Arteriovenous Access Failure, Stenosis, and Thrombosis

Direct anastomosis indwelling needle puncture: a rapid and safe transitional hemodialysis access for patients with renal failure

OBJECTIVES

Vascular access thrombosis (VAT) is a common complication in patients with end-stage renal disease (ESRD), significantly impacting hemodialysis efficacy and patient survival. Currently, temporary dialysis access is typically established via deep vein catheterization (VC), however, this method is highly invasive and associated with risks of infection and other complications. This study aims to explore the feasibility of using direct anastomosis indwelling needle puncture (DAINP) for temporary dialysis access.

METHODS

Between March 2023 and March 2024, patients VAT were recruited at Sir Run Run Shaw Hospital of Zhejiang University School of Medicine to undergo DAINP. Clinical data, including age, gender, dry and wet body weight, and blood biochemical parameters, were collected. Patient VA types, locations, and insertion vessels were documented. Detailed assessments and records of VAT were performed for all patients, including the distance of thrombus from the anastomosis, residual blood flow at the VA anastomosis, and corresponding selection of the DAINP insertion site. Ultrasound was utilized to measure and record the puncture depth. Concurrently, clinical data of patients undergoing venous catheterization (VC) for temporary dialysis access were collected. The operative time for both groups, defined as the interval from ultrasound assessment initiation to completion of the procedure, was recorded and compared.

RESULTS

A total of 74 patients successfully underwent DAINP, with a 100% puncture success rate. Among them, 20 patients had residual blood flow at the VA stump, and the distance between the anastomosis and arterial flow was ≥ 1 cm. Patients with VA located at the elbow demonstrated the greatest puncture depth. Moreover, the operative time for the DAINP group was significantly shorter compared to the 17 patients who underwent VC for VAT during the same period. However, patients with VA located in the groin required a longer operative time for DAINP.

CONCLUSIONS

This study demonstrates that DAINP provides a rapid and safe method for establishing temporary hemodialysis access in VAT patients, effectively reducing the invasiveness and risks associated with traditional VC.

Brachial plexus block versus local anesthesia for percutaneous transluminal angioplasty of dysfunctional arteriovenous fistula: 12-month results of a propensity score weighted study

OBJECTIVE

The study aimed to compare ultrasound-guided brachial plexus block (BPB) with local anesthesia (LA) on efficacy, safety and 12-month patency rate for percutaneous transluminal angioplasty (PTA) treatment of dysfunctional arteriovenous fistula (AVF).

METHODS

Consecutive patients with dysfunctional AVF who underwent PTA from January 2021 to December 2022 were included. Overlap weighting was performed to adjust for significant differences between the two groups. The primary efficacy outcomes included visual analogue scale (VAS) score and 12-month target-lesion primary patency rate. The secondary efficacy outcomes included target-lesion primary-assisted patency rate, secondary patency rate, access-circuit thrombosis rate, access-circuit reintervention rate, and number of reinterventions within 12 months. Univariate analysis and multivariate analysis by log-binomial regression were used to identify the independent factors associated with intraoperative pain.

RESULTS

218 patients were included in the study: 82 patients underwent PTA under BPB and 136 patients underwent PTA under LA. After overlap weighting, the baseline, lesion characteristics and intraoperative details had no significant difference between the two groups. Patients under BPB had significantly lower VAS scores than those under LA (2.4 ± 1.4 vs 5.1 ± 1.9, p < 0.001). The 12-month target-lesion primary patency rate was significantly higher in the BPB group than that in the LA group (58.3% vs 40.0%, p = 0.037). The 12-month target-lesion primary-assisted patency rate and access-circuit secondary patency rate were significantly higher in the BPB group than those in the LA group (p = 0.023 and p = 0.028). The access-circuit thrombosis rate was significantly lower in the BPB group (10.0%) than that in the LA group (28.3%) (p = 0.011). BPB was the only independent factor associated with mild pain (p < 0.001, OR: 0.037, 95%CI: 0.011-0.119).

CONCLUSIONS

BPB could decrease the intraoperative pain and improve the 12-month primary patency rates compared with LA for patients underwent PTA treatment of dysfunctional AVF.

Six-month safety and efficacy outcomes from the randomized-controlled arm of the WRAPSODY Arteriovenous Access Efficacy (WAVE) trial

Stenosis within the arteriovenous fistula (AVF) of hemodialysis patients leads to vascular access dysfunction and inadequate hemodialysis. Percutaneous transluminal angioplasty (PTA) is the standard therapy for stenosis. However, rates of restenosis and loss of access patency remain high. Outcomes of a novel cell-impermeable endoprosthesis (CIE) have not been investigated in this setting. Therefore, our study was designed to address this as a prospective, international, multicenter pivotal trial (NCT04540302) with 245 patients with stenosis in their venous outflow circuit randomized to treatment: 122 receiving CIE and 123 receiving PTA across 43 international centers. Primary endpoints included target lesion primary patency (TLPP) at six months (freedom from clinically driven target lesion revascularization or target lesion thrombosis) and freedom from safety events through 30 days post-index procedure that affected the access circuit and resulted in reintervention, hospitalization, or death. Access circuit primary patency (ACPP) was evaluated as a secondary efficacy endpoint. Six-month TLPP and ACPP were significantly higher for the CIE cohort versus PTA (TLPP: 89.6% vs. 62.3%; ACPP: 72.2% vs. 57.0%). Thirty days post-index procedure, there was no statistically significant difference in the freedom from safety events for the CIE versus PTA (96.6 vs. 95.0%). No differences were observed in adverse events between either cohort. Our study shows that among patients with stenosis in their AVF, the CIE was superior to PTA with respect to six-month TLPP and ACPP with no observed difference in 30-day primary safety events.

The Alpha to Omega of Dialysis Access: Evaluation, Interventions, Innovations (Part 2)

Background: End-stage kidney disease (ESKD) is a growing global health concern, significantly impacting patient morbidity and mortality, particularly among patients on hemodialysis. Vascular access remains a major challenge, often limiting the effectiveness of hemodialysis and requiring strategic planning to optimize outcomes. Purpose: This review examines the current evidence on vascular access for dialysis, with a focus on pre- and post-operative assessments, necessary interventions for complications, and innovations in vascular access materials and techniques. Research Design: This is a literature review analyzing existing studies, clinical trials and guidelines to evaluate the different vascular access options, interventions, and emerging technologies in dialysis access. Results: Findings highlight the importance of thorough preoperative assessment, including vascular imaging and patient-specific considerations, to optimize access placement. Postoperative assessments and early interventions are crucial in ensuring access longevity. Innovations such as drug-coated balloons, stent technologies, and biologically engineered grafts have improved patient outcomes and reduced complications. Conclusion: Strategic planning and advancements in vascular access technology play a critical role in improving dialysis efficiency and patient outcomes. Continued research and innovation are needed to refine vascular access techniques and address challenges associated with ESKD management.

Thrombus stiffness as an independent predictor of endovascular treatment success in hemodialysis fistulas: a study using ultrasound elastography

PURPOSE

This study aimed to evaluate the prognostic value of thrombus stiffness, measured by strain elastography, in independently predicting the success of endovascular treatment for thrombosed hemodialysis fistulas.

METHODS

The study employed a retrospective observational design. Forty-nine patients with chronic kidney disease undergoing hemodialysis and experiencing fistula dysfunction were included. Various factors were evaluated, including patient age, sex, comorbidities, arteriovenous fistula (AVF) type, use of antiplatelet agents, duration of thrombosed AVF dysfunction, thrombus length, thrombus stiffness, and thrombus strain ratio (SR). Thrombus stiffness was measured using strain ultrasound elastography.

RESULTS

The presence of comorbidities (P=0.018), duration of AVF dysfunction due to thrombosis (P=0.005), thrombus stiffness (P<0.001), and thrombus SR (P<0.001) were statistically significant predictors of treatment success, while other factors were not. Thrombus stiffness and SR, assessed by two independent radiologists with excellent inter-reader agreement, demonstrated high reliability. The optimal SR cut-off for treatment success was 1.4 (sensitivity, 0.947; specificity, 0.901; area under the curve, 0.935). Multivariable logistic regression analysis revealed that both thrombus SR and thrombus stiffness significantly influenced treatment outcomes (P=0.003 and P=0.007, respectively). A 0.1-unit increase in thrombus SR was associated with 9.37% reduction in the likelihood of treatment success, while a smilar increase in thrombus stiffness exhibited an 8.06% reduction, underscoring their importance as prognostic factors in clinical setting.

CONCLUSION

This study demonstrates the utility of strain ultrasound elastography in assessing thrombus stiffness in thrombosed hemodialysis AVFs and its correlation with treatment success.

Ankle-brachial index associates with arteriovenous fistula stenosis

BACKGROUND

Arteriovenous fistula (AVF) stenosis is associated with pre-existing arterial atherosclerosis of AVF and results in significant morbidity and hospitalization for hemodialysis patients. The ankle brachial index (ABI) is a noninvasive method of assessing atherosclerosis. This study was to examine whether ABI is a significant predictor for AVF stenosis.

METHODS

This was a retrospective, longitudinal cohort study. Patients with hemodialysis between 1 January 2016 and 31 December 2022 were reviewed. ABI was assessed in January 2016. AVF stenosis was diagnosed by fistulography.

RESULTS

A total of 82 patients were included. Forty-two patients experienced AVF stenosis. The univariate logistic regression analysis showed that AVF stenosis was associated with age (OR: 1.045, p = 0.033), DM status (OR: 5.529, p = 0.013), 7-year averaged cholesterol level (OR: 1.018, p = 0.034), 7-year averaged triglyceride level (OR: 1.007, p = 0.017), and ABI (OR: 0.011, p < 0.001). In multivariate logistic regression analysis, ABI was a strong predictor for AVF stenosis (OR: 0.036, p = 0.023). Then, a cut-off point of ABI with optimal sensitivity and specificity for AVF stenosis was 1.01. An analysis of time to events with adjustment for other variables showed that patients with ABI < 1.01 were significantly associated with AVF stenosis (HR: 3.859, p < 0.001).

CONCLUSIONS

ABI below 1.01 was associated with AVF stenosis. This finding may be useful in tailoring surveillance programs for monitoring AVF function.

Implantable Biosensors for Vascular Diseases: Directions for the Next Generation of Active Diagnostic and Therapeutic Medical Device Technologies

Cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Key challenges such as atherosclerosis, in-stent restenosis, and maintaining arteriovenous access, pose urgent problems for effective treatments for both coronary artery disease and chronic kidney disease. The next generation of active implantables will offer innovative solutions and research opportunities to reduce the economic and human cost of disease. Current treatments rely on vascular stents or synthetic implantable grafts to treat vessels when they block such as through in-stent restenosis and haemodialysis graft failure. This is often driven by vascular cell overgrowth termed neointimal hyperplasia, often in response to inflammation and injury. The integration of biosensors into existing approved implants will bring a revolution in cardiovascular devices and into a promising new era. Biosensors that allow real-time vascular monitoring will provide early detection and warning of pathological cell growth. This will enable proactive wireless treatment outside of the traditional hospital settings. Ongoing research focuses on the development of self-reporting smart cardiovascular devices, which have shown promising results using a combination of virtual in silico modelling, bench testing, and preclinical in vivo testing. This innovative approach holds the key to a new generation of wireless data solutions and wireless powered implants to enhance patient outcomes and alleviate the burden on global healthcare budgets.

Classifications of haemodialysis vascular access stenosis: a scoping review

OBJECTIVES

Vascular access (VA) stenoses play a significant role in the morbidity of the haemodialysed population. Classifications for diagnosis, assessment and proposal of treatment strategies can be useful clinical and methodological tools. This review aims to present a comprehensive summary and propose further methodological approaches.

DESIGN

A systematic review of the literature, evaluating classifications for dialysis-related VA stenosis.

DATA SOURCES

Web of Science, Scopus, PubMed, Google Scholar and the ClinicalTrials.gov registry were searched from inception to 7 December 2024.

ELIGIBILITY CRITERIA

All articles containing classifications regarding dialysis VA were eligible, with no restrictions on the study type or language of the full text.

DATA EXTRACTION AND SYNTHESIS

Two independent researchers performed the search and initial screening. Four vascular surgeons assessed the included classifications using a modified Buchbinder's critical appraisal tool to evaluate quality.

RESULTS

From 4771 screened papers, 59 full-text papers were retrieved and 24 articles contained classifications. Three classifications were dedicated to VA stenosis, all based on the anatomical location of lesions. According to the modified Buchbinder's appraisal, the classifications were assessed as moderate-to-good quality. The literature disposes of immense inconsistency in terms of the definition of significant stenosis indicated for treatment.

CONCLUSIONS

VA significant stenosis and its classification is a non-uniformly understood issue with many different criteria and categorisations. This basic methodological problem leads to inconsistent results. We recommend the unification of the criteria and their validation in prospective studies.

A soft thermal sensor for the continuous assessment of flow in vascular access

Hemodialysis for chronic kidney disease (CKD) relies on vascular access (VA) devices, such as arteriovenous fistulas (AVF), grafts (AVG), or catheters, to maintain blood flow. Nonetheless, unpredictable progressive vascular stenosis due to neointimal formation or complete occlusion from acute thrombosis remains the primary cause of mature VA failure. Despite emergent surgical intervention efforts, the lack of a reliable early detection tool significantly reduces patient outcomes and survival rates. This study introduces a soft, wearable device that continuously monitors blood flow for early detection of VA failure. Using thermal anemometry, integrated sensors noninvasively measure flow changes in large vessels. Bench testing with AVF and AVG models shows agreement with finite element analysis (FEA) simulations, while human and preclinical swine trials demonstrate the device's sensitivity. Wireless adaptation could enable at-home monitoring, improving detection of VA-related complications and survival in CKD patients.

Complete stent graft relining of the hemodialysis access circuit for access salvage

BACKGROUND

Stent grafts (SGs) are widely used in hemodialysis access procedures to maintain function and patency of the access circuit. There are no reports to date describing complete relining of the access circuit with SGs for extreme access salvage.

OBJECTIVE

To report outcomes and experience with complete SG relining of the hemodialysis access circuit.

METHODS

From April 2020 to May 2023, all hemodialysis salvage procedures that included complete relining of the access circuit with SGs were retrospectively analyzed from a prospectively collected database of 970 hemodialysis access interventions. SGs were placed for various pathologies including residual stenosis, perforation, aneurysm, and thrombosis. Follow up outcomes included primary patency, primary assisted patency, and secondary patency.

RESULTS

A total of 16 patients were included in the study. Average stented length was 30 cm. Average follow up was 283 days (range 38-647 days). The primary patency of the entire covered segment was 80% and 68% at 6 and 12 months, respectively. The primary assisted patency of the segment was 88% and 77% at 6 and 12 months, respectively. Secondary patency of the access circuit was 94% at both 6 and 12 months. There were no issues with SG cannulation and zero cases of SG fracture or infection.

CONCLUSIONS

Salvage of failing hemodialysis access circuits by complete SG relining should be considered for a limited subgroup of patients where the access circuit would otherwise be deemed unsalvageable. Complete SG relining has both good immediate outcomes and 6- and 12-month patency rates.

Management of thrombosed or failed dialysis access

Hemodialysis (HD) access for patients with end-stage renal disease is a steadily increasing necessity, and maintaining patency of native or synthetic fistulas can be challenging. The main physiologic changes of an HD access that cause it to fail are inflow or outflow vessel stenosis or access thrombosis. These are propagated by factors intrinsic to end-stage renal disease, altered hemodynamics from a fistula, and typically further exacerbated by associated comorbidities. Diagnosis of fistula dysfunction can be made with a combination of history, physical examination, HD dynamic measurements, laboratory findings, and invasive or noninvasive imaging. Stenoses can be managed with endovascular interventions, including angioplasty with or without stenting, or open operations. Thrombosis of HD access, which is most often a result of an underlying stenosis, can be managed similarly with either endovascular or surgical thrombectomy with adjunctive treatment. Our goal was to review the pathophysiology of the most common forms of fistula failure, diagnosis, and endovascular and surgical options for flow restoration.

Outcomes of Endovascular Treatment for Salvaging Failed Hemodialysis Arteriovenous Fistula - Role of Balloon Angioplasty as Initial Therapy

Background

This study aims to evaluate the technical and clinical outcomes of endovascular treatment for failed native hemodialysis fistulas, mainly the role of balloon angioplasty in salvaging thrombosed and stenosed arteriovenous fistulas.

Materials and Methods

This retrospective study was done on 23 patients who had presented with non-functioning dialysis fistulas. The mean age of the patients was 58.7 ± 2.3 years. The cause of failure was thrombosis in 14 cases (61%) and stenosis in 9 cases (39%). All patients initially underwent percutaneous transluminal angioplasty (PTA), followed by thromboaspiration depending on the thrombus load and extent.

Results

A total of 27 salvage procedures were performed on 23 patients. Technical success was achieved in 24 procedures (88.8%), and clinical success was 81.5%. Patients were followed up for mean duration of 9.5 months (range: 1-19 months). Eight out of 23 accesses initially revised failed again due to repeat thrombosis, of which four patients underwent repeat procedures. The mean duration to re-intervention was 5.5 ± 1.3 months. The primary patency rates were 79% at 3 months and 60% at 6, 12, and 18 months. The cumulative (secondary) patency rates were 73% at 6 months and 66% at 12 and 18 months. Minor complications were seen in three procedures (11%), which included venous extravasation in two cases and prolonged bleeding from puncture site in one case.

Conclusion

Percutaneous balloon angioplasty can be used as first-line procedure in failed hemodialysis fistulas, in both cases of stenosis and/or thrombosis, followed by thromboaspiration if required.

Computational Fluid Dynamics (CFD) in Arteriovenous (AV) Graft Implantation Through End-to-Side Anastomosis with Varying Tube Diameters Across Different Vascular Access Locations for Dialysis Treatment

Background/Objectives: Arteriovenous (AV) graft is a procedure for hemodialysis performed in the arm. Optimizing AV graft design is vital to enhance haemodialytic efficiency in patients with kidney disease. Despite being a standard procedure, making it work optimally is still difficult due to various graft diameters and anastomosis configurations, which have limited studies. This research aims to find the ideal AV graft tube diameter on blood flow and pressure gradients and the ideal body site for AV graft implantation and to study their angles for dialysate flow. Methods: Nine models were designed in Autodesk Fusion 360 with 40°, 50°, and 60° angles each having 2 mm, 5.1 mm, and 14.5 mm diameters, all following specific equations on continuity, momentum (Navier-Stokes Equation)), and the Reynolds Stress Model (RSM). The CFD simulation of these models was performed in ANSYS Fluent with an established parameter of 0.3 m/s inlet velocity and stiff/no-slip graft and artery wall boundary condition. Results: As a result, the design with a diameter of 14.5 mm and a 40° angle was overall the most ideal in terms of minimal wall shear stress and turbulence. Conclusions: Thus the brachiocephalic area or the forearm is calculated to be the most optimal implantation site. Additionally, varying angles do affect dialysate flow, as smaller values cause less stress.

Influence of balloon type and lesion location on outcomes following fistuloplasty

BACKGROUND

There is limited evidence supporting the optimal use of fistuloplasty to maintain vascular access at various lesion sites, despite its critical role in facilitating renal replacement therapy and the overall high failure rates of arteriovenous fistulas (AVFs). This study aims to identify covariates affecting primary and secondary patency following fistuloplasty of native upper limb vascular access AVFs.

METHODS

This retrospective study included all patients who underwent fistuloplasty at a tertiary vascular centre over 4 years. Baseline characteristics were recorded, and factors associated with primary and secondary patency rates were analysed.

RESULTS

A total of 206 patients (88 male, 118 female) with a mean age of 68 (±14) years underwent fistuloplasty during the study period. The prevalence of diabetes, ischaemic heart disease and antiplatelet usage were 33%, 21% and 70%, respectively. The median number of fistuloplasties per access during the follow-up period was 2 [1-3]. Fistulas were classified as radiocephalic (65), brachiocephalic (102) and brachiobasilic transposition (39). Recurrent stenosis (RS) was identified in 60 patients who had previous fistuloplasty before the study period, while 146 patients had de novo stenoses (DNS). Stenosis location significantly differed between RS and DNS (p = .03), with DNS primarily being anastomotic and RS predominantly in central and mixed locations. Younger fistulas were more likely to have anastomotic stenoses compared to those older than 1 year (p = .001). While no significant differences in primary patency (PP) were observed, secondary patency (SP) varied by stenosis location: Central 32 [13-42] months, Fistula vein 20 [12.5-35.5] months, Mixed 25 [13.5-37.5] months and Anastomotic 19 [7-29.5] months (p = .012).

CONCLUSION

Stenosis location in AVFs is associated with the age and type of the fistula. Younger fistulas often fail due to anastomotic stenoses, which have lower secondary patency compared to stenoses at other sites. Preliminary data suggest that central stenoses, primarily occurring in older fistulas, exhibit better secondary patency following fistuloplasty than stenoses at other locations.

Reliable Stenosis Detection Based on Thrill Waveform Analysis Using Non-Contact Arteriovenous Fistula Imaging

Hemodialysis therapy is an extracorporeal circulation treatment that serves as a substitute for renal function. In Japan, patients receive this efficient four-hour treatment, three times per week, allowing them to maintain a social life nearly equivalent to that of healthy individuals. Before the treatment, two punctures are performed to establish extracorporeal circulation, and a high blood flow rate is essential to ensure efficient therapy. Specialized blood vessels created through arteriovenous fistula (AVF) surgery are utilized to achieve high blood flow rates. Although the AVF allows safe and efficient dialysis treatment, AVF stenosis leads to a serious problem in dialysis. To early detect this abnormal blood flow, auscultation and palpation methods are widely used in hospitals. However, these methods can only provide qualitative judgment of the AVF condition, so the results cannot be shared among other doctors and staff. Additionally, since the conventional methods require contact with the skin, some issues require consideration regarding infection and low reproducibility. In our previous study, we proposed an alternative method for auscultation using non-contact optical imaging technology. This study aims to construct a reliable AVF stenosis detection method using Thrill waveform analysis based on the developed non-contact device to solve the problem with the contact palpation method. This paper demonstrates the performance validation of the non-contact imaging in the normal AVF group (206 total data, 75 patients, mean age: 69.1 years) and in the treatable stenosis group (107 total data, 17 patients, mean age: 70.1 years). The experimental results of the Mann-Whitney U test showed a significant difference (p=0.0002) between the normal and abnormal groups, which indicated the effectiveness of the proposed method as a new possible alternative to palpation.

Vascular Access Considerations in Home Hemodialysis

There is a global interest in expanding home dialysis utilization among patients with ESKD. Home hemodialysis (HHD) is an appealing KRT option for this population because of its multiple clinical and quality of life benefits. Central to successful HHD is the establishment and maintenance of a functioning vascular access that serves as a patient's lifeline while on therapy. While the selection of a vascular access type is influenced by individual patient circumstances, the arteriovenous fistula is generally the preferred access method. Training patients to use their dialysis access requires attention to safety, risk management, and monitoring for complications to minimize adverse events and technique failure. Policies incorporating systematic frameworks for quality improvement and assurance, in conjunction with the measurement of metrics relating to vascular access, are tools that should be used by HHD programs to enhance the value of care delivered. In this perspective, we aim to describe what is currently known about the various vascular access options in HHD and to elucidate what needs to be taken into consideration in the selection and care of this access.

A Miniaturized Dual-Band Circularly Polarized Implantable Antenna for Use in Hemodialysis

Hemodialysis is achieved by implanting a smart arteriovenous graft (AVG) to build a vascular pathway, but reliability and stability in data transmission cannot be guaranteed. To address this issue, a miniaturized dual-band circularly polarized implantable antenna operating at 1.4 GHz (for energy transmission) and 2.45 GHz (for wireless telemetry), implanted in a wireless arteriovenous graft monitoring device (WAGMD), has been designed. The antenna design incorporates a rectangular serpentine structure on the radiation surface to reduce its volume to 9.144 mm3. Furthermore, matching rectangular slots on the radiation surface and the ground plane enhance the antenna's circular polarization performance. The simulated effective 3 dB axial ratio (AR) bandwidths are 11.43% (1.4 GHz) and 12.65% (2.45 GHz). The simulated peak gains of the antenna are -19.55 dBi and -22.85 dBi at 1.4 GHz and 2.45 GHz, respectively. The designed antenna is implanted in a WAGMD both in the simulation and the experiment. The performance of the system is simulated in homogeneous human tissue models of skin, fat, and muscle layers, as well as a realistic adult male forearm model. The measurement results in a minced pork environment align closely with the simulation results.

Tunneled central venous catheters for hemodialysis-unfairly condemned? Catheter-related complications in a university hospital setting

BACKGROUND

Central venous catheters (CVCs) provide an immediate hemodialysis access but are considered to be of elevated risk for complications. It remains unclear, if CVCs per se have relevant impact on clinical outcome. We provide an assessment of CVC-associated complications and their impact on mortality.

METHODS

In a single center retrospective study, CVC patients between JAN2015-JUN2021 were included. Data on duration of CVC use, complications and comorbidities was collected. Estimated 6-month mortality was compared to actual death rate.

RESULTS

About 478 CVCs were analyzed. Initiation of dialysis was the main reason for CVC implantation. Death was predominant for termination of CVC use. Infections were rare (0.6/1000 catheter days), complications were associated with certain comorbidities. Actual 6-month mortality was lower than predicted (14.3% vs 19.6%).

CONCLUSION

(1) CVCs are predominantly implanted for initiation of hemodialysis; (2) serious complications are rare; (3) complications are associated with certain comorbidities; and (4) CVC patients survive longer than predicted.

Early access flow rate predicts vascular access patency-related intervention in the first year: A retrospective cohort study

INTRODUCTION

Arteriovenous fistulas and grafts are lifelines for most hemodialysis patients, and a low access flow rate often requires patency-related intervention, such as angioplasty or thrombectomy, to prevent access failure. We examined whether early access flow rate, measured after initial fistula/graft cannulation, predicts vascular access patency-related intervention within 1 year.

METHODS

This was a single-center retrospective cohort study. Among 172 patients undergoing surgical creation of a fistula/graft, 52 (30.2%) had documented access flow rates measurement by the Transonic™ ultrasound dilution technique, performed within an average of 48 days from initial access cannulation. The need for a patency-related intervention, defined as undergoing a fistulogram, angioplasty, thrombectomy, or surgical revision, was ascertained within 1 year. A receiver-operating characteristic curve (ROC) was generated to evaluate the diagnostic performance of first and average access flow rates for predicting patency-related intervention within 1 year.

FINDINGS

Twenty-eight (53.8%) of the 52 study subjects required a patency-related intervention within 1 year. Their characteristics were not significantly different from those who did not require patency-related interventions. However, first access flow rates were significantly lower in patients requiring patency-related intervention compared to those who did not (898 vs. 1471 mL/min; p = 0.003), as were average access flow rates (841 vs. 1506 mL/min; p < 0.001). The ROC analyses revealed that first access flow rates and average access flow rates predicted the need for patency-related intervention within 1 year, with an area under-the-ROC curve of 0.743 (95% confidence interval [CI] 0.608, 0.877) and 0.775 (95% CI 0.648, 0.903), respectively, demonstrating acceptable discrimination.

DISCUSSION

In adults undergoing hemodialysis, early access flow rate measurement can predict patency-related intervention within 1 year after initial vascular access cannulation. Additional studies are required to confirm these findings and identify optimal access flow rate cut-off values to predict vascular accesses at higher risk of stenosis.

Utility of a ML analytics on real time risk stratification and re-intervention risk prediction on AV access outcomes and cost

BACKGROUND

Vascular access is the lifeline for patients on hemodialysis. The average survival rates of dialysis dependent patients have been improving over the last 5 years and hence their dialysis access needs longevity for uninterrupted optimal dialysis. With the lack of genomic vascular access failure predictors, there is an unmet need for predicting an event and the appropriate approach to mitigate recurrence of the event that could have cost and outcome implications.

METHODS

We performed a single center experience that extracted relevant clinical (access flow, laboratory data and CKD details), access intervention (prior interventions, type & location of lesion, type of balloon used, use of stents etc.) and demographic (age, vintage on dialysis, sex, social determinants, other medical conditions) data in real time and feeds it into validated ML algorithms to predict risk of reintervention. (Plexus EMR LLC).

RESULTS

About 200 prevalent hemodialysis patients with a AV graft or AV fistula were included for this analysis. Need for re-intervention and use of stent/ flow reduction/new access creation were the outcomes analyzed. Plexus EMR is a licensed Azure based platform. R software was used to develop the ML algorithms. Regression factors were developed to assess and test the validity of individual attributes across all the data attributes. Each patient had a real time risk calculator available to the interventionalist on risk of reintervention/ year. Of the 200 patients, 148 had a AV fistula and the remaining 52 had a AV graft. Mean interventions in the year prior to analysis was 1.8 in patients with AV fistulas and 3.4 in AV grafts which decreased to 1.1 in AV fistulas and to 2.4 in AV grafts (p < 0.01) post tool deployment. There were 62 AV graft thrombectomies done in the observation year and 62% of those were repeat thrombectomies. Stent utilization increased to 37 (22 in AV grafts and 15 in AV fistulas) and 2 patients had AV access flow reduction surgery. The cumulative cost (predicted) preintervention was $712,609 and decreased to $512,172 post intervention. Stent utilization increased by 68% in the evaluation year and 89% of the stents used were PTFE coated stents.

CONCLUSION

Utilizing AI with ML based algorithms that includes clinical, demographic and patency maintenance variables could become new standards of care to optimally manage AV accesses and lower cost of care.

Direct Percutaneous Thrombolysis (DPT): A novel method of salvaging Thrombosed Native Arteriovenous Fistula

INTRODUCTION

Thrombosed arteriovenous fistulas (AVFs) are either treated by thrombectomy or pharmaco-mechanical thrombolysis with or without percutaneous balloon angioplasty. In this study, we have described an effective and economical technique of salvaging these fistulae using a 20-22-gauge spinal needle and urokinase and have named it direct percutaneous thrombolysis (DPT).

MATERIALS AND METHOD

This prospective study comprised of 148 patients out of which 120 patients presented with AVF thrombosis and were divided into two groups; those with no obvious stenosis on ultrasound (n = 38) and second with venous stenosis (n = 82). Remaining 28 patients developed thrombosis post angioplasty for venous stenosis. Percutaneous injection of urokinase into the thrombus was done under ultrasound guidance, followed by balloon angioplasty if there was associated stenosis.

RESULTS

In 38 patients who didn't have any stenosis, 32 AVFs were successfully thrombolysed by DPT, with technical success of 84.2%. Remaining six patients required angioplasty because of chronic nature of clot. In 82 patients who had venous stenosis, 80 cases were treated successfully by DPT followed by angioplasty with technical success of 97.5%. In third group (n = 28), who developed thrombosis post angioplasty, 100% success rate was noted. The mean length of thrombus was 31.4 ± 4.6 mm and mean diameter of thrombosed vein was 10.5 ± 1.2 mm. There were no major complications encountered during the procedure. Minor complications were seen in 19 patients which included prolonged oozing from puncture site and local hematoma formation.

CONCLUSION

Ultrasound guided DPT with urokinase is a safe and economical option for salvaging thrombosed AVF without vascular stenosis that does not need angioplasty.

Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation, and neointimal hyperplasia

Clinical failure of arteriovenous neointimal hyperplasia (NIH) fistulae (AVF) is frequently due to juxta-anastomotic NIH (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared with the outflow vein. AVF was created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. The neointima in the JAA shows increased volume compared with the outflow vein. Computational modeling shows an increased volume of disturbed flow at the JAA compared with the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1,862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence the later development of JANIH.NEW & NOTEWORTHY Disturbed flow and focal endothelial cell loss in the juxta-anastomotic area of the mouse AVF colocalizes with acute thrombus formation followed by late neointimal hyperplasia. Differential flow patterns between the juxta-anastomotic area and the outflow vein correlate with differential expression of genes regulating coagulation, proliferation, collagen metabolism, and the immune response. The rat jugular vein to carotid artery AVF model shows changes similar to the mouse AVF model.

A Cost-Effective Approach to Resistant AV Fistula Stenosis: Successful Treatment Using Coronary OPN NC® Balloon in a Low-Income Setting

Stenosis in the anastomotic site or venous limb of an arteriovenous fistula (AVF) is the most frequent cause of AVF failure. Percutaneous angioplasty with a standard or high-pressure balloon is the first-line treatment for AVF stenosis due to its higher technical success rate (90%) and lower complication rate (4%). Almost 20% of stenosis cases are resistant or undilatable by regular-pressure balloon angioplasty due to fibrosis, leading to technical failure or restenosis. Alternative therapies, such as atherectomy devices or cutting balloons, are expensive and difficult to obtain in low-income developing countries. We successfully treated resistant AVF stenosis with a coronary OPN-NC® ultra-high-pressure balloon and produced a good angiographic result with technical success. Coronary hardware is easily available and relatively cheaper compared to dedicated peripheral balloons or devices in our country due to reuse, which can be a boon in such type of cases. According to the standard hospital protocol, Cathlab hardware was reused.

Association between heart failure and arteriovenous access patency in patients with end-stage renal disease on hemodialysis

BACKGROUND

Heart disease and chronic kidney disease are often comorbid conditions owing to shared risk factors, including diabetes and hypertension. However, the effect of congestive heart failure (CHF) on arteriovenous fistula (AVF) and AV graft (AVG) patency rates is poorly understood. We hypothesize preexisting HF may diminish blood flow to the developing AVF and worsen patency.

METHODS

We conducted a single-institution retrospective review of 412 patients with end-stage renal disease who underwent hemodialysis access creation from 2015 to 2021. Patients were stratified based on presence of preexisting CHF, defined as clinical symptoms plus evidence of reduced left ventricular ejection fraction (EF) (<50%) or diastolic dysfunction on preoperative echocardiography. Baseline demographics, preoperative measures of cardiac function, and dialysis access-related surgical history were collected. Kaplan-Meier time-to-event analyses were performed for primary patency, primary-assisted patency, and secondary patency using standard definitions for patency from the literature. We assessed differences in patency for patients with CHF vs patients without CHF, patients with a reduced vs a normal EF, and AVG vs AVF in patients with CHF.

RESULTS

We included 204 patients (50%) with preexisting CHF with confirmatory echocardiography. Patients with CHF were more likely to be male and have comorbidities including, diabetes, chronic obstructive pulmonary disease, hypertension, and a history of cerebrovascular accident. The groups were not significantly different in terms of prior fistula history (P = .99), body mass index (P = .74), or type of hemodialysis access created (P = .54). There was no statistically significant difference in primary patency, primary-assisted patency, or secondary patency over time in the CHF vs non-CHF group (log-rank P > .05 for all three patency measures). When stratified by preoperative left ventricular EF, patients with an EF of <50% had lower primary (38% vs 51% at 1 year), primary-assisted (76% vs 82% at 1 year), and secondary patency (86% vs 93% at 1 year) rates than those with a normal EF. Difference reached significance for secondary patency only (log-rank P = .029). AVG patency was compared against AVF patency within the CHF subgroup, with significantly lower primary-assisted (39% vs 87% at 1 year) and secondary (62% vs 95%) patency rates for AVG (P < .0001 for both).

CONCLUSIONS

In this 7-year experience of hemodialysis access creation, reduced EF is associated with lower secondary patency. Preoperative CHF (including HF with reduced EF and HF with preserved EF together) is not associated with significant differences in overall hemodialysis access patency rates over time, but patients with CHF who receive AVG have markedly worse patency than those who receive AVF. For patients with end-stage renal disease and CHF, the risks and benefits must be carefully weighed, particularly for those with low EF or lack of a suitable vein for fistula creation.

Risk Factors for Thromboembolic Events in Patients With Dialysis-Dependent CKD: Pooled Analysis of Phase 3 Roxadustat Trials in Japan

INTRODUCTION

Thromboembolic events have occurred in clinical trials of roxadustat. This post hoc analysis explored potential factors related to thromboembolic events in dialysis-dependent patients treated with roxadustat in four phase 3 clinical trials in Japan.

METHODS

Thromboembolic events with onset before and after week 12 were evaluated. Baseline risk factors for thromboembolic events were investigated by Cox regression analyses. Nested case-control analyses using conditional logistic models with matched pairs of case-control data explored relationships between thromboembolic events and laboratory parameters.

RESULTS

Of the 444 patients, 56 thromboembolic events were observed in 44 patients during ≤ 52 weeks of treatment. The proportion of venous and arterial thromboembolic events gradually increased after week 12. Baseline risk factors included hemodialysis (vs peritoneal dialysis), advanced age (≥ 65 years), shorter dialysis vintage (< 4 months), and history of thromboembolism. The absence of concomitant intravenous or oral iron therapy (including ferric citrate) was associated with thromboembolic events before week 12 (hazard ratio 11.25; 95% confidence interval [CI] 3.36-37.71; vs presence). Case-control analysis revealed that low average transferrin saturation (< 10%; unadjusted odds ratio [OR] 6.25; 95% CI 1.52-25.62; vs ≥ 20%), high average transferrin level (≥ 2.5 g/L; unadjusted OR 4.36; 95% CI 1.23-15.39; vs < 2.0 g/L), and high average roxadustat dose (≥ 150 mg; unadjusted OR 5.95; 95% CI 1.07-33.16; vs < 50 mg) over the previous 8 weeks before the event onset were associated with thromboembolic events after week 12. However, adjustment for iron status extinguished the significant relationship between roxadustat dose and events. Multivariate case-control analysis showed that increased transferrin from baseline (≥ 1.0 g/L; adjusted OR 7.85; 95% CI 1.82-33.90; vs < 0.5 g/dL) and decreased mean corpuscular volume (< - 2 fL; adjusted OR 5.55; 95% CI 1.73-17.83; vs ≥ 0 fL) were associated with increased risk of thromboembolic events.

CONCLUSION

In addition to established risk factors, iron deficiency may be related to thromboembolic events. Graphical Abstract available for this article.

TRIAL REGISTRATION

NCT02780726, NCT02952092, NCT02780141, NCT02779764.

Impact of COVID-19 pandemic on hemodialysis access thrombosis

BACKGROUND

Delay in care of suspected stenosis or thrombosis can increase the chance of losing a functioning hemodialysis access. Access to care and resources were restricted during the COVID-19 pandemic. To evaluate the impact of the pandemic on arteriovenous fistula (AVF) and arteriovenous graft (AVG) procedures we have assessed the number and success of thrombectomies done before and during the COVID-19 pandemic.

METHODS

We examined all AVF and AVG angiograms with and without interventions, including thrombectomies, performed at a single center during April 2017-March 2021 (pre-COVID-19 era) and April 2020-March 2021 (COVID-19 era).

RESULTS

The proportion of procedures that were thrombectomies was higher during the COVID-19 era compared to the pre-COVID-19 era (13.3% vs 8.7%, p = 0.009). The proportion of thrombectomy procedures was higher during COVID-19 for AVF (8.2% vs 3.0%, p < 0.001) but there was no difference for AVG (26.5% vs 27%, p = 0.99). There was a trend toward a higher likelihood of unsuccessful thrombectomy during COVID-19 (33.3% vs 20.4%, p = 0.08).

CONCLUSIONS

More dialysis access thromboses and unsuccessful thrombectomies were noted during the COVID-19 pandemic. This difference could be due to a delay in patients getting procedures to maintain their dialysis accesses.

Realtime monitoring of thrombus formation in vivo using a self-reporting vascular access graft

BACKGROUND

Chronic kidney disease (CKD) affects 10% of the global population costing over a hundred billion dollars per annum and leading to increased risk of cardiovascular disease. Many patients with CKD require regular haemodialyses. Synthetic arteriovenous grafts (AVG) are increasingly used to provide rapid vascular connection for dialysis. Initially, they have excellent patency rates but are critically limited by neointimal hyperplasia at the venous anastomosis, which drives subsequent thrombosis, graft failure and death.

METHODS

Here, we describe a system in which electrical impedance spectroscopy sensors are incorporated circumferentially into the wall of a synthetic arteriovenous graft. This is combined with an implantable radiotelemetry system for data transmission outside the patient. The system was tested using monolayers of endothelial and smooth muscle cells as well as swine blood and clots with explanted human carotid artery plaques. Sensor testing was then performed in vitro and the device was implanted in vivo in female swine.

RESULTS

The device can wirelessly report the accumulation of biological material, both cells and blood. Differences are also detected when comparing controls with pathological atheroma. In swine differences between blockage formation in a graft were remotely obtained and wireless reported.

CONCLUSIONS

Combining electrical impedance spectroscopy and an implantable radiotelemetry system enables graft surveillance. This has the potential to be used for early detection of venous stenosis and blood clot formation in real-time in vivo. In principle, the concept could apply to other cardiovascular diseases and vascular implantable devices.

Stent Grafts Across the Elbow Joint for Access Salvage

PURPOSE

Covered stent grafts (SGs) are currently being used in a wide variety of situations to maintain function and patency of hemodialysis access circuits. Stent grafts are rarely placed across the elbow joint (EJ), however, due to fear of stent fracture. This study reports on the experience and patency rates with SGs across the EJ.

MATERIALS AND METHODS

From April 2020 to August 2023, all procedures with SGs placed across the EJ were retrospectively analyzed. A total of 21 patients with SGs placed across the EJ were included in the study. The Covera Vascular Covered Stent (BD, Franklin Lakes, New Jersey, USA) was used in all cases. Of these, 18 were arteriovenous (AV) fistulae, and 3 were AV grafts. Stent grafts were placed for various pathologies, including residual stenosis, perforation, aneurysm, and thrombosis. Follow-up outcomes were obtained from angiographic images on follow-up angiography and included primary patency, primary assisted patency, and secondary patency.

RESULTS

The primary patency of the target lesion was 85% (CI=70%-100%) and 85% (CI=70%-100%) at 6 and 12 months, respectively. The primary assisted patency was 85% (CI=70%-100%) and 85% (CI=70%-100%) at 6 and 12 months, respectively. Secondary patency of the access circuit was 95% (CI=86%-100%) at 6 months and 89% (CI=75%-100%) at 12 months. The average follow-up duration was 393 days (range=27-768 days). There were no instances of stent fracture during follow-up.

CONCLUSIONS

Stent grafts should be placed across the EJ for good short-term and mid-term patency rates.

CLINICAL IMPACT

The placement of stent grafts across the elbow joint in hemodialysis patients for access salvage is controversial due to the fear of stent fracture or occlusion. This retrospective study evaluated the placement of stent grafts for access salvage in 21 patients for various etiologies. Good patency rates were seen out to 12 months and no stent fractures were observed. Although longer term data is needed, stent grafts should be considered an acceptable option for access salvage when treating lesions that cross the elbow joint.

Delamination and dissection of arteriovenous grafts: A multicenter report of four cases

Arteriovenous (AV) grafts are an alternative vascular access for chronic hemodialysis. AV graft failure is often due to stenosis of the feeding artery, graft, or draining vein. We report four cases of AV graft dysfunction and failure rarely caused by graft delamination and dissection. Two males and two females aged 47-67 years had been on chronic hemodialysis. Ultrasound examination detected graft delamination and dissection between 1 and 33 months after Acuseal AV graft implantation. Two cases were successfully treated with stenting and partial graft replacement, respectively. False lumen volume reduction by fluid withdrawal failed to salvage the delaminated graft in one of the patients. The delamination and dissection of another case spontaneously resolved 5 months later. Graft delamination and dissection should be considered as a possible cause for AV graft dysfunction and failure. Stenting and graft replacement may be recommended to treat AV graft dissection and delamination.

Small Caliber Distal Cephalic Veins Undergo Significant Dilation under Anesthesia and Can Successfully Be Used for Arteriovenous Fistula Creation

BACKGROUND

Successful arteriovenous fistula (AVF) maturation and use for dialysis is highly dependent on preoperative diameter. Small veins (<2 mm) exhibit high failure rates and are typically avoided. This study investigates the effects of anesthesia on the distal cephalic vein diameter as compared to preoperative outpatient vein mapping for the purpose of hemodialysis access creation.

METHODS

One hundred eight consecutive procedures for dialysis access placement met inclusion criteria and were reviewed. All patients received preoperative venous mapping and postanesthesia ultrasound mapping (PAUS). All patients received either regional and/or general anesthesia. A multiple regression was conducted to determine predictors of venous dilatation. The independent variables included both demographical and operative-specific variables such as the type of anesthesia. Outcomes of fistula maturation (successful cannulation and dialysis) were analyzed.

RESULTS

In this cohort, the mean preoperative vein diameter was 1.85 mm and the mean PAUS diameter was 3.45 mm, a 2.21× increase, with only 2 patient veins failing to increase in diameter. Smaller veins (<2 mm) exhibited significantly more dilation than larger veins after anesthesia (2.73 vs. 1.47×, P < 0.001). In the multiple regression analysis, smaller vein diameter was correlated with a significantly greater degree of dilation (P < 0.001). The degree of venous dilation was not affected by patient demographic-specific factors or by the type of anesthesia (regional block versus general) in the multiple regression analysis. 6 month follow-up data for fistula maturation was available for 75 of 108 patients. Small veins (<2 mm) on preoperative ultrasound matured at a similar rate as larger veins (90% vs. 91.4%, P = 0.833).

CONCLUSIONS

Small caliber distal cephalic veins experience a significant degree of dilation under regional and general anesthesia and can successfully be used for AVF creation. Consideration should be made to perform a postanesthesia vein mapping for all patients undergoing access placement despite preoperative venous mapping results.

Persistent median artery on computed tomographic arteriovenous fistulograms in patients on haemodialysis

INTRODUCTION

Cadaveric studies suggest an increasing prevalence of the persistent median artery (PMA) over a prolonged timeframe. The aim of this retrospective cross-sectional study was to evaluate the PMA prevalence in haemodialysis patients who had computed tomographic fistulograms (CTFs), and if present, their calibres and origins.

METHODS

All consecutive adult patients referred for an upper limb CTFs for assessment of arteriovenous fistula (AVF) dysfunction from 2006 to 2021 were included. Patients whose CTF did not include the forearm were excluded. PMA was identified as an artery running alongside the median nerve between flexor digitorum superficialis and flexor digitorum profundus. Patient demographics, presence of PMA including size and origin were recorded.

RESULTS

A PMA was found in 91/170 (53.5%) CTFs (7:3 male-to-female ratio, mean age 71-years). When stratified by age, prevalence increased with decreasing age; 51% in >70-year-olds, 54% in 50-70-year-olds and 67% in <50-year-olds. The average PMA diameter was 2.2 mm proximally and 1.8 mm distally. No stenosis was observed in the PMAs.

CONCLUSION

The PMA prevalence appears to increase with decreasing age and is a frequently encountered anatomical variant. Radiologists assessing forearm vasculature need to be aware of this anatomical variant and potentially include it in their future reports. Further research into the PMA may make its potential use as arterial conduits for AVF, potential donor grafts for coronary artery bypass surgery or additional vascular access options possible. Whether the reducing prevalence with age reflects an overall increasing prevalence is yet to be determined.

Maintenance and Salvage of Hemodialysis Access

Many end-stage kidney failure patients require hemodialysis as a life-sustaining treatment. Hemodialysis access via arteriovenous fistula or graft creation is preferred over long-term dialysis catheters, but intervention to maintain patency and prevent access failure is common. Endovascular and open surgical techniques are both utilized to address the underlying etiology of failure. Endovascular options include balloon angioplasty, angioplasty with stenting, and drug-eluting stents. Open revision is commonly needed for recurrent stenosis, aneurysmal or pseudoaneurysmal change, hemodialysis access-induced distal ischemia, and infection. Treatment plans should be guided by patient's individualized goals of care and require a multidisciplinary approach to the management of this complex disease.

Acute hemodynamic changes during far infrared treatment of the arteriovenous fistula in hemodialysis patients

BACKGROUND

The arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis (HD) treatment and preservation of a stable vascular access is crucial. Long term Far Infrared Radiation (FIR) has been found to increase access flow together with an enhanced maturation and patency of the AVF. The acute effects of FIR on access flow have been sparsely described and the results are contradictory, perhaps due to differences in measurement conditions and other factors of importance for access flow.

METHODS

Twenty patients in HD with an AVF were included. Each patient was randomized to receive either FIR (FIR group) or no FIR (control group). The acute changes in access flow were investigated in both groups on the second dialysis day of the week and during the first 1.5 h of the dialysis session. Concomitant changes in hemodynamic parameters of importance for access flow were also explored.

RESULTS

There was no significant change in access flow in the FIR group compared with the control group (median (Interquartile Range)) (-10 (-413.8; 21.3) ml/min vs -17.5 (-83.8; 76.3) ml/min, p = 0.58). There was no significant difference in any of the hemodynamic parameters between the FIR and the control group; cardiac output (-0.7 (-1.2; -0.2) l/min vs -0.4 (-0.9; 0.1) l/min, p = 0.58), cardiac index (-0.3 (-0.5; -0.1)) l/min/m2 vs -0.3 (-0.4; 0) l/min/m2, p = 0.68), mean arterial pressure (5.5 (-1.8; 8.4) mmHg vs 1.5 (-3; 6.3) mmHg, p = 0.35) and total peripheral resistance (2 (1.8; 3.4) mmHg × min/l vs 1 (-0.3; 3.1) mmHg × min/l, p = 0.12).

CONCLUSION

In this trial, with a highly standardized set-up, one session of FIR did not result in any acute changes in access flow. This was not due to differences in the hemodynamic parameters between the groups.

Clinical implications of inflammation in atheroma formation and novel therapies in cardiovascular diseases

Cardiovascular diseases (CVD) are the leading causes of death and disability in the world. Among all CVD, the most common is coronary artery disease (CAD). CAD results from the complications promoted by atherosclerosis, which is characterized by the accumulation of atherosclerotic plaques that limit and block the blood flow of the arteries involved in heart oxygenation. Atherosclerotic disease is usually treated by stents implantation and angioplasty, but these surgical interventions also favour thrombosis and restenosis which often lead to device failure. Hence, efficient and long-lasting therapeutic options that are easily accessible to patients are in high demand. Advanced technologies including nanotechnology or vascular tissue engineering may provide promising solutions for CVD. Moreover, advances in the understanding of the biological processes underlying atherosclerosis can lead to a significant improvement in the management of CVD and even to the development of novel efficient drugs. To note, over the last years, the observation that inflammation leads to atherosclerosis has gained interest providing a link between atheroma formation and oncogenesis. Here, we have focused on the description of the available therapy for atherosclerosis, including surgical treatment and experimental treatment, the mechanisms of atheroma formation, and possible novel therapeutic candidates such as the use of anti-inflammatory treatments to reduce CVD.

Thrombectomy approach for access maintenance in the end stage renal disease population: a narrative review

Objective

This article reviews current practices and outcomes in endovascular thrombectomy techniques for the treatment of thrombosed arteriovenous grafts (AVGs) and fistulas (AVFs).

Background

Arteriovenous (AV) access allows patients with end-stage renal disease (ESRD) to receive hemodialysis. Thrombosis of AV access can lead to delay in hemodialysis or abandonment of access requiring dialysis catheter placement. Endovascular approach has become the preferred treatment option for thrombosed access over surgery. Interventions include removal of thrombus from the AV circuit and treatment of the underlying anatomical abnormality, such as an anastomotic stenosis. Thrombolysis, or the act of dissolving thrombus, is performed by using infusion catheters or pulse injector devices for the administration of fibrinolytic agents. Thrombectomy, or the mechanical removal of thrombus, is performed by using embolectomy balloon catheters, rotating baskets or wires, rheolytic and aspiration mechanisms. Adjunctive methods such as cutting balloon angioplasty, drug-coated balloon (DCB) angioplasty, and stent placement are also used to treat stenoses in the AV circuit. Complications of these procedures include vessel rupture, arterial embolism, pulmonary embolism (PE), and paradoxical embolism to the brain.

Methods

This narrative review article was written based on literature search from electronic databases, including PubMed and Google Scholar.

Conclusions

The understanding of thrombectomy techniques and their potential complications is essential in the management of patients with thrombosed AV access.

Angioplasty of Dysfunctional Dialysis Fistula or Graft with Resveratrol-Excipient and Paclitaxel-Coated Balloon Improves Primary Patency Rates Compared to Plain Angioplasty Alone

In this prospective randomized single-blinded study (reg. ISRCTN11414306), 76 patients with a dysfunctional dialysis fistula or graft due to a single de novo or recurrent stenosis in the access circuit were randomized to receive either conventional PTA (POBA) as a standard of care (n = 38) or PTA + adjunctive PTA with a drug-coated (paclitaxel-resveratrol matrix) SeQuent^® Please OTW balloon (n = 38, DCB). Patients were scheduled for follow-up PTA at 3, 6, 9, and 12 months. The time of clinically driven target-lesion reintervention rate (primary patency rate) after the index procedure was analyzed using the log-rank test. The primary patency rates at 12 months after the index procedure were 17% (DCB) vs. 11% (POBA). At 3 months, they were 87% vs. 74%, at 6 months they were 53% vs. 26%, and at 9 months they were 22% vs. 11%. The hazard ratio for DCB was 0.55 (95%CI 0.32 to 0.95). The median time needed for target-lesion reintervention was longer in the DCB group (181 days) than in the conventional PTA group (98 days, p = 0.019). We conclude that PTA with the paclitaxel-resveratrol drug-coated SeQuent^® Please OTW balloon in patients with de novo or recurrent stenosis in dialysis arteriovenous fistulas or grafts prolongs the time needed for target lesion reintervention and improves primary patency rates in the first year after the index procedure.

Difficult cannulation of hemodialysis arteriovenous fistula - Role of imaging in access management (DICAF STUDY)

BACKGROUND

Difficulty in cannulation of arteriovenous fistula (AVF) can lead to inadequate dialysis, transient to permanent loss of access and increases dependency on bridging catheters. This study aimed to analyze the causes for difficult fistula cannulation, using various imaging modalities.

METHODOLOGY

This was a retrospective single-center observational study conducted between October 2017 and June 2018. Patients whose fistulae were difficult to cannulate were initially evaluated by physical examination followed by doppler ultrasonography or/and fistulogram as necessary. The patients were divided into two groups that is, primary difficult cannulation (within first three months of creation of fistula) or secondary difficult cannulation (after three months).

RESULTS

We encountered difficult cannulation in 43 patients. About 60% were primary difficult cannulations. Most common causes for difficulty in cannulation were cannulation zone (CZ) stenosis (23.3%), immature fistula (20.9%), outflow stenosis (18.6%), inflow stenosis (11.6%), anatomical abnormalities (11.6%), outflow plus CZ stenosis (9.3%) and inflow plus CZ stenosis (4.7%). Among patients with primary difficult cannulation, immature fistula (34.6%) was the most common cause, whereas CZ stenosis (47.1%) was the most common etiology for secondary difficult cannulation. Edema leading to difficult cannulation was found in 12 patients (27.9%), all of which was due to central vein stenosis. Cannulation resulted in hematoma, fistula thrombosis, failure of fistula and pseudoaneurysm in 83.7%, 27.9%, 16.3%, and 2.3% of cases respectively. Bridging temporary dialysis catheter placement was required in 67.4% patients. Ultrasound doppler had lower diagnostic value when compared to fistulogram (71.4% vs 93.9%, p = 0.014).

CONCLUSION

Difficulty in cannulating the arteriovenous fistula is a common problem in hemodialysis patients. We suggest that patients whose fistulae are difficult to cannulate should undergo early radiological evaluation to decrease catheter dependency and access failure.

Early Failure of Arteriovenous Fistula (AVF): The Effect of Diabetes and Hypertension in a Cross-Sectional Study

Background: Identification and control of clinical predictors of arteriovenous (AVF) failure can improve the long-term outcome of hemodialysis patients. The effects of these factors on the outcome of AVF are not still clear. So, we aimed this study to compare the effect of hypertension and diabetes on early failure of AVF. Methods: In this retrospective study, we evaluated 400 patients with ESRD referred to our clinic for the creation of the first AVF from July 14, 2001, through August 7, 2018. One month after AVF creation, the patients were referred to the clinic for patency control. Demographic characteristics, previous history of diabetes and hypertension, and laboratory data of all patients were recorded preoperatively. Data were entered to SPSS v.24 and Study data were analyzed with chi-square and independent student t-test. Then, early failure of AVF and its relationship with a history of diabetes and hypertension were assessed. Results: There was no statistically significant relationship between the history of diabetes and early AVF failure risk in ESRD patients (OR, 0.78; 95% CI, 0.25 to 2.43). Furthermore, the history of hypertension was significantly lower in the early failure of AVF group (OR, -2.82; 95% CI, -1.42 to -5.59). Although, this effect faded when using regression analysis (OR, -2.67; 95% CI, -0.97 to -7.36). There was a higher Body mass index in the non-early failure group (p = 0.041). There was no significant difference in age (p = 0.512), gender (p = 0.091), history of smoking (p = 0.605), treatment with insulin (p = 0.683), oral antidiabetic agents (p = 0.734), duration of diabetes (p = 0.384), and duration of hypertension (p = 0.093). Conclusion: We reported that the history of diabetes was not higher in the early failure group, while there was a lower risk of AVF failure in patients with a previous history of hypertension.

Uncommon Surgical Management by AVF between the Great Saphenous Vein and Anterior Tibial Artery for Old Radiocephalic AVF Failure

Introduction: Autologous native arteriovenous fistula (AVF) created in the non-dominant arm is the gold standard vascular access for dialysis in end-stage renal disease, but the post-surgical vascular access dysfunction causes a reduction in the patient’s quality of life. Creating a functional upper extremity permanent arteriovenous access is limited by the upper limb’s vascular resources, so good management of a complicated arteriovenous fistula may improve patient outcomes. This article highlights the importance of new surgical options in treating complicated AVFs. Case report: We present the case of a patient with a 17-year-old complex radio-cephalic arterio-venous fistula and a series of surgical interventions performed for life salvage in the first place and functional vascular access in the second place. Furthermore, we describe a successfully created uncommon type of fistula in the lower extremity between the great saphenous vein and the anterior tibial artery as the last possible access for hemodialysis in this patient. Results: The patient underwent the first successful dialysis using the newly created lower limb fistula 1 month after the surgery. Conclusion: Applying new surgical techniques to manage AVFs gives a unique chance to improve the quality of life and reduce morbidity and mortality in these patients.

Transcriptomic Analysis Identifies Differentially Expressed Genes Associated with Vascular Cuffing and Chronic Inflammation Mediating Early Thrombosis in Arteriovenous Fistula

Arteriovenous fistula (AVF) is vascular access created for hemodialysis in end-stage renal disease patients. AVF creation causes increased blood flow in the outflow vein with increased pressure. Increased blood flow, blood volume, and shear stress causes outward remodeling so that the outflow vein can withstand the increased pressure. Outward remodeling of the vein involved in AVF is necessary for AVF maturation, however, inward remodeling due to excessive neointimal hyperplasia (NIH) and chronic inflammation may end up with vessel thrombosis and AVF maturation failure. Early thrombosis of the vessel may be due to the luminal factors including NIH and chronic inflammation or due to chronic inflammation of the adventitial due to perivascular cuffing. Inflammation may either be due to an immune response to the vascular injury during AVF creation or injury to the surrounding muscles and fascia. Several studies have discussed the role of inflammation in vascular thrombosis due to intimal injury during AVF creation, but there is limited information on the role of inflammation due to surrounding factors like a muscle injury. The concept of perivascular cuffing has been reported in the nervous system, but there is no study of perivascular cuffing in AVF early thrombosis. We performed the bulk RNA sequencing of the femoral arterial tissue and contralateral arteries as we found thrombosed arteries after AVF creation. RNA sequencing revealed several significantly differentially expressed genes (DEGs) related to chronic inflammation and perivascular cuffing, including tripartite motif-containing protein 55 (TRIM55). Additionally, DEGs like myoblast determination protein 1 (MYOD1) increased after muscle injury and relates to skeletal muscle differentiation, and network analysis revealed regulation of various genes regulating inflammation via MYOD1. The findings of this study revealed multiple genes with increased expression in the AVF femoral artery and may provide potential therapeutic targets or biomarkers of early thrombosis in AVF maturation failure. Thus, not only the luminal factors but also the surrounding factors mediating vascular cuffing contribute to vessel thrombosis and AVF failure via early thrombosis, and targeting the key regulatory factors may have therapeutic potential.

Development and validation of a risk score to prioritize patients for evaluation of access stenosis

Background

Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc‐Alert surveillance device could be used to predict subsequent interventions.

Methods

Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients).

Results

Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).

Conclusions

This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.

Mathematical Models for Blood Flow Quantification in Dialysis Access Using Angiography: A Comparative Study

Blood flow rate in dialysis (vascular) access is the key parameter to examine patency and to evaluate the outcomes of various endovascular interve7ntions. While angiography is extensively used for dialysis access–salvage procedures, to date, there is no image-based blood flow measurement application commercially available in the angiography suite. We aim to calculate the blood flow rate in the dialysis access based on cine-angiographic and fluoroscopic image sequences. In this study, we discuss image-based methods to quantify access blood flow in a flow phantom model. Digital subtraction angiography (DSA) and fluoroscopy were used to acquire images at various sampling rates (DSA—3 and 6 frames/s, fluoroscopy—4 and 10 pulses/s). Flow rates were computed based on two bolus tracking algorithms, peak-to-peak and cross-correlation, and modeled with three curve-fitting functions, gamma variate, lagged normal, and polynomial, to correct errors with transit time measurement. Dye propagation distance and the cross-sectional area were calculated by analyzing the contrast enhancement in the vessel. The calculated flow rates were correlated versus an in-line flow sensor measurement. The cross-correlation algorithm with gamma-variate curve fitting had the best accuracy and least variability in both imaging modes. The absolute percent error (mean ± SEM) of flow quantification in the DSA mode at 6 frames/s was 21.4 ± 1.9%, and in the fluoroscopic mode at 10 pulses/s was 37.4 ± 3.6%. The radiation dose varied linearly with the sampling rate in both imaging modes and was substantially low to invoke any tissue reactions or stochastic effects. The cross-correlation algorithm and gamma-variate curve fitting for DSA acquisition at 6 frames/s had the best correlation with the flow sensor measurements. These findings will be helpful to develop a software-based vascular access flow measurement tool for the angiography suite and to optimize the imaging protocol amenable for computational flow applications.

Intimal Hyperplasia and Arteriovenous Fistula Failure: Looking Beyond Size Differences

The development of venous intimal hyperplasia (IH) has been historically associated with failure of arteriovenous fistulas (AVF) used for hemodialysis. This long-standing assumption, based on histological observations, has been recently challenged by clinical studies indicating that the size of the intima by itself is not enough to explain stenosis or AVF maturation failure. Irrespective of this lack of association, IH is present in most native veins and fistulas, is prominent in many cases, and suggests a role in the vein that may not be reflected by its dimensions. Therefore, the contribution of IH to AVF dysfunction remains controversial. Using only clinical data and avoiding extrapolations from animal models, we critically discuss the biological significance of IH in vein remodeling, vascular access function, and the response of the venous wall to repeated trauma in hemodialysis patients. We address questions and pose new ones such as: What are the factors that contribute to IH in pre-access veins and AVFs? Do cellular phenotypes and composition of the intima influence AVF function? Are there protective roles of the venous intima? This review explores these possibilities, with hopes of rekindling a critical discussion about venous IH that goes beyond thickness and AVF outcomes.

Factors influencing arteriovenous fistulas: A multicenter study

In this cross-sectional, descriptive study, the arteriovenous fistulas (AVF) of HD patients were evaluated by physical examination and factors associated with AVF function and longevity were investigated. Data were collected using a patient information form and the Arteriovenous Fistula Assessment Scale (AVF-AS). The study population included 279 patients under chronic HD treatment. Their mean age was 61.14 ± 14.00 years and 58.6% were men. Age, AVF location, and number of AVFs created were identified as factors associated with AVF needle entry site and flow problems, stenosis, and risk of developing ischemic complications (p = 0.005, p = 0.000, p = 0.006, respectively). AVF dysfunction adversely affected HD pump speed (p = 0.000) and HD adequacy (p = 0.000). It was determined that gender, AVF location, last AVF duration, and total number of previous AVF were identified as the risk of AVF complications. The results of this study revealed that regular follow-up and evaluation are needed to minimize the risk of dysfunction and failure due to AVF complications.

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.

Effectiveness and safety of repeated percutaneous intervention in an office-based endovascular center in maintaining hemodialysis access

OBJECTIVES

Percutaneous dialysis access interventions are routinely used to maintain the patency of dialysis access despite the lack of data regarding their long-term effectiveness. This retrospective study was undertaken to study the effectiveness and safety of percutaneous dialysis access interventions in arm fistulas and bridge grafts in an office-based endovascular center.

METHODS

Patients who had a percutaneous dialysis access intervention in their upper extremity access site, performed at a single office-based endovascular center over a nine-year period (2007-2016) were included in this study. The patients' demographic factors, patency, and complications were analyzed. Patients were entered in the study after first percutaneous dialysis access intervention.

RESULTS

A total of 298 limbs in 259 patients had 913 procedures carried out over a nine-year period. There were 190 access arteriovenous fistulas and 108 arteriovenous grafts. The two most common arteriovenous fistulas were the brachiocephalic fistula (n = 74, 39%) and radio cephalic fistula (n = 69, 36%). Arteriovenous grafts were most commonly placed in the upper arm (n = 66, 61%) followed by the forearm (n = 42, 39%). The mean overall patency for all limbs was 50.86 months. Arteriovenous fistulas had a significantly longer patency than arteriovenous grafts (51.65 vs. 42.09 months; P = 0.01). In addition, patients with two or more percutaneous dialysis access intervention in their arteriovenous fistula had significantly greater patency than those with only one percutaneous dialysis access intervention (58.5 vs. 7.6 months; hazard ratio 0.41; P = 0.0008). This was not true for the arteriovenous graft group. Women represented 49% of the patient group. Their accesses had shorter patency than men (39.8 vs. 60 months; P = 0.0007).

CONCLUSIONS

This data support the use of repeated percutaneous dialysis access intervention to maintain long-term patency of dialysis access sites in an office-based endovascular center. Overall, fistulas have longer patency than grafts and women have poorer outcomes as compared to men.

Vascular access cannulation and haemostasis: a national observational study of French practices

BACKGROUND

We report the results of an observational study of arteriovenous fistula (AVF) cannulation and haemostasis practices in France.

METHODS

The study (sponsored by Brothier Pharmaceutical Inc.) was conducted in 150 dialysis units. Data obtained from 150 supervisory nurses, 1538 nurses and 3588 patients with an AVF were analysed.

RESULTS

The nurses reported using rope-ladder, area or buttonhole cannulation techniques in 68, 26 and 6% of cases, respectively. Metal needles were used most frequently (64%), with mainly a diameter of 15 G or 16 G. The needle was introduced with the bevel up in 56% of cases. Compression applied using dressings (in particular, pure calcium alginate dressings) was the method of choice for haemostasis of the puncture sites and was assessed as being strong by most of the nurses and very strong in cases of prolonged bleeding. Most (82%) of the patients reported the use of local anaesthetic before cannulation and 23% reported an allergic skin reaction to the anaesthetic. Bleeding of the puncture sites lasted for >10 min for 48% of the patients and it reappeared between two sessions for 29% of the patients. Whereas the nurses appeared to have a good understanding of AVF, more than half of the patients did not know how to care for it, with 55% requiring more information.

CONCLUSIONS

This study underlines the lack of national consensus concerning AVF cannulation practices. It suggests that haemostasis methods of the puncture sites can be improved and it highlights the need to improve patient knowledge.

Effect of pore size and spacing on neovascularization of a biodegradble shape memory polymer perivascular wrap

Neointimal hyperplasia (NH) is a main source of failures in arteriovenous fistulas and vascular grafts. Several studies have demonstrated the promise of perivascular wraps to reduce NH via promotion of adventitial neovascularization and providing mechanical support. Limited clinical success thus far may be due to inappropriate material selection (e.g., nondegradable, too stiff) and geometric design (e.g., pore size and spacing, diameter). The influence of pore size and spacing on implant neovascularization is investigated here for a new biodegradable, thermoresponsive shape memory polymer (SMP) perivascular wrap. Following an initial pilot, 21 mice were each implanted with six scaffolds: four candidate SMP macroporous designs (a-d), a nonporous SMP control (e), and microporous GORETEX (f). Mice were sacrificed after 4 (N = 5), 14 (N = 8), and 28 (N = 8) days. There was a statistically significant increase in neovascularization score between all macroporous groups compared to nonporous SMP (p < .023) and microporous GORETEX (p < .007) controls at Day 28. Wider-spaced, smaller-sized pore designs (223 μm-spaced, 640 μm-diameter Design c) induced the most robust angiogenic response, with greater microvessel number (p < .0114) and area (p < .0055) than nonporous SMPs and GORETEX at Day 28. This design also produced significantly greater microvessel density than nonporous SMPs (p = 0.0028) and a smaller-spaced, larger-sized pore (155 μm-spaced, 1,180 μm-sized Design b) design (p = .0013). Strong neovascularization is expected to reduce NH, motivating further investigation of this SMP wrap with controlled pore spacing and size in more advanced arteriovenous models.