were used to create a quantitative map of oscillatory shear stress as well as enabling visualisation of streamline patterns within the AVF. CFD data was compared to ultrasound-based turbulence quantification and examined alongside structural and functional changes in the access site over time.
UNASSIGNED: This work further supports the notion that flow limiting neointimal hyperplasia development in vascular access fistulae, occurs in response to oscillatory wall shear stress, and provides proof of concept for the idea that non-invasive ultrasound turbulence quantification tools could play a role in predicting vascular access outcomes.
UNASSIGNED: In addition to providing insight into the haemodynamic environment surrounding the development of flow limiting neointimal hyperplasia, we hope that this paper will promote discussion and further thinking about how our learnings from in-silico studies can be incorporated into clinical practice through novel uses of existing diagnostic tools.

OBJECTIVE: To compare the primary patency and restenosis rates in treatment naieve dialysis arteriovenous fistulas (AVFs) after drug-coated balloons (DCB) versus plain balloon angioplasty (PTA).
METHODS: This retrospective study included 157 patients who underwent AVF angioplasty for treatment-native AVF stenosis between January 2012 to 2022. The fistulas were Brachiocephalic (75%), Brachiobasilic (17%), and radiocephalic (8%). The index intervention was with either DCB or percutaneous transluminal angioplasty (PTA) with subsequent follow up. Patients with central venous stenosis, thrombosed fistula, fistula stents, AV graft or surgical intervention after the index procedure were excluded.
RESULTS: Arteriovenous fistula angioplasty was done in 28 patients using DCB and in 129 patients using PTA. A total of 108 patients presented with a single stenosis, 42 with 2 stenoses, and 7 with 3 stenoses. The location of these stenoses was in the venous outflow (57%), the juxta anastomotic segment (31%), and cephalic arch (12%). The median time to re-intervention for the PTA was 216 days compared to 304 days for the DCB (p=0.079). Primary patency at 6 months was 60.4% for PTA and 75% for DCB (p=0.141) CONCLUSION: Although DCB angioplasty of treatmentnaïve dysfunctional AVF tends to improve the time to intervention and 6-month primary patency compared to PTA, this difference did not reach statistical significance.

A definitive randomised controlled trial of arteriovenous fistula (AVF) versus arteriovenous grafts (AVG) has been advocated for more than a decade, but as yet, none has been completed. The aim of this article is to summarise the theoretical barriers, review the difficulties in trial design and practicalities that have thus far prevented this from occurring.

UNASSIGNED: This study aimed to compare the efficacy and safety of cutting balloon angioplasty (CBA) and conventional balloon angioplasty (control group) for recurrent vascular access stenosis in arteriovenous fistulas.
UNASSIGNED: This prospective, randomized single-center clinical trial included patients with hemodynamically significant recurrent vascular access stenosis of an arteriovenous fistula. The Kaplan-Meier method was used to assess primary patency, whereas the log-rank test was used to evaluate differences in patency between groups. Functional evaluations were performed using Doppler ultrasonography.
UNASSIGNED: Patients (n = 122) were randomly assigned to undergo CBA or conventional balloon angioplasty between December 2012 and November 2017. The clinical success rate was 100% in both groups. The anatomical success rates were 65% and 56% in the CBA and control groups, respectively. The primary patency of the target lesion was significantly better in the CBA group (33.3%) than in the control group (16.1%) at 6 months (hazard ratio, 0.50; 95% confidence interval, 0.33-0.77; p = 0.00171). The stenosis percentage decreased significantly after angioplasty in the CBA group (Δ-50.7%) compared with the control group (Δ-41.9%) (p = 0.0008). Access flow, measured using duplex Doppler ultrasonography, improved after angioplasty in both groups (300-526 ml/min in the control group and, 268-546 ml/min in the CBA group). Change in access flow (Δ + 278 ± 162) in the CBA group tended to be greater than that in the control group (Δ + 226 ± 151) (p = 0.07). However, the difference was not statistically significant.
UNASSIGNED: In patients with recurrent vascular access stenosis of the arteriovenous fistula CBA is effective and superior to conventional angioplasty.

BACKGROUND: The right internal jugular vein is the preferred approach to tunnelled haemodialysis catheter placement. However, the effect of the insertion site on long-term catheter outcomes remains uncertain.
OBJECTIVE: We aimed to analyse a large cohort of tunnelled haemodialysis catheter placements to compare short-term and long-term results according to central venous catheter location.
METHODS: A retrospective cohort study was performed on consecutive tunnelled catheter insertions at two centres over 7 years. The primary outcome was catheter survival, compared according to the central vein site. We used the Kaplan-Meier curve method and Cox proportional hazards modelling to determine the effect of the catheterisation route on primary patency, adjusted for clinical risk factors for catheter failure.
RESULTS: There were 967 tunnelled dialysis catheter placements in 620 patients. The median survival for right internal jugular vein catheters was 569 days. There were no differences in rates of catheter failure between right internal jugular, left internal jugular (adjusted hazard ratio [HR], 0.80; 95% confidence interval [CI], 0.52-1.21), external jugular (HR, 0.79; CI, 0.33-3.13), subclavian (HR, 0.67; CI, 0.58-2.44) and femoral vein (HR, 1.20; CI, 0.36-1.33) catheters following multivariable analysis. There were no major differences in functionality or complications between the groups.
CONCLUSIONS: This study identified no statistically significant relationship between tunnelled haemodialysis catheter insertion site and catheter survival. The contemporary approach to dialysis vascular access should be tailored to specific patient circumstances.

UNASSIGNED: Percutaneous transluminal angioplasty is the preferred treatment of stenosed failing arteriovenous fistulas (AVF) but is hampered by increasing rates of vascular restenosis because of development of myointimal hyperplasia.
UNASSIGNED: This multicenter observational study of polymer-coated low-dose paclitaxel-eluting stents (ELUvia stents by Boston Scientific) in stenosed AVF undergoing hemoDIAlysis (ELUDIA) was jointly conducted in three tertiary hospitals from Greece and Singapore. Failure of AVF was defined according to K-DOQI criteria and significant fistula stenosis (>50%DS by visual estimate) was determined with subtraction angiography. Patients were considered for ELUVIA stent insertion based on significant elastic recoil following balloon angioplasty for the treatment of a single vascular stenosis within a native AVF. The primary outcome measure was sustained long-term patency of the treated lesion/fistula circuit defined as successful stent placement with resumption of uninterrupted hemodialysis and without significant vascular restenosis (50%DS threshold) or other secondary interventions during follow-up.
UNASSIGNED: Some 23 patients received the ELUVIA paclitaxel-eluting stent (eight radiocephalic, 12 brachiocephalic, and three transposed brachiobasilic native AVFs). Mean AVF age at the time of failure was 33.9 ± 20.4 months. Treated lesions included 12 stenoses at the juxta-anastomotic segment, nine at the outflow veins, and two cephalic arch lesions with a mean diameter stenosis of 86 ± 8%. Median stent diameter and length used were 7 mm and 40 mm, respectively. After a median follow-up period of 20 months, some 18 stents out of 23 cases remained patent (cumulative rate 78.3%) without any clinical or imaging evidence of recurrent stenosis. Estimated primary patency of the ELUVIA stents was 80.6% and of the corresponding fistula circuit 65.1% at 2 years by Kaplan-Meier methods.
UNASSIGNED: This observational study has shown promising long-term results of polymer-coated paclitaxel-eluting stents for the treatment of failing arteriovenous fistulas. Large-scale controlled studies are necessary.

OBJECTIVE: There is a lack of adjudicated and prospectively randomized published outcomes on the use of drug-coated balloons (DCB) to treat dysfunctional arteriovenous fistula in Asian patients. This post hoc subgroup analysis of 112 Japanese participants from the global IN.PACT AV Access trial reports outcomes through 12 months.
METHODS: Participants were treated with DCB (n = 58) or standard non-coated percutaneous transluminal angioplasty (PTA) balloons (n = 54). Outcomes included target lesion primary patency (TLPP), access circuit primary patency, and safety.
RESULTS: Through 6 months, TLPP was 86.0% (49/57) in the DCB group and 49.1% (26/53) in the PTA group (p < 0.001). Through 12 months, TLPP was 67.3% (37/55) in the DCB group and 43.4% (23/53) in the PTA group (p = 0.013).
CONCLUSIONS: In this post hoc analysis of Japanese participants from the IN.PACT AV Access trial, participants treated with DCB had higher TLPP through 6 and 12 months compared with PTA.

UNASSIGNED: A prospective, pilot study was designed to test the feasibility of using sirolimus-coated balloon (SCB) to treat graft vein junction of thrombosed arteriovenous graft (AVG) following successful pharmacomechanical thrombectomy. The present report provides the 1-year results of this study.
UNASSIGNED: This is a 1-year follow-up of a single, prospective, single-arm study that was conducted from 2018 to 2019 in 20 patients who presented to a tertiary institution with thrombosed AVG. The recruited patients received SCB angioplasty at the graft-vein junction following successful endovascular thrombectomy of a thrombosed AVG. One year after recruitment, there were three deaths, one AVG revision, and one AVG explantation among the participants recruited. The outcomes of 15 subjects at 1-year following the index procedure obtained from electronic medical records were re-examined.
UNASSIGNED: The 1-year access circuit primary patency rate was 40%, while assisted primary and secondary patency rates were 46.7% and 73.3%, respectively. A total of 16 interventions (4 angioplasties, 12 thrombectomies) were performed in 9 patients over the 12 months. Four AVGs were abandoned. The median number of interventions per patient was 1 (0-3) per year. Using Kaplan-Meier analysis, the mean estimated post-intervention access circuit primary patency was 230 (95% CI: 162-300) days, while access circuit assisted primary patency was 253 (95% CI: 187-320) days, and access circuit secondary patency was 292 (95% CI: 230-356) days. Sub-group analysis did not show a significant difference in the mean estimated primary patency between AVG with de novo and recurrent stenosis (245 days, 95% CI: 151-339 vs 210 days, 95% CI: 113-307; p = 0.29).
UNASSIGNED: SCB may help sustain the patency of thrombosed AVG following successful thrombectomy.

UNASSIGNED: Posterior wall puncture of the AVG causes serious vascular access complications, but there is no concrete technical recommendation for AVG cannulation with plastic cannula. The purpose of this study is to identify cannulation techniques to reduce posterior wall puncture of the AVG using plastic cannula.
UNASSIGNED: Sixty-three hemodialysis nurses\' cannulations on experimental models were recorded and included in this study. Cannulations were conducted on AVG and AVF models with a plastic cannulation needle. We analyzed the angle of the needle, the motion of the needle, and the location of the needle in the graft lumen.
UNASSIGNED: The occurrence of posterior wall puncture of the AVG model was 22.2%. The cannulation angles in the AVG model were greater than those in the AVF model (p < 0.05). In the posterior wall puncture group of the AVG model, after the tip of the needle had reached into the graft lumen, the angle of the needle was not flattened (p < 0.05) and the outer sleeve of the needle was not inserted into the graft (p < 0.05). Furthermore, posterior wall puncture of the AVG model were observed in the group with less than 5 years of dialysis nursing experience (p < 0.05).
UNASSIGNED: From this study, after the tip of the needle had reached into the graft lumen, flattening the angle of the needle and inserting the outer sleeve of the needle into the graft were suggested as specific cannulation techniques to reduce posterior wall puncture of the AVG. Furthermore, this study also suggests the importance of cannulation technique education for new dialysis nurses to reduce cannulation-caused complications.

Blood flow rate in dialysis (vascular) access is the key parameter to examine patency and to evaluate the outcomes of various endovascular interve7ntions. While angiography is extensively used for dialysis access-salvage procedures, to date, there is no image-based blood flow measurement application commercially available in the angiography suite. We aim to calculate the blood flow rate in the dialysis access based on cine-angiographic and fluoroscopic image sequences. In this study, we discuss image-based methods to quantify access blood flow in a flow phantom model. Digital subtraction angiography (DSA) and fluoroscopy were used to acquire images at various sampling rates (DSA-3 and 6 frames/s, fluoroscopy-4 and 10 pulses/s). Flow rates were computed based on two bolus tracking algorithms, peak-to-peak and cross-correlation, and modeled with three curve-fitting functions, gamma variate, lagged normal, and polynomial, to correct errors with transit time measurement. Dye propagation distance and the cross-sectional area were calculated by analyzing the contrast enhancement in the vessel. The calculated flow rates were correlated versus an in-line flow sensor measurement. The cross-correlation algorithm with gamma-variate curve fitting had the best accuracy and least variability in both imaging modes. The absolute percent error (mean ± SEM) of flow quantification in the DSA mode at 6 frames/s was 21.4 ± 1.9%, and in the fluoroscopic mode at 10 pulses/s was 37.4 ± 3.6%. The radiation dose varied linearly with the sampling rate in both imaging modes and was substantially low to invoke any tissue reactions or stochastic effects. The cross-correlation algorithm and gamma-variate curve fitting for DSA acquisition at 6 frames/s had the best correlation with the flow sensor measurements. These findings will be helpful to develop a software-based vascular access flow measurement tool for the angiography suite and to optimize the imaging protocol amenable for computational flow applications.