Arteriovenous Fistula Stenosis Research Articles

Outcomes of Surgical and Endovascular Treatment for Cephalic Arch Stenosis in Proximal Arteriovenous Fistula.

The cephalic arch is a significant site of stenosis in proximal arteriovenous fistulas (AVFs) that contributes to access dysfunction and thrombosis. This study aimed to evaluate the outcomes of surgical treatment (ST) and endovascular treatment (ET) for cephalic arch stenosis (CAS). A total of 62 patients with proximal AVF who underwent CAS revision using either ST or ET were enrolled between January 2018 and March 2023. In the ET group, only the initial ET following AVF formation was considered, to mitigate bias. In the ST group, central transposition of the native AVF (transposition group) or interposition of the prosthetic graft into the proximal basilic or axillary vein (interposition group) was performed. We evaluated primary and functional patency based on these groups and calculated the number of patency loss events after CAS treatment. Of the 62 patients, 38 (61%) were male, with a mean age of 66.4 years. ST was performed in 26 (42%) patients, including transposition in 16 and interposition in 10, whereas ET was administered to 36 patients during the study period. Among the ST recipients, 42% had a history of ET for CAS. The incidence of AVF thrombosis was marginally higher in the ST group than in the ET group (39% vs. 19%, P=0.098). The primary patency rates at 6 months, 1 year, and 3 years were 87%, 87%, and 66% in the transposition group; 45%, 23%, and 11% in the interposition group; and 66%, 49%, and 17% in the ET group, respectively. Notably, the primary patency of the transposition group was significantly higher than that of the interposition (P=0.001) and ET groups (P=0.016). The frequency of patency loss events per person-year after the initial revision was 0.40, 0.52, and 1.42 in the transposition, interposition, and ET groups, respectively. Transposition exhibited the most favorable primary patency rate and the lowest number of subsequent patency loss events during follow-up despite the higher rates of AVF thrombosis and previous ET at presentation. Consequently, transposition should be actively considered in eligible patients with CAS.

Imaging diagnosis and treatment results of arteriovenous fistulas stenosis complication among hemodialysis patients

ABSTRACT Introduction: Percutaneous transluminal angioplasty (PTA) presents several advantages in addressing arteriovenous fistula (AVF) stenosis compared to surgical approaches. In addition, Doppler ultrasonography (DUS) serves as a noninvasive technique for stenosis measurement and access flow volume calculation. This study aimed to evaluate the agreement in stenosis diagnosis using PTA and DUS before intervention and to assess the effectiveness of the PTA method after intervention. Method: A non - controlled intervention study involved 15 chronic HD patients with a mature AVF in place for over three months, presenting AVF stenosis ≥ 50%, who underwent PTA intervention. Correlation analysis was employed to assess the similarity of AVF stenosis evaluations using DUS and PTA. The study also compared pre - and post - intervention indicators to evaluate the effectiveness of PTA intervention. Results: The results indicated a strong positive correlation between the two techniques (r = 0.997, r2 = 0.994, p < 0.001). Following intervention, all patients were considered successful, with significant reductions observed in various indicators, including alterations in murmurs along AVF, VAPR, the number of patients with AVF stenosis ≥ 50% on DUS, and none with Qmin < 500 mL/min. Conclusion: This study recommends utilizing DUS to evaluate stenosis before contemplating PTA intervention, owing to the correlation and similarity observed in the results of AVF stenosis examination between these two techniques. Ultimately, our research endorses PTA intervention as the preferred method for HD patients with AVF stenosis, considering the observed enhancements in clinical, hemodialysis, and DUS parameters

Application of Freehand 3D Ultrasound Guidance in Percutaneous Transluminal Angioplasty for Autogenous Arteriovenous Fistula Stenosis

Objective: Using freehand three dimensional (3D) ultrasound imaging to evaluate arteriovenous fistula stenosis. Comparing the value of freehand 3D ultrasound and Doppler ultrasound in the application of percutaneous transluminal angioplasty (PTA) treatment for stenosis of an arteriovenous fistula. Methods: A retrospective analysis was conducted on 34 patients with arteriovenous fistula (AVF) stenosis who were treated at the 903RD Hospital of PLA and the Kidney Center of Zhejiang Provincial People's Hospital from August 2021 to August 2022. Based on the different types of surgical assistance, the patients were divided into two groups: the Doppler ultrasound group (Group A, n = 17) and the freehand 3D ultrasound imaging group (Group B, n = 17). Freehand 3D ultrasound and Doppler ultrasound were used to assess the narrowing of arteriovenous fistulas, and images and relevant data were collected before and after the PTA procedure. The differences in the time of puncture and sheath placement, guidewire insertion time, the duration of the procedure, complications, and methods to measure stenosis were compared between the two groups of patients, as well as the technical success rate, the initial patency rate, and the primary patency rates at 1, 3, 6 and 9 months post-surgery. This study discusses the clinical efficacy of using these two types of ultrasound to assist in the PTA treatment of arteriovenous fistula stenosis. Results: The differences in baseline demographics between the conventional ultrasound group (Group A) and the 3D ultrasound group (Group B) were not statistically significant (p > 0.05). The intraoperative guidewire insertion time (4.647 ± 1.347 min vs. 2.824 ± 0.326 min) and the operating times (75.941 ± 7.557 min vs. 59.824 ± 8.175 min) between the two groups were statistically significant (t = 2.788, 3.069, p < 0.01). The technical success rates for the two groups were 94.1% vs. 100%, not statistically significant (t = 1.03, p = 0.31). The first-time patency rates were 88.2% vs. 94.1%, with no statistically significant difference (t = 0.366, p = 0.545). No complications occurred in Group A, while one case of hematoma occurred postoperatively in Group B, with an incidence of 5.9% (1/17), which was not statistically significant (t = 1.03, p > 0.05). Comparing the primary patency rates at 1, 3, 6 and 9 months post-surgery between Groups A and B, there were no statistically significant differences (p > 0.05). However, the patency rates at different time points for Group B were consistently higher than Group A (94.1%, 82.4%, 82.4%, 82.4% vs. 88.2%, 82.4%, 76.5%, 76.5%). Conclusion: Freehand 3D ultrasound imaging can provide more intuitive, high-resolution, and high-definition three-dimensional images, clearly defining the lesion site and vascular structures. Its accuracy in assessing complications of arteriovenous fistulas is similar to that with conventional ultrasound. When used as an adjunct to PTA treatment, its efficacy is equivalent. It can significantly reduce guidewire insertion time and operation time, decrease postoperative recovery time, and alleviate the patients' concerns regarding surgical risks. It can be considered a new method for diagnosing, treating, and patients with AVF stenosis.

Pentoxifylline decreases the activity of the nucleotide-binding oligomerization domain-like receptor protein 3 pathway: potential role for preventing arteriovenous fistula stenosis.

This study aimed to determine the effect of pentoxifylline (PTX) on the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome pathway and its role in preventing arteriovenous fistula (AVF) failure. Vein samples were collected from AVF failure patients and from patients who underwent surgical AVF as a control. The expressions of CD34 and NLRP3 in AVF tissues were detected by immunohistochemistry and Western blotting. Arteriovenous fistula rat models were established by the end-to-end anastomosis of the common carotid artery and external jugular vein. The AVF models were divided into the following groups: AVF, AVF + PTX, AVF + uraemia and AVF + uraemia + PTX. Six weeks after surgery, the AVF tissues in each group were collected to detect the expressions of CD34, NLRP3, caspase-1 and interleukin (IL)-1β by immunohistochemistry, Western blotting and real-time polymerase chain reaction. The expressions of NLRP3 and CD34 in human AVF failure tissues were significantly higher than those in normal veins (p < 0.001), indicating that NLRP3 was upregulated in patients with AVF failure. In our animal study, the veins in the AVF + uraemia group exhibited heavy hyperplasia, and the boundary between the media and the adventitia was not clear. However, PTX alleviated this hyperplasia. Compared with the AVF models, the AVF + uraemia models had much higher expressions of NLRP3, caspase-1, IL-1β and CD34 (p < 0.001). However, PTX had the opposite effect against uraemia on the NLRP3 inflammasome pathway at both the gene and protein levels. Our findings provide new insights that show that PTX can decrease the activity of the NLRP3 inflammasome pathway in AVF models. Pentoxifylline has the potential as a drug for preventing intimal hyperplasia and AVF failure.

Ankle-brachial index associates with arteriovenous fistula stenosis.

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

Endovascular Fistula Salvage for Preserving Arteriovenous Fistula Failure in Haemodialysis Patient: Tertiary Referral Hospital, a Single-Centre Experience

Abstract: Efficacy of endovascular intervention for the preservation of failing accesses is very important in hemodialysis patients. This study aimed to determine the efficacy of endovascular balloon angioplasty in preserving the patency of hemodialysis arteriovenous fistula (AVF) failure. This was a retrospective study of hemodialysis patients who received endovascular intervention due to access difficulties. A single-center study was created between January 2022 and June 2022. Fistulography was conducted on patients suspected of having access stenosis, and balloon angioplasty was performed in the same setting if stenosis of 50% was confirmed. Post-operative complications and access restenosis or failure were monitored. The results obtained 69 patients with hemodialysis access failure due to AVF stenosis, occlusion, and thrombosis that were admitted or referred to our hospital. The majority of patients were 40-60 years (50.7%); 88.4% patients were male and 11.6% were female, with a mean age of 56.3±11.6 (range, 18–77). The sites of AVF failure were brachiocephalic (81.1%) and radiocephalic (18.9%). There was no complication recorded. The procedure succes rate was 81.1%. In conclusion, endovascular balloon angioplasty is effective in restoring hemodialysis access patency. Recurrence is common, and interventions must be repeated. Keeping access open can save lives. Percutaneous transluminal angioplasty (PTA) can be used to achieve safely and successfully repair arteriovenous fistulas failure. Keywords: angioplasty; arteriovenous fistula; arteriovenous graft; hemodialysis

Efficacy of cutting balloon angioplasty versus high-pressure balloon angioplasty for the treatment of arteriovenous fistula stenoses in patients undergoing hemodialysis: Systematic review and meta-analysis.

This systematic review and meta-analysis aimed to assess and compare the therapeutic outcomes of cutting balloon angioplasty and high-pressure balloon angioplasty for arteriovenous fistula stenosis in hemodialysis patients. All studies indexed in PubMed, Embase, and Cochrane Library Web of Science were retrieved. The retrieval deadline was July 15, 2023. Risk of bias 2.0 was used to evaluate the quality of the included studies. Revman 5.4 software was used for data analysis. This review included three studies and 180 patients, with 90 patients in the cutting balloon angioplasty group and 90 patients in the high-pressure balloon angioplasty group. The results of the meta-analysis suggested that compared with high-pressure balloon angioplasty, cutting balloon angioplasty can improve primary lesion patency rates of internal arteriovenous fistulas at 6 months (relative risk, 1.45; 95% confidence interval, 1.08-1.96; P = 0.01). However, there were no significant differences between the technical success rate (relative risk, 0.99; 95% confidence interval, 0.93-1.05; P = 0.72) and clinical success rate (relative risk, 1.01; 95% confidence interval, 0.95-1.07; P = 0.73). Therefore, cutting balloon angioplasty is likely to increase primary lesion patency rates at 6 months. However, more high-quality, large-sample, multicenter, randomized controlled trials are needed for further validation due to the limited number of included studies.

Comparison of ultrasound features and lesion sites in dysfunctional arteriovenous fistula

This study aimed to investigate ultrasound features of arteriovenous fistula stenosis and their relationship with primary patency after percutaneous transluminal angioplasty (post-intervention primary patency) and compare this classification with that using lesion location. Hemodialysis patients who underwent ultrasound-guided percutaneous transluminal angioplasty for arteriovenous fistula stenosis from July 2020 to December 2021 were retrospectively evaluated. Lesions (excluding inflow arteries) were categorized into five groups based on ultrasound features, and the clinical characteristics and risk factors affecting the post-intervention primary patency of the arteriovenous fistula were analyzed. Among 185 patients, 100 (54.05%), 36 (19.46%), 22 (11.89%), 11 (5.95%), and 16 (8.65%) were classified into the intima-dominant, non-intima-dominant, valve obstruction, vascular calcification, and mixed groups, respectively. The dialysis duration and arteriovenous fistula use time were the highest in the vascular calcification group at 86 (interquartile range: 49–140) and 77 (interquartile range: 49–110) months, respectively. Diabetes mellitus was most common in the intima-dominant group (42.0%). In Kaplan–Meier and univariate Cox analysis, type III lesion location (stenosis in the venous confluence site) was associated with the lower post-intervention primary patency. In the multivariate Cox analysis, percutaneous transluminal angioplasty times (the number of times patients were treated with percutaneous transluminal angioplasty for arteriovenous fistula stenosis dysfunction), vascular calcification, calcification at the lesion site requiring percutaneous transluminal angioplasty, and serum parathyroid hormone levels were independent risk factors for post-intervention primary patency. Ultrasound features showed that calcification of the arteriovenous fistula was detrimental to the post-intervention primary patency of arteriovenous fistula.

Rate of Arteriovenous Fistula Stenosis and Access Recirculation among Individuals Receiving Maintenance Hemodialysis

Background: Arteriovenous fistula stenosis and access recirculation in hemodialysis represent critical challenges, influencing the efficiency of vascular access and dialysis treatment outcomes. Objective: The objective is to assess the prevalence of arteriovenous fistula (the AVF) stenosis as well as access recirculation (AR) in patients of hemodialysis. Study Design: Cross sectional study. Settings: Department of Nephrology, Bolan Medical Complex Hospital, Quetta. Duration: From 1st April 2022 to 1st September, 2022. Methods: Adult patients having age 18 years to 80 years receiving maintenance hemodialysis 3 times in a week were included in this study. Patients who were willing to provide informed consent participated in the study. Patients with active infections or sepsis, with a history of vascular access interventions within the last three months, pregnant or lactating women as well as patients with cognitive impairment were excluded from study. Outcome variables will be incidence of AVF Stenosis which was determined by regular ultrasound assessments and monitoring of clinical symptoms. Statistical analyses were performed using SPS version 22. Results: The study comprised 150 maintenance hemodialysis patients with a mean age of 55±10. Age distribution showed that 20% were between 18-40 years, 53.3% between 41-60 years, 23.3% between 61-80 years, and 3.3% were older than 80 years. Sixty percent (60%) of the participants were male, while 40% were female. The mean duration of AV fistula use was 3.21± 2.65 years, with 14.66% having duration of 6-12 months, 41.33% between 1-3 years, and 44% using AV fistulas for more than 3 years. Seventy-five point three percent (75.3%) of patients had hypertension, 40.0% had diabetes mellitus, and 28.0% had cardiovascular disease. Additionally, 16.7% of patients presented with other comorbidities. Out of total 25 (16.7%) patients were affected by arteriovenous fistula (AVF) stenosis, while access recirculation was observed in 20 patients (13.3%). Conclusion: In conclusion, our study reveals a notable incidence of arteriovenous fistula (AVF) stenosis and access recirculation among maintenance hemodialysis patients. The observed associations with age and AVF duration underscore the complexity of vascular access complications.

Evaluation of arteriovenous fistula for hemodialysis with a new generation digital stethoscope: a pilot study.

The management of complications of arteriovenous fistula (AVF) for hemodialysis, principally stenosis, remains a major challenge for clinicians with a substantial impact on health resources. Stenosis not infrequently preludes to thrombotic events with the loss of AVF functionality. A functioning AVF, when listened by a stethoscope, has a continuous systolic-diastolic low-frequency murmur, while with stenosis, the frequency of the murmur increases and the duration of diastolic component decreases, disappearing in severe stenosis. These evidences are strictly subjective and dependent from operator skill and experience. New generation digital stethoscopes are able to record sound and subsequently dedicated software allows to extract quantitative variables that characterize the sound in an absolutely objective and repeatable way. The aim of our study was to analyze with an appropriate software sounds from AVFs taken by a commercial digital stethoscope and to investigate the potentiality to develop an objective way to detect stenosis. Between September 2022 and January 2023, 64 chronic hemodialysis (HD) patients were screened by two blinded experienced examiners for recognized criteria for stenosis by Doppler ultrasound (DUS) and, consequently, the sound coming from the AVFs using a 3M™ Littmann® CORE Digital Stethoscope 8570 in standardized sites was recorded. The sound waves were transformed into quantitative variables (amplitude and frequency) using a sound analysis software. The practical usefulness of the core digital stethoscope for a quick identification of an AVF stenosis was further evaluated through a pragmatic trial. Eight young nephrologist trainees underwent a simple auscultatory training consisting of two sessions of sound auscultation focusing two times on a "normal" AVF sound by placing the digital stethoscope on a convenience site of a functional AVF. In 48 patients eligible, all sound components displayed, alone, a remarkable diagnostic capacity. More in detail, the AUC of the average power was 0.872 [95% CI 0.729-0.951], while that of the mean normalized frequency was 0.822 [95% 0.656-0.930]. From a total of 32 auscultations (eight different block sequences, each one comprising four auscultations), the young clinicians were able to identify the correct sound (stenosis/normal AVF) in 25 cases, corresponding to an overall accuracy of 78.12% (95% CI 60.03-90.72%). The analysis of sound waves by a digital stethoscope permitted us to distinguish between stenotic and no stenotic AVFs. The standardization of this technique and the introducing of data in a deep learning algorithm could allow an objective and fast method for a frequent monitoring of AVF.

Angioplasty for dysfunctional arteriovenous fistulas: A meta-analysis of recent randomized controlled trials compared paclitaxel-coated balloon versus conventional balloon angioplasty.

Stenosis in arteriovenous fistulas (AVF) due to neointimal hyperplasia is one of the most common causes of hemodialysis vascular access dysfunction. Treating patients with dysfunctional AVF with drug-coated balloon (DCB) angioplasty may potentially improve outcomes. This systematic review aimed to compare the effectiveness and safety of DCB angioplasty versus conventional balloon angioplasty by pooling evidence from the most recent randomized controlled trials. We conducted a comprehensive literature search in the Web of Science, Embase, and Cochrane central databases. Two independent researchers screened the article, extracted interest, and evaluated included studies for risk of bias. Pooled estimation was conducted in terms of 6-month target-lesion primary patency (TLPP) and target-lesion reintervention (TLR), as well as other outcomes. Results were expressed with odds ratio (OR) and 95% confidence interval (CI). A total of five RCTs were identified and included in the meta-analyses, with 1107 participants. DCB has a trend of a higher rate of TLPP (OR 1.79, 95% CI 0.66-4.90, p = 0.181) and a significantly lower rate of TLR (0.52, 95% CI 0.29-0.92, p = 0.034), as compared to conventional balloon angioplasty. No difference in the 6-month access circuit primary patency and reinvention was observed between the two groups. DCB may be an alternative treatment of dysfunctional AVF given a trend of a higher rate of TLPP and a significantly lower rate of TLR than conventional balloon angioplasty within 6 months after the indexed procedure. Moreover, DCB was non-inferior to conventional balloon angioplasty in terms of safety. Considering variations in the DCB technique, further studies are warranted for a standardized process.

USE of IMplanting the Biotronik PassEo-18 Lux drug coated balloon to treat failing haemodialysis arteRiovenous FIstulas and grafts (SEMPER FI Study)

Background: Plain old balloon angioplasty has been the mainstay of treatment for arteriovenous fistula (AVF) stenoses. Recent studies suggest that drug coated balloons (DCB) may significantly reduce re-intervention rates on native and recurrent lesions. The Passeo-18 Lux DCB (Biotronik AG, Buelach, Switzerland) is packaged with a 3.0 µg/mm2 dose of paclitaxel. The hypothesis is that its use provides better target lesion primary patency (TLPP), primary assisted patency (PP), secondary patency (SP) rates and reduces the number of visits for re-intervention in a cohort of patients with stenotic AVF and arteriovenous grafts (AVGs). Methods: The USE of IMplanting the Biotronik PassEo-18 Lux DCB to treat failing haemodialysis arteRiovenous FIstulas and grafts trial (SEMPER FI) was a prospective double-centre, multi-investigator, non-consecutive, non-blinded single-arm study investigating the efficacy and safety of the Passeo-18 Lux DCB in patients with stenotic AVF/AVG lesions between January 2021 and January 2022. Patient demographics, clinical characteristics, vascular access history, operative indications, details and outcomes were collected prospectively. TLPP, circuit access primary patency (CAP), PP, SP and deaths 6- and 12-months post-intervention were studied. Results: Ninety-one patients with 110 lesions were recruited across the two centres. 62.6% ( n = 57) were male with a median age of 63.5 years (SD = 10.5). 62.6% ( n = 57) were taking anti-platelets. Eighty-five AVFs and six AVGs were treated. 60% ( n = 54) of AVFs intervened were radiocephalic. 52.7% ( n = 58) of targeted lesions were juxta-anastomotic stenosis (JAS) and one-third ( n = 33) at the AVF/AVG outflow. 70.9% ( n = 78) of lesions were recurrent. Median time from last intervention was 219 days. 78% of target lesions ( n = 85) and circuits ( n = 70) were patent at 6-months, of which 96.7% ( n = 87) of those requiring assisted intervention were patent. Conclusion: This study shows that the Passeo-18 Lux DCB can be an effective and safe tool in the treatment of failing haemodialysis AVFs/AVGs.

Arteriovenous Fistula Stenosis: Correlating Degree of Neointimal Hyperplasia With Reduction in Volume Flow Measured on Ultrasound and Ultrasound Characterization Based on Stenosis Morphology

Introduction: Duplex ultrasound (DUS) is commonly used to diagnose and grade arteriovenous fistula (AVF) stenosis. Duplex ultrasound may also be used to examine stenosis type based on measurement of intimal-medial thickness (IMT). There are, as yet, no criteria in use to define the different stenosis types based on measurement of percentage IMT (%IMT). In this study, we have examined stenosis morphology using ultrasound. We have examined consecutive DUS examinations to assess the incidence and degree of IMT and correlated %IMT with volume flow as an indicator of AVF dysfunction. Methods: Duplex ultrasound was performed as per standard of care. Volume flow was measured within the ipsilateral brachial artery. Measurements of luminal diameter and vessel wall diameter were used to calculate %IMT. Results: The study group included 156 consecutive DUS examinations demonstrating a greater than 50% AVF stenosis. Mean %IMT was 45%. There were 17 (11%) lesions where there was no measurable IMT; the remainder had measurable IMT. On receiver-operating characteristic (ROC) analysis, a %IMT of 54% predicted low flow with 62.5% sensitivity and 62.7% specificity. Conclusion: Intimal-medial thickness has a moderate predictive value in predicting volume flow. Based on our results, there are 4 lesion types: (1) lesions with no measurable intimal hyperplasia, (2) a predominantly intimal hyperplastic lesion, (3) those with nonpredominant intimal hyperplasia, and (4) those with a valve type stenosis. A value based on correlation with volume flow could be considered based on our results at 54%IMT or based on morphology at 45%IMT to distinguish between predominant and nonpredominant intimal hyperplasia groups. Including measurements of %IMT in clinical trials could further our knowledge of how lesions with no measurable IMT and those with different degrees of intimal hyperplasia respond to different percutaneous interventions. This could potentially improve outcomes for patients and target more costly treatment options where there is most benefit.

An effective AI model for automatically detecting arteriovenous fistula stenosis

In this study, a novel artificial intelligence (AI) model is proposed to detect stenosis in arteriovenous fistulas (AVFs) using inexpensive and non-invasive audio recordings. The proposed model is a combination of two new input features based on short-time Fourier transform (STFT) and sample entropy, as well as two associated classification models (ResNet50 and ANN). The model’s hyper-parameters were optimized through the use of the design of the experiment (DOE). The proposed AI model demonstrates high performance with all essential metrics, including sensitivity, specificity, accuracy, precision, and F1-score, exceeding 0.90 at detecting stenosis greater than 50%. These promising results suggest that our approach can lead to new insights and knowledge in this field. Moreover, the robust performance of our model, combined with the affordability of the audio recording device, makes it a valuable tool for detecting AVF stenosis in home-care settings.

Hemodynamics in AVF over time: A protective role of vascular remodeling toward flow stabilization.

The mechanisms underlying vascular stenosis formation in the arteriovenous fistula (AVF) for hemodialysis (HD) remain mostly unknown. Several computational fluid dynamics (CFD) studies have suggested a potential role for unsteady flow in inducing intimal hyperplasia and AVF stenosis, but the majority of these observations have been limited to a single time point after surgical creation. The aim of the present study was to investigate the relation between hemodynamic conditions and AVF vascular remodeling through a CFD longitudinal study. Non contrast-enhanced MR images and Doppler Ultrasound (US) examinations were acquired at 3 days, 40 days, 6 months, 1 year, and 1.5 years after surgery in a 72-year male referred for native radio-cephalic AVF. Three-dimensional AVF models were generated and high fidelity CFD simulations were performed using pimpleFoam, setting patient-specific boundary conditions derived from US. Morphological and hemodynamic changes over time were then analyzed. Analysis of vessel morphology and hemodynamics during follow-up showed that the AVF had a successful maturation process, characterized by a massive arterial and venous dilatation within the 6 months after surgery, a corresponding increase in blood flow volume and important flow instabilities. Between 6 months and 1 year, a stenosis developed in the juxta-anastomotic vein and caused AVF failure at 1.5 years. The development of stenosis was paralleled by the regularization of blood flow velocity pattern and consequent decrease in the near-wall disturbed flow metrics. These results suggest that development of intimal hyperplasia and vessel stenosis, triggered by unsteady flow, could be the result of vascular inward remodeling toward regularization of turbulent-like flow.

Osteopontin is a key regulator of vascular smooth muscle cell proliferation in the outflow vein of arteriovenous fistulas.

Despite advances in the maintenance of arteriovenous fistulas (AVFs), the patency rates remain suboptimal. Most AVFs fail due to outflow vein stenosis; however, the underlying mechanism of AVF stenosis remains unclear. The present study aimed to identify key factors associated with AVF outflow stenosis. We obtained gene expression profiling data for the outflow vein of AVF from three Gene Expression Omnibus database datasets (GSE39488, GSE97377, and GSE116268) and analyzed the common differentially expressed genes (DEGs). We evaluated a common DEG in an aortocaval mouse model and the stenotic outflow veins of AVFs collected from patients. Furthermore, we isolated vascular smooth muscle cells (VSMCs) from the inferior vena cava (IVC) of wild-type (WT) and osteopontin (Opn)-knockout (KO) mice and assessed the proliferation of VSMCs following stimulation with platelet-derived growth factors (PDGFs). OPN was the only common upregulated DEG among all datasets. OPN was expressed in the medial layer of the outflow vein of AVF in aortocaval mouse models and co-stained with the VSMC marker (α-smooth muscle actin). OPN expression was markedly increased in the VSMCs of stenotic outflow veins of AVF collected from patients undergoing hemodialysis compared to presurgical veins acquired during AVF formation surgery. PDGF-induced VSMC proliferation was significantly increased in the VSMCs isolated from the IVC of WT mice but not in those isolated from the IVC of Opn-KO mice. OPN may be a key gene involved in VSMC proliferation in the AVF outflow veins and a therapeutic target to improve the AVF patency rate.

Deep learning analysis of blood flow sounds to detect arteriovenous fistula stenosis

For hemodialysis patients, arteriovenous fistula (AVF) patency determines whether adequate hemofiltration can be achieved, and directly influences clinical outcomes. Here, we report the development and performance of a deep learning model for automated AVF stenosis screening based on the sound of AVF blood flow using supervised learning with data validated by ultrasound. We demonstrate the importance of contextualizing the sound with location metadata as the characteristics of the blood flow sound varies significantly along the AVF. We found the best model to be a vision transformer trained on spectrogram images. Our model can screen for stenosis at a performance level comparable to that of a nephrologist performing a physical exam, but with the advantage of being automated and scalable. In a high-volume, resource-limited clinical setting, automated AVF stenosis screening can help ensure patient safety via early detection of at-risk vascular access, streamline the dialysis workflow, and serve as a patient-facing tool to allow for at-home, self-screening.

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

To increase the efficiency of hemodialysis, an appropriate vascular pathway must be created, and its function must be maintained. This study aimed to identify the effects of an arteriovenous fistula (AVF) stenosis prevention program on upper muscular strength, blood flow, physiological indexes, and self-efficacy among patients receiving hemodialysis. The participants were patients receiving hemodialysis at Keimyung University Dongsan Medical Center in Daegu, Republic of Korea. They were divided into experimental and control groups based on the day of the week they received hemodialysis at the outpatient department and included 25 participants each. The study was conducted for 8 weeks. The AVF stenosis prevention program was effective in improving upper extremity muscle strength (F=15.23, p<0.001) and blood flow rate (F=36.00, p<0.001). As a result of the program, the phosphorus index level, which is a physiological indicator in hemodialysis patients, decreased (F=8.64, p<0.001). Encouragement and support through text messages and practice lists also resulted in an increase in self-efficacy (F=18.62, p<0.001). The AVF stenosis prevention program in this study resulted in an increase in upper extremity muscle strength through grip strength exercises and was effective in preventing AVF stenosis by increasing the blood flow rate.

Detection of Abnormal Wall Shear Stress and Oscillatory Shear Index via Ultrasound Vector Flow Imaging as Possible Indicators for Arteriovenous Fistula Stenosis in Hemodialysis.

The arteriovenous fistula (AVF) is an essential vascular access for hemodialysis patients. AVF stenosis may occur at sites with abnormal wall shear stress (WSS) and oscillatory shear index (OSI), which are caused by the complex flow in the AVF. At present, an effective method for rapid determination of the WSS and OSI of the AVF is lacking. The objective of this study was to apply an ultrasound-based method for determination of the WSS and OSI to explore the risk sites of the AVF. In this study, the ultrasound vector flow imaging technique V Flow was applied to measure the WSS and OSI at four different regions of the AVF to detect and analyze the risk sites: (i) anastomosis region, (ii) curved region, (iii) proximal vein and (iv) distal vein. Twenty-one patients were included in this study. The relative residence time was calculated based on the measured WSS and OSI. The curved region had the lowest WSS; the anastomosis region had a significantly higher OSI (p < 0.05) compared with the venous regions, and the curved region had a significantly higher RRT (p < 0.05) compared with the proximal vein region. V Flow is a feasible tool for studying WSS variations in AVF. The possible risk site in the AVF may be located in the anastomosis and curved regions, where the latter could present a higher risk for AVF stenosis.

Tensor decomposition and machine learning for the detection of arteriovenous fistula stenosis: An initial evaluation.

Duplex ultrasound (DUS) is the most widely used method for surveillance of arteriovenous fistulae (AVF) created for dialysis. However, DUS is poor at predicting AVF outcomes and there is a need for novel methods that can more accurately evaluate multidirectional AVF flow. In this study we aimed to evaluate the feasibility of detecting AVF stenosis using a novel method combining tensor-decomposition of B-mode ultrasound cine loops (videos) of blood flow and machine learning classification. Classification of stenosis was based on the DUS assessment of blood flow volume, vessel diameter size, flow velocity, and spectral waveform features. Real-time B-mode cine loops of the arterial inflow, anastomosis, and venous outflow of the AVFs were analysed. Tensor decompositions were computed from both the 'full-frame' (whole-image) videos and 'cropped' videos (to include areas of blood flow only). The resulting output were labelled for the presence of stenosis, as per the DUS findings, and used as a set of features for classification using a Long Short-Term Memory (LSTM) neural network. A total of 61 out of 66 available videos were used for analysis. The whole-image classifier failed to beat random guessing, achieving a mean area under the receiver operating characteristics (AUROC) value of 0.49 (CI 0.48 to 0.50). In contrast, the 'cropped' video classifier performed better with a mean AUROC of 0.82 (CI 0.66 to 0.96), showing promising predictive power despite the small size of the dataset. The combined application of tensor decomposition and machine learning are promising for the detection of AVF stenosis and warrant further investigation.