Arteriovenous Access Failure Research Articles

Incidence and Determinants of Primary Arteriovenous Access Failure in Dialysis Patients: A Qatar-Based Retrospective Analysis

Incidence and Determinants of Primary Arteriovenous Access Failure in Dialysis Patients: A Qatar-Based Retrospective Analysis

Frailty screening for determination of hemodialysis access placement

ObjectiveChoosing the right hemodialysis vascular access for frail patients remains difficult because the patient's preferences and the likelihood of access function and survival must be considered. We hypothesize that patients identified before arteriovenous (AV) access as frail by the PRISMA-7 score may have worse outcomes, indicating that fistula creation may not be the most clinically beneficial option and it would be in the best interest of the patient to receive either AV graft (AVG) placement or dialysis through a percutaneous catheter. Our pilot study aims to determine whether an association exists between patient frailty as defined by PRISMA-7 and newly created AV fistula (AVF) and AVG access outcomes. MethodsThis was a single institutional prospective cohort study of patients undergoing new AVF or AVG intervention from April 2021 to May 2023. Patients were assessed using the PRISMA-7 frailty questionnaire before their AV access surgery. Patients were grouped by frailty score and score groups were examined for trends. Univariable analysis was performed for baseline differences between frail and nonfrail patients. Failure to achieve maturation, postoperative infection, and 180-day mortality difference was also investigated for frail vs nonfrail patients. Univariable analysis was performed for nonmaturation using standard comorbidities, arterial and venous diameters, and frailty. Multivariable binary logistic regression was performed for the outcome of nonmaturation using frailty as one of the variables in conjunction with the univariable risks associated with nonmaturation. ResultsA total of 40 patients undergoing new AV access placement were investigated, among whom 53% were designated as frail (PRISMA-7 score ≥3). When comparing the frail and nonfrail new AV access groups, the access (AVF and AVG combined) failed in 48% (10/21) of the frail patients, but only failed in 5% (1/19) of the nonfrail patients 1 (P = .012). When distinguishing between AV access types, AVF creations followed the overall trend with 60% of AVF access (9/15) sites in frail patients failing to mature when compared with nonfrail patients, who all had fistulas that matured to use (P = .049). Surgical site infection was absent in all frail patients and present in 5% of nonfrail patients (1/19). Both 30-day and 60-day readmission rates were higher in the frail group compared with the nonfrail group. There was 180-day mortality present in 5 of frail patients % (1/21) and absent in nonfrail patients. Multivariable analysis revealed that both frailty (adjusted odd ratio, 10.19; 95% confidence interval, 1.20-82.25); P = .033) and younger age (adjusted odd ratio, 0.953; 95% confidence interval, 0.923-0.983; P = .002) both had a significant association with nonmaturation. Power analysis revealed a power statistic of 0.898 indicating a probability of type 2 error of 10.02% with a P value of .002. Hosmer-Lemeshow goodness of fit for the logistic regression had 75% overall accuracy for the model. ConclusionsPatient frailty is significantly associated with an increased incidence of AV access failure to mature.

Repeated failure of arterio-venous haemodialysis access

Background: The subsequent development of vascular access techniques and devices now permits patients to be maintained on dialysis for decades. Aim of study: To evaluate the most possible causes behind repeated arteriovenous (AV) access failure in ESRD patients and finding the relationship between those causes and the timing of access failure, and putting the possible solutions in the form of interventions and guidelines for those patients. Patients and methods: This retrospective non-randomized study was conducted in department of vascular surgery, Al-Azhar University Hospitals – Cairo (Al-Hussein and Sayed Glal Hospitals). This study was conducted on 100 ESRD patients on regular hemodialysis and with repeated AV access failure; at least two failed accesses for each patient. The total number of failed accesses was 245 where 230 accesses were autogenous AV fistulae and 15 were synthetic bridge grafts in upper limb. Results: Among the cases of access thrombosis 25.5% were associated with access stenosis, 10.5% with hypotension, and 2.5% with external compression. Among the cases of failure of maturation 16% were due to small vein diameter (less than 2.5 mm), 9% associated with hypotension, and 7% with hypotension together with central venous stenosis.

Thrombophilic risk factors and ABO blood group profile for arteriovenous access failure in end stage kidney disease patients: a single-center experience

Introduction Thrombosis of fistula occurs most frequently in end-stage kidney disease (ESKD) patients receiving hemodialysis. However, the role of thrombophilia in arteriovenous fistula (AVF) failure has not been well established. Hence, this study was aimed at assessing the roles of hereditary and acquired thrombophilic factors in association with AVF failure among patients with ESKD undergoing hemodialysis. Methods A cross-sectional study was conducted on 100 ESKD patients, of whom 50 patients with well-functioning AVFs with no fistula failures earlier were enrolled as Group 1, and 50 patients who have had AVF failure were enrolled as Group 2. The hereditary factors as factor V Leiden, factor XIII, prothrombin, and methylene tetrahydrofolate reductase and the acquired factors as lipoprotein (a), fibrinogen, homocysteine, and anticardiolipin antibodies IgG and IgM were studied. Results Among the hereditary factors, no statistically significant difference was observed in relation to factor V Leiden and Prothrombin (p > 0.05). However, for factor XIII and methylene tetrahydrofolate reductase, a statistically significant difference was observed between patients with well-functioning AVFs and patients who have had AVF failure (p < 0.05). We found a statistically significant increase in all the acquired factors in patients who have had AVF failure in comparison with patients with well-functioning AVFs (p < 0.001). Association between ABO blood groups and thrombophilic factors showed significant association between factor V Leiden, anticardiolipin antibody IgG and IgM and ABO blood groups (p < 0.05), whereas none of the other thrombophilic factors showed significant association (p > 0.05). Conclusion Thus, our study suggests significant role of acquired factors in causing AVF failure.

Is fetuin-A a biomarker of dialysis access dysfunction?

The arteriovenous (AV) access function of hemodialysis (HD) patients can be impaired by afferent artery stiffness due to preexisting microcalcification and by venous stenosis secondary to neointimal hyperplasia in whose development participates an upregulated local inflammatory process. Fetuin-A is a circulating potent inhibitor of vascular calcification and plays an important anti-inflammatory role. The aims of this prospective study were to investigate the relationship between baseline serum fetuin-A levels and: blood flow (QA) values at baseline, AV access failure (thrombosis or intervention for stenosis) during follow-up and primary unassisted AV access patency. We measured baseline serum fetuin-A levels and QA values of the AV access in 64 HD patients under routine QA surveillance for stenosis. Patients were classified into tertiles according to their baseline fetuin-A levels (g/L): <0.5 (tertile-1), 0.5-1.20 (tertile-2), and >1.20 (tertile-3). Fetuin-A was positively correlated with QA (Spearman coefficient = 0.311, p = 0.012). Fourteen patients (21.9%) underwent AV access failure and they had lower fetuin-A (0.59 ± 0.32 g/L) and lower QA (739.4 ± 438.8 mL/min) values at baseline compared with the remaining patients (1.05 ± 0.65 g/L and 1273.0 ± 596.3 mL/min, respectively) (p = 0.027 and p < 0.001, respectively). The AV access failure rate was highest (34.8%) in tertile-1 (lowest fetuin-A level). Unadjusted Cox regression analysis showed a decrease in the risk of AV access patency loss by increasing fetuin-A concentration (hazard ratio 0.395 (95% confidence interval: 1.42-1.69), p = 0.044) but it was not confirmed in the adjusted model, although the hazard ratio was low (0.523). Kaplan-Meier analysis showed that patients in tertile-3 (highest fetuin-A concentration) had the highest primary unassisted AV access patency (λ2 = 4.68, p = 0.030, log-rank test). If our results are confirmed in further studies, fetuin-A could be used as a circulating biomarker to identify HD patients at greater risk for AV access dysfunction, who would benefit from much closer dialysis access surveillance.

Covered stents versus balloon angioplasty for failure of arteriovenous access: a systematic review and meta-analysis

IntroductionPatients with end-stage renal disease may require arteriovenous (AV) access in the form of arteriovenous fistulae (AVFs) or arteriovenous grafts (AVGs) for haemodialysis. AV access dysfunction requires intervention such as...

Arteriovenous Fistula Versus Graft Access Strategy in Older Adults Receiving Hemodialysis: A Pilot Randomized Trial

BackgroundIt is unclear whether surgical placement of an arteriovenous (AV) fistula (AVF) confers substantial clinical benefits over an AV graft (AVG) in older adults with end-stage kidney disease (ESKD). We report vascular access outcomes of a pilot clinical trial.Study DesignPilot randomized parallel-group open-label trial.Setting & ParticipantsPatients 65 years and older with ESKD and no prior AV access receiving maintenance hemodialysis through a tunneled central venous catheter referred for AV access placement by their treating nephrologist.InterventionParticipants were randomly assigned in a 1:1 ratio to surgical placement of an AVG or AVF.OutcomesIndex AV access primary failure, successful cannulation, adjuvant interventions and infections.ResultsOf 122 older adults receiving hemodialysis and no prior AV access surgery, 24% died before (n = 18) or were too sick for (n = 11) referral for a permanent AV access. Of 46 eligible patients, 36 (78%) consented and were randomly assigned to AVG (n = 18) and AVF (n = 18) placement, of whom 13 (72%) and 16 (89%) underwent index AV access surgical placement, respectively. At a median follow-up of 321.0 days, primary AV access failure was noted in 31% in each group. The proportion of patients with successful cannulation was 62% (8 of 13) in the AVG and 50% (8 of 16) in the AVF group; median times to successful cannulation were 75.0 and 113.5 days, respectively. Endovascular procedures were recorded in 38% and 44%, and surgical reinterventions, in 23% and 25%, respectively. AV access infection was seen in 3 (23%) and 2 (13%) patients, respectively.LimitationsSmall sample size precludes statistical inference.ConclusionsAlmost one-quarter of older adults with incident ESKD and a central venous catheter as primary access were not referred for AV access placement due to medical reasons. Based on these limited results, there is little reason to favor either an AVF or AVG in this population until results from a larger randomized clinical trial become available.FundingGovernment funding to an author (Dr Murea is supported by National Institutes of Health∖National Institute on Aging grant 1R03 AG060178-01).Trial RegistrationNCT03545113.

Influence of intradialytic systolic blood pressure changes on arteriovenous access thrombosis in maintenance hemodialysis patients.

Arteriovenous access (AV) thrombosis is an important and preventable problem amongst chronic hemodialysis (HD) patients. Systolic blood pressure (SBP) fluctuation relates to higher cardiovascular mortality amongst these patients. We proposed there is a close relation between SBP changes and arteriovenous (AV) access thrombosis. We also determined other risk factors and biochemical parameters related to AV access failure. 50 HD patients with thrombosis and 50 HD patients without thrombosis were included in the study. Odds ratios and 95% confidence intervals were estimated with multivariate-adjusted logistic regression models to determine the association between potential thrombosis-related risk factors and thrombosis risk. Elder adults, women, and patients with AV grafts, lower intradialytic SBP and higher SBP variations during HD sessions had higher incidence of AV access thrombosis. AV access infection and decreased blood flow (BF) velocity were associated with an increased incidence of thrombotic events, whereas the use of anti-thrombotic agents was associated with a decreased incidence of thrombotic events. Further, anaemia, hypoalbuminemia, hyperlipidemia, and impaired mineral metabolism parameters were also found to be associated with AV access thrombosis. Close monitoring and management of intradialytic hypotension and SBP fluctuation in every HD session are important. Some important and novel modifiable risk factors related to AV access thrombosis were identified in this study (eg, AV access infection, decreased BF and abnormal biochemical parameters, etc). Earlier surveillance and modification of these risk factors is crucial to prevent AV access failure in HD patients.

Restoring arteriovenous access: Pilot study using a scoring balloon in 50 patients.

Arteriovenous access failure is most often due to the development of neointimal hyperplastic stenoses. Balloon angioplasty remains standard of care for endovascular treatment of stenoses obstructing blood flow in hemodialysis fistulas and grafts. Scoring balloon technologies have been developed to disrupt the atheromatous plaque and have shown to be safe and effective for treating stenosis in the hemodialysis access circuit. However, improvement in patency has yet to be established. This prospective, single-arm study included 50 patients with stenosed hemodialysis fistula/grafts treated with the AngioSculpt® scoring balloon (Philips) and followed for 6 months. The primary endpoint was target lesion primary patency at 2 and 6 months defined as freedom from re-intervention. Treatment with the scoring balloon resulted in a reduction in stenosis from 78% ± 13.36% to 7.2% ± 7.57% (mean ± standard deviation). Scoring balloon inflation pressures averaged 11.4 atm; no slippage/dissections occurred. After 2 months, 10% of patients required re-intervention. At 6 months, 19% of patients required re-intervention. The 6-month freedom from re-intervention rate was higher for patients with stenosed fistulas (83.3%) compared to patients with stenosed grafts (71.4%). Six-month patency rates were highest for patients with no or one previous intervention (91.6% and 90.0%, respectively); patients with two to five preceding interventions had a 6-month patency rate of 80%, and those with more than five previous interventions had a 50% 6-month patency rate. Results from this pilot study suggest that the AngioSculpt scoring balloon may be a viable treatment option for stenosed arteriovenous fistula/graft access.

Promising results of stent graft placement for cephalic arch stenosis after repeated failure of angioplasty in patients on hemodialysis

ObjectiveCephalic arch stenosis (CAS) causes repeated dysfunction and failure of arteriovenous access. Percutaneous transluminal angioplasty is the standard initial treatment for CAS, but its outcome is unsatisfactory. This study aimed to evaluate the outcome of stent graft placement for CAS in patients on hemodialysis.MethodsA retrospective chart review from a tertiary medical center was performed in patients receiving stent graft placement for CAS between January 2012 and 2016. Patency was analyzed using the Kaplan–Meier method.ResultsTwenty-one patients received stent graft placement for CAS. Technical and clinical success rates were 100%. Primary target lesion patency was 95% (95% confidence interval [CI], 86%–100%), 76% (95% CI, 58%–94%), and 43% (95% CI, 22%–64%) at 3, 6, and 12 months, respectively. No significant difference in patency was observed between the arteriovenous fistula and arteriovenous graft groups. Assisted primary patency was 95% (95% CI, 86%–100%), 71% (95% CI, 52%–91%), and 57% (95% CI, 36%–78%) at 3, 6, and 12 months, respectively. Secondary patency was 100% at 3, 6, and 12 months.ConclusionsAfter repeated failed angioplasty for cephalic arch stenosis, patients on hemodialysis who receive stent graft placement have effective and durable outcomes.

Higher body mass index is associated with reinterventions and lower maturation rates after upper extremity arteriovenous access creation

ObjectiveA patient's body mass index (BMI) can affect both perioperative and postoperative outcomes across all surgical specialties. Given that obesity and end-stage renal disease are growing in prevalence, we aimed to evaluate the association between BMI and outcomes of upper extremity arteriovenous (AV) access creation. MethodsA retrospective single-institution review was conducted for AV access creations from 2014 to 2018. Patient demographics, comorbidities, and AV access details were recorded. BMI groups were defined as normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), obese (30-39.9 kg/m2), and morbidly obese (>40 kg/m2). Perioperative complications and long-term outcomes including access maturation (defined as access being used for hemodialysis or the surgeon's judgment that access was ready for use in patients not yet on hemodialysis), occlusion, and reintervention were evaluated. ResultsA total of 611 upper extremity AV access creations were performed on patients who were normal weight (29.6%), overweight (31.3%), obese (29.6%), and morbidly obese (9.5%). Access type included brachiocephalic (43.2%), brachiobasilic (25.5%), and radiocephalic (14.2%) fistulas and AV grafts (14.2%). Median age was 60.9 years, and 59.6% were male. Univariable analysis showed no difference between BMI groups for perioperative steal, hematoma, home discharge, or 30-day primary patency. Freedom from reintervention at 2 years on Kaplan-Meier analysis differed by BMI (44.5% ± 4.6% normal weight, 29% ± 3.8% overweight, 39.8% ± 4.3% obese, 34.7% ± 8% morbidly obese; P = .041). There was no difference in 2-year freedom from new access creation or survival. AV access maturity within 180 days differed between BMI groups (74.3% normal weight, 66% overweight, 65.7% obese, 46.6% morbidly obese; P < .001). On multivariable analysis, failure to mature within 180 days was associated with overweight (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.14-3.29; P = .002), obese (OR, 2.12; 95% CI, 1.19-3.47; P = .009), and morbidly obese (OR, 3.68; 95% CI, 1.85-7.3; P < .001) relative to normal weight BMI. AV access reintervention was associated with overweight (hazard ratio [HR], 1.83; 95% CI, 1.34-2.5), obese (HR, 1.56; 95% CI, 1.12-2.16), and morbidly obese (HR, 1.69; 95% CI, 1.1-2.58; P = .02) relative to normal weight BMI. BMI was not independently associated with long-term readmission or survival. ConclusionsObesity is associated with higher rates of AV access failure to mature and reintervention. Surgeons performing access creation on obese patients must consider this for planning and setting expectations. Weight loss assistance may need to be incorporated into treatment algorithms.

Endovascular Management for Salvage of Failing Arteriovenous Fistula

Background: Failure of arteriovenous access for hemodialysis is a challenging problem. Maintaining the patency of this access is one of the most important corner stones in the care of patients with chronic renal failure. Recently, percutaneous transluminal balloon angioplasty (PTA) is considered the first line of treatment for dealing with this issue. Aim: The purpose of this retrospective observational study was to evaluate the primary and secondary patency rates after initial endovascular intervention to restore and preserve the patency of failing autogenous arteriovenous fistulae and to identify the potential factors that affect the durability of the procedure. Methods:The results of 56 patients with failing autogenous arteriovenous fistulae were retrospectively analyzed after being treated with percutaneous transluminal balloon angioplasty from November 2014 to December 2018. Technical & clinical success rates were reported. The variables, including patients’ demographics, co-morbidities, medications, fistula age, fistula type, site, number of lesions and degree of stenosis were analyzed and correlated with primary and secondary patency rates. Results: The mean age of the fistulae included in the study since their creation was 17.4 ± 9.6 months, most of which were radiocephalic fistulas (64.3%). The most common cause of autogenous access dysfunction was 90-99% stenosis while the most common site of stenosis was juxta-anastomotic. Technical and clinical success rates of the study population were 92.9% and 89.3%, respectively. The mean primary and secondary patency were 12.3 and 19.9 months, respectively. Primary patency rates at 6,12,18 and 24 months were 79%, 64%, 57% and 44% respectively. Secondary patency rates at 6,12,18 and 24 months were 85%, 76%, 68% and 52% respectively. Patient age ≥ 60 years old was associated with reduced post-PTA primary patency (P < 0.001) and secondary patency (P = 0.018). Dyslipidemia showed marked decrease in both primary and secondary patency rates (P < 0.001). Insulin intake (P < 0.001) was a predictor of primary patency decrease while use of antiplatlets was to a less extent predictor of secondary patency loss (P = 0.004). Radiocephalic fistulae had short primary patency (P = 0.016), while stenotic lesions > 90% showed a significant decrease (P < 0.001) in primary patency more obvious than with secondary patency (P = 0.006). Lesions at arteriovenous anastomosis were significantly associated with decrease in primary patency (P < 0.001). Statins were the only medications associated with longer primary patency (P < 0.001). Age of fistula and number of lesions were independent factors. Conclusion: Endovascular treatment is both safe and effective in managing failing autogenous arteriovenous fistulas. Although its technical and success rates are high, primary and secondary patency rates are still questionable. Dyslipidemia, insulin, statin and antiplatelet intake together with age of patient, degree and site of stenosis are potential risk factors that affect these rates.

Omega-3 Polyunsaturated Fatty Acid Supplementation to Prevent Arteriovenous Fistula and Graft Failure: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Arteriovenous access failure frequently occurs in people on hemodialysis and is associated with morbidity, mortality and large healthcare expenditures. Omega-3 polyunsaturated fatty acids (omega-3 PUFA) may improve access outcomes via pleiotropic effects on access maturation and function, but may cause bleeding complications. Systematic review with meta-analysis. Adults requiring hemodialysis via arteriovenous fistula or graft. Trials evaluating omega-3 PUFA for arteriovenous access outcomes identified by searches in CENTRAL, MEDLINE, and Embase to 24 January 2017. Omega-3 PUFA. Primary patency loss, dialysis suitability failure, access abandonment, interventions to maintain patency or assist maturation, bleeding, gastrointestinal side-effects, all-cause and cardiovascular mortality, hospitalization, and treatment adherence. Treatment effects were summarized as relative risks (RR) and 95% confidence intervals (CI). Evidence was assessed using GRADE. Five eligible trials (833 participants) with a median follow-up of 12 months compared peri-operative omega-3 PUFA supplementation with placebo. One trial (n=567) evaluated treatment for fistulae and four (n=266) for grafts. Omega-3 PUFA supplementation prevented primary patency loss with moderate certainty (761 participants, RR 0.81, CI 0.68-0.98). Low quality evidence suggested, that omega-3 PUFA may have had little or no effect on dialysis suitability failure (536 participants, RR 0.95, CI 0.73-1.23), access abandonment (732 participants, RR 0.78, CI 0.59-1.03), need for interventions (732 participants, RR 0.82, CI 0.64-1.04), or all-cause mortality (799 participants, RR 0.99, CI 0.51-1.92). Bleeding risk (793 participants, RR 1.40, CI 0.78-2.49) or gastrointestinal side-effects (816 participants, RR 1.22, CI 0.64-2.34) from treatment were uncertain. There was no evidence of different treatment effects for grafts and fistulae. Small number and methodological limitations of included trials. Omega-3 PUFA supplementation probably protects against primary loss of arteriovenous access patency, but may have little or no effect on dialysis suitability failure, access interventions or access abandonment. Potential treatment harms are uncertain.

Risk Factors for Early Failure of Arteriovenous Vascular Access Among Patients With Type 2 Diabetes Mellitus.

The aim of the study was to identify the potential risk factors for early arteriovenous access failure in a diabetic population. The data of 223 end-stage renal disease (ESRD) patients with type 2 diabetes who had an arteriovenous fistula (AVF) or arteriovenous graft (AVG) placed as their initial vascular accesses were retrospectively reviewed. The association between clinical factors and risk for early failure was then analyzed. In multivariate analysis, the predictors associated with early failure were female gender (odds ratio (95% confidence interval): 2.52 (1.32-4.81); P = 0.005), AVF with prior peritoneal dialysis (3.26 (1.05-10.11); P = 0.039), and lower hemoglobin level (P = 0.015). The results of significant predictors in the AVF group remained similar to the entire study population. In conclusion, there was an association of female gender, AVF with prior peritoneal dialysis and lower hemoglobin level with early arteriovenous access failure in a diabetic ESRD population.

Acute Arteriovenous Access Failure: Long-Term Outcomes of Endovascular Salvage and Assessment of Co-Variates Affecting Patency

Aims: This study reports long-term outcomes after endovascular salvage (EVS) for acute dialysis fistula/graft dysfunction. Methods: All patients presenting with acute fistula or graft dysfunction, excluding primary failures, referred for endovascular salvage were included in this single-centre prospective study. Results: Altogether, 410 procedures were carried out in 232 patients. Overall, the incidence of thrombosis/occlusion (per patient-year) was 0.12 for fistulae and 0.9 for grafts. The anatomical success rate for EVS was 94% for fistulae and 92% for grafts. Primary patency rates for fistulae at 1, 6, 12, 24 and 36 months were 82, 64, 44, 34 and 26%, respectively, whereas secondary patency rates were 88, 84, 74, 69 and 61%, respectively. Primary patency rates for grafts at 1, 6 and 12 months were 50, 14 and 8%. The overall rate of complications was 6% with no incidence of symptomatic pulmonary embolism. In a Cox regression model, upper-arm location of fistula (HR 1.9, p = 0.04, n = 144) was associated with lower primary patency, whereas the presence of thrombosis was associated lower primary (HR 1.9, p = 0.004, n = 144) and secondary patency (HR 3.7, p < 0.001, n = 144). Aspirin therapy was associated with longer primary patency (HR 0.6, p = 0.02, n = 144) and secondary patency (HR 0.58, p = 0.08, n = 144). Conclusion: EVS is effective but longer-term outcomes are poor. Presence of thrombosis portends poor fistula survival and strategies for prevention need attention. Balloon maceration, our preferred declotting technique, is safe and the most cost-effective method. Aspirin therapy for patients presenting with failure of fistulae deserves further investigation.

Animal Models for Studying Pathophysiology of Hemodialysis Access

Despite extensive efforts, most approaches to reduce arteriovenous (AV) access-related complications did not results in substantial improvement of AV access patency thus far. Part of this disappointing progress relates to incomplete understanding of the underlying pathophysiology of hemodialysis access failure. In order to unravel the pathophysiology of hemodialysis access failure, animal models that closely mimic human pathology are of utmost importance. Indeed, it is impossible to study the extremely complex response of the AV access at a molecular and cellular level in great detail in dialysis patients. Over the past decades, numerous animal models have been developed in an attempt to unravel the vascular pathology of AV access failure and to design new therapeutic strategies aimed to improve durability of these vascular conduits. While large animals such as pigs are suitable for intervention studies, murine models have the greatest potential to gain more insight in the molecular mechanisms underlying AV access failure due to the availability of transgenic mice. In the present review, we describe several existing models of AV access failure and discuss the advantages and limitations of these models.

Arteriovenous access failure: more than just intimal hyperplasia?

Haemodialysis vascular access patency is severely compromised by fistula non-maturation and access stenosis. Intimal hyperplasia (IH) is considered the culprit lesion in failed fistulas, resulting in luminal narrowing and stenosis. This review focuses on the biology and pathophysiology of fistula failure and highlights not only the classically associated IH but also some relatively neglected but potentially important contributors such as inadequate outward remodelling. In addition, the complex process and fragile balance of successful fistula maturation might be partially hindered by pre-existent chronic kidney disease-mediated vasculopathy. Further unravelling the (patho)physiology of outward remodelling and IH could contribute to novel therapies and enhance fistula patency.

Expression of caspase‐3‐dependent apoptosis in mural thrombi leukocytes

Failure of arteriovenous access is mostly due to graft thrombosis and multifactorial, with medical and surgical etiologies. Apoptosis of blood cells, such as macrophages, lymphocytes and eosinophils, may play an important role in thrombus formation. We also investigated caspase-3-dependent apoptosis in thrombi. We recorded clinical parameters in 43 consecutive patients with vascular access failure (13 men, 30 women; mean age+/-SD, 64.6+/-14.2 years) who underwent surgical thrombectomy. Major presentations included absent (92%) and/or near near-absent (16%) flow through the access during hemodialysis. Cardiovascular risk factors were hypertension (70%), hyperlipidemia (47%), diabetes mellitus (47%), chronic obstructive pulmonary disease (12%), heart failure (12%), coronary artery disease (21%), and stroke (16%). Laboratory data included hemoglobin level of 100+/-17 g/L, total white blood cell count of 7.65+/-2.14 x 10(9)/L, and platelet count of 205.6+/-57.9 1000/ìL. Abnormal biochemistry data included elevated blood urea nitrogen level of 63.5+/-24.4 mg/dL and creatinine level of 8.6+/-4.0 mg/dL (normal <1.4 mg/dL). Thrombi were characterized by apoptosis (32%) in a caspase-dependent pathway in all types of leukocytes. Thrombi in arteriovenous access failure demonstrate apoptosis by means of the caspase-3 pathway in white blood cells.

Medical factors affecting patency of arteriovenous access

Arteriovenous access failure is multifactorial in nature with contributions from both medical and surgical etiologies. Medical causes of arteriovenous access failure are rare, and therefore infrequently identified as a major contributing source of malfunction. Although they account for only 10–15% of all cases of access failure, their importance should not be underestimated, especially in cases where a surgical source cannot be identified. Most medical causes are derived from Virchow’s triad of endothelial cell injury, stasis, and hypercoaguability. Endothelial cell injury occurs through oxidative stress, activated platelets, increased levels of circulating tumor necrosis factor-α, and preexisting intimal hyperplasia. Stasis can occur through prolonged access compression, hypotension, or hypoalbuminemia. Finally, patients with renal failure requiring hemodialysis are frequently at increased risk for hypercoaguable states, except for situations of platelet dysfunction, and therefore access failure. Potential treatments include identifying and removing the offending source, as well as innovative, new medications to prevent their reoccurrence. Treatment is aimed at improving quality of life, as well as decreasing morbidity and hospital admissions in this difficult patient population.

A novel technique designed to minimize the morbidity of failure of arteriovenous access in hemodialysis patients

The failure of dialysis access grafts leads to significant morbidity rates in patients with end-stage renal disease. We describe a novel technique for the insertion of new polytetrafluoroethylene graft segments designed to reduce this morbidity rate. Patients found to have significant intragraft deterioration at thrombectomy undergo insertion of a new nonanastamosed graft parallel to the existing graft. At the next failure of the existing graft, the nonanastamosed segment is anastamosed and used immediately for dialysis, obviating the need for a temporary catheter. Thirty patients have undergone this technique, and 89% of those who returned to surgery have had successful anastamosis of their new segments. Two patients were found to have inadequate incorporation of their new segments into the subcutaneous tissue, and one became frankly infected. (J Vasc Surg 2002;35:1013-5.)