Randomized controlled trial of clopidogrel plus aspirin to prevent hemodialysis access graft thrombosis

Hemodialysis Arteriovenous Graft and The Effect of Obesity on Patency. A Retrospective Study

BACKGROUND

Obesity is growing in the hemodialysis (HD) population. Few scholars report variable effects of increased body mass index (BMI) on native fistula. Reports on obesity effects on arteriovenous graft (AVG) patency are lacking. We report our experience.

METHODS

AVGs placed in our center between January 2006 and December 2010 were included. Data were collected retrospectively from electronic records. The primary end point was AVG thrombosis. The secondary end points were death, kidney transplant, or lost to follow-up. Graft patency and first intervention outcome were recorded. Study groups were divided into obese and nonobese groups. IBM SPSS 20 was used for analysis. A P value < 0.05 was considered significant.

RESULTS

143 AVGs were included. The follow-up was 669 ± 708 [0, 3,042 days (mean ± SD, min, max)], and 0.49% (70) of grafts were placed in obese patients. The BMI ranged between 17 and 51 Kg/m2 (29.8 ± 8). There was no difference in the technical failure rate between obese and nonobese groups (12.9% vs. 11%, P=0.56, Fisher's exact test). Obesity was not a risk factor of loss of patency. No significant difference was observed in the overall patency between obese (54%, 25%, and 17%) and nonobese groups (56%, 30%, and 18%) at 1, 3, and 5 years. (P=0.85, Log-rank Kaplan -Meier). Similarly, the success rate (88.2% vs. 83.3%, P=0.73, Fisher's exact test) and requirement of more than 1 intervention (61.8% vs. 61.1%, P=1.0, Fisher's exact test) were similar. Finally, the infection rate was similar in both groups (10% vs. 9.6%, P=1.0, Fisher's exact test) CONCLUSIONS: Higher BMI and obesity were not risk factors for AVG loss. Overall patency in obese patients is not inferior to that in nonobese AVGs. In obese patients, AVG insertion should be considered if the native arteriovenous fistula (AVF) options are exhausted or not available.

A randomized controlled trial evaluated the efficacy and safety of apixaban for prevention of recurrent thrombosis after thrombectomy of hemodialysis vascular access

Dialysis vascular access thrombosis poses a substantial challenge for individuals undergoing hemodialysis. The efficacy and safety of apixaban, a direct oral coagulation factor Xa inhibitor, in preventing recurrent access thrombosis have yet to be explored. Here, a multicenter randomized control study (NCT04489849) enrolled hemodialysis patients to evaluate this who underwent successful endovascular thrombectomy within 48 hours. Participants were assigned to standard care or standard care plus apixaban, 2.5 mg twice daily for three months. The trial design involved open-label administration, with independent adjudication of endpoints. The primary efficacy endpoint was recurrent access thrombosis within three months after thrombectomy. A total of 186 patients with well-balanced baseline characteristics were enrolled, 93 randomized to the apixaban group and 93 to the control group. The apixaban group demonstrated a significantly lower rate of access thrombosis at three months than the control group (24.0% vs. 40.8%; hazard ratio, 0.52 [95% confidence interval 0.31-0.88]), along with a significantly better primary patency failure rate (32.2% vs. 49.5%, 0.57 [0.36-0.91]). Safety outcomes showed comparable death rates and major bleeding incidents but significantly higher incidence of minor bleeding in the apixaban group (22.6% vs. 7.5%). The effect of apixaban did not show interaction in subgroups of different access types, antiplatelet usage, severity of comorbidities, or history of thrombosis. Thus, apixaban effectively reduced the risk of recurrent thrombosis in hemodialysis vascular access post-thrombectomy. Despite a minor increase in bleeding adverse effects, the net clinical benefit favors the use of apixaban in this context.

Single or Dual Antiplatelet Therapy Improves One-Year Arteriovenous Graft Patency and Overall Survival

BACKGROUND

Following new dialysis access creation there is no consensus on the optimal use of anti-thrombotic therapy. Recent studies have suggested that single antiplatelet therapy may improve hospital mortality as well as patency. The aim of this study was to assess the role of different antiplatelet and anticoagulation therapies on outcomes following dialysis access creation.

MATERIAL AND METHODS

A retrospective study was conducted utilizing patients from the Vascular Quality Initiative who underwent AV fistula (AVF) and AV graft (AVG) creation from 2011-2023. Patients who were antiplatelet and anticoagulation naive were separated into 4 cohorts: no antiplatelet (No APT), single antiplatelet (SAPT), dual antiplatelet (DAPT), and aspirin with anticoagulation (ASA + AC). Univariate Kaplan-Meier (KM) and multivariable regression analyses were conducted to assess overall survival, primary patency, and secondary patency.

RESULTS

49,980 patients with AVF creation and 12,688 patients with AVG creation were identified. AVG patients had improved 1-year primary patency with SAPT compared to No APT (48% vs. 44%, P = 0.03) on KM analysis. No difference on KM analysis was observed for AVF. Regression analysis showed decreased risk of loss of primary patency for AVF (HR 0.90, CI 0.83-0.97, P = 0.009). AVG with SAPT showed decreased risk of mortality (HR 0.80, CI 0.64-1.00, P = 0.05) and decreased risk of loss of primary patency (HR 0.80, CI 0.67-0.94, P = 0.009). DAPT also showed decreased risk of loss of primary patency for AVG (HR 0.64, CI 0.43-0.95, P = 0.028). Survival was worse for both AVF and AVG patients on ASA + AC on KM analysis.

CONCLUSIONS

Single antiplatelet therapy following access creation improves primary patency for both AVF and AVG, as well as overall survival for those with AVG. DAPT may further improve primary patency in those with AVG. The use of anticoagulation shows no clear benefit and may be harmful, however is more likely to reflect higher risk patients with other co-morbidities. These results suggest that following an AVF one should consider discharging patients on SAPT, and following an AVG one should consider SAPT or DAPT.

Existing and Evolving Therapies for Arteriovenous Fistula and Graft Dysfunction

A functional vascular access (VA) is of paramount importance to patients on hemodialysis therapy. While arteriovenous fistula (AVF) remains the preferred VA, their long-term patency is unpredictable. A dysfunctional VA contributes to a high morbidity rate, an increased susceptibility to major adverse cardiovascular events, recurrent hospitalization, and a poor quality of life. The recent innovations in devices and technologies have significantly expanded our options to create and prolong VA patency. Endovascular devices such as WavelinQ and Ellipsys are recent additions to creating a VA. The endovascular creation of AVF helps reduce the wait time and potentially avoids or reduces the duration of catheter use. The bioengineered graft and immediate access arteriovenous graft offer reasonable alternatives in a select group of patients. There is growing evidence that covered stents and drug-coated balloons offer options to prolong the VA patency. Finally, the role of stem cell therapy in VA is currently being explored. This article presents a comprehensive review of the conventional and current developments in the management of a dysfunctional VA.

Efficacy and safety of low dose, weight-based subcutaneous enoxaparin protocol in recurrent arteriovenous access thrombosis

BACKGROUND

This study aims to evaluate the safety and efficacy of a short-term, low dose, weight-based subcutaneous enoxaparin protocol (SEP) in maintaining the patency of arteriovenous (AV) access with recurrent thrombosis.

METHODS

Prospective follow-up of 25 patients who presented to a tertiary institution with recurrent AV access thrombosis and treated with anticoagulation according to SEP following successful thrombectomy. Patency and safety outcomes of SEP were studied.

RESULTS

The participants were 66.4 ± 10.2 years old and predominantly male (60%) and of Chinese ethnicity (72%). The AV accesses had a median age of 1.4 (0.6, 5.6) years with 60% being non-autogenous arteriovenous access while 40% were autogenous arteriovenous access. Thrombolytic agents (urokinase (72%) or alteplase (28%)) were used in all procedures while adjunct thrombectomy device was used in only four procedures. The mean dose of enoxaparin was 36.0 ± 8.2 mg or 0.64 ± 0.1 mg/kg/day for a mean duration 30.0 days (Interquartile range: 27.5, 31.0). One patient developed minor bleeding episode. Kaplan-Meier analysis demonstrated that the mean thrombosis-free survival pre- versus post-SEP adoption was 27.3 (95% CI 17.9-36.7) versus 183.5 (95% CI 100.1-266.9) days (p < 0.001). After adjusting for the type of thrombolytic agent, use of adjunct thrombectomy device, cutting balloon, drug-coated balloon, and stent graft, SEP remained a significant factor associated with longer thrombosis-free patency (HR 0.166: 95% CI 0.070-0.392, p < 0.001).

DISCUSSION

SEP appears to be a feasible and safe thromboprophylaxis method to improve thrombosis-free patency for AV access with recurrent thrombosis.

Rebuilding vascular access: from the viewpoint of mechanics and materials

This review presents a comprehensive analysis of vascular access in hemodialysis, focusing on the current modalities, their associated challenges, and recent technological advancements. It closely examines the status of three primary types of vascular access: arteriovenous fistulas, arteriovenous grafts, and central venous catheters. The review delves into the complications and pathologies associated with these access types, emphasizing the mechanobiology-related pathogenesis of arteriovenous access. Furthermore, it explores recent clinical trials, biomaterials, and device innovations, highlighting novel pharmaceutical approaches, advanced materials, device designs, and cutting-edge technologies aimed at enhancing the efficacy, safety, and longevity of vascular access in hemodialysis. This synthesis of current knowledge and emerging trends underscores the dynamic evolution of vascular access strategies and their critical role in improving patient care in hemodialysis.

Challenges and potential solutions to enrollment in a clinical trial of arteriovenous fistula vs arteriovenous graft vascular access strategy

This article presents the rationale, challenges, and adaptive strategies employed during the initiation and execution of the arteriovenous (AV) access trial-a multicenter randomized controlled trial (RCT) comparing AV fistulas and AV grafts for hemodialysis in older adults with major comorbidities. Motivated by shifts in epidemiologic landscapes and evolving guidelines moving away from a fistula-first approach and to more patient-centric approaches, the objective of this randomized controlled trial was to fill critical knowledge gaps in determining the optimal vascular access for this complex patient population. We outline the challenges encountered in patient recruitment along with measures employed to overcome these obstacles in recruitment. We emphasize the pivotal role of continuous research in overcoming these challenges, underscoring its necessity to achieve a thorough comprehension of optimal vascular access strategies for this complex patient population.

A review of the current recommendations and practices for hemodialysis access monitoring and maintenance procedures

The growing number of prevalent arteriovenous (AV) accesses has been associated with an increase in the incidence of procedures being performed to maintain patency. To reduce the rate of unnecessary procedures, the 2019 Kidney Disease Outcome Quality Initiative guidelines addended the AV access surveillance recommendations, which includes clinical monitoring and assessment of dialysis adequacy alone. Abnormal clinical findings would necessitate follow-up angiography with or without confirmatory duplex ultrasound. Due to poor patency, increased surveillance schedules have been proposed to identify stenosis early and potentially prevent acute thrombotic events and AV access failure. In this review, we outlined current AV access monitoring and maintenance procedure recommendations, as described by the Centers for Medicare and Medicaid Services and 2019 Kidney Disease Outcome Quality Initiative guidelines. In addition, we highlight the findings of recently published randomized controlled trials that have examined increased surveillance schedules.

Efficacy and safety of Apixaban for the prevention of thrombosis in arteriovenous grafts

This research aims to fill a vital gap in existing studies by evaluating the efficacy and safety of Apixaban, a direct oral anticoagulant, in the prevention of arteriovenous graft (AVG) thrombosis, thereby offering substantial insights into alternative anticoagulant options for hemodialysis patients. Conducted as a multi-center, randomized, double-blind, placebo-controlled trial, this study involved end-stage renal disease (ESRD) patients who had recently received polytetrafluoroethylene grafts. Participants were assigned to receive either Apixaban at a dose of 2.5 mg twice daily or a placebo. The primary outcome measure was the occurrence of graft thrombosis, while secondary outcomes focused on the incidence and severity of bleeding. Analytical methods included Kaplan-Meier estimates, Cox proportional hazards models, and conventional statistical tests. With 96 patients enrolled, the study found that Apixaban significantly reduced the incidence of AVG thrombosis compared to placebo (16.7% vs. 62.5%, P < 0.0001). Notably, this reduction in thrombosis incidence was not accompanied by an increase in bleeding events, thus affirming the safety profile of Apixaban as established in prior research. Apixaban is identified as an efficacious alternative to traditional anticoagulants in the prevention of AVG thrombosis among hemodialysis patients, representing a notable advancement in the care of individuals with ESRD. The results of this study support further investigations into the optimal dosing strategies specifically tailored for this patient demographic.

Bleeding Risk in Hemodialysis Patients

Cardiovascular diseases are highly prevalent among patients on dialysis. For these diseases, antiplatelets and antithrombotic therapies including heparin, vitamin K antagonists, and direct oral anticoagulants, are being used. However, the benefit-risk balance of these therapies could differ for dialysis patients compared with the general population. This review article focuses on the bleeding risk associated with the use of heparin, antiplatelets, vitamin K antagonists, and direct oral anticoagulants in patients receiving hemodialysis.

Role of neutrophil extracellular traps in vascular access thrombosis in hemodialysis patients

BACKGROUND

A patent vascular access (VA) is a lifeline for hemodialysis (HD) patients. However, vascular access is prone to thrombosis, which, if left untreated, can lead to permanent VA loss and increased mortality. Neutrophil extracellular traps (NETs) are known to be involved in intravascular thrombosis. We evaluated the relationship between NETs and VA thrombosis and their impact on VA prognosis.

METHODS

A total of 189 patients with VA flow problems were enrolled. Among these, 93 patients underwent percutaneous transluminal angioplasty (PTA) for stenosis, and 96 patients underwent PTA with thrombectomy for thrombosis. Plasma nucleosome, myeloperoxidase-DNA complex, and von Willebrand factor (vWF) were measured as markers of circulating NETs and thrombosis risk, respectively. The primary outcome was permanent VA loss and the secondary outcome was recurrent thrombotic occlusion within 6 months. In addition, the presence of NETs in thrombi was evaluated by histopathological analysis.

RESULTS

Circulating nucleosome levels were closely associated with plasma vWF levels (r = 0.172, p = 0.025), and both were higher in thrombectomy cases than in PTA alone cases (nucleosome; 0.83 ± 0.70 vs. 0.35 ± 0.26, p < 0.001, vWF: 9.0 ± 7.6 vs. 7.3 ± 6.2, p = 0.038). The highest quartile of nucleosomes (Q4) was associated with an 18-fold increased rate of access thrombotic occlusion (p < 0.001). In addition, multivariate analysis showed that the rates of permanent access loss (HR 2.77, 95 % CI 1.35-5.77) and recurrent thrombosis (HR 2.35, 95 % CI 1.22-4.54) were much higher in patients with the Q4 nucleosome group than in those with Q1-3. In addition, higher neutrophil infiltration and NET expression in thrombi were also associated with poor VA prognosis.

CONCLUSIONS

Higher levels of circulating NETs and the amount of NET expression in thrombi may be associated with VA thrombosis and poor VA outcomes.

Frequent vascular access thrombosis in a patient with end stage kidney disease on hemodialysis

Vascular access thrombosis (VAT) is common among patients receiving hemodialysis and leads to missed dialysis treatments, hospitalizations, catheter placement, and graft/fistula abandonment. This article reviews the association between hypercoagulability and VAT and the high prevalence of hypercoagulable states in end-stage kidney disease (ESKD). This article reviews the role of antithrombotic and anticoagulant medications in preventing VAT. The article concludes by reviewing the unique challenges of using vitamin K antagonists in patients with ESKD.

The role of venous pressure variability during hemodialysis in the prediction of impending arteriovenous graft occlusion

BACKGROUND

Elevated venous pressure during hemodialysis (VPHD) is associated with arteriovenous graft (AVG) stenosis. This study investigated the role of VPHD variations in the prediction of impending AVG occlusion.

METHODS

Data were retrieved from 118 operations to treat AVG occlusion (occlusion group) and 149 operations to treat significant AVG stenosis (stenosis group). In addition to analyzing the VPHD values for the three hemodialysis (HD) sessions prior to the intervention, VPHD values were normalized to mean blood pressure (MBP), blood flow rate (BFR), BFR × MBP, and BFR2 × MBP to yield ratios for analysis. The coefficient of variation (CV) was used to measure relative variations.

RESULTS

The within-group comparisons for both groups revealed no significant differences in the VPHD mean and CV values among the three HD sessions prior to intervention. However, the CVs for VPHD/MBP, VPHD/(BFR × MBP), and VPHD/(BFR2 × MBP) exhibited significant elevation in the occlusion group during the last HD session prior to intervention compared with both the penultimate and antepenultimate within-group HD data (p < 0.05). In the receiver operating characteristic curve analysis, the CV for VPHD/(BFR2 × MBP) was the only parameter able to discriminate between the last and the penultimate HD outcomes (p < 0.001). According to a multivariate analysis, after controlling for covariates, CV for VPHD/(BFR2 × MBP) >8.76% was associated with a higher risk of AVG thrombosis (odds ratio: 3.17, p < 0.001).

CONCLUSIONS

Increasing the variation in VPHD/(BFR2 × MBP) may increase the probability of AVG occlusion.

Mid-term cumulative patency of fistula and PTFE grafts among hemodialysis patients: A retrospective, single-center study from Palestine

BACKGROUND

Due to the long waiting time for kidney transplantation, most End-Stage renal disease patients are commenced on either hemodialysis or peritoneal dialysis. Reusable fistulas have the lowest risk for death, cardiovascular events, and infections among all vascular accesses. This study aims to report the outcomes of the arteriovenous fistulas and PTFE grafts and the related predictive clinical and demographic variables.

METHODS

This retrospective study reviewed the charts of all hemodialysis patients between January 2017 and January 2021 at the Dialysis Center of An-Najah National University Hospital, Nablus, Palestine. Our outcomes were a primary failure, primary and secondary patency, and the related factors. Survival analysis using the Kaplan-Meier method was conducted, and the log-rank test was used to compare patency rates. The Cox proportional hazards regression model tested factors relevant to primary and secondary patency rates in univariate and multivariate analyses.

RESULTS

A total of 312 procedures were performed during the study period. Primary failure was 7.1% for AVF, 13.9% for arterio-venous graft (AVG) procedures. Peripheral arterial disease and left-sided AVF were associated with more primary failure rates. AVF, primary patency rates at 1, 2, and 3 years were 82%, 69%, and 59%, respectively, while secondary patency rates at 1, 2, and 3 years were 85%, 72%, and 63%, respectively. Factors associated with increased AVF patency in a proportional hazard model were younger age and dual antiplatelet administration.

CONCLUSION

Our study adds further evidence that autogenous AVF has better results than prosthetic AVG in both primary and secondary patency rates as well as less primary failure rates. Therefore, we encourage further longitudinal studies that assess the benefits of using antiplatelet on AVF outcome versus risks of bleeding, especially with dual agents.

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.

Temporal regulation of notch activation improves arteriovenous fistula maturation

BACKGROUND

Arteriovenous fistula (AVF) maturation is a process involving remodeling of venous arm of the AVFs. It is a challenge to balance adaptive AVF remodeling and neointima formation. In this study we temporally controlled Notch activation to promote AVF maturation while avoiding neointima formation.

METHODS

Temporal Notch activation was controlled by regulating the expression of Notch transcription factor, RBP-Jκ, or dnMAML1 (dominant negative MAML2) in vascular smooth muscle cells (VSMCs). AVF mouse model was created and VSMC phenotype dynamic changes during AVF remodeling were determined.

RESULTS

Activated Notch was found in the nuclei of neointimal VSMCs in AVFs from uremic mice. We found that the VSMCs near the anastomosis became dedifferentiated and activated after AVF creation. These dedifferentiated VSMCs regained smooth muscle contractile markers later during AVF remodeling. However, global or VSMC-specific KO of RBP-Jκ at early stage (before or 1 week after AVF surgery) blocked VSMC differentiation and neointima formation in AVFs. These un-matured AVFs showed less intact endothelium and increased infiltration of inflammatory cells. Consequently, the VSMC fate in the neointima was completely shut down, leading to an un-arterialized AVF. In contrast, KO of RBP-Jκ at late stage (3 weeks after AVF surgery), it could not block neointima formation and vascular stenosis. Inhibition of Notch activation at week 1 or 2, could maintain VSMC contractile markers expression and facilitate AVF maturation.

CONCLUSIONS

This work uncovers the molecular and cellular events in each segment of AVF remodeling and found that neither sustained increasing nor blocking of Notch signaling improves AVF maturation. It highlights a novel strategy to improve AVF patency: temporally controlled Notch activation can achieve a balance between adaptive AVF remodeling and neointima formation to improve AVF maturation.

TRANSLATIONAL PERSPECTIVE

Adaptive vascular remodeling is required for AVF maturation. The balance of wall thickening of the vein and neointima formation in AVF determines the fate of AVF function. Sustained activation of Notch signaling in VSMCs promotes neointima formation, while deficiency of Notch signaling at early stage during AVF remodeling prevents VSMC accumulation and differentiation from forming a functional AVFs. These responses also delay EC regeneration and impair EC barrier function with increased inflammation leading to failed vascular remodeling of AVFs. Thus, a strategy to temporal regulate Notch activation will improve AVF maturation.

Prevalence and clinical significance of anatomic variant in cephalic arch on preoperative mapping venography

The aim of the current study was to determine the prevalence of anatomic variant in cephalic arch on preoperative mapping venography and evaluate patency rates and predictors of patency in patients with brachiocephalic fistulas. The prevalence of anatomic variant in cephalic arch was retrospectively evaluated in 1004 consecutive patients who underwent bilateral preoperative mapping venography from July 2006 to December 2018 in a single center. The overall prevalence of anatomic variant in cephalic arch was 17.2% (173/1004). For patency analysis, 128 patients with brachiocephalic fistulas were divided into two groups: a standard anatomy (SA) group (n = 97) and a variant anatomy (VA) group (n = 31). There were no significant differences in clinical characteristics between the two groups. The primary patency rate did not differ significantly between the two groups. The secondary patency rate was significantly (p = 0.009) lower in the VA group than in the SA group. Older age (HR 1.03; 95% CI 1.01-1.05; p = 0.007) was a negative predictor of primary patency, and antiplatelet agent (HR 0.53; 95% CI 0.33-0.84; p = 0.007) and large-diameter cephalic vein (HR 0.52; 95% CI 0.31-0.86; p = 0.012) were positive predictors of primary patency. Older age (HR 1.04; 95% CI 1.01-1.07; p = 0.011) and anatomic variant in cephalic arch (HR 2.9; 95% CI 1.19-7.06; p = 0.019) were negative predictors of secondary patency. The current study provides insight into the clinical significance of anatomic variant in cephalic arch. Anatomic variant in cephalic arch should be considered as a potential risk factor for decreased patency of brachiocephalic fistula during preoperative planning.

Age Modifies Intracranial and Gastrointestinal Bleeding Risk from P2Y12 Inhibitors in Patients Receiving Dialysis

Background

Individuals aged ≥75 years are the fastest-growing population starting dialysis for end-stage kidney disease (ESKD) due to living longer with coronary artery disease. ESKD alone can increase bleeding risk, but P2Y₁₂ inhibitor (P2Y12-I) antiplatelet medications prescribed for cardiovascular treatment can exacerbate this risk in patients with ESKD. The age-specific rates of bleeding complications in dialysis patients with ESKD on P2Y12-I remain unclear, as does how age modifies the bleeding risk from P2Y12-I use in these patients.

Methods

In a retrospective cohort study, we collected data on 40,972 patients receiving maintenance hemo- or peritoneal dialysis who were newly prescribed P2Y12-I therapy between 2011 and 2015 from the USRDS registry. We analyzed the effect of age on the time to first bleed and the interactions between age and P2Y12-I type on modifying the effects of a bleed.

Results

Twenty percent of the cohort were aged ≥75 years. There were 3096 (8%) gastrointestinal (GI) and 1298 (3%) intracranial (IC) bleeding events during a median follow-up of 1 year. Annual incidence rates for IC bleeds were 2% in those aged <55 years and 3% in those aged ≥75 years. Rates for GI bleeds were 4% in those aged <55 years and 9% in those aged ≥75 years. On clopidogrel, prasugrel, and ticagrelor, for every decade increase in age of the cohort members, the risk of IC bleed increased by 9%, 55%, and 59%, and the risk of GI bleed increased by 21%, 28%, and 39%, respectively. At age ≥75 years, prasugrel was associated with a greater risk of IC bleed than clopidogrel. At age ≥60 years, ticagrelor was associated with a greater risk of GI bleed than clopidogrel.

Conclusions

More potent P2Y12-Is (prasugrel and ticagrelor) were associated with a disproportionately higher risk of IC bleed with increasing age compared with that of clopidogrel-prasugrel was much worse than clopidogrel at age ≥75 years. All three drugs were associated with only modest increase in the risk of GI bleed with every decade increase in age-ticagrelor was much worse than clopidogrel at ≥60 years of age. These results highlight the need for head-to-head clinical trials for the use of P2Y12-Is in patients with ESKD to determine age cutoffs where the risk of bleeding outweighs the benefits of thrombosis prevention.

The related factors to the re-thrombosis of hemodialysis arteriovenous graft after endovascular salvage

BACKGROUND

Only a few issues of the related factors to hemodialysis access dysfunction have been evaluated, and the effects of antiplatelets to improve the patency of hemodialysis access remained controversial. Hence, this study aimed to determine the related factors to the re-thrombosis of arteriovenous grafts (AVGs) after endovascular treatment.

METHODS

This retrospective study was conducted at a university-affiliated teaching hospital in Southern Thailand. All patients who underwent hemodialysis with thrombosed AVG, who had pharmacomechanical thrombolysis from January 2016 to December 2018, were enrolled. Post-intervention primary patency was analyzed by the Kaplan-Meier method, and the related factors to the re-thrombosis of AVG were evaluated using logistic regression.

RESULTS

A total of 157 patients with thrombosed hemodialysis AVG were enrolled. The most common graft location and configuration was a forearm loop graft (65%). Post-intervention primary patency rate at 1, 3, and 6 months were 79.0%, 67.1%, and 54.0%, respectively. Diabetes mellitus (DM) was a significant related factor for re-thrombosis (hazard ratio [HR], 1.89; 95% confidence interval [CI], 1.20-2.98; p = 0.006). A single antiplatelet after the procedure was a protective factor for re-thrombosis (HR, 0.58; 95% CI, 0.38-0.89; p = 0.013). The median post-intervention primary patency was 15.7 months in the group of single antiplatelet usage, which was better than that of the non-antiplatelet group (p = 0.012).

CONCLUSION

DM and antiplatelet usage were significant related factors to the re-thrombosis of hemodialysis AVG after endovascular salvage.

Antiplatelet agents for chronic kidney disease

BACKGROUND

Antiplatelet agents are widely used to prevent cardiovascular events. The risks and benefits of antiplatelet agents may be different in people with chronic kidney disease (CKD) for whom occlusive atherosclerotic events are less prevalent, and bleeding hazards might be increased. This is an update of a review first published in 2013.

OBJECTIVES

To evaluate the benefits and harms of antiplatelet agents in people with any form of CKD, including those with CKD not receiving renal replacement therapy, patients receiving any form of dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 13 July 2021 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We selected randomised controlled trials of any antiplatelet agents versus placebo or no treatment, or direct head-to-head antiplatelet agent studies in people with CKD. Studies were included if they enrolled participants with CKD, or included people in broader at-risk populations in which data for subgroups with CKD could be disaggregated.

DATA COLLECTION AND ANALYSIS

Four authors independently extracted data from primary study reports and any available supplementary information for study population, interventions, outcomes, and risks of bias. Risk ratios (RR) and 95% confidence intervals (CI) were calculated from numbers of events and numbers of participants at risk which were extracted from each included study. The reported RRs were extracted where crude event rates were not provided. Data were pooled using the random-effects model. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 113 studies, enrolling 51,959 participants; 90 studies (40,597 CKD participants) compared an antiplatelet agent with placebo or no treatment, and 29 studies (11,805 CKD participants) directly compared one antiplatelet agent with another. Fifty-six new studies were added to this 2021 update. Seven studies originally excluded from the 2013 review were included, although they had a follow-up lower than two months. Random sequence generation and allocation concealment were at low risk of bias in 16 and 22 studies, respectively. Sixty-four studies reported low-risk methods for blinding of participants and investigators; outcome assessment was blinded in 41 studies. Forty-one studies were at low risk of attrition bias, 50 studies were at low risk of selective reporting bias, and 57 studies were at low risk of other potential sources of bias. Compared to placebo or no treatment, antiplatelet agents probably reduces myocardial infarction (18 studies, 15,289 participants: RR 0.88, 95% CI 0.79 to 0.99, I² = 0%; moderate certainty). Antiplatelet agents has uncertain effects on fatal or nonfatal stroke (12 studies, 10.382 participants: RR 1.01, 95% CI 0.64 to 1.59, I² = 37%; very low certainty) and may have little or no effect on death from any cause (35 studies, 18,241 participants: RR 0.94, 95 % CI 0.84 to 1.06, I² = 14%; low certainty). Antiplatelet therapy probably increases major bleeding in people with CKD and those treated with haemodialysis (HD) (29 studies, 16,194 participants: RR 1.35, 95% CI 1.10 to 1.65, I² = 12%; moderate certainty). In addition, antiplatelet therapy may increase minor bleeding in people with CKD and those treated with HD (21 studies, 13,218 participants: RR 1.55, 95% CI 1.27 to 1.90, I² = 58%; low certainty). Antiplatelet treatment may reduce early dialysis vascular access thrombosis (8 studies, 1525 participants) RR 0.52, 95% CI 0.38 to 0.70; low certainty). Antiplatelet agents may reduce doubling of serum creatinine in CKD (3 studies, 217 participants: RR 0.39, 95% CI 0.17 to 0.86, I² = 8%; low certainty). The treatment effects of antiplatelet agents on stroke, cardiovascular death, kidney failure, kidney transplant graft loss, transplant rejection, creatinine clearance, proteinuria, dialysis access failure, loss of primary unassisted patency, failure to attain suitability for dialysis, need of intervention and cardiovascular hospitalisation were uncertain. Limited data were available for direct head-to-head comparisons of antiplatelet drugs, including prasugrel, ticagrelor, different doses of clopidogrel, abciximab, defibrotide, sarpogrelate and beraprost.

AUTHORS' CONCLUSIONS

Antiplatelet agents probably reduced myocardial infarction and increased major bleeding, but do not appear to reduce all-cause and cardiovascular death among people with CKD and those treated with dialysis. The treatment effects of antiplatelet agents compared with each other are uncertain.

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.

Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields

Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate  ([Formula: see text]) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.

Effect of short-term low molecular weight heparin on patency following successful salvage of arteriovenous access with recurrent thrombosis

AIM

This study aims to investigate the effect of low molecular weight heparin (LMWH) in maintaining the patency of arteriovenous (AV) access with recurrent thrombosis.

METHODS

Following successful thrombectomy, 66 patients with recurrent thrombosis were included in the study. The primary, assisted primary and secondary patency rates of patients who received LMWH (n = 24) were compared with those who did not receive anticoagulant (n = 42) using Kaplan-Meier analysis. Cox-regression analysis was performed to investigate potential predictors of patency rates.

RESULTS

The mean dose of enoxaparin used was 40 ± 13.1 mg or 0.74 ± 0.2 mg/kg daily for a median duration of 14 (IQR 7,28) days. The mean trough anti-Xa concentrations measured after two doses of LMWH was 0.17 ± 0.13 IU/mL. Kaplan-Meier analyses for mean primary, assisted primary and secondary patency rates of LMWH vs no anticoagulation groups were 149 (95% CI: 91 - 207) vs 87 (95% CI: 42-132) days (P < .006), 230 (95% CI: 142-320) vs 107 (95% CI: 62-150) days (P = .01) and 438 (299-579) vs 294 (95% CI: 197-392) days (P = .08) respectively. LMWH remained a significant protective predictor of primary (HR: 0.49; 95% CI: 0.25-0.86; P = .02) and assisted primary patency rates (HR: 0.51; 95% CI: 0.27-0.98; P = .04) after adjusting for patient age, access age, type of AV access, presence of peripheral vascular disease and haemoglobin levels.

CONCLUSION

LMWH may improve short and mid-term patency rates for AV accesses with recurrent thrombosis.

Clinical outcomes of prolonged dual antiplatelet therapy after coronary drug-eluting stent implantation in dialysis patients

Background

End-stage renal disease yields susceptibility to both ischemia and bleeding. The optimal duration of dual antiplatelet therapy (DAPT) after drug-eluting stent (DES) implantation is not established in dialysis patients, who are usually excluded from randomized studies. Since recent studies implied the benefits of prolonged DAPT >12 months in chronic kidney disease, we investigated the effectiveness and safety of prolonged DAPT in dialysis patients with higher cardiovascular risks.

Methods

In this nationwide population-based study, we analyzed dialysis patients who underwent DES implantation from 2008 to 2015. Continued DAPT was compared with discontinued DAPT using landmark analyses, including free-of-event participants at 12 (n = 2246), 15 (n = 1925) and 18 months (n = 1692) after DES implantation. The primary outcome was major adverse cardiovascular events (MACEs): a composite of mortality, nonfatal myocardial infarction, coronary revascularization and stroke. Major bleeding was a safety outcome. Inverse probability of treatment weighting Cox regression was performed.

Results

Mean follow-up periods were 278.3-292.4 days, depending on landmarks. Overall, incidences of major bleeding were far lower than those of MACE. Continued DAPT groups showed lower incidences of MACE and higher incidences of major bleeding, compared with discontinued DAPT groups. In Cox analyses, continued DAPT reduced the hazards of MACE at the 12- [hazard ratio (HR) = 0.74, 95% confidence interval (CI) 0.61-0.90; P = 0.003], 15- (HR = 0.78, 95% CI 0.64-0.96; P = 0.019) and 18-month landmarks (HR = 0.79, 95% CI 0.63-0.99; P = 0.041), but without a significant increase in major bleeding at 12 (HR = 1.39, 95% CI 0.90-2.16; P = 0.14), 15 (HR = 1.13, 95% CI 0.75-1.70; P = 0.55) or 18 months (HR = 1.27, 95% CI 0.83-1.95; P = 0.27).

Conclusions

Prolonged DAPT reduced MACE without significantly increasing major bleeding in patients who were event-free at 12 months after DES implantation. In deciding on DAPT duration, prolonged DAPT should be considered in dialysis patients.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

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

The risk of bleeding for antiplatelet agents in Haemodialysis patients: a Meta-analysis

Background

The safety of antiplatelet therapy in haemodialysis (HD) patients remains controversial. we conducted the first meta-analysis to evaluate the bleeding risk with antiplatelet agents in these populations.

Methods

The relevant literature was searched using the following electronic databases without any language restrictions: the Cochrane Library, EMBASE, Global Health, MEDLINE, PubMed, and the Chinese Biomedical Database.

Results

Seven randomized controlled trials (RCTs) and 2 prospective cohort studies, consisting of 1131 patients, were identified for detailed evaluation. The meta-analysis suggested that the use of double antiplatelet agents increased the risk of bleeding in HD patients [odds ratio (OR) = 2.78; 95% confidence interval (CI) 1.63 to 4.76; I² = 0], and antiplatelet agents increased the risk of bleeding in 7 RCTs [odds ratio (RR) = 1.40, 95% CI 1.08 to 1.79; I² = 23%,]; however, the use of a single antiplatelet agent was not found to significantly increase the risk of bleeding (RR = 0.88; 95% CI 0.51 to 1.50; I² = 0).

Conclusion

The results suggested that the use of double antiplatelet agents increased the risk of bleeding in HD patients.

Effects of aspirin resistance and mean platelet volume on vascular access failure in hemodialysis patients

BACKGROUND/AIMS

Maintaining the patency of vascular access (VA) in hemodialysis (HD) patients is important and can be life-saving. We investigated the effects of aspirin resistance and mean platelet volume (MPV) on VA failure in HD patients.

METHODS

We enrolled 163 patients on maintenance HD. VA failure was defined as thrombosis or a decrease of > 50% of the normal vessel diameter, as revealed by angiography.

RESULTS

Aspirin resistance was observed in 17 of 109 patients in whom this parameter was measured, and was not significantly associated with VA failure (p = 0.051). The mean MPV was 9.15 ± 0.05 fL. The 163 patients were grouped by the median MPV value (9.08 fL) at baseline; patients with higher MPVs (n = 82) had lower platelet counts (p = 0.002) and albumin levels (p = 0.009). During 34 months of follow-up, 65 VA failures (39.9%) occurred. The Kaplan-Meier curve revealed significant differences between the two groups in terms of cumulative VA failure (54.1% vs. 35.3%, p = 0.018). On multivariate analysis, the MPV (hazard ratio [HR], 1.794; 95% confidence interval [CI], 1.066 to 3.020; p = 0.028), platelet count (HR, 1.003; 95% CI, 1.001 to 1.006; p = 0.01), and smoking status (HR, 1.894; 95% CI, 1.019 to 3.519; p = 0.043) independently predicted VA failure.

CONCLUSION

A high MPV was associated with an increased risk of VA failure, whereas aspirin resistance showed only a weak association. The MPV may predict VA survival in HD patients.

Effect of antiplatelet therapy on cardiovascular and kidney outcomes in patients with chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

The benefits and risks of antiplatelet therapy for patients with chronic kidney disease (CKD) remain controversial. We undertook a systematic review and meta-analysis to investigate the effects of antiplatelet therapy on major clinical outcomes.

METHODS

We systematically searched MEDLINE, Embase, and the Cochrane Library for trials published before April 2019 without language restriction. We included rrandomized controlled trials that involved adults with CKD and compared antiplatelet agents with controls.

RESULTS

Fifty eligible trials that included at least one event were identified, providing data for 27773patients with CKD, including 4518 major cardiovascular events and 1962 all-cause deaths. Antiplatelet therapy produced a 15% (OR, 0.85; 95% CI 0.74-0.94) reduction in the odds of major cardiovascular events (P = 0.002), a 48% reduction for access failure events (OR, 0.52; 95% CI, 0.31-0.73), but had no significantly effect on all-cause death (OR, 0.87; 95% CI, 0.71-1.01) or kidney failure events (OR, 0.87; 95% CI, 0.32-1.55). Adverse events were significantly increased by antiplatelet therapy, including major (OR, 1.33; 95% CI, 1.11-1.59) or minor bleeding (OR, 1.66; 95% CI, 1.27-2.05). Among every 1000 persons with CKD treated with antiplatelet therapy for 12 months, 23 major cardiovascular events will be prevented while nine major bleeding events will occur.

CONCLUSIONS

Major prevention with antiplatelet agents (cardiovascular events and access failure), might outweigh the risk of bleeding, and there seemed to be an overall net benefit. Individual evaluation and careful monitoring are required.

Diagnosis and treatment of myocardial infarction in patient with end - stage renal disease on chronic hemodialysis

This review represents different aspects of myocardial infarction in patient with end - stage renal disease on chronic hemodialysis. We discuss difficulties in diagnosis, optimal method of coronary revascularization, timing of hemodialysis session, medical therapy, as well as epidemiology and prognosis. There are no unambiguous answers to these problems because patients with end - stage renal disease were excluded from most of the studies.

Notch signaling in bone marrow-derived FSP-1 cells initiates neointima formation in arteriovenous fistulas

Neointima formation is a major contributor to arteriovenous fistula (AVF) failure. We have previously shown that activation of the Notch signaling pathway contributes to neointima formation by promoting the migration of vascular smooth muscle cells (VSMCs) into the venous anastomosis. In the current study we investigated the mechanisms underlying the dedifferentiation and migration of VSMCs, and in particular the role of bone marrow-derived fibroblast specific protein 1 (FSP-1)+ cells, another cell type found in models of vascular injury. Using VSMC-specific reporter mice, we found that most of the VSMCs participating in AVF neointima formation originated from dedifferentiated VSMCs. We also observed infiltration of bone marrow-derived FSP-1+ cells into the arterial anastomosis where they could interact with VSMCs. In vitro, conditioned media from FSP-1+ cells stimulated VSMC proliferation and phenotype switching. Activated Notch signaling transformed FSP-1+ cells into type I macrophages and stimulated secretion of cytokines and growth factors. Pretreatment with a Notch inhibitor or knockout of the canonical downstream factor RBP-Jκ in bone marrow-derived FSP1+ cells decreased FSP1+ cell infiltration into murine AVFs, attenuating VSMC dedifferentiation and neointima formation. Our results suggest that targeting Notch signaling could provide a new therapeutic strategy to improve AVF patency.

Functional Vascular Tissue Engineering Inspired by Matricellular Proteins

Modern regenerative medicine, and tissue engineering specifically, has benefited from a greater appreciation of the native extracellular matrix (ECM). Fibronectin, collagen, and elastin have entered the tissue engineer's toolkit; however, as fully decellularized biomaterials have come to the forefront in vascular engineering it has become apparent that the ECM is comprised of more than just fibronectin, collagen, and elastin, and that cell-instructive molecules known as matricellular proteins are critical for desired outcomes. In brief, matricellular proteins are ECM constituents that contrast with the canonical structural proteins of the ECM in that their primary role is to interact with the cell. Of late, matricellular genes have been linked to diseases including connective tissue disorders, cardiovascular disease, and cancer. Despite the range of biological activities, this class of biomolecules has not been actively used in the field of regenerative medicine. The intent of this review is to bring matricellular proteins into wider use in the context of vascular tissue engineering. Matricellular proteins orchestrate the formation of new collagen and elastin fibers that have proper mechanical properties-these will be essential components for a fully biological small diameter tissue engineered vascular graft (TEVG). Matricellular proteins also regulate the initiation of thrombosis via fibrin deposition and platelet activation, and the clearance of thrombus when it is no longer needed-proper regulation of thrombosis will be critical for maintaining patency of a TEVG after implantation. Matricellular proteins regulate the adhesion, migration, and proliferation of endothelial cells-all are biological functions that will be critical for formation of a thrombus-resistant endothelium within a TEVG. Lastly, matricellular proteins regulate the adhesion, migration, proliferation, and activation of smooth muscle cells-proper control of these biological activities will be critical for a TEVG that recellularizes and resists neointimal formation/stenosis. We review all of these functions for matricellular proteins here, in addition to reviewing the few studies that have been performed at the intersection of matricellular protein biology and vascular tissue engineering.

Hybrid arteriovenous graft for hemodialysis vascular access in a multicenter registry

OBJECTIVE

The aim of our study was to identify patients' characteristics that predicted a higher chance of arteriovenous graft patency in patients undergoing Gore Hybrid Vascular Graft (GHVG; W. L. Gore & Associates, Flagstaff, Ariz) implantation for hemodialysis access. The GHVG is a polytetrafluroethylene (PTFE) prosthesis with a nitinol-reinforced section (NRS) at the venous end.

METHODS

All consecutive patients undergoing GHVG implantation for hemodialysis access at 10 tertiary referral centers between December 2013 and January 2018 were included in the study and compared with a control group of patients undergoing standard PTFE graft implantation. Selection of patients for hybrid graft implantation was based on the impossibility of autogenous vascular access creation.

RESULTS

There were 145 patients included in the GHVG group and 218 in the PTFE group. In the GHVG and the PTFE groups, the mean age was 67 ± 13 years and 65 ± 13 years, and male patients totaled 52% and 46%, respectively. The technical success was 99%. The mean duration of the intervention was 100 minutes (median, 95 minutes; interquartile range, 80-120 minutes). The brachial-axillary configuration was used in the majority of cases (n = 78 [54%]). The 5-cm NRS length was prevalent (n = 108 [75%]). The median NRS oversize was 14% (interquartile range, 0%-21%). Mean follow-up was 13 months (range, 0-55 months). Seventy-one patients (49%) underwent at least one reintervention. Primary, assisted primary, and secondary patency estimates at 12 months were 44% ± 5%, 47% ± 5%, and 65% ± 4% for the GHVG group and 41% ± 4%, 53% ± 4%, and 75% ± 3% for the control group, respectively (P = NS). One-year survival was 90% ± 3%. On multivariable Cox regression analysis, hypotension (P < .001; hazard ratio [HR], 5.8; confidence interval [CI], 2.6-13) and diabetes (P = .024; HR, 1.9; CI, 1.1-3.2) were significant predictors of GHVG loss. A larger graft size was protective against GHVG loss (P = .042; HR, 0.73; CI, 0.54-0.99). The 10-cm-long graft showed a tendency toward improved patency but did not reach statistical significance (P = .074; HR, 0.48; CI, 0.21-1.07).

CONCLUSIONS

Diabetes and hypotension were predictors of loss of hybrid arteriovenous access. Smaller diameters of NRS were more prone to thrombosis, whereas the 10-cm length seemed to perform better than the 5-cm one.

Preventing arteriovenous shunt failure in hemodialysis patients: a population-based cohort study

Essentials Uncertainty remains about antiplatelets for vascular access patency in hemodialysis patients. 95 971 people under hemodialysis were followed in a claims database in Taiwan. Aspirin reduced vascular access failure rate and did not increase major bleeding rate. Clopidogrel, Aggrenox, and warfarin might increase major bleeding rate. SUMMARY: Background Dialysis adequacy is a major determinant of survival for patients with end-stage renal disease. Good vascular access is essential to achieve adequate dialysis. Objectives This study evaluated the impacts of different drugs on the vascular access failure rate of an arteriovenous fistula or an arteriovenous graft and the rate of major bleeding in hemodialysis patients. Patients and methods We studied patients with end-stage renal disease registered in the Taiwan National Health Insurance program from 1 January 1997 to 31 December 2012. A total of 95 971 patients were enrolled in our study. Vascular access dysfunction was defined as the need for thrombectomy or percutaneous angioplasty. Major bleeding was defined as emergency department visits or hospitalization with a primary diagnosis of gastrointestinal bleeding or intracerebral hemorrhage. The adjusted odds ratios between person-quarters with or without antiplatelet or oral anticoagulant use were calculated using a generalized estimating equation. Results The odds ratio of vascular access failure was 0.21 (0.11-0.39) for aspirin, 0.76 (0.74-0.79) for clopidogrel, 0.67 (0.59-0.77) for dipyridamole, 0.67 (0.53-0.86) for Aggrenox and 0.96 (0.90-1.03) for warfarin. The highest odds ratio for intracerebral hemorrhage was 5.33 (1.25-22.72) in younger patients using Aggrenox. The highest odds ratio for gastrointestinal bleeding was 1.34 (1.10-1.64) for clopidogrel. Conclusion Antiplatelet agents, but not warfarin, might reduce the vascular access thrombosis rate. The gastrointestinal bleeding rate was increased in the group using clopidogrel. Aggrenox should be used with caution in young individuals because it might increase the rate of intracerebral hemorrhage.

Adverse Effect of Antithrombotic Medications on Bleeding Events and Comparison of Antithrombotic Agents in Hemodialysis Patients

Antithrombotic medications (AM) are mandatory for many hemodialysis patients, but the bleeding risk associated with this therapy is elevated. The frequency of bleeding events requiring discontinuation of AM, cessation of heparin use, and/or hospitalization was compared between hemodialysis patients with and without AM. All the hemodialysis patients in our clinic were investigated. AM were prescribed in 130 of 222 patients. Except for patients with cilostazol, those with AM had significantly more frequent bleeding events than those without AM (P < 0.01). Bleeding event frequency per 10 000 days of aspirin, clopidogrel, cilostazol, and warfarin prescription was 7.37, 5.95, 2.41, and 9.81, respectively, when restricted to administration of a single AM, which was 4.96, 2.87, 0.7, and 16.06, respectively. In patients without AM, it was 0.91. The bleeding risk associated with AM is elevated in hemodialysis patients and differs markedly depending on the agent used, with the lowest risk associated with cilostazol.

Thrombophilia Associated with Early Post-angioplasty Thrombosis of Dialysis Vascular Access

AIM

Percutaneous transluminal angioplasty (PTA) is widely used as the primary treatment for dialysis vascular access dysfunction. Nonetheless, many patients develop early occlusion after angioplasty. Thus, we investigated the role of thrombophilia in access occlusion within 30 days of angioplasty.

MATERIALS AND METHODS

This case-control study included patients who underwent PTA for dialysis vascular access dysfunction. Patients who experienced occlusion within 30 days of angioplasty were included in the case group and those without occlusion for at least 30 days after angioplasty were included in the control group. All patients were tested for protein C, protein S, antithrombin III, lupus anticoagulant, and anticardiolipin antibodies.

RESULTS

From February to October 2015, 462 patients underwent PTA for dialysis vascular access dysfunction. Forty-one patients (8.9%) had early occlusion within 30 days of angioplasty. The case group had more graft accesses (73 vs. 31%, P < 0.001) and thrombotic occlusions (67 vs. 15%, P < 0.001). A higher incidence of protein C (10 vs. 2%), protein S (15 vs. 5%), and antithrombin III (10 vs. 2%) deficiency and elevated anticardiolipin antibody (22 vs. 10%) levels were observed in the case group. Overall, 26 patients (63%) in the case group had at least one thrombophilic factor, compared with 15 patients (37%) in the control group (unadjusted odds ratio [OR], 3.004; 95% confidence interval [CI], 1.223-7.380; P = 0.027). After adjustment for confounding factors, the association between thrombophilic factors and early occlusion remained (adjusted OR, 3.806; 95% CI, 1.018-14.220; P = 0.047).

CONCLUSION

Thrombophilia is associated with early occlusion after angioplasty for hemodialysis vascular access.

Effect of low dose aspirin and dipyridamole on primary patency of arteriovenous grafts in hemodialysis patients: a randomized double-blind placebo-controlled trial

Background

There is some evidence for the efficacy of antiplatelet therapies in increasing the vascular access patency duration or decreasing the thrombosis of arteriovenous grafts.

Objective

To determine the effect of low dose aspirin and dipyridamole on primary patency of arteriovenous grafts in hemodialysis patients

Methods

This randomized, double-blind, placebo-controlled trial was done at Imam Reza Hospital in Mashhad, Iran from September 10, 2015 to July 05, 2016. Sixty hemodialysis patients, after the placement of a new arteriovenous graft, were divided into three study groups which including; Group 1, who received 80 mg aspirin tablet daily, Group 2 received 80 mg aspirin plus 75 mg dipyridamole daily and Group 3 received placebo daily. Primary unassisted patency was recorded in follow-up until 12 months and the outcomes were analysed using one-way ANOVA test.

Results

Primary patency time in Group 1 (Aspirin) was 324.75±147.00 day and for Group 2 (Aspirin + Dipyridamole) was 399.05±92.09 day and for Group 3 (Placebo) was 383.55±108.23 day. There were no significant differences between the 3 groups (p>0.05). Successful dialysis was done in 16.7% in Group 1, 37.5% in Group 2 and 45% in Group 3 from brachial arteriovenous grafts after 1-year follow-up (p=0.746).

Conclusions

In treating dialysis patients, treatment with low dose aspirin and dipyridamole is not effective on increasing the synthetic grafts primary patency duration.

Trial registration

The trial was registered at the Thai Clinical Trials Registry (http://www.clinicaltrials.in.th) with the Trct id: TCTR20160920003.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis.

Methods

Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups.

Results

Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2).

Conclusion

SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

Primary Thromboprophylaxis with Heparins for Arteriovenous Fistula Failure in Pediatric Patients

Background

To reduce the incidence of early arteriovenous fistula failure (AVF) due to thrombosis in pediatric hemodialysis (HD) patients, a primary thromboprophylaxis (PTP) protocol was initiated at author's institution in June 2005. The goal of this study is to report author's experience with this protocol one year later.

Methods and Results

19 AVFs (14 patients, Historical group) and 8 AVFs (7 patients, PTP group) were created prior to and after initiation of PTP respectively. PTP consisted of unfractionated heparin (5–10 units/kg/hr) infusion postoperatively, followed by subcutaneous low molecular weigh heparin (LMWH) until AVF was matured. LMWH dosing was “Prophylactic” (0.5 mg/kg/d, anti-factor Xa levels: peak 0.25–0.5 and trough < 0.3 units/mL) and “Therapeutic” (1 mg/kg/d, anti-factor Xa level: peak 0.5-1 and trough < 0.5 units/mL) based on thrombosis predisposition. In Historical group, 12 AVFs did not receive thromboprophylaxis (No-treatment group), 5 received 81 mg aspirin/day (Aspirin group), and 2 received LMWH. In No-treatment group 10/12 AVFs failed: 9 thromboses and 1 stenosis. In Aspirin group 1/5 AVFs failed due to thrombosis. In PTP group 1/8 AVFs failed due to stenosis; the first 2 AVFs developed hematoma prompting a reduction in LMWH dose and monitoring trough anti-factor Xa levels, one AVF required thrombectomy after LMWH was transiently held. The incidence of thrombosis was less in PTP group (12.5%) when comparing to No-treatment group (83%) (p < 0.05).

Conclusion

PTP is a feasible option to prevent early thrombosis at AVF. Close clinical and laboratory monitoring including trough anti-factor Xa levels is required to adjust optimum anticoagulation. Larger studies are needed to clarify safety and efficacy of our PTP protocol.

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.