Predictors of successful arteriovenous fistula maturation

Role of Hypoxia and Metabolism in the Development of Neointimal Hyperplasia in Arteriovenous Fistulas

For patients with end-stage renal disease requiring hemodialysis, their vascular access is both their lifeline and their Achilles heel. Despite being recommended as primary vascular access, the arteriovenous fistula (AVF) shows sub-optimal results, with about 50% of patients needing a revision during the year following creation. After the AVF is created, the venous wall must adapt to new environment. While hemodynamic changes are responsible for the adaptation of the extracellular matrix and activation of the endothelium, surgical dissection and mobilization of the vein disrupt the vasa vasorum, causing wall ischemia and oxidative stress. As a consequence, migration and proliferation of vascular cells participate in venous wall thickening by a mechanism of neointimal hyperplasia (NH). When aggressive, NH causes stenosis and AVF dysfunction. In this review we show how hypoxia, metabolism, and flow parameters are intricate mechanisms responsible for the development of NH and stenosis during AVF maturation.

Determinants of successful arteriovenous fistulae creation including intraoperative transit time flow measurement

BACKGROUND

The prevalence of hemodialysis patients is increasing, and it is important to create the arteriovenous fistula as early as possible to avoid hemodialysis by central venous catheter. International guidelines recommend arteriovenous fistula as the vascular access of first choice. Arteriovenous fistulae are associated with a failure rate of 23%. The success of an arteriovenous fistula can be evaluated intraoperatively by physical examination and by measuring the blood flow.

OBJECTIVES

The aim of the study is to describe the predictive value of various factors for fistula maturation in the context to the current literature.

METHODS

We report on a prospective cohort study of 41 patients, undergoing a primary arteriovenous fistula at the upper extremity. The primary endpoint of the study was the successful fistula maturation after 6 weeks.

RESULTS

The intraoperative measurement of the blood flow in the outflow vein has been identified as the unique significant parameter for the fistula maturation.

CONCLUSION

The predictive value of intraoperative flow measurement is superior to intraoperative physical examination and could help reduce the fistula dysmaturation rate. Intraoperative transit time flow measurement is an easy method and can be used to predict successful fistula maturation in a high percentage rate.

Factors affecting arteriovenous fistula dysfunction: A narrative review

Vascular access dysfunction is one of the most important causes of morbidity and mortality in haemodialysis patients, contributing to up to one third of hospitalisations and accounting for a significant amount of the health care costs of these patients. In the past decades, significant scientific advances in understanding mechanisms of arteriovenous fistula maturation and failure have contributed to an increase in the amount of research into techniques for creation and strategies for arteriovenous fistula dysfunction prevention and treatment, in order to improve patient care and outcomes. The aim of this review is to describe the pathogenesis of vascular access failure and provide a comprehensive analysis of the associated risk factors and causes of vascular access failure, in order to interpret possible future therapeutic approaches. Arteriovenous fistula failure is a multifactorial process resulting from the combination of upstream and downstream events with consequent venous neo-intimal hyperplasia and/or inadequate outward remodelling. Inflammation appears to be central in the biology of arteriovenous fistula dysfunction but important triggers still need to be revealed. Given the significant association of arteriovenous fistula failure and patient's prognosis, it is therefore imperative to further research in this area in order to improve prevention, surveillance and treatment, and ultimately patient care and outcomes.

The effect of endothelial nitric oxide synthase on the hemodynamics and wall mechanics in murine arteriovenous fistulas

Creation of a hemodialysis arteriovenous fistula (AVF) causes aberrant vascular mechanics at and near the AVF anastomosis. When inadequately regulated, these aberrant mechanical factors may impede AVF lumen expansion to cause AVF maturation failure, a significant clinical problem with no effective treatments. The endothelial nitric oxide synthase (NOS3) system is crucial for vascular health and function, but its effect on AVF maturation has not been fully characterized. We hypothesize that NOS3 promotes AVF maturation by regulating local vascular mechanics following AVF creation. Here we report the first MRI-based fluid-structure interaction (FSI) study in a murine AVF model using three mouse strains: NOS3 overexpression (NOS3 OE) and knockout (NOS3-/-) on C57BL/6 background, with C57BL/6 as the wild-type control (NOS3+/+). When compared to NOS3+/+ and NOS3-/-, AVFs in the OE mice had larger lumen area. AVFs in the OE mice also had smoother blood flow streamlines, as well as lower blood shear stress at the wall, blood vorticity, inner wall circumferential stretch, and radial wall thinning at the anastomosis. Our results demonstrate that overexpression of NOS3 resulted in distinct hemodynamic and wall mechanical profiles associated with favorable AVF remodeling. Enhancing NOS3 expression may be a potential therapeutic approach for promoting AVF maturation.

Disruptive technological advances in vascular access for dialysis: an overview

End-stage kidney disease (ESKD), one of the most prevalent diseases in the world and with increasing incidence, is associated with significant morbidity and mortality. Current available modes of renal replacement therapy (RRT) include dialysis and renal transplantation. Though renal transplantation is the preferred and ideal mode of RRT, this modality may not be available to all patients with ESKD. Moreover, renal transplant recipients are constantly at risk of complications associated with immunosuppression and immunosuppressant use, and posttransplant lymphoproliferative disorder. Dialysis may be the only available modality in certain patients. However, dialysis has its limitations, which include issues associated with lack of vascular access, risks of infections and vascular thrombosis, decreased quality of life, and absence of biosynthetic functions of the kidney. In particular, the creation and maintenance of hemodialysis vascular access in children poses a unique set of challenges to the pediatric nephrologist owing to the smaller vessel diameters and vascular hyperreactivity compared with adult patients. Vascular access issues continue to be one of the major limiting factors prohibiting the delivery of adequate dialysis in ESKD patients and is the Achilles' heel of hemodialysis. This review aims to provide a critical overview of disruptive technological advances and innovations for vascular access. Novel strategies in preventing neointimal hyperplasia, novel bioengineered products, grafts and devices for vascular access will be discussed. The potential impact of these solutions on improving the morbidity encountered by dialysis patients will also be examined.

Correlation between preoperative vein and artery diameters and arteriovenous fistula outcome in patients with end-stage renal disease

BACKGROUND AND AIMS

Arteriovenous fistula (AVF) maturation failure rates remain high in patients with end-stage renal disease (ESRD). Although preoperative morphological and functional assessment of blood vessels by duplex ultrasonography (DUS) has been shown to improve AVF maturation, there is no consensus regarding the optimal vein (VD) and artery (AD) diameters to be universally used for AVF creation. To improve patient selection, set out to investigate if there is a correlation between preoperative VD/AD and clinical covariates, and postoperative AVF outcome.

METHODS

This was a prospective cohort study conducted during January-August 2014. ESRD patients referred to "Niculae Stăncioiu" Heart Institute Cluj-Napoca, who had a VD ≥1.9 mm and AD ≥1.5 mm, as measured by DUS, and underwent AVF creation were enrolled. We assessed whether preoperative VD/AD and clinical covariates were associated with AVF maturation rate and primary patency at 2 years after AVF creation.

RESULTS

Of 115 patients referred for AVF creation, 93 were included in the study. Mean (± standard deviation) VD was 3.3 ± 1.1 mm and VDs were distributed in quartile Q1 <2.55 mm, Q2: 2.56-3.10 mm, Q3: 3.11-3.70 mm and Q4: >3.71 mm. Mean AD was 3.3 ± 1.4 mm and ADs were distributed in Q1 <2.55 mm, Q2: 2.56-3.10 mm, Q3: 3.11-3.70 mm, and Q4, >3.71 mm. AVF maturation rate increased proportionally with VD from Q1 (62%) to Q2 (70%), Q3 (82%) to Q4 (96%) (p=0.03). Based on AD, a higher AVF maturation rate was observed in Q3 (86%), Q4 (83%) vs Q1 (71%) and Q2 (67%). Long-term primary patency of AVFs seemed not to be influenced by VD and AD. In older patients and those with peripheral arterial disease, AVF maturation failure tended to be higher.

CONCLUSIONS

Our findings suggest that a preoperative VD ≥1.9 mm and AD ≥1.5 mm have a successful maturation rate of AVF greater than 60% in ESRD patients. The maturation rate of surgical AVF increases proportionally with the size of VD used for AVF creation.

Predictive parameters of arteriovenous fistula maturation in patients with end-stage renal disease

Background

The objevctive of the present study was to explore the potential influence of blood markers and patient factors such as risk factors, kidney function profile, coagulation profile, lipid profile, body mass index, blood pressure, and vein diameter on the maturation of arteriovenous fistula (AVF) in patients with end-stage renal disease.

Methods

Retrospective data from 300 patients who had undergone AVF creation at the Royal Infirmary of Edinburgh were examined. A predictive logistic regression model was developed using a backward stepwise procedure. Model performance, discrimination, and calibration were assessed using the receiver operating characteristic (ROC) curve and Hosmer–Lemeshow goodness-of-fit test. The final model was externally validated by 100 prospective patients who received a new fistula at the Royal Infirmary of Edinburgh.

Results

A total of 400 (300 retrospective and 100 prospective) patients were recruited for this study, with a mean age of 60.14 ± 15.9 years (development set) and 58 ± 15 years (validation set), respectively (P = 0.208). Study results showed that males were twice as likely to undergo fistula maturation as females, while patients with no evidence of peripheral vascular disease (PVD) were three times more likely to mature their fistula and a preoperative vein diameter > 2.5 mm resulted in a fivefold increase in fistula maturation as compared with a vein size of less than 2.5 mm. The model for fistula maturation had fair discrimination, as indicated by the area under the ROC curve (0.68), but good calibration as indicated by the Hosmer–Lemeshow test (P = 0.79). The area under the receiver operating curve for the validation model in the validation set was 0.59. Similarly, in the validation set, the Hosmer–Lemeshow statistic indicated an agreement between the observed and predicted probabilities of maturation (P > 0.05).

Conclusion

Gender, PVD, and vein size are independent predictors of AVF maturation. The clinical utility of these risk categories in the maturation of AVF requires further evaluation in longer follow-up.

Intraoperative Heparin Use during Upper Extremity Arteriovenous Access Creation Does Not Affect Outcomes

BACKGROUND

There are conflicting data about the effect of heparin use on perioperative outcomes during upper extremity arteriovenous (AV) access creation. Our goal was to assess the effect of the use and degree of intraoperative heparin on perioperative outcomes after AV access creation.

METHODS

All upper extremity AV access cases performed at a tertiary academic medical center between 2014 and 2017 were reviewed. Patient and procedural details including intraoperative heparin use and dosing as well as protamine use were analyzed. Full heparin dose was defined as 80-100 U/kg and partial heparin dose as less than 80 U/kg. Perioperative arterial thrombosis or distal embolism, hematoma, and early loss of primary patency within 30 days were evaluated. Multivariate analysis was performed to assess the effect of heparin use.

RESULTS

There were 550 AV access cases identified: brachiocephalic (37.5%), brachiobasilic (29.3%), and radiocephalic fistulas (12.9%), and AV grafts (16.9%). Average patient age was 62.6 years and 58.9% were male. Full heparinization was used in 21.3%, partial heparinization in 58.7%, and no heparin was used in 20% of cases. Protamine was used in 94.9% of full heparin cases and 51.4% of partial heparin cases. No perioperative arterial thrombosis or distal embolism was observed. Perioperative wound hematoma rate was 3.4%, 3.1%, and 0.9% in full heparin, partial heparin, and no heparin cohorts, respectively (P = 0.42). Early loss of primary patency was 11.1%, 7.7%, and 6.4% for full heparin, partial heparin, and no heparin cases, respectively (P = 0.39). There were no differences in return to the operating room or perioperative survival. On multivariable analysis, full heparin use (odds ratio [OR] 3.82, 95% confidence interval [CI] 0.41-35.9, P = 0.24) and partial heparin (OR 4.03, 95% CI 0.5-32.6, P = 0.19) use were not significantly different from no heparin cases with respect to 30-day perioperative hematoma rate. Full heparin (OR 1.76, 95% CI 0.65-4.78, P = 0.26) and partial heparin (OR 1.13, 95% CI 0.46-2.75, P = 0.79) were not significantly different from no heparin cases with respect to early loss of primary patency.

CONCLUSIONS

Intraoperative heparin use, at full or partial doses, did not affect perioperative outcomes after AV access creation. Overall complication event rate was low for all groups. AV access can be safely performed without intraoperative heparin use.

Drug-Coated Versus Plain Balloon Angioplasty In Arteriovenous Fistulas: A Randomized, Controlled Study With 1-Year Follow-Up (The Drecorest Ii-Study)

Background and Aims:

Stenosis due to intimal hyperplasia and restenosis after initially successful percutaneous angioplasty are common reasons for failing arteriovenous fistulas. The aim of this study was to evaluate the effect of drug-coated balloons in the treatment of arteriovenous fistula stenosis.

Design:

Single-center, parallel group, randomized controlled trial. Block randomized by sealed envelope 1:1.

Materials and Methods:

A total of 39 patients with primary or recurrent stenosis in a failing native arteriovenous fistulas were randomized to drug-coated balloon (n = 19) or standard balloon angioplasty (n = 20). Follow-up was 1 year. Primary outcome measure was target lesion revascularization.

Results:

In all, 36 stenoses were analyzed; three patients were excluded due to technical failure after randomization. A total of 88.9% (16/18) in the drug-coated balloon group was revascularized or occluded within 1 year, compared to 22.2% (4/18) of the stenoses in the balloon angioplasty group (relative risk for drug-coated balloon 7.09). Mean time-to- target lesion revascularization was 110 and 193 days after the drug-coated balloon and balloon angioplasty, respectively (p = 0.06).

Conclusions:

With 1-year follow-up, the target lesion revascularization-free survival after drug-coated balloon-treatment was clearly worse. The reason for this remains unknown, but it may be due to differences in the biological response to paclitaxel in the venous arteriovenous fistula-wall compared to its antiproliferative effect in the arterial wall after drug-coated balloon treatment of atherosclerotic occlusive lesions. Trial registration: ClinicalTrials.gov NCT03036241

Spanish Clinical Guidelines on Vascular Access for Haemodialysis

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Outcomes of the First and Second Hemodialysis Fistula: A Cohort Study

RATIONALE & OBJECTIVE

Fistulas are the preferred form of hemodialysis access; however, many fistulas fail to mature into usable accesses after creation. Data for outcomes after placement of a second fistula are limited.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

People who initiated hemodialysis therapy in any of 5 Canadian dialysis programs (2004-2012) and had at least 1 hemodialysis fistula placed.

PREDICTOR

Second versus initial fistula; receipt of 2 versus 1 fistula; second versus first fistula in recipients of 2 fistulas.

OUTCOMES

Catheter-free fistula use during 1 year following initiation of hemodialysis therapy or following fistula creation, if created after hemodialysis therapy start; proportion of time with catheter-free use; time to catheter free use; time of functional patency.

ANALYTICAL APPROACH

Logistic regression; fractional regression.

RESULTS

Among the 1,091 study participants (mean age, 64±15 [SD] years; 63% men; 59% with diabetes), 901 received 1 and 190 received 2 fistulas. 38% of second fistulas versus 46% of first fistulas were used catheter free at least once. Average percentages of time that second and initial fistulas were used catheter free were 34% and 42%, respectively (OR, 0.72; 95% CI, 0.54-0.94). Compared with people who received 1 fistula, those who received 2 fistulas were less likely to achieve catheter-free use (26% vs 56%) and remain catheter free (23% vs 49% of time; OR, 0.30, 95% CI, 0.24-0.39). Among people who received 2 fistulas, the proportion of time that the second fistula was used catheter free was 11% higher with each 10% greater proportion of time that the first fistula was used catheter free (95% CI, 1%-22%). Model discrimination was modest (C index, 0.69).

LIMITATIONS

Unknown criteria for patient selection for 1 or 2 fistulas; unknown reasons for prolonged catheter use.

CONCLUSIONS

Outcomes of a second fistula may be inferior to outcomes of the initial fistula. First and second fistula outcomes are weakly correlated and difficult to predict based on clinical characteristics.

Early application of an intermittent pneumatic compression device assists dilation of radiocephalic fistulas

INTRODUCTION:

Radiocephalic fistulas are the preferred type of arteriovenous fistula due to their advantageous location. However, radiocephalic fistula maturation has historically been inferior to brachiocephalic fistulas. Research indicates that intermittent compression may aid in forearm vein dilation. Early use of a compression device may assist radiocephalic fistula maturation.

OBJECTIVES:

This prospective, randomized, placebo controlled study evaluates device safety and the effect of intermittent compression on vein size of radiocephalic fistulas and brachiocephalic fistulas.

METHODS:

This was an institutional review board-approved study. After fistula creation, a novel, intermittent pneumatic compression device (Fist Assist^®) was worn 15 cm proximal to fistulas 6 h daily for 30 days. Those in the treatment group (n = 43) wore Fist Assist^® (24 with brachiocephalic fistulas and 19 with radiocephalic fistulas). Clinical controls (n = 16) wore a sham device. Vein diameter was measured at 0 and 30 days by duplex measurement. Percentage increase was recorded and tested for significance.

RESULTS:

After 30 days, the mean percentage increase in vein diameter in the radiocephalic fistula treatment group was significantly larger than brachiocephalic fistulas in the treatment group at all proximal locations from the anastomosis. Increases in percentage vein dilation for those in the radiocephalic fistula treatment group were significantly larger than those in the control group. All fistulas treated with Fist Assist^® are still functional with no reported complications.

CONCLUSION:

Early application of the Fist Assist^® device may be more effective at helping radiocephalic fistula mature as compared to brachiocephalic fistulas. Successful radiocephalic fistula maturation may decrease vascular access costs, reduce complications, and preserve upper arm veins for future use in vascular access.

Heterogeneity in the nonplanarity and arterial curvature of arteriovenous fistulas in vivo

OBJECTIVE

Native arteriovenous fistulas (AVFs) for hemodialysis are susceptible to nonmaturation. Adverse features of local blood flow have been implicated in the formation of perianastomotic neointimal hyperplasia that may underpin nonmaturation. Whereas computational fluid dynamic simulations of idealized models highlight the importance of geometry on fluid and vessel wall interactions, little is known in vivo about AVF geometry and its role in adverse clinical outcomes. This study set out to examine the three-dimensional geometry of native AVFs and the geometric correlates of AVF failure.

METHODS

As part of an observational study between 2013 and 2016, patients underwent creation of an upper limb AVF according to current surgical best practice. Phase-contrast magnetic resonance imaging was performed on the day of surgery to obtain luminal geometry along with ultrasound measurements of flow. Magnetic resonance imaging data sets were segmented and reconstructed for quantitative and qualitative analysis of local geometry. Clinical maturation was evaluated at 6 weeks.

RESULTS

There were 60 patients who were successfully imaged on the day of surgery. Radiocephalic (n = 17), brachiocephalic (n = 40), and brachiobasilic (n = 3) fistulas were included in the study. Centerlines extracted from segmented vessel lumen exhibited significant heterogeneity in arterial nonplanarity and curvature. Furthermore, these features are more marked in brachiocephalic than in radiocephalic fistulas. Across the cohort, the projected bifurcation angle was 73 ± 16 degrees (mean ± standard deviation). Geometry was preserved at 2 weeks in 20 patients who underwent repeated imaging. A greater degree of arterial nonplanarity (log odds ratio [logOR], 0.95 per 0.1/vessel diameter; 95% confidence interval [CI], 0.22-1.90; P = .03) and a larger bifurcation angle (logOR, 0.05 per degree; 95% CI, 0.01-0.09; P = .02) are associated with a greater rate of maturation, as is fistula location (upper vs lower arm; logOR, -1.9; 95% CI, -3.2 to 0.7; P = .002).

CONCLUSIONS

There is significant heterogeneity in the three-dimensional geometry of AVFs, in particular, arterial nonplanarity and curvature. In this largest cohort of AVF geometry to date, the effect of individual geometric correlates on maturation is uncertain but supports the premise that future modeling studies will need to acknowledge the complex geometry of AVFs.

Early application of an intermittent pneumatic compression device is safe and results in proximal arteriovenous fistula enlargement

Introduction:

Delays in arteriovenous fistula maturation can cause care delays and increased costs. Increased distention pressure and intermittent wall shear stress may dilate veins based on prior research. Early use of non-invasive devices may help assist clinical arteriovenous fistula dilation.

Methods:

This was an Institutional Review Board approved study. After arteriovenous fistula creation, a novel, intermittent pneumatic compression device (Fist Assist®) was applied 15 cm proximal to arteriovenous fistula enabling 60 mmHg of cyclic compression for 6 h daily for 30 days. Among the patients who completed 1 month follow-up, 30 (n = 30) arteriovenous fistula patients were in the study arm to test vein dilation with Fist Assist. Controls (n = 16) used a sham device. Vein size was measured and recorded at baseline and after 30 days by duplex measurement. Clinical results (percentage increase) were recorded and tested for significance.

Results:

No patients experienced thrombosis or adverse effects. Patient compliance and satisfaction was high. After 1 month, the mean percentage increase in vein diameter in the Fist Assist treatment group was significantly larger (p = 0.026) than controls in the first 5 mm segment of the fistula after the anastomosis. All fistulas treated with Fist Assist are still functional with no reported thrombosis or extravasations.

Conclusions:

Early application of an intermittent pneumatic compression device may assist in arteriovenous fistula dilation and are safe. Non-invasive devices like Fist Assist may have clinical utility to help fistulae development and decrease costs as they may eventually assist maturation.

Predicting Technical Success after Fistuloplasty: An Analysis of 176 Procedures

BACKGROUND

Significant stenoses in arteriovenous fistulae (AVFs) or arteriovenous grafts (AVGs) with limitation of flow and dialysis inadequacy should prompt consideration for fistuloplasty. We sought to identify fistulae, lesions, and patient-specific variables, which predict for outcomes after fistuloplasty.

METHODS

Data were extracted retrospectively from a renal access database from 2011 to 2016 of patients undergoing fistuloplasty. Demographics, comorbidities, outcomes of intervention, and flow rates documented on preintervention and postintervention duplex were collected. Secondary analysis of factors associated with postfistuloplasty flow rates of >600 mL/min, previously shown to be predictive of not requiring future intervention, was performed.

RESULTS

Of 204 attempted fistuloplasties, 176 were completed. One hundred forty (79.5%) were native AVFs and 34 (19.3%), AVGs (no data for 2). Median stenosis treated was 75%, with a majority (43.8%) in the proximal outflow vein. Flow rate on duplex after fistuloplasty was significantly better in AVFs (mean improvement 189.2 mL/min) than that in AVGs (mean improvement 51.8 mL/min; P = 0.034). Greatest flow improvement occurred for needling site stenotic lesions compared with other locations (from anastomosis to central vein) but was not significant. Brachio-brachial or brachio-axillary AVGs did significantly (P < 0.05) worse than all other fistulae types. The presence of hypertension was predicted for postfistuloplasty flow rate of >600 mL/min.

CONCLUSIONS

Flow rates after fistuloplasty vary depending on the type of fistula treated and the presence of hypertension. Knowledge of this can lead to better patient selection and counseling for fistuloplasty.

Comparison of surgical and radiological interventions for thrombosed arteriovenous access

INTRODUCTION:

To compare open surgical and radiological interventions for thrombosed arteriovenous access for dialysis.

METHODS:

A retrospective analysis of access procedures and dialysis episodes from 1 December 2002 to 30 November 2015 with follow-up up to 1 August 2016. Hospital records and dialysis database interrogated for further interventions and length of functional use.

RESULTS:

Some 128 surgical and 27 radiological thrombectomies were compared. Radiological treatment was successful in 24 (89%) cases and surgical interventions in 65 cases (51%; p < 0.001). In all, 82 (64%) of the 128 surgical thrombectomies had no additional treatment, 43 (34%) had a surgical revision and 3 cases (2%) had an on-table balloon angioplasty. All 27 interventional thrombectomies had an additional balloon angioplasty. Success rate was significantly increased after a surgical revision (74%) or balloon angioplasty (87%) compared to no adjuvant procedure (38%; p < 0.001). There was a trend towards higher primary failure rates of arteriovenous fistula thrombectomies in the upper arm (57%) compared to the arteriovenous fistula thrombectomies in forearm (40%) and arteriovenous graft thrombectomies (33%; p = 0.056). Assisted primary patency was better after interventional treatment compared to surgery (p = 0.02) and significantly better after thrombectomy with additional treatment (p = 0.005). Patency after surgical revision or balloon angioplasty of the access was similar (p = 0.15). More procedures were required to maintain the access after balloon angioplasty than after surgical revision, and intervention-free survival was better after surgical revision (p = 0.02).

CONCLUSION:

Revision procedures significantly increase success rate of access thrombectomies. Radiological thrombectomies have higher success rates but lower intervention-free survival and need more additional procedures to maintain patency.

Impact of pre-operative venography on the planning and outcome of vascular access for hemodialysis patients

Objective

Pre-operative venous mapping has increased dramatically in most dialysis units since the Dialysis Outcome Quality Initiative (DOQI) guidelines recommended a native arteriovenous venous fistula (AVF) rather than a graft for hemodialysis (HD) access procedures. However, there are conflicting consequences as a result of this policy. Some studies have showed that routine mapping has resulted in a marked increase in maturation rate while others have observed the reverse. This study aimed to evaluate the impact of pre-operative venography on the planning and outcome of AVF for our HD patients.

Patients and methods

A prospective study was performed on all patients with end-stage renal disease (ESRD) who had HD access procedures and pre-operative venography between October 2003 and November 2005. Upper limb venography was done for all patients except those that required primary access and had visible veins. All patients had HD immediately after the venography. Access procedure selection was based on the result of the venography. The complications of venography, the surgical procedure and the outcome were recorded.

Results

One hundred and twenty-nine patients with ESRD who had pre-operative venography were included in this study. They were mostly middle age (mean age ± SD = 41 ± 15.5 yrs) with a high rate of diabetes mellitus (53%). No single complication was reported. A graft was placed in six patients (5%) only. Unsuccessful surgical exploration was 0%. Early failure was in 10 patients (8%).

Conclusion

Pre-operative venography resulted in an increase in the number of AVFs. It can improve the results of HD access procedures by selecting the most suitable veins.

Hemodialysis Arteriovenous Fistulas: A Nineteenth Century View of a Twenty First Century Problem

This is a literature review which approaches the problem of successful use of arteriovenous fistulas for dialysis within the construct of Virchow's triad. By organizing the literature with regard to Virchow's concepts of blood flow, vascular injury, and thrombophilia an improved understanding arteriovenous fistula placement, maintenance and repair can be obtained. This process is designed to increase understanding and options for treatment by looking at this problem and using scientific knowledge gained in cardiology, oncology and vascular surgery medicine. Future approaches to fistulas will hopefully be a multifaceted and based in cellular pathophysiology as well as surgical and radiologic interventions and repairs.

Vascular Access: Past, Present, and Future

Vascular access is the Achilles’ heel of hemodialysis. Current vascular access approaches for hemodialysis include arteriovenous (AV) fistula, AV graft, and central venous catheter. Strengths and weaknesses of each access type are described. New technology and procedures in introducing an access, monitoring access function, and salvaging a non-functioning access are also described.

Outcomes of arteriovenous fistula creation, effect of preoperative vein mapping and predictors of fistula success in incident haemodialysis patients: A single-centre experience

AIM

Vascular access in haemodialysis is critical for effective therapy. We aim to evaluate the outcomes of arteriovenous fistula (AVF) creation in incident haemodialysis patients, impact of preoperative vein mapping and predictors of successful AVF maturation in our centre.

METHODS

Data of End-stage Renal Disease (ESRD) patients initiated on haemodialysis from January 2010 to December 2012 in our centre were retrospectively obtained from electronic medical records and clinical notes. Demographic characteristics, medical comorbidities, perioperative details were collected, and patients were followed up until 1 January 2014.

RESULTS

A total of 708 patients (median age 64, IQR 55-72) were included with mean duration of follow up of 2.3 ± 1.2 years, with access of AVF and arteriovenous graft (AVG) in 694 (98%) and 14 (2%) patients respectively. Eight patients were lost to follow-up. Successful AVF maturation was achieved in 542 patients (78%), with 1-year cumulative patency rate of 74%. Multivariate analysis revealed male gender, upper arm AVF and good postoperative thrill and pulse as predictors of successful AVF maturation. Preoperative vein mapping was performed in 42.5% (295/694) of patients, with mean vein diameter of 2.44 ± 0.82 mm. Maturation rates with and without vein mapping were 72.2% and 82.4%, respectively, (P = 0.001). In patients with vein diameters of <2 mm and ≥2 mm, there was no statistically significant difference in maturation rates (71.3% vs. 72.6%; P = 0.887) and median maturation time (66 vs. 78 days; P = 0.73).

CONCLUSION

Arteriovenous fistula can be successfully created in most incident haemodialysis patients. Routine vein mapping is not necessary if veins are suitable on physical examination alone, and vein sizes of <2 mm on ultrasound is not associated with lower AVF maturation rate.

Choice of Hemodialysis Access in Older Adults: A Cost-Effectiveness Analysis

BACKGROUND AND OBJECTIVES

Although arteriovenous fistulas have been found to be the most cost-effective form of hemodialysis access, the relative benefits of placing an arteriovenous fistula versus an arteriovenous graft seem to be least certain for older adults and when placed preemptively. However, older adults' life expectancy is heterogeneous, and most patients do not undergo permanent access creation until after dialysis initiation. We evaluated cost-effectiveness of arteriovenous fistula placement after dialysis initiation in older adults as a function of age and life expectancy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using a hypothetical cohort of patients on incident hemodialysis with central venous catheters, we constructed Markov models of three treatment options: (1) arteriovenous fistula placement, (2) arteriovenous graft placement, or (3) continued catheter use. Costs, utilities, and transitional probabilities were derived from existing literature. Probabilistic sensitivity analyses were performed by age group (65-69, 70-74, 75-79, 80-84, and 85-89 years old) and quartile of life expectancy. Costs, quality-adjusted life-months, and incremental cost-effectiveness ratios were evaluated for up to 5 years.

RESULTS

The arteriovenous fistula option was cost effective compared with continued catheter use for all age and life expectancy groups, except for 85-89 year olds in the lowest life expectancy quartile. The arteriovenous fistula option was more cost effective than the arteriovenous graft option for all quartiles of life expectancy among the 65- to 69-year-old age group. For older age groups, differences in cost-effectiveness between the strategies were attenuated, and the arteriovenous fistula option tended to only be cost effective in patients with life expectancy >2 years. For groups for which the arteriovenous fistula option was not cost saving, the cost to gain one quality-adjusted life-month ranged from $2294 to $14,042.

CONCLUSIONS

Among older adults, the cost-effectiveness of an arteriovenous fistula placed within the first month of dialysis diminishes with increasing age and lower life expectancy and is not the most cost-effective option for those with the most limited life expectancy.

Cost-effectiveness Analysis of Vascular Access Referral Policies in CKD

BACKGROUND

The optimal timing of vascular access referral for patients with chronic kidney disease who may need hemodialysis (HD) is a pressing question in nephrology. Current referral policies have not been rigorously compared with respect to costs and benefits and do not consider patient-specific factors such as age.

STUDY DESIGN

Monte Carlo simulation model.

SETTING & POPULATION

Patients with chronic kidney disease, referred to a multidisciplinary kidney clinic in a universal health care system.

MODEL, PERSPECTIVE, & TIMEFRAME

Cost-effectiveness analysis, payer perspective, lifetime horizon.

INTERVENTION

The following vascular access referral policies are considered: central venous catheter (CVC) only, arteriovenous fistula (AVF) or graft (AVG) referral upon HD initiation, AVF (or AVG) referral when HD is forecast to begin within 12 (or 3 for AVG) months, AVF (or AVG) referral when estimated glomerular filtration rate is <15 (or <10 for AVG) mL/min/1.73m².

OUTCOMES

Incremental cost-effectiveness ratios (ICERs, in 2014 US dollars per quality-adjusted life-year [QALY] gained).

RESULTS

The ICER of AVF (AVG) referral within 12 (3) months of forecasted HD initiation, compared to using only a CVC, is ∼$105k/QALY ($101k/QALY) at a population level (HD costs included). Pre-HD AVF or AVG referral dominates delaying referral until HD initiation. The ICER of pre-HD referral increases with patient age. Results are most sensitive to erythropoietin costs, ongoing HD costs, and patients' utilities for HD. When ongoing HD costs are excluded from the analysis, pre-HD AVF dominates both pre-HD AVG and CVC-only policies.

LIMITATIONS

Literature-based estimates for HD, AVF, and AVG utilities are limited.

CONCLUSIONS

The cost-effectiveness of vascular access referral is largely driven by the annual costs of HD, erythropoietin costs, and access-specific utilities. Further research is needed in the field of dialysis-related quality of life to inform decision making regarding vascular access referral.

Optimal timing for vascular access creation

Many guidelines recommend that end-stage renal disease (ESRD) patients should have a permanent vascular access, preferably an autologous arteriovenous fistula (AVF), at the start of renal replacement therapy. Nevertheless, a large proportion of patients still start hemodialysis with a central venous catheter (CVC). On the other hand, there are increasing numbers of patients in whom an AVF has been created, but who never actually end up on dialysis, as well as a substantial number of patients in whom creation of a vascular access has been attempted unsuccessfully.To improve this situation, timely exploration to assess suitability for and creation of preemptive AVF should be promoted. Decision to construct an AVF should depend on the likelihood and rate of progression to ESRD. For this goal, some reliable prediction models are available. Also, the likelihood that such an attempt will result in a successful outcome should be taken into account, but suitable validated models to accurately make such estimates are lacking. Next to patient-specific factors, some local conditions such as easy access to a vascular surgeon should also be incorporated in the decision-making process between the nephrology team and the patient.

Evaluation of Diagnostic Values of Clinical Assessment in Determining the Maturation of Arteriovenous Fistulas for Satisfactory Hemodialysis

BACKGROUND

Fistulas are the preferred permanent hemodialysis vascular access, but a significant obstacle to increasing their prevalence is the fistula's high "failure to mature" (FTM) rate. This study aimed to identify postoperative clinical characteristics that are predictive of fistula FTM.

MATERIALS AND METHODS

This descriptive cross-sectional study was performed on 80 end-stage renal disease patients who referred to Al Zahra Hospital, Isfahan, for brachiocephalic fistula placement. After 4 weeks, the clinical criteria (trill, firmness, vein length, and venous engorgement) examined and the fistulas situation divided to favorable or unfavorable by each criterion, and the results comprised with dialysis possibility. Data were analyzed with SPSS version 21. Diagnostic index for CLINICAL examination was calculated.

RESULTS

Among the 80 cases, 25 (31.2%) female and 55 (68.8%) male were studied with the mean age of 51.9 (standard deviation = 17) year ranged between 18 and 86 years old. Sixty-two (77.5%) cases had successful hemodialysis. All four clinical assessments were significantly more acceptable in patients with successful dialysis (P < 0.001). According to the results of our study, the accuracy of all physical assessments was above 70% and except vein length other criteria had a sensitivity and negative predictive value of 100%. In this study, firmness of vein has highest specificity and positive predictive value (83.9% and 64.3%, respectively).

CONCLUSION

Results of our study showed that high sensitivity and relatively low specificity of the clinical criterion. It means that unfavorable results of each clinical criterion predict unfavorable dialysis. Clinical evaluation of a newly created fistula 4-6 weeks after surgery should be considered mandatory.

Clinical Utility of a New Predicting Score for Radiocephalic Arteriovenous Fistula Survival

BACKGROUND

Radiocephalic arteriovenous fistula (RC-AVF) is the recommended first choice for vascular access (VA). The CAVeA₂T₂ scoring system was recently published (ipsilateral central venous catheter access, age >73 years, vein <2.2 mm, lower limb angioplasty, and absent intraoperative thrill). The aim of the present study was to assess the clinical utility of the CAVeA₂T₂ scoring system for predicting RC-AVFs survival in our center and its subsequent application in VA management.

MATERIAL AND METHODS

In this single-center retrospective study, all RC-AVFs performed from January 2010 to July 2014 were included. The CAVeA₂T₂ was applied. Primary, assisted primary, and secondary patency rates were measured.

RESULTS

Sixty RC-AVFs were analyzed. Mean age was 64.3 ± 14.7 years. Mean CAVeA₂T₂ score was 1.23 ± 1.2. The median fistula secondary patency was 13.7 ± 1.6 months. Secondary patency was at 6 weeks and at 6, 12, and 24 months: 88.3%, 66.7%, 55%, and 31.7%, respectively. Increasing score (≥2) was associated with a decrease in primary (log-rank, χ² = 16.7, dif = 1, P = 0.0001) and secondary patency rate survival (log-rank, χ² = 5.4, dif = 1, P = 0.0001). In addition, stratification of the CAVeA₂T₂ score into 3 groups (scores 0-1, 2, and 3+) retained its significance for primary (log-rank, χ² = 19.4, dif = 2, P = 0.0001) and secondary patency rate survival (log-rank, χ² = 5.5, dif = 2, P = 0.046) at the end of the study.

CONCLUSIONS

In the present study, the CAVeA₂T₂ scoring system has proved to be a useful, easy to apply tool that is highly predictive of RC-AVF survival. Based on our results, we should avoid perform RC-AVFs, in those patients with CAVeA₂T₂ score ≥2 and late nephrology referral. Prospective studies should be designed to establish the management of patients with a higher CAVeA₂T₂ score.

Cilostazol May Improve Maturation Rates and Durability of Vascular Access for Hemodialysis

Cilostazol is effective in controlling pathophysiological pathways similar or identical to those involved in nonmaturation and failure of the arteriovenous access. This case–control study examined whether cilostazol would improve maturation rates and durability of vascular access for hemodialysis. The treatment group included 33 patients who received cilostazol for ≥30 days prior to creation of a dialysis access and continued with cilostazol therapy for ≥60 days after surgery. The matched (gender, age, race, diabetes, and the year of surgery) control group included 116 patients who underwent the same procedure but did not receive cilostazol prior to and at least 3 months after surgery. Primary outcomes were maturation and, for those that matured, time of functioning access, defined as the time from the first use to irreparable failure of the access. Secondary outcomes were time to maturation, complications, and time to first complication. Study group patients were 3.8 times more likely to experience fistula maturation compared to the controls (88% vs 66%, RR = 3.8, 95% confidence interval: 1.3-11.6, P = .016). Fewer patients in the study group had complications (76% vs 92%, P = .025), and the time from construction of the fistula to the first complication was longer (345.6 ± 441 days vs 198.3 ± 185.0 days, P = .025). Time to maturation was similar in both groups (119.3 ± 62.9 days vs 100.2 ± 61.7 days, P = .2). However, once matured, time to failure was significantly longer in the treatment group (903.7 ± 543.6 vs 381.6 ± 317.2 days, P = .001). Multivariate analysis confirmed that the likelihood of maturation was significantly higher in the treatment group patients. These results suggest that dialysis access patients may benefit from preoperative and postoperative cilostazol therapy. If confirmed by a randomized trial, this treatment will have a major beneficial impact on patients dependent on a well-functioning access for their hemodialysis.

An Increase in Mean Platelet Volume/Platelet Count Ratio Is Associated with Vascular Access Failure in Hemodialysis Patients

After stenosis of arteriovenous vascular access in hemodialysis patients, platelets play a crucial role in subsequent thrombus formation, leading to access failure. In a previous study, the mean platelet volume (MPV)/platelet count ratio, but not MPV alone, was shown to be an independent predictor of 4-year mortality after myocardial infarction. However, little is known about the potential influence of MPV/platelet count ratio on vascular access patency in hemodialysis patients. A total of 143 patients undergoing routine hemodialysis were recruited between January 2013 and February 2016. Vascular access failure (VAF) was defined as thrombosis or a decrease of greater than 50% of normal vessel diameter, requiring either surgical revision or percutaneous transluminal angioplasty. Cox proportional hazards model analysis ascertained that the change of MPV/platelet count ratio between baseline and 3 months [Δ(MPV/platelet count ratio)_3mo-baseline] had prognostic value for VAF. Additionally, the changes of MPV/platelet count ratio over time were compared in patients with and without VAF by using linear mixed model analysis. Of the 143 patients, 38 (26.6%) were diagnosed with VAF. During a median follow-up of 26.9 months (interquartile range 13.0–36.0 months), Δ(MPV/platelet count ratio)_3mo-baseline significantly increased in patients with VAF compared to that in patients without VAF [11.6 (6.3–19.0) vs. 0.8 (-1.8–4.0), P< 0.001]. In multivariate analysis, Δ(MPV/platelet ratio count)_3mo-baseline was an independent predictor of VAF, after adjusting for age, sex, diabetes, hypertension, coronary artery disease, cerebrovascular disease, vascular access type, the presence of previous VAF, and antiplatelet drug use (hazard ratio, 1.15; 95% confidence interval, 1.10–1.21; P< 0.001). Moreover, a liner mixed model revealed that there was a significant increase of MPV/platelet count ratio over time in patients with VAF compared to those without VAF (P< 0.001). An increase in MPV/platelet count ratio over time was an independent risk factor for VAF. Therefore, continuous monitoring of the MPV/platelet count ratio may be useful to screen the risk of VAF in patients undergoing routine hemodialysis.

The molecular mechanisms of hemodialysis vascular access failure

The arteriovenous fistula has been used for more than 50 years to provide vascular access for patients undergoing hemodialysis. More than 1.5 million patients worldwide have end stage renal disease and this population will continue to grow. The arteriovenous fistula is the preferred vascular access for patients, but its patency rate at 1 year is only 60%. The majority of arteriovenous fistulas fail because of intimal hyperplasia. In recent years, there have been many studies investigating the molecular mechanisms responsible for intimal hyperplasia and subsequent thrombosis. These studies have identified common pathways including inflammation, uremia, hypoxia, sheer stress, and increased thrombogenicity. These cellular mechanisms lead to increased proliferation, migration, and eventually stenosis. These pathways work synergistically through shared molecular messengers. In this review, we will examine the literature concerning the molecular basis of hemodialysis vascular access malfunction.

Intradialytic Ultrafiltration Volume and Vascular Access Outcomes: A Japan Dialysis Outcomes and Practice Patterns Study Subanalysis

Introduction

The relationship between intradialytic ultrafiltration volume and vascular access (VA) patency remains unclear. Using data from the Japan Dialysis Outcomes and Practice Patterns Study, we analyzed whether large-volume ultrafiltration was associated with VA failure in hemodialysis patients.

Methods

We included 2736 patients for whom it was possible to evaluate VA patency and bodyweight change during dialysis. Patients were divided into three groups according to the tertile of intradialytic ultrafiltration by bodyweight: low, -9.5%-3.8%; middle, 3.8%-5.1%; and high, 5.1%-13.7%. Primary VA patency was defined as the time to first VA intervention, and secondary patency as the time to creation of a new VA. Hazard ratios for VA failure were compared across groups by using Cox regression models adjusted for age, sex, body mass index, diabetes, hemoglobin and phosphorus levels, Kt/V, and erythropoiesis-stimulating agent and antiplatelet use.

Results

For the low, middle, and high groups, the incidences of primary and secondary VA patency were 4.7, 5.6, and 6.7 events/100 person-years and 1.3, 1.6, and 1.7 events/100 person-years, respectively. Adjusted hazard ratios for primary VA patency in the middle and high groups versus the low group were 1.16 (95% confidence interval [CI], 0.88-1.52) and 1.41 (95% CI, 1.07-1.87), respectively; those for secondary VA patency were 1.29 (95% CI, 0.78-2.13) and 1.45 (95% CI, 0.86-2.45), respectively.

Discussion

Large-volume ultrafiltration during dialysis tended to increase VA failure in hemodialysis patients. We thus recommend smaller ultrafiltration volumes during hemodialysis to secure VA safely.

Future research directions to improve fistula maturation and reduce access failure

With the increasing prevalence of end-stage renal disease, there is a growing need for hemodialysis. Arteriovenous fistulae (AVF) are the preferred type of vascular access for hemodialysis, but maturation and failure continue to present significant barriers to successful fistula use. AVF maturation integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes in the setting of uremia, systemic inflammation, oxidative stress, and pre-existent vascular pathology. AVF can fail due to both failure to mature adequately to support hemodialysis and development of neointimal hyperplasia that narrows the AVF lumen, typically near the fistula anastomosis. Failure due to neointimal hyperplasia involves vascular cell activation and migration and extracellular matrix remodeling with complex interactions of growth factors, adhesion molecules, inflammatory mediators, and chemokines, all of which result in maladaptive remodeling. Different strategies have been proposed to prevent and treat AVF failure based on current understanding of the modes and pathology of access failure; these approaches range from appropriate patient selection and use of alternative surgical strategies for fistula creation, to the use of novel interventional techniques or drugs to treat failing fistulae. Effective treatments to prevent or treat AVF failure require a multidisciplinary approach involving nephrologists, vascular surgeons, and interventional radiologists, careful patient selection, and the use of tailored systemic or localized interventions to improve patient-specific outcomes. This review provides contemporary information on the underlying mechanisms of AVF maturation and failure and discusses the broad spectrum of options that can be tailored for specific therapy.

Prospective Evaluation of Factors Associated with Early Failure of Arteriovenous Fistulae in Hemodialysis Patients

Recent guidelines have recommended performing native arteriovenous fistulae (AVF) in hemodialysis patients rather than synthetic grafts whenever possible. However, early failure of AVF may reach up to 50%. The purpose of this study was to assess the factors associated with early failure of such procedures in hemodialysis patients.

A prospective study was performed on all patients with end-stage renal disease who had an AVF between June 2003 and March 2005. Data including patient characteristics and the type of AVF were recorded. The internal diameter of the vein and artery and intraoperative blood flow were measured. Patients were followed up for 3 months.

One hundred twenty-six AVF were included in this study. Early failure was in 14 (9%) patients. The internal diameter of the vein and artery and intraoperative blood flow were significantly lower in the failure group than in the patent group. The failure rate was not significantly related to other parameters.

Our data showed that intraoperative blood flow is a reliable parameter that determines the early failure of an AVF. Careful selection of the vein and the artery may reduce the rate of failure.

Leptin, pre-existing vascular disease, and increased arteriovenous fistula maturation failure in dialysis patients

BACKGROUND

The adipocytokine leptin is an independent cardiovascular risk factor and exerts proatherogenic effect. Pre-existing vascular disease is an important cause of arteriovenous fistula (AVF) maturation failure. We explored the association between serum leptin, pre-existing vascular disease, and AVF maturation failure in incident hemodialysis patients.

METHODS

Vein samples from 62 patients were collected at the time of AVF creation. Pre-existing vascular disease was evaluated with histologic changes and immunohistochemical characteristics of cellular phenotypes in intima. AVF maturation failure was defined as an AVF that could not be used successfully by the third month after its creation.

RESULTS

The prevalence of body mass index ≥30 kg/m² was 17%, and AVF maturation failure occurred in 28 (45%) patients. Patients within the highest leptin tertile showed significantly higher maturation failure rate, independent of age, gender, diabetes, and body mass index. On histologic examination, significant differences in intimal hyperplasia (13.3 ± 4.5 vs 18.2 ± 5.2 vs 30.3 ± 14.3 μm) and medial thickening (76.8 ± 23.7 vs 103.9 ± 33.6 vs 109.3 ± 36.5 μm) were observed across leptin tertiles. Similarly, medial fibrosis was most severe in the highest tertile. According to the immunohistochemical staining, most intimal cells were α-smooth muscle actin-positive, vimentin-positive, desmin-negative myofibroblasts. However, in the lowest tertile, desmin-positive contractile smooth muscle cells were also frequently observed, suggesting relatively slow phenotypic changes in this group. Furthermore, as leptin tertiles increased, the expression of leptin receptor in the luminal border of intima was significantly decreased.

CONCLUSIONS

Obesity-related higher fistula maturation failure rate may be partly mediated by higher leptin level-associated pre-existing vascular diseases in end-stage renal disease patients. Decreased expression of leptin receptor may be related to this association.

The Biology of Hemodialysis Vascular Access Failure

Arteriovenous fistulas (AVFs) are essential for patients and clinicians faced with end-stage renal disease (ESRD). While this method of vascular access for hemodialysis is preferred to others due to its reduced rate of infection and complications, they are plagued by intimal hyperplasia. The pathogenesis of intimal hyperplasia and subsequent thrombosis is brought on by uremia, hypoxia, and shear stress. These forces upregulate inflammatory and proliferative cytokines acting on leukocytes, fibroblasts, smooth muscle cells, and platelets. This activation begins initially with the progression of uremia, which induces platelet dysfunction and primes the body for an inflammatory response. The vasculature subsequently undergoes changes in oxygenation and shear stress during AVF creation. This propagates a strong inflammatory response in the vessel leading to cellular proliferation. This combined response is then further subjected to the stressors of cannulation and dialysis, eventually leading to stenosis and thrombosis. This review aims to help interventional radiologists understand the biological changes and pathogenesis of access failure.

Arteriovenous fistula in dialysis patients: Factors implicated in early and late AVF maturation failure

Increasing numbers of patients are being diagnosed with end-stage renal disease (ESRD), and the demand for on haemodialysis (HD) is rising. Arteriovenous fistulae (AVFs) remain the best conduit for adequate HD, with fewer complications associated with long-term use compared to bypass grafts and central venous catheters. However, it is known that many newly formed fistulae do not mature to provide useful HD access. The paper provides a narrative overview of factors influencing the process of AVF maturation failure.

Importance of monitoring and treatment of failed maturation in radiocephalic arteriovenous fistula in predialysis: Role of ultrasound

The aim of the study was to analyse outcomes of AVF-RC in predialysis stage in which a clinical and radiological follow up of its maturation had been done and primary failure had been treated.

MATERIAL AND METHODS

We studied 127 RC-AVF in 117 predialysis patients. All cases had a preoperative map. The RC-AVF was considered mature if it had a brachial artery flow ≥500ml/min and a cephalic vein diameter of ≥4mm. Primary failure was treated radiologically or surgically depending on the type of lesion. Fifty-eight patients started dialysis at the time of the study.

RESULTS

In 106 RC-AVF without thrombosis, 72 (68%) were mature and 34 (32%) were immature. A total of 97% of the immature had at least one lesion, and the most common site was the post-anastomotic vein. Lesions were found in 31% of mature RC-AVF, and 18% of patients required treatment. Radiological treatment was the most frequent for maturation failure. After 6 months, primary and secondary patency were 59% and 78%, while after 12 months they were 48% and 77%, respectively. The 80% of patients started dialysis with a distal AVF (76% RC-AVF and 4% ulnar basilic). None of the patients with treated immature RC-AVF started dialysis with CVC, while 78% of the patients started with said AVF.

CONCLUSION

Ultrasonography for monitoring maturation provides advantages over clinical monitoring. With our management of RC-AVF in predialysis, 80% of patients start dialysis with an adequate distal AVF.

Predictive models for arteriovenous fistula maturation

PURPOSE

Haemodialysis (HD) is a lifeline therapy for patients with end-stage renal disease (ESRD). A critical factor in the survival of renal dialysis patients is the surgical creation of vascular access, and international guidelines recommend arteriovenous fistulas (AVF) as the gold standard of vascular access for haemodialysis. Despite this, AVFs have been associated with high failure rates. Although risk factors for AVF failure have been identified, their utility for predicting AVF failure through predictive models remains unclear. The objectives of this review are to systematically and critically assess the methodology and reporting of studies developing prognostic predictive models for AVF outcomes and assess them for suitability in clinical practice.

METHODS

Electronic databases were searched for studies reporting prognostic predictive models for AVF outcomes. Dual review was conducted to identify studies that reported on the development or validation of a model constructed to predict AVF outcome following creation. Data were extracted on study characteristics, risk predictors, statistical methodology, model type, as well as validation process.

RESULTS

We included four different studies reporting five different predictive models. Parameters identified that were common to all scoring system were age and cardiovascular disease.

CONCLUSIONS

This review has found a small number of predictive models in vascular access. The disparity between each study limits the development of a unified predictive model.

Hemodialysis arteriovenous fistula as first option not necessary in elderly patients

OBJECTIVE

Kidney Disease Outcomes Quality Initiative guidelines recommend arteriovenous fistulas as the preferred access for hemodialysis patients. However, this may not hold across all populations of patients, especially the elderly, given their comorbidities and relatively reduced life expectancy. Therefore, we investigated whether fistulas held benefit over arteriovenous grafts as hemodialysis access in elderly patients.

METHODS

We retrospectively searched a vascular access database to compare the outcomes for 138 fistulas and 44 grafts that were placed in elderly patients (≥75 years old) during a 4-year period at a tertiary medical center.

RESULTS

The primary failure rate was higher for the fistulas compared with the grafts (odds ratio, 2.89; P = .008), and more fistulas required one or more interventions before their successful use compared with grafts (31% vs 10%, respectively; P = .03). In addition, the time to catheter-free dialysis was longer for fistulas than for grafts (P < .001). However, the primary and secondary patency rates were comparable between the fistulas and grafts and between the different access locations. The all-cause mortality rates were also comparable between the fistula and graft groups.

CONCLUSIONS

Despite the Fistula First Initiative recommendations, grafts need not be discounted as a first-line hemodialysis access option in select elderly patients.

Interrupting Rivaling Access-flow with Nonsurgical Image-guided ligation: the "IRANI" Procedure

The presence of collateral veins is one of the most common causes of fistula failure to mature. The traditional approach to eliminate collateral vessel flow is coil embolization under fluoroscopy or surgical cut down and branch vessel ligation. However, both approaches are expensive and time consuming. Here, we described an image-guided nonsurgical method to ligate collateral veins. The collateral veins were ligated using Hawkins-Akins needle under ultrasound guidance. The average time for one ligation procedure was 17 minutes. There was a significant increase of blood flow in the venous outflow postligation procedure. Four weeks postprocedure ultrasound demonstrated occlusion of the target vessels. This procedure was well tolerated without major complications. In summary, the novel procedure described here offers an image-guided nonsurgical approach for collateral vein occlusion.

Preoperative and Intraoperative Factors for Early Failure of Native Arteriovenous Fistulas

The aim of the study was to assess the potential predictive factors for early arteriovenous fistula (AVF) failure following the fistula first initiative. We retrospectively reviewed the data of 159 end-stage renal disease (ESRD) patients who underwent AVF creation. The preoperative factors such as demographic, comorbidity condition, laboratory parameters and medication, and intraoperative or surgical-related factors were assessed. In multivariate logistic regression analysis, significant predictive factors of early AVF failure were female gender (odds ratio (95% confidence interval): 2.63 (1.19-5.81); P = 0.017), higher body mass index (P = 0.038), and lower hemoglobin level (P = 0.048), while adjusting for preoperative factors or all factors. For adjusting of intraoperative factors, reduced venous diameter (P = 0.056) tended to be associated with early AVF failure. In conclusion, female gender, higher body mass index and lower hemoglobin level predicted the occurrence of early AVF failure in ESRD patients.