Medical Adjuvant Treatment to Improve the Patency of Arteriovenous Fistulae and Grafts: A Systematic Review and Meta-analysis

Therapeutic strategies based on non-ionizing radiation to prevent venous neointimal hyperplasia: the relevance for stenosed arteriovenous fistula, and the role of vascular compliance

We have reviewed the development and current status of therapies based on exposure to non-ionizing radiation (with a photon energy less than 10 eV) aimed at suppressing the venous neointimal hyperplasia, and consequentially at avoiding stenosis in arteriovenous grafts. Due to the drawbacks associated with the medical use of ionizing radiation, prominently the radiation-induced cardiovascular disease, the availability of procedures using non-ionizing radiation is becoming a noteworthy objective for the current research. Further, the focus of the review was the use of such procedures for improving the vascular access function and assuring the clinical success of arteriovenous fistulae in hemodialysis patients. Following a brief discussion of the physical principles underlying radiotherapy, the current methods based on non-ionizing radiation, either in use or under development, were described in detail. There are currently five such techniques, including photodynamic therapy (PDT), far-infrared therapy, photochemical tissue passivation (PTP), Alucent vascular scaffolding, and adventitial photocrosslinking. The last three are contingent on the mechanical stiffening achievable by the exogenous photochemical crosslinking of tissular collagen, a process that leads to the decrease of venous compliance. As there are conflicting opinions on the role of compliance mismatch between arterial and venous conduits in a graft, this aspect was also considered in our review.

Long-term patency of arteriovenous fistulas for hemodialysis: A decade's experience in a transplant unit

BACKGROUND

The heterogeneous quality of studies on arteriovenous fistulas outcome, with variable clinical settings and large variations in definitions of patency and failure rates, leads to frequent misinterpretations and overestimation of arteriovenous fistula patency. Hence, this study aimed to provide realistic and clinically relevant long-term arteriovenous fistula outcomes.

METHODS

We retrospectively analyzed all autologous arteriovenous fistulas at our center over a 10-year period (2012-2022). Primary and secondary patency analysis was conducted using the Kaplan-Meier method; multivariate analysis of variance was used to detect outcome predictors. Vascular access-specific endpoints were defined according to the European guidelines on vascular access formation.

FINDINGS

Of 312 arteriovenous fistulas, 57.5% (n = 181) were radio-cephalic (RC_AVF), 35.2% (n = 111) brachio-cephalic (BC_AVF), and 6.3% (n = 20) brachio-basilic (BB_AVF). 6, 12, and 24 months follow-up was available in 290 (92.1%), 282 (89.5%), and 259 (82.2%) patients, respectively. Primary patency rates at 6, 12, and 24 months were 39.5%, 34.8%, and 27.2% for RC_AVF, 58.3%, 44.4%, and 27.8% for BC_AVF, and 40.0%, 42.1%, and 22.2% for BB_AVF (p = 0.15). Secondary patency rates at 6, 12, and 24 months were 65.7%, 63.8%, and 59.0% for RC_AVF, 77.7%, 72.0%, and 59.6% for BC_AVF, and 65.0%, 68.4%, and 61.1% for BB_AVF (p = 0.29). Factors associated with lower primary and secondary patency were hemodialysis at time of arteriovenous fistula formation (p = 0.037 and p = 0.024, respectively) and higher Charlson Comorbidity Index (p = 0.036 and p < 0.001, respectively). Previous kidney transplant showed inferior primary patency (p = 0.005); higher age inferior secondary patency (p < 0.001).

DISCUSSION

Vascular access care remains challenging and salvage interventions are often needed to achieve maturation or maintain patency. Strict adherence to standardized outcome reporting in vascular access surgery paints a more realistic picture of arteriovenous fistula patency and enables reliable intercenter comparison.

Effects of an arteriovenous fistula stenosis prevention program in patients receiving hemodialysis

BACKGROUND

To increase the efficiency of hemodialysis, an appropriate vascular pathway must be created, and its function must be maintained. This study aimed to identify the effects of an arteriovenous fistula (AVF) stenosis prevention program on upper muscular strength, blood flow, physiological indexes, and self-efficacy among patients receiving hemodialysis.

METHODS

The participants were patients receiving hemodialysis at Keimyung University Dongsan Medical Center in Daegu, Republic of Korea. They were divided into experimental and control groups based on the day of the week they received hemodialysis at the outpatient department and included 25 participants each. The study was conducted for 8 weeks.

RESULTS

The AVF stenosis prevention program was effective in improving upper extremity muscle strength (F=15.23, p<0.001) and blood flow rate (F=36.00, p<0.001). As a result of the program, the phosphorus index level, which is a physiological indicator in hemodialysis patients, decreased (F=8.64, p<0.001). Encouragement and support through text messages and practice lists also resulted in an increase in self-efficacy (F=18.62, p<0.001).

CONCLUSION

The AVF stenosis prevention program in this study resulted in an increase in upper extremity muscle strength through grip strength exercises and was effective in preventing AVF stenosis by increasing the blood flow rate.

Hydrogel delivery of purinergic enzymes improves cardiac ischemia/reperfusion injury

RATIONALE

The innate immune response contributes to cardiac injury in myocardial ischemia/reperfusion (MI/R). Neutrophils are an important early part of the innate immune response to MI/R. Adenosine, an endogenous purine, is a known innate immune modulator and inhibitor of neutrophil activation. However, its delivery to the heart is limited by its short half-life (<30 s) and off-target side effects. CD39 and CD73 are anti-inflammatory homeostatic enzymes that can generate adenosine from phosphorylated adenosine substrate such as ATP released from injured tissue.

OBJECTIVE

We hypothesize that hydrogel-delivered CD39 and CD73 target the local early innate immune response, reduce neutrophil activation, and preserve cardiac function in MI/R injury.

METHODS AND RESULTS

We engineered a poly(ethylene) glycol (PEG) hydrogel loaded with the adenosine-generating enzymes CD39 and CD73. We incubated the hydrogels with neutrophils in vitro and showed a reduction in hydrogen peroxide production using Amplex Red. We demonstrated availability of substrate for the enzymes in the myocardium in MI/R by LC/MS, and tested release kinetics from the hydrogel. On echocardiography, global longitudinal strain (GLS) was preserved in MI/R hearts treated with the loaded hydrogel. Delivery of purinergic enzymes via this synthetic hydrogel resulted in lower innate immune infiltration into the myocardium post-MI/R, decreased markers of macrophage and neutrophil activation (NETosis), and decreased leukocyte-platelet complexes in circulation.

CONCLUSIONS

In a rat model of MI/R injury, CD39 and CD73 delivered via a hydrogel preserve cardiac function by modulating the innate immune response.

Role of Antiplatelet Therapy in Hemodialysis Arteriovenous Graft Secondary Patency Following Successful Percutaneous Thrombectomy

PURPOSE

The purpose of this study was to elicit the relationship of antiplatelet therapy (AP) in maintaining arteriovenous graft (AVG) patency after successful percutaneous pharmacomechanical thrombectomy ("declot").

MATERIALS AND METHODS

This was an institutional review board-approved retrospective review of AVG declot procedures between July 2019 and August 2020. AVG characteristics, bleeding complications, anticoagulation and antiplatelet medication regimens, and thrombosis free survival were evaluated. Recurrent time-to-event analysis was performed using a Prentice-Williams-Peterson Gap time model was performed to evaluate AVG thrombosis free survival.

RESULTS

A total of 109 declots were technically successful and performed in 63 individual patients. The majority of procedures were performed in upper arm grafts (71%, n = 45). Dual antiplatelet (DAPT) was prescribed after 52 declots (48%), single antiplatelet was prescribed after 36 declots (33%), and anticoagulation was prescribed after 31 declots (28%). Median thrombosis free survival was 37 days (range 1-412 days) in the no antiplatelet group, 84 days (range 1-427 days) in the single antiplatelet group, and 93 days (range 3-407 days) in the DAPT group. Anti-platelet medications trended towards protective of AVG thrombosis in multivariate analysis (hazard ratio 0.84, 95% confidence interval 0.60-1.19); however, this did not reach statistical significance (P = 0.33). A total of 4 major and 5 minor bleeding events occurred.

CONCLUSION

The results of this study support further evaluation of AP therapy in preventing secondary rethrombosis of dialysis AVG.

Association of Permanent Vascular Access Dysfunction with Subsequent Risk of Cardiovascular Disease: A Population-Based Cohort Study

A functional permanent vascular access (VA) is required to perform a successful hemodialysis procedure. Hemodialysis VA dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population. Cardiovascular disease (CVD) is the leading cause of death in patients receiving chronic hemodialysis. Information about CVD associated with hemodialysis VA dysfunction is unclear. We analyzed the association between dialysis VA dysfunction and the risk of developing CVD in hemodialysis patients. This nationwide population-based cohort study was conducted using data from the National Health Insurance Research Database in Taiwan. One million subjects were sampled from 23 million beneficiaries and data was collected from 2000 to 2013. Patients with end-stage renal disease who had received permanent VA construction and hemodialysis and were aged at least 20 years old from 2000 to 2007 were included in the study population. The primary outcome was CVD, as defined by ICD-9-CM codes 410–414 and 430–437. A total of 197 individuals with permanent VA dysfunction were selected as the test group, and 100 individuals with non-permanent VA dysfunction were selected as the control group. Compared with the control group, the adjusted hazard ratio of CVD for the VA dysfunction group was 3.05 (95% CI: 1.14–8.20). A Kaplan–Meier analysis revealed that the cumulative incidence of CVD was higher in the permanent VA dysfunction group than in the comparison group. Permanent VA dysfunction is significantly associated with an increased risk of subsequent CVD.

Brachial artery transposition versus catheters as tertiary vascular access for maintenance hemodialysis: a single-center retrospective study

Some hemodialysis patients are not suitable for creation of an arteriovenous fistula (AVF) or arteriovenous graft (AVG). However, they can receive a tunneled cuffed central venous catheter (tcCVC), but this carries risks of infection and mortality. We aimed to evaluate the safety and effectiveness of brachial artery transposition (BAT) versus those of tcCVC. This retrospective study evaluated hemodialysis patients who underwent BAT or tcCVC placement because of severe heart failure, hand ischemia, central venous stenosis or occlusion, inadequate vessels for creating standard arteriovenous access, or limited life expectancy. The primary outcome was whole access circuit patency. Thirty-eight patients who underwent BAT and 25 who underwent tcCVC placement were included. One-year patency rates for the whole access circuit were 84.6% and 44.9% in the BAT and tcCVC groups, respectively. The BAT group was more likely to maintain patency (unadjusted hazard ratio: 0.17, 95% confidence interval: 0.05–0.60, p = 0.006). The two groups did not have significantly different overall survival (log-rank p = 0.146), although severe complications were less common in the BAT group (3% vs. 28%, p = 0.005). Relative to tcCVC placement, BAT is safe and effective with acceptable patency in hemodialysis patients not suitable for AVF or AVG creation.

Medical Adjuvant Therapy in Reducing Thrombosis With Arteriovenous Grafts and Fistulae Use: A Meta-Analysis of Randomized Controlled Trials

Hemodialysis is required for patients with end-stage renal disease (ESRD) that require arteriovenous (AV) grafts or fistulas for vascular access. These access points are prone to thrombosis. To determine the effect of medical adjuvant therapy on AV graft/fistula patency among patients with ESRD on hemodialysis. Adhering to the PRISMA 2020 statement, a systematic search was conducted until August 20, 2021, with keywords including arteriovenous graft, fistula, patency, thrombosis, hemodialysis, adjuvant treatment. The following databases were searched: PubMed, Scopus, Web of Science, CINAHL Plus, and Cochrane. A random-effects model was employed using Review Manager 5.4 for data analysis. The meta-analysis pooled in 1985 participants with 1000 (50.4%) in the medical adjuvant treatment group. At a snapshot, medical adjuvant therapy reduced the risk for graft thrombosis (RR = 0.64, P = .02). Notable medications included aspirin for graft thrombosis (RR = 0.36, P = .006) and ticlopidine for fistula thrombosis (RR = 0.53, P = .01). Certain antiplatelet therapies (aspirin and ticlopidine) reduced the number of patients with AV fistula/graft thrombosis among patients with high heterogeneity among the trials. Other therapies (fish oil, sulfinpyrazone, clopidogrel, and aspirin/dipyridamole) did not demonstrate significant improvement but may be promising once concrete evidence is available. Potential benefits of anti-platelet therapies may be explored to maintain the potency of AV grafts/fistulas through well-designed placebo-controlled trials and long-term follow-up.

Expert consensus on the establishment and maintenance of native arteriovenous fistula

Vascular access is the lifeline of hemodialysis patients. There are great differences in the establishment and use of vascular access in different countries and regions around the world. We believe that on the basis of good evaluation and planning, it is recommended that hemodialysis patients choose native arteriovenous fistula first. In view of the new progress of vascular access views domestic and international at home and abroad in recent years, we organized experts to recommend the establishment and maintenance of arteriovenous fistula (AVF) for the Chinese population, including preoperative evaluation and planning of the establishment of AVF, AVF surgery, perioperative drug intervention measures and postoperative maintenance, and put forward suggestions for future research directions. The recommendations in this consensus are general and clinicians need to make treatment decisions based on the actual situation.

Medical adjuvant treatment to increase patency of arteriovenous fistulae and grafts

BACKGROUND

People with end-stage renal disease (ESRD) often require either the formation of an arteriovenous fistula (AVF) or an interposition prosthetic arteriovenous graft (AVG) for haemodialysis. These access sites should ideally have a long life and a low rate of complications (e.g. thrombosis, infection, stenosis, aneurysm formation and distal limb ischaemia). Although some of the complications may be unavoidable, any adjuvant technique or medical treatment aimed at decreasing complications would be welcome. This is the fourth update of the review first published in 2003.

OBJECTIVES

To assess the effects of adjuvant drug treatment in people with ESRD on haemodialysis via autologous AVFs or prosthetic interposition AVGs.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases and ClinicalTrials.gov trials register to 6 August 2020.

SELECTION CRITERIA

Randomised controlled trials of active drug versus placebo in people with ESRD undergoing haemodialysis via an AVF or prosthetic interposition AVG.

DATA COLLECTION AND ANALYSIS

For this update, two review authors (IM, MFAK) independently selected trials for inclusion, extracted data, assessed risk of bias and assessed the certainty of the evidence according to GRADE. We resolved disagreements by discussion or consultation with another review author (ADS). The primary outcome was the long-term fistula or graft patency rate. Secondary outcomes included duration of hospital stay; complications such as infection, aneurysm formation, stenosis and distal limb ischaemia; and number of related surgical or radiological interventions.

MAIN RESULTS

For this update, one additional study was suitable for inclusion, making a total of 13 trials with 2080 participants. Overall the certainty of the evidence was low or moderate due to short follow-up periods, heterogeneity between trials, small sample sizes, and risk of bias due to incomplete reporting. Medical adjuvant treatments used in the included trials were aspirin, ticlopidine, dipyridamole, dipyridamole plus aspirin, warfarin, fish oil, clopidogrel, sulphinpyrazone and glyceryl trinitrate (GTN) patch.  All included studies reported on graft patency by measuring graft thrombosis. There was insufficient evidence to determine if there was a difference in graft patency in studies comparing aspirin versus placebo (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.07 to 2.25; 3 studies, 175 participants; low-certainty evidence). The meta-analysis for graft patency comparing ticlopidine versus placebo favoured ticlopidine (OR 0.45, 95% CI 0.25 to 0.82; 3 studies, 339 participants; moderate-certainty evidence). There was insufficient evidence to determine if there was a difference in graft patency in studies comparing fish oil versus placebo (OR 0.24, 95% CI 0.03 to 1.95; 2 studies, 220 participants; low-certainty evidence); and studies comparing clopidogrel and placebo (OR 0.40, 95% CI 0.13 to 1.19; 2 studies, 959 participants; moderate-certainty evidence). Similarly, there was insufficient evidence to determine if there was a difference in graft patency comparing the effect of dipyridamole versus placebo (OR 0.46, 95% CI 0.11 to 1.94; 1 study, 42 participants, moderate-certainty evidence) and dipyridamole plus aspirin versus placebo (OR 0.64, CI 0.16 to 2.56; 1 study, 41 participants; moderate-certainty evidence); comparing low-intensity warfarin with placebo (OR 1.76, 95% CI 0.78 to 3.99; 1 study, 107 participants; low-certainty evidence); comparing sulphinpyrazone versus placebo (OR 0.43, 95% CI 0.03 to 5.98; 1 study, 16 participants; low-certainty evidence) and comparing GTN patch and placebo (OR 1.26, 95% CI 0.63 to 2.54; 1 study, 167 participants; moderate-certainty evidence). The single trial evaluating warfarin was terminated early because of major bleeding events in the warfarin group. Only two studies published data on the secondary outcome of related interventions (surgical or radiological); there was insufficient evidence to determine if there was a difference in related interventions between placebo and treatment groups. None of the included studies reported on the duration of hospital stay.  Most studies reported complications ranging from mortality to nausea. However, data on complications were limited and reporting varied between studies.

AUTHORS' CONCLUSIONS

The meta-analyses of three studies for ticlopidine (an antiplatelet treatment), which all used the same dose of treatment but with a short follow-up of only one month, suggest ticlopidine may have a beneficial effect as an adjuvant treatment to increase the patency of AVFs and AVGs in the short term. There was insufficient evidence to determine if there was a difference in graft patency between placebo and other treatments such as aspirin, fish oil, clopidogrel, dipyridamole, dipyridamole plus aspirin, warfarin, sulphinpyrazone and GTN patch. The certainty of the evidence was low to moderate due to short follow-up periods, the small number of studies for each comparison, small sample sizes, heterogeneity between trials and risk of bias due to incomplete reporting. Therefore, it appears reasonable to suggest further prospective studies be undertaken to assess the use of these antiplatelet drugs in renal patients with an AVF or AVG.

Update on the creation and maintenance of arteriovenous fistulas for haemodialysis in children

Arteriovenous fistulas (AVFs) are widely used for haemodialysis (HD) in adults with stage 5 chronic kidney disease (CKD 5) and are generally considered the best form of vascular access (VA). The 'Fistula First' initiative in 2003 helped to change the culture of VA in adults. However, this cultural change has not yet been adopted in children despite the fact that a functioning AVF is associated with lower complication rates and longer access survival than a central venous line (CVL). For children with CKD 5, especially when kidney failure starts early in life, there is a risk that all VA options will be exhausted. Therefore, it is essential to develop long-term strategies for optimal VA creation and maintenance. Whilst AVFs are the preferred VA in the paediatric population on chronic HD, they may not be suitable for every child. Recent guidelines and observational data in the paediatric CKD 5 population recommend switching from a 'Catheter First' to 'Catheter Last' approach. In this review, recent evidence is summarized in order to promote change in current practices.

Endothelial nitric oxide synthase (eNOS) mediates neointimal thickness in arteriovenous fistulae with different anastomotic angles in rats

BACKGROUND

It is known that the anastomotic angle can influence neointimal hyperplasia and patency in arteriovenous fistulae (AVF). Endothelial nitric oxide synthase (eNOS) is released from the vascular endothelium and can inhibit neointimal hyperplasia. Therefore, here, we aimed to test the hypothesis that the manipulation of eNOS expression could influence neointimal thickness in a rat AVF model with different anastomosis angles.

METHODS

Rat carotid artery (inflow, CA) and jugular vein (outflow, JV) AVF were created with acute, blunt, or end-to-end (ETE) anastomosis angles. Aspirin was used to increase eNOS expression in the acute angle group, while N(G)-nitro-L-arginine methyl ester (L-name) was used to decrease eNOS expression in the obtuse angle group. The rats were sacrificed on day 21, and tissues were harvested and analyzed histologically and with immunostaining.

RESULTS

A larger anastomosis diameter (p < 0.016) and smaller neointimal area (p < 0.01) were observed in the obtuse and end-to-end (ETE) groups compared to in the acute group. In the acute angle group, there were more proliferating cell nuclear antigen (PCNA) and α-actin dual-positive cells (p < 0.0001) and fewer phospho (p)-eNOS-positive endothelial cells (p < 0.0001) in the neointima than in the obtuse and ETE angle groups. On treating the acute angle and blunt angle groups with aspirin and L-name, respectively, no significant differences in the neointima/lumen rate were observed (p = 0.6526) between the groups; however, there were fewer von Willebrand factor (vWF) and p-eNOS dual-positive cells in the obtuse angle group treated with L-name (p = 0.0045).

CONCLUSIONS

We demonstrated that eNOS plays an important role in neointimal hyperplasia in AVF with different anastomosis angles; further, eNOS could potentially be used as a therapeutic target in patients with AVF in the future.

Endovascular Arteriovenous Dialysis Fistula Intervention: Outcomes and Factors Contributing to Fistula Failure

RATIONALE & OBJECTIVE

Primary patency is variable with arteriovenous fistulas, and many patients require angiographic procedures to obtain patency. Accordingly, we determined postintervention patency rates and contributing factors for fistula failure following intervention to establish secondary patency in non-dialysis-dependent patients with advanced chronic kidney disease following creation of an arteriovenous fistula.

STUDY DESIGN

Observational study from a single referral center.

SETTING & PARTICIPANTS

210 non-dialysis-dependent patients with advanced chronic kidney disease who underwent upper-extremity fistula creation for anticipated dialysis between October 1995 and January 2015 and who required subsequent endovascular therapy to establish or maintain patency were reviewed.

EXPOSURE

Endovascular therapy for dialysis arteriovenous fistula primary patency failure.

OUTCOMES

Postintervention patency duration following endovascular therapy.

ANALYTICAL APPROACH

Descriptive study with outcomes determined using Cox proportional hazards models.

RESULTS

Multiple fistula configurations were reviewed: 138 (65.7%) brachiocephalic, 39 (18.6%) radiocephalic, 30 (14.3%) brachiobasilic, 2 (1.0%) ulnocephalic, and 1 (0.5%) radiobasilic. There were 261 initial stenoses treated. Postintervention primary patency is defined as the time from the index intervention to repeat intervention for stenosis. Postintervention primary-assisted patency is the time from the index intervention to thrombectomy for fistula thrombosis or change in modality. Postintervention secondary patency is the time from the index intervention to fistula abandonment. Median postintervention primary patency, postintervention primary-assisted patency, and secondary patency were 2.7, 3.2, and 3.6 years, respectively. The overall 1-year primary, primary-assisted, and secondary patency rates in this cohort were 53.0%, 87.7%, and 83.5%, respectively. Compared with radiocephalic fistulas, brachiocephalic fistulas had higher risk for postintervention primary patency loss (HR, 1.90; 95% CI, 1.13-3.20; P = 0.02).

LIMITATIONS

Dialysis fistula revascularization techniques varied.

CONCLUSIONS

The radiocephalic fistula configuration had the best postintervention primary patency in this cohort. Postintervention primary-assisted patency and secondary patency were not significantly different among different fistula configurations.

Vascular access in children requiring maintenance haemodialysis: a consensus document by the European Society for Paediatric Nephrology Dialysis Working Group

BACKGROUND

There are three principle forms of vascular access available for the treatment of children with end stage kidney disease (ESKD) by haemodialysis: tunnelled catheters placed in a central vein (central venous lines, CVLs), arteriovenous fistulas (AVF), and arteriovenous grafts (AVG) using prosthetic or biological material. Compared with the adult literature, there are few studies in children to provide evidence based guidelines for optimal vascular access type or its management and outcomes in children with ESKD.

METHODS

The European Society for Paediatric Nephrology Dialysis Working Group (ESPN Dialysis WG) have developed recommendations for the choice of access type, pre-operative evaluation, monitoring, and prevention and management of complications of different access types in children with ESKD.

RESULTS

For adults with ESKD on haemodialysis, the principle of "Fistula First" has been key to changing the attitude to vascular access for haemodialysis. However, data from multiple observational studies and the International Paediatric Haemodialysis Network registry suggest that CVLs are associated with a significantly higher rate of infections and access dysfunction, and need for access replacement. Despite this, AVFs are used in only ∼25% of children on haemodialysis. It is important to provide the right access for the right patient at the right time in their life-course of renal replacement therapy, with an emphasis on venous preservation at all times. While AVFs may not be suitable in the very young or those with an anticipated short dialysis course before transplantation, many paediatric studies have shown that AVFs are superior to CVLs.

CONCLUSIONS

Here we present clinical practice recommendations for AVFs and CVLs in children with ESKD. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system has been used to develop and GRADE the recommendations. In the absence of high quality evidence, the opinion of experts from the ESPN Dialysis WG is provided, but is clearly GRADE-ed as such and must be carefully considered by the treating physician, and adapted to local expertise and individual patient needs as appropriate.

Oral Charcoal Adsorbents Attenuate Neointima Formation of Arteriovenous Fistulas

Chronic kidney disease (CKD) accelerates the development of neointima formation at the anastomosis site of arteriovenous (AV) fistulas. Accumulation of certain uremic toxins has a deleterious effect on the cardiovascular system. The oral charcoal adsorbent, AST-120, reduces circulating and tissue uremic toxins, but its effect on neointima formation at an AV fistula is unknown. To understand the effect of CKD and AST-120 on neointima formation, we created AV fistulas (common carotid artery to the external jugular vein in an end-to-side anastomosis) in mice with and without CKD. AST-120 was administered in chow before and after AV fistula creation. Administration of AST-120 significantly decreased serum indoxyl sulfate levels in CKD mice. CKD mice had a larger neointima area than non-CKD mice, and administration of AST-120 in CKD mice attenuated neointima formation. Both smooth muscle cell and fibrin components were increased in CKD mice, and AST-120 decreased both. RNA expression of MMP-2, MMP-9, TNFα, and TGFβ was increased in neointima tissue of CKD mice, and AST-120 administration neutralized the expression. Our results provided in vivo evidence to support the role of uremic toxin-binding therapy on the prevention of neointima formation. Peri-operative AST-120 administration deserves further investigation as a potential therapy to improve AV fistula patency.

High low-density lipoprotein cholesterol level is the independent risk factor of primary patency rate of arteriovenous fistula

OBJECTIVES

An arteriovenous fistula is the first choice of vascular access in dialysis patients. However, the correlations between patient factors and the arteriovenous fistula patency rate remain unclear. Therefore, we examined the effect of dialysis patient factors on arteriovenous fistula patency rate.

METHODS

This study included 101 patients who received maintenance dialysis and used arteriovenous fistula for vascular access at Atami Hospital, International University of Health and Welfare in July 2018. A retrospective review was performed from the time of arteriovenous fistula creation to July 2018, and the primary and secondary arteriovenous fistula patency rates were investigated. The patency rate was calculated using the Kaplan-Meier method, and risk factor analysis was performed using Cox proportional hazards regression analysis.

RESULTS

The primary patency rate of arteriovenous fistula was 71.2% at one year and 43.0% at five years, and the secondary patency rate was 92.7% at one year and 79.8% at five years. In the multivariate analysis, high low-density lipoprotein cholesterol (LDL-C) level and a history of diabetes were considered significant risk factors (HR 1.023, p value <0.01 and HR 2.550, p value <0.01, respectively). A log rank test was conducted on the groups of patients with LDL <90 mg/dl and LDL ≥90 mg/dl, and the <90 mg/dl group resulted in a good primary patency rate (p value 0.0327).

CONCLUSIONS

High LDL-C level was considered the independent risk factors of arteriovenous fistula primary patency 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 Aspirin on Preventing Vascular Access Dysfunction in Incident Hemodialysis Patients: A Prospective Cohort Study in Korean Clinical Research Centers for End-Stage Renal Disease (CRC for ESRD)

Background: Aspirin is often prescribed empirically to improve the patency of hemodialysis (HD) vascular access. Therefore, this study aimed to investigate the impact of aspirin on the survival of vascular access in incident HD patients with arteriovenous fistula (AVF) or arteriovenous graft (AVG). Methods: A prospective cohort of 881 incident HD patients was enrolled between 2009 and 2014. The primary outcome was defined as the first AVF/AVG intervention or salvage procedure, including percutaneous transluminal angioplasty or surgery for vascular access failure. Cox analyses were performed to determine the association between aspirin usage and the occurrence of the primary outcome. Results: The mean age of the patient group was 57.9 ± 13.4, and 63.8% of the patients were male. Aspirin was prescribed in 241 (27.4%) patients, and the median follow-up duration was 30 months. During follow-up, 180 (20.4%) patients experienced the primary outcome event. Univariate analysis showed that age, gender, presence of diabetes mellitus (DM), preexisting peripheral arterial disease, and the type of vascular access used (AVG versus AVF) were significantly associated with the development of the primary outcome. However, aspirin usage from the baseline was not significantly associated with primary outcome events (hazard ratio (HR): 1.16; 95% confidence interval (CI): 0.84–1.60; p = 0.378). Multivariate analysis showed that gender, the presence of DM, and the type of vascular access were still significantly associated with the occurrence of the primary outcome. Moreover, we did not observe the protective effect of taking aspirin on primary vascular access failure, even in subgroup analyses stratified according to gender, the presence of DM, and the type of vascular access. Conclusion: Physicians should carefully consider when they prescribe aspirin for the prevention of primary vascular access failure in Korean incident HD patients. In addition, larger prospective interventional studies are needed to elucidate the effect of aspirin on vascular access failure.

C-reactive protein as a prognostic risk factor for loss of arteriovenous fistula patency in hemodialyzed patients

BACKGROUND

Inflammation is a cardiovascular risk factor in hemodialysis patients, but its influence on vascular access patency is still debatable. Our prospective study investigated this issue.

METHODS

A total of 258 patients receiving an arteriovenous fistula (AVF) between 2006 and 2016 at the Municipal Hospital Arad were included. Demographic, clinical, and laboratory characteristics were collected at the time of creation of the AVF. The primary study end point was AVF patency loss, defined as an event occurring at least 2 months after AVF formation and requiring surgical revision or replacement of the fistula. The patients were followed up for a median time of 26 months.

RESULTS

In our group, the mean age was 59.7 ± 13.2 years (median, 62 years), and 60.1% were male. During follow-up, 134 patients (51.9%) maintained AVF patency, whereas 124 (48.1%) lost AVF patency within a mean time of 23.3 ± 28.1 months (median, 10.5 months). We found that age (hazard ratio [HR], 1.015; P = .035) and C-reactive protein (CRP) level (HR, 1.17; P < .0001) were associated with a higher risk of loss of AVF patency. The protective factors for AVF patency were autosomal dominant polycystic kidney disease (HR, 0.336; P = .009), pre-emptive AVF (HR, 0.648; P = .031), and higher level of triglycerides (HR, 0.998; P = .035). In the multivariate adjusted Cox model, CRP level remained an independent predictor for loss of AVF patency (HR, 1.17; 95% confidence interval, 1.1-1.3; P < .0001).

CONCLUSIONS

In our study, CRP level was an independent predictor of AVF patency loss, whereas better AVF survival was independently associated with autosomal dominant polycystic kidney disease and pre-emptive AVF. As a simple noninvasive marker of chronic inflammation, CRP level may be a useful tool to predict AVF outcomes. Further research is needed to assess the protective effects of inflammation reduction on AVF survival.

Arteriovenous graft patency outcomes and prognostic factors

OBJECTIVES

Arteriovenous graft for hemodialysis shows poorer outcomes than arteriovenous fistula, due to frequent stenosis and thrombosis. We investigated arteriovenous graft patency outcomes and prognostic factors for these outcomes.

METHODS

We included a single-center cohort of patients receiving arteriovenous graft for hemodialysis access from 2010 to 2014. Demographics, laboratory data, comorbidities, and medications were collected from medical records. Surgical factors related to graft operation including the type and diameter of connected vessels, graft location, and type of operation (elective or emergency) were also recorded. Outcomes included primary and secondary patency. Survival analysis was conducted using the Kaplan-Meier method; univariate and multivariate analyses were used to evaluate the prognostic factors.

RESULTS

Data from 225 grafts were analyzed. During the follow-up period (mean: 583 days, range: 1-1717 days), 138 (61%) grafts required intervention and 46 (20%) permanently failed. Primary patency at one, two, and three years was 42%, 20%, and 16%, respectively. Secondary patency at one, two, and three years was 85%, 72%, and 64%, respectively. Multivariate analysis showed that primary patency was negatively associated with increasing age and location of vessel anastomosis (reference-brachiobrachial anastomosis; brachiobasilic - HR, 0.569; 95% CI, 0.376-0.860; p = 0.007; brachioaxillary anastomosis - HR 0.407; 95% CI, 0.263-0.631; p < 0.0001); secondary patency was positively associated with diastolic blood pressure, serum albumin level, and hemoglobin over 10 g/dL. Adverse events other than stenosis or thrombosis, such as infection/inflammation or pseudoaneurysm were observed in approximately 20% of grafts.

CONCLUSIONS

Factors associated with diminished primary arteriovenous graft patency included increased patient age and location of vessel anastomosis (brachiobrachial type compared to brachiobasilic or brachioaxillary type); diminished secondary patency was associated with low diastolic blood pressure, low serum albumin, and hemoglobin level under 10 g/dL. Among these factors, diastolic blood pressure, serum albumin, and hemoglobin level may be modifiable and could improve arteriovenous graft patency outcomes.

Role of antiplatelet therapy in the durability of hemodialysis access

BACKGROUND

Antiplatelet therapy (APT) is often used on anecdotal grounds to improve vascular access patency. The aim of this study was to assess the role of APT in hemodialysis (HD) patients undergoing arteriovenous fistula (AVF) or graft (AVG) placement.

METHODS

All patients in a large HD vascular qualitative initiative database (2011-2017) were included and divided into no antiplatelet therapy (no-APT) vs. any APT [aspirin (ASA) or P2Y12 inhibitors (PI)]. Multivariate [logistic (MLR) and Cox (MCR) regression] analyses were used as appropriate.

RESULTS

A total of 24,847 patients undergoing HD access creation were identified (78% AVF). APT was noted among 49 and 46% of AVG and AVF patients, respectively. In MLR analysis, patients on no-APT vs. APT had a 12-fold increased risk of in-hospital mortality (odds ratio (OR) 11.79, [95% confidence interval 5.30-26.26]) and the risk of developing steal syndrome was higher among patients discharged on APT (OR 1.81, [1.19-2.76]). In patients undergoing AVF, primary patency (PP) was similar between APT and no-APT. However, in patients undergoing AVG, PP rates at 12 months were significantly higher for APT: ASA (47 vs. 41%) and PI (51 vs. 41%) than for no-APT (p = 0.008). At MCR analysis, the loss of PP at 12 months was 13% lower in ASA users (hazard ratio (HR) 0.87, [0.77-0.97], p = 0.02) and 24% lower in PI users (HR 0.76, [0.57-0.99], p = 0.046) compared to no-APT.

CONCLUSION

In a large national database, we showed that antiplatelet therapy was associated with lower in-hospital mortality. Aspirin and P2Y12-inhibitor use among AVG patients demonstrated improved PP rates compared to no antiplatelet therapy. We recommend the use of antiplatelet therapy especially in patients on AVG.

The polyunsaturated fatty acid balance in kidney health and disease: A review

Epidemiological studies show that circulating polyunsaturated fatty acids contribute to preserve renal function. In renal disease states there is generally a lack of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) as measured in biological samples, but despite intense research for more than 30 years, it is still unclear how and to what extent their supplementation would benefit kidney disorders. Studies evaluating the n-6 series and the kidney are less frequent. The last compilation of clinical trials with n-3 LCPUFA supplements focusing on renal function and damage dates back to 2012. We here discuss n-3 and n-6 fatty acids in relation to the kidney summarizing single- and double blind randomized controlled trials performed between 2012 and 2016. Nine were sub-studies/post-hoc analyses of previous parent trials. Twelve out of the twenty trials reported on fatty acid profile or fatty acid species. Factors that may explain inconsistent results obtained after supplementation with the n-3 LCPUFA EPA and DHA in kidney disease are discussed such as baseline levels determining response, drug interaction. The need of evaluating fatty acid status before and after intervention is emphasized, to match changes in outcome measure with changes of any fatty acid potentially involved.

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.