Predicting the maturity of haemodialysis arteriovenous fistulas with colour Doppler ultrasound: a single-centre study from China

Modified no-touch technique for radio-cephalic arteriovenous fistula increases primary patency and decreases juxta-anastomotic stenosis

OBJECTIVE

Low primary patency rate is a major problem of radio-cephalic arteriovenous fistula (RC-AVF) creation. Radial artery deviation and reimplantation (RADAR) is associated with low juxta-anastomotic stenosis rate. However, inflow artery stenosis is prominent with RADAR. To further reduce injury to veins and arteries during operation, a modified no-touch technique (MNTT) was used to create RC-AVF.

METHODS

We retrospectively reviewed our prospectively maintained database of patients with end-stage renal disease (ESRD)s undergoing RC-AVF creation for hemodialysis using either the MNTT between January 2021 and January 2022 (MNTT group) or conventional surgical procedure ( end-to-side vein-to-artery anastomosis) between October 2016 and October 2017 (Control group). Patients who chose to undergo RC-AVF surgery underwent standardized preoperative mapping and postoperative fistula evaluations using duplex ultrasound. Additionally, 4D flow MRI data were used to visualize and quantify the hemodynamics of one RC-AVF by MNTT. Outcomes included primary patency, juxta-anastomotic stenosis, and maturation rates.

RESULTS

Forty patients underwent RC-AVFs by MNTT, compared to 60 patients in the control group. The MNTT group had a higher primary unassisted patency rate than the control group (p = 0.038). Juxta-anastomotic stenosis (all on the cephalic vein) occurred in 4 (10%) patients who underwent MNTT. RC-AVF maturation rates after 3 months were not different between both groups (maturation rate: 90% and 81.7% in the MNTT and control groups, respectively, p = 0.253). COX regression showed that both conventional AVF surgery (p = 0.031) and smaller cephalic vein diameter (p = 0.034) were associated with higher odds of RC-AVF failure. The AVF flow within the proximal vein remained helical during cardiac cycle. The distribution of wall shear stress (WSS) and oscillatory shear index (OSI) differed from that of conventional surgical AVF.

CONCLUSION

RC-AVF by MNTT increases primary patency rate and decreases juxta-anastomotic stenosis rate. The improvement in hemodynamics may be one of the important reasons for the better patency rate of in the RC-AVF by MNTT group.

Role of Doppler Evaluation in Assessing the Maturation of the Arteriovenous Fistula for Hemodialysis: An Observational Study

Introduction Arteriovenous fistulas (AVFs) are the preferred type of vascular access for hemodialysis due to their lower risk of complications. This study aimed to determine the role of Doppler evaluation in assessing AVF. Materials and methods We conducted an 18-month prospective observational study of 33 hemodialysis patients who underwent a procedure for the creation of AVF at the Department of Radio-Diagnosis at Sri Devaraj Urs Academy of Higher Education and Research. Patients were evaluated using color Doppler ultrasound. Participants underwent a careful history and clinical examination to diagnose the disease. All relevant parameters were documented in a structured study proforma. AVF maturation was assessed postoperatively at four weeks using Doppler ultrasound color flow evaluation by looking for vascular components (flow volume, vein, and arterial diameter). Data were analyzed using CoGuide V 1.0.3 Statistical Software (CoGuide, Bangalore, India). Results A total of 33 patients, with a mean age of 54.6 ± 7.8 years, were evaluated. Of the 33 participants, 24 (72.7%) were male, and nine (27.3%) were female. The majority (47%, n=16) of participants had diabetes mellitus, eight (24%) had hypertension, and 10 (29%) had both diabetes mellitus and hypertension. A brachiocephalic fistula was created in 45.5% of participants, and 33.33% had radiocephalic anastomoses. Five participants were diagnosed with AVF complications: two had a pseudoaneurysm, and three had a cephalic vein thrombus. Clinical and demographic characteristics (age, vascular components, and complications) were not significantly related to AVF maturation. Conclusions Doppler ultrasound plays an important role in selecting vessels for AVF preoperatively and assessing AVF maturation postoperatively, thus reducing the primary fistula failure rate. The findings suggest that Doppler evaluation can be a reliable tool for assessing AVF maturation and predicting surgical success, which could help healthcare providers make informed decisions about the best course of treatment for their patients. Continued research is warranted in this area to further understand the role of Doppler ultrasound in evaluating AVF surgery.

Automated 3D ultrasound enables novice users to measure arteriovenous fistula maturation parameters with comparable accuracy to conventional duplex by trained sonographers: Results of a benchtop study

BACKGROUND

Arteriovenous fistulae (AVF) are considered the preferred hemodialysis access but up to 50% of all AVF created in the United States never mature. Doppler ultrasound (DUS) is useful for predicting fistula maturity and impending fistula failure. DUS is resource-intensive and is associated with poor compliance rates in dialysis patients, ranging from 12% to 33%.

METHODS

EchoSure is an FDA-cleared 3D Doppler ultrasound device that automatically delivers quantitative blood flow and anatomic vascular information. The technology can be used at the bedside by personnel without formal sonographic training, nullifying limitations of traditional Duplex ultrasound imaging. This study compared the EchoSure system in the hands of inexpert personnel to a traditional expert-operated DUS for rapid assessment of a benchtop model vascular system with flow, diameter, and depth expected in a human AVF.

RESULTS

Both Duplex and EchoSure performed within the expected tolerance of ultrasound readings (35%) for volume flow, with the average error (AE) between the observed measurement and the ground truth being 8% for Duplex and 8% for EchoSure. However, the average coefficient of variation (CV) for Duplex pooled over all flow rate measurements was 17% versus 4% for EchoSure. Regarding diameter, Duplex measurements had AE of 15% with an average CV of 6% across all measurements versus EchoSure AE of 4% and average CV of 2%. Duplex and EchoSure measurements over all depths had the same AE of 2%. The two modalities were not statistically different for depth measurement (p = 0.05) but EchoSure measured closer to the ground truth for flow rate and vessel diameter (flow: p = 0.028, ρ = -0.07; diameter: p < 0.001, ρ = 0.69). The inexpert personnel using EchoSure acquired data 62% faster than the expert sonographers using the Duplex ultrasound (141 min for Duplex vs 87 min for EchoSure).

CONCLUSIONS

EchoSure may offer an accurate and convenient alternative for imaging fistulas in the clinic.

Differential hemodynamics between arteriovenous fistulas with or without intervention before successful use

A significant number of arteriovenous fistulas (AVFs) fail to maturate for dialysis. Although interventions promote maturation, functional primary patency loss is higher for AVFs with interventions (assisted maturation) than AVFs without interventions (un-assisted maturation). Although blood flow-associated hemodynamics have long been proposed to affect AVF remodeling, the optimal hemodynamic parameters for un-assisted maturation are unclear. Additionally, AVF maturation progress is generally not investigated until 6 weeks after AVF creation, and the examination is focused on the AVF's venous limb. In this exploratory study, patients (n = 6) underwent magnetic resonance imaging (MRI) at 1 day, 6 weeks, and 6 months after AVF creation surgery. Before successful use for hemodialysis, three AVFs required intervention and three did not. MRI of the AVFs were used to calculate lumen cross-sectional area (CSA) and perform computational fluid dynamics (CFD) to analyze hemodynamics, including velocity, wall shear stress (WSS), and vorticity. For the venous limb, the no-intervention group and intervention group had similar pre-surgery vein diameter and 1-day post-surgery venous CSA. However, the no-intervention group had statistically larger 1-day venous velocity (0.97 ± 0.67 m/s; mean ± SD), WSS (333 ± 336 dyne/cm2) and vorticity (1709 ± 1290 1/s) than the intervention group (velocity = 0.23 ± 0.10 m/s; WSS = 49 ± 40 dyne/cm2; vorticity = 493.1 ± 227 1/s) (P < 0.05). At 6 months, the no-intervention group had statistically larger venous CSA (43.5 ± 27.4 mm2) than the intervention group (15.1 ± 6.2 mm2) (P < 0.05). Regarding the arterial limb, no-intervention AVF arteries also had statistically larger 1-day velocity (1.17 ± 1.0 m/s), WSS (340 ± 423 dyne/cm2), vorticity (1787 ± 1694 1/s), and 6-month CSA (22.6 ± 22.7 mm2) than the intervention group (velocity = 0.64 ± 0.36 m/s; WSS = 104 ± 116 dyne/cm2, P < 0.05; vorticity = 867 ± 4551/s; CSA = 10.7 ± 6.0 mm2, P < 0.05). Larger venous velocity, WSS, and vorticity immediately after AVF creation surgery may be important for later lumen enlargement and AVF maturation, with the potential to be used as a tool to help diagnose poor AVF maturation earlier. However, future studies using a larger cohort are needed to validate this finding and determine cut off values, if any.

New hemodynamic variables as predictors of arteriovenous fistula maturation

INTRODUCTION

Failure to mature of native arteriovenous fistula (AVF) assessed by image is not well documented.

METHODS

The aim of this study is to evaluate AVF maturation by Doppler ultrasound within 6 weeks after surgery and check for new hemodynamic variables as prognostic factors.

RESULTS

A total of 155 native AVFs were created in 3 years. Median age of patients was 71 years (60;79), with male gender predominance of 59.4% (n = 92). Diabetes was present in 60.6% (n = 94). AVF was created in distal forearm in 49.7% (n = 77). Un-assisted and overall maturation was of 67.1% (n = 104) and 83.9% (n = 130), respectively. Failure to mature occurred in 21.3% (n = 33) and primary failure in 9.7% (n = 15). In univariate analysis, preoperative variables such as diameter of artery (3.5 vs. 2.2 mm; p < 0.001) and pulsatility index (7.9 vs. 6.6; p = 0.055) were associated with failure to mature of AVF. Postoperative variables as Qa (994 vs. 401 mL/min; p < 0.001), resistance index (0.52 vs. 0.63; p < 0.001), pulsatility index (0.74 vs. 1.21; p < 0.001), and acceleration time (0.17 vs. 0.12; p < 0.001) also predicted an unfunctional AVF. Spearman correlation coefficient (r) was good for resistance index (-0.628) and pulsatility index (-0.707) in comparison with blood flow (Qa). In multivariate analysis, postoperative pulsatility index was an independent predictor of AVF dysfunction (OR: 16.5; p < 0.001).

CONCLUSIONS

Failure to mature was of 21.3%. Pulsatility index could be an important tool as new hemodynamic variable to predict failure to mature of native AVF.

Arteriovenous fistula maturation: Physical exam versus flow study

PURPOSE

The purpose of this study was to determine the utility of routine duplex flow study 4 to 6 weeks after primary AVF creation and to compare physical exam against a duplex flow study in predicting fistula maturation. A surveillance algorithm was established to evaluate the naïve fistula after primary creation.

METHODS

This was a single institution retrospective review of 155 veterans with primary autogenous AVF creation from 2016 to 2018. All patients received a duplex flow study evaluation after primary creation. A comparison was made between physical exam (PE) and flow study at 4 to 6 weeks post creation. Sensitivities and specificities of physical exam and duplex flow study were compared head-to-head in predicting unassisted fistula maturation. A mature AVF was defined as a fistula that could be repetitively cannulated and provided adequate flow for dialysis. Failure of maturation was defined as an AVF that was never usable for dialysis. An abnormal duplex included thrombosis, stenosis (> 50% on gray scale imaging), inadequate vein diameter (< 4 mm), inadequate vein length or superficialization, or poor flow (< 500 ml/min). Bivariate comparisons were conducted using Pearson's χ², Fishers exact test, and Wilcoxon test depending on distribution. Significance was defined as P < 0.05.

RESULTS

There were 53 patients with radiocephalic (RC) fistulas, 41 patients with brachiocephalic (BC) fistulas, and 6 patients with brachiobasilic (BB) fistulas. Of patients with a confirmed abnormal duplex ultrasound, 53% had an abnormal PE (sensitivity 53%; PPV 96.3%, P < 0.001). Of the patients with a confirmed normal duplex, 98% had a normal PE (specificity 98%; NPV 68.5%, P < 0.001). An abnormal duplex flow study had a 67% sensitivity for predicting AVF failure or need for reintervention while an abnormal physical examination had a 42% sensitivity in predicting AVF failure or need for reintervention (P < 0.001). In total, 48 fistulas needed reintervention, however only 20 (42%) were associated with an abnormal physical examination. Of those 48 reinterventions, 20 (42%) fistulas exhibited primary assisted maturation (P < 0.001). On duplex flow study alone, 32 patients had hemodynamically significant lesions necessitating reintervention, which went on to afford 9 (28%) primary assisted mature fistulas (P = 0.69).

CONCLUSION

Abnormal duplex flow studies have a better sensitivity for detecting AVF failure or the need for reintervention compared to physical exam alone. An abnormal duplex correlates more with needing a reintervention to achieve maturation than physical exam. Therefore, we advocate routine use of a postoperative duplex flow study to identify potentially correctable issues and optimize fistula maturation.

Study on prediction of arterio-venous fistula maturation by flow mediated dilatation and AVF blood flow

BACKGROUND

The physiology and pathology of AVF maturation depends on the vessels characteristics and its ability to remodel. Outcome of AVF using flow mediated dilatation (FMD), AVF blood flow and diameter has been studied.

METHODOLOGY

Present observational study included single stage AVF (both Radiocephalic and Brachiocephalic) in consecutive CKD five patients (n = 158) prospectively over 1 year. Demographic and Doppler ultrasound parameters of upper limb (for vessel diameter and FMD) at baseline were recorded. Blood flow, diameter and depth of AVF were studied at 2, 6 and 12 weeks and their association with clinical maturation (usage of fistula with two needles for 75% of dialysis sessions during 15 day period) was studied (n = 129, after excluding lost to followup and expired patients; accordingly cohort was divided in matured (M) or non-matured (NM) groups. Clinical and radiological parameters between both groups were compared; receiver operator curve (ROC) and correlation of Doppler parameters were analysed.

RESULTS

Of 129 AVF, 67.4% were matured and 32.5% non-matured. Mean age was 40 years with male predominance75% in both the groups. The mean arterial diameter for distal (NM = 1.96 ± 0.58 and M = 2.02 ± 0.41) and proximal AVF (NM = 3.37 ± 0.82 and M = 3.36 ± 0.75) was not statistically different in both the groups. The matured fistula group had a mean FMD of 11.67 ± 4.09 as against FMD value of 9.365 ± 3.55 in the failed fistula group (p value 0.01). For maturation prediction, sensitivity and specificity of blood flow at 2 weeks were 86.2% and 59.5% and at 6 weeks 96.6% and 64.3%, respectively. In multivariate analysis predictors for AVF maturation were FMD (adjusted odds ratio (AOR) = 1.15) and blood flow (AOR = 1.67).

CONCLUSION

Second and Sixth week AVF blood flow was found to be predicting AVF maturation. Higher baseline FMD correlated with the AVF maturation, but not with vessel diameter.

A prospective cohort study of predictors of upper extremity arteriovenous fistula maturation

BACKGROUND

A substantial proportion of arteriovenous fistulas fail to function adequately for hemodialysis. Existing studies on arteriovenous fistula failure prediction assess patency rather than the more clinically relevant outcome of arteriovenous fistula function. We hypothesized that preoperative demographic and ultrasound characteristics, and postoperative assessment by an experienced vascular access nurse would predict which arteriovenous fistulas will not function adequately for hemodialysis.

METHODS

Prospective cohort study of chronic kidney disease patients at a tertiary care center in Vancouver, Canada, with arteriovenous fistula creation between 2009 and 2013. Pre and postoperative clinical assessment and ultrasound blood vessel mapping were performed by an experienced vascular access nurse. The primary outcome was failure to achieve a fistula used successfully for hemodialysis (FUSH).

RESULTS

Outcomes were assessed in 200 patients; 123 (61.5%) arteriovenous fistulas were radiocephalic. Overall, 26.5% of arteriovenous fistulas had FUSH failure (34.1% of lower arm vs 14.3% of upper arm, p = 0.002). Univariate predictors of FUSH failure included older age (p = 0.03), female sex (p = 0.05), smaller arterial diameter (p ⩽ 0.001), lower artery volume flow (p = 0.04), and smaller vein diameter (p = 0.01). In multivariable analysis, artery diameter (odds ratio: 0.44, 95% confidence interval: 0.28-0.68) most significantly predicted FUSH failure. Vascular access nurse assessment 6 weeks postoperatively correctly predicted outcome in 83.8% of FUSH and 65.0% of FUSH failure.

CONCLUSION

Smaller artery diameter most strongly predicted FUSH failure. Early postoperative nursing assessment was more useful to predict FUSH than FUSH failure, and as such was insufficient in determining which arteriovenous fistulas should be abandoned as many predicted to fail could be salvaged with further intervention.

Point-of-care ultrasound for assessing arteriovenous fistula maturity in outpatient hemodialysis

BACKGROUND

Point-of-care ultrasound in end-stage renal disease is on the rise. Presently the decision to cannulate an arteriovenous fistula is based on its duration since surgery and physical exam. This study examines the effects of point-of-care ultrasound on decreasing the time to arteriovenous fistula cannulation, time spent with a central venous catheter, and the complications and infections that arise.

METHODS

Prospective point-of-care ultrasound patients were recruited between January 2015 and January 2018, while retrospective data (non-point-of-care ultrasound) were collected via chart review from patients who had fistula creation between November 2011 and May 2014. Patients had point-of-care ultrasound within 3 weeks after arteriovenous fistula creation and were followed for 1 year. Arteriovenous fistula cannulation was initiated when the following parameters were met: diameter > 6 mm (with no depreciable narrowing of more than 20% throughout), depth < 6 mm, and length > 6 cm. Demographic data, as well as time to cannulation and central venous catheter removal, number of infections, complications, and interventions were compared between point-of-care ultrasound and non-point-of-care ultrasound groups using unpaired t-test, chi-square, and Fisher exact test statistical analysis.

RESULTS

A total of 37 patients with new arteriovenous fistulas were followed by point-of-care ultrasound compared to 29 non-point-of-care ultrasound patients. Point-of-care ultrasound patients had earlier cannulations (35.5 vs 63.3 days, p < 0.05), shorter central venous catheter duration (68.2 vs 98.3 days, p < 0.05), and less infections (12 vs 19) without differences in complication compared to the non-point-of-care ultrasound.

CONCLUSION

Point-of-care ultrasound facilitates early and safe arteriovenous fistula cannulation leading to a reduction in central venous catheter time and risk of infection. Point-of-care ultrasound may also aid in earlier identification of complications and difficult cannulations.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Characteristics of non-mature but functional autogenous radiocephalic fistulas in hemodialysis patients: A prospective cohort study

TARGET

To compare the ultrasound characteristics between functional, mature arteriovenous fistulas and functional, non-mature arteriovenous fistulas and to identify the predictors of arteriovenous fistula maturation in the forearm.

METHODS

Patients with newly set-up functional arteriovenous fistulas were enrolled in this prospective cohort study. Ultrasound examinations were conducted pre-operatively and post-operatively. The inner vessel diameter, blood flow volume, and resistance index were measured and compared between the maturation group (Group M) and non-maturation group (Group N). Baseline parameters were calculated to determine the predictors of non-maturation of arteriovenous fistulas.

RESULTS

All 52 patients with functional arteriovenous fistulas, who were categorized into Group M (25 patients, 48.08%) and Group N (27 patients, 51.92%), finished 24 weeks of follow-up after arteriovenous fistula surgery. The arteriovenous fistulas displayed a significant and rapid increase in the vessel diameter (mean increase of 1.34 times in the arteries and 1.92 times in the veins) and blood flow volume (mean increase of 9.29 times of the arteries and 43.66 times of the veins) and a decrease in the resistance index (mean decrease in 48.00% in the arteries) 8 weeks after surgery. Group N had a lesser increase in the vessel diameters (1.78 times vs 2.06 times, t = -3.136, p = 0.003) and blood flow volume (33.98 times vs 54.11 times, t = -2.383, p = 0.021) of the cephalic vein draining segments (a6) than Group M. The baseline diameter of a6 was the only independent predictor (regression coefficient = 26.229, p = 0.008) of maturation of the functional arteriovenous fistulas after correcting for sex, age, diabetes kidney disease, weight, and height.

CONCLUSION

The baseline diameter of the cephalic vein was the only predictor of arteriovenous fistula maturation based on the pre-operative ultrasound measurements in Chinese hemodialysis patients.

Prediction of Arteriovenous Fistula Clinical Maturation from Postoperative Ultrasound Measurements: Findings from the Hemodialysis Fistula Maturation Study

BACKGROUND

The utility of early postoperative ultrasound measurements in predicting arteriovenous fistula (AVF) clinical maturation is uncertain.

METHODS

We investigated the relationships of ultrasound parameters with AVF clinical maturation in newly created AVF, measured at 1 day and 2 and 6 weeks, in 602 participants of a multicenter, observational cohort study. A backward elimination algorithm identified ultrasound measurements that independently predicted unassisted and overall AVF maturation. Candidate variables included AVF blood flow, diameter, and depth, upper arm arterial diameter, presence of stenosis, presence of accessory veins, seven case-mix factors (age, sex, black race, AVF location, diabetes, dialysis status, and body mass index), and clinical center. We evaluated the accuracy of the resulting models for clinical prediction.

RESULTS

At each ultrasound measurement time, AVF blood flow, diameter, and depth each predicted in a statistically significant manner both unassisted and overall clinical maturation. Moreover, neither the remaining ultrasound parameters nor case-mix factors were associated with clinical AVF maturation after accounting for blood flow, diameter, and depth, although maturation probabilities differed among clinical centers before and after accounting for these parameters. The crossvalidated area under the receiver operating characteristic curve for models constructed using these three ultrasound parameters was 0.69, 0.74, and 0.79 at 1 day and 2 and 6 weeks, respectively, for unassisted AVF clinical maturation and 0.69, 0.71, and 0.76, respectively, for overall AVF maturation.

CONCLUSIONS

AVF blood flow, diameter, and depth moderately predicted unassisted and overall AVF clinical maturation. The other factors considered did not further improve AVF maturation prediction.

Postoperative Ultrasound, Unassisted Maturation, and Subsequent Primary Patency of Arteriovenous Fistulas

BACKGROUND AND OBJECTIVES

Postoperative ultrasound is commonly used to assess arteriovenous fistula (AVF) maturation for hemodialysis, but its utility for predicting unassisted AVF maturation or primary AVF patency for hemodialysis has not been well defined. This study assessed the predictive value of postoperative AVF ultrasound measurements for these clinical AVF outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We queried a prospective vascular access database to identify 246 patients on catheter-dependent hemodialysis who underwent AVF creation between 2010 and 2016 and obtained a postoperative ultrasound within 90 days. Multivariable logistic regression was used to evaluate the association of clinical characteristics and postoperative ultrasound measurements with unassisted AVF maturation. A receiver operating characteristic curve estimated the predictive value of these factors for unassisted AVF maturation. Finally, multivariable survival analysis was used to identify factors associated with primary AVF patency in patients with unassisted AVF maturation.

RESULTS

Unassisted AVF maturation occurred in 121 out of 246 patients (49%), assisted maturation in 55 patients (22%), and failure to mature in 70 patients (28%). Using multivariable logistic regression, unassisted AVF maturation was associated with AVF blood flow (odds ratio [OR], 1.30; 95% confidence interval [95% CI], 1.18 to 1.45 per 100 ml/min increase; P<0.001), forearm location (OR, 0.37; 95% CI, 0.08 to 1.78; P=0.21), presence of stenosis (OR, 0.45; 95% CI, 0.23 to 0.88; P=0.02); AVF depth (OR, 0.88; 95% CI, 0.77 to 1.00 per 1 mm increase; P=0.05), and AVF location interaction with depth (OR, 0.50; 95% CI, 0.28 to 0.84; P=0.02). The area under the receiver operating characteristic curve, using all these factors, was 0.84 (95% CI, 0.79 to 0.89; P<0.001). Primary AVF patency in patients with unassisted maturation was associated only with AVF diameter (hazard ratio, 0.84; 95% CI, 0.76 to 0.94 per 1 mm increase; P=0.002).

CONCLUSIONS

Unassisted AVF maturation is predicted by AVF blood flow, location, depth, and stenosis. AVF patency after unassisted maturation is predicted only by the postoperative AVF diameter.

Definitions and End Points for Interventional Studies for Arteriovenous Dialysis Access

This paper is part of the Clinical Trial Endpoints for Dialysis Vascular Access Project of the American Society of Nephrology Kidney Health Initiative. The purpose of this project is to promote research in vascular access by clarifying trial end points which would be best suited to inform decisions in those situations in which supportive clinical data are required. The focus of a portion of the project is directed toward arteriovenous access. There is a potential for interventional studies to be directed toward any of the events that may be associated with an arteriovenous access' evolution throughout its life cycle, which has been divided into five distinct phases. Each one of these has the potential for relatively unique problems. The first three of these correspond to three distinct stages of arteriovenous access development, each one of which has been characterized by objective direct and/or indirect criteria. These are characterized as: stage 1-patent arteriovenous access, stage 2-physiologically mature arteriovenous access, and stage 3-clinically functional arteriovenous access. Once the requirements of a stage 3-clinically functional arteriovenous access have been met, the fourth phase of its life cycle begins. This is the phase of sustained clinical use from which the arteriovenous access may move back and forth between it and the fifth phase, dysfunction. From this phase of its life cycle, the arteriovenous access requires a maintenance procedure to preserve or restore sustained clinical use. Using these definitions, clinical trial end points appropriate to the various phases that characterize the evolution of the arteriovenous access life cycle have been identified. It is anticipated that by using these definitions and potential end points, clinical trials can be designed that more closely correlate with the goals of the intervention and provide appropriate supportive data for clinical, regulatory, and coverage decisions.

Comparison of postoperative ultrasound criteria to predict unassisted use of arteriovenous fistulas for hemodialysis

Introduction:

Arteriovenous fistulas (AVF) frequently fail to mature. Postoperative ultrasounds provide objective measurements to predict unassisted AVF use for hemodialysis (unassisted use) and guide interventions to salvage nonmaturing AVFs. The optimal ultrasound criteria to assess AVF maturation are uncertain. We analyzed data from a multicenter, randomized, controlled, clinical trial to compare 2 published ultrasound maturation criteria used to predict unassisted AVF use for hemodialysis.

Methods:

We retrospectively analyzed prospective data on 105 patients undergoing new AVF creation, who underwent standardized postoperative ultrasounds at 6 and 12 weeks to measure AVF diameter and blood flow. Unassisted AVF use was defined as successful cannulation for ≥90 days without requiring prior surgical or percutaneous interventions. Two ultrasound criteria were assessed: (i) National Kidney Foundation (NKF) Kidney Disease Outcome Quality Initiative criteria: AVF outflow vein lumen diameter ≥6 mm and blood flow ≥600 mL/min; and (ii) University of Alabama at Birmingham (UAB) criteria: AVF outflow vein lumen diameter ≥4 mm and blood flow ≥500 mL/min. Performance characteristics were calculated for both criteria.

Results:

Compared to the NKF criteria, the UAB criteria had a higher sensitivity (89 vs.68%), but a lower specificity (42 vs. 70%) for unassisted AVF use. For radiocephalic AVFs, the UAB criteria had higher sensitivity (86 vs. 46%) and lower specificity (58 vs. 83%). For brachiocephalic AVFs, both UAB and NKF had high sensitivity (90 and 80%) but low specificity (21 and 53%), respectively.

Conclusions:

Using the UAB ultrasound criteria would minimize unnecessary early interventions in AVFs likely to mature without an intervention, but would delay interventions in AVFs that are unlikely to mature. The UAB criteria may be preferred in patients receiving a radiocephalic AVF.