Project description:An autogenous arteriovenous fistula is considered the ideal access for hemodialysis delivery. However, surgical creation of an arteriovenous fistula is associated with less than optimal technical success, and multiple interventions are often required to assist maturation or maintain early patency. Given these shortcomings, multiple new approaches are now under investigation that possibly improve on surgical techniques and/or outcomes. Minimally invasive methods of creation with novel devices are under investigation, with preliminary published results available.
Project description:Preoperative assessment prior to surgical arteriovenous fistulas (AVFs) including ultrasound-guided mapping has been shown to have beneficial effects on their immediate success as well as early outcomes. This has led to their wide acceptance and adoption however clinical practice criteria is variable and is reflected in variabilities in practice. When transposing this to percutaneously created endovascular AVFs (endoAVFs), variable preoperative assessment criteria could equally result in variable practice and potentially subsequent and expectant outcomes. We aimed to review literature on reported validated methodologies and workflows of preoperative assessment for surgical AVF creation as reported in highest levels of available evidence, specifically randomized controlled trials. Published practice recommendations and guidelines on best clinical practice as well as systematic reviews and meta-analyses of published studies were also reviewed. Data on practice methodology from identified trial publications and protocols was collated and a summative narrative synthesis was carried out which compared these methodologies to additional assessments that may be required when targeting assessment for percutaneous endoAVF formation, based on our units experience as part of an international multicentre trial. In this review we present a brief overview of published literature and guidelines and propose a unified and uniform workflow for preoperative assessment for surgical AVFs and endoAVFs to aide clinical and imaging practice.
Project description:Rates of arteriovenous fistula maturation failure are still high, especially when suboptimal size veins are used. During successful maturation, the vein undergoes lumen dilatation and medial thickening, adapting to the increased hemodynamic forces. The vascular extracellular matrix plays an important role in regulating these adaptive changes and may be a target for promoting fistula maturation. In this study, we tested whether a device-enabled photochemical treatment of the vein prior to fistula creation facilitates maturation. Sheep cephalic veins were treated using a balloon catheter coated by a photoactivatable molecule (10-8-10 Dimer) and carrying an internal light fiber. As a result of the photochemical reaction, new covalent bonds were created during light activation among oxidizable amino acids of the vein wall matrix proteins. The treated vein lumen diameter and media area became significantly larger than the contralateral control fistula vein at 1 week (p = 0.035 and p = 0.034, respectively). There was also a higher percentage of proliferating smooth muscle cells in the treated veins than in the control veins (p = 0.029), without noticeable intimal hyperplasia. To prepare for the clinical testing of this treatment, we performed balloon over-dilatation of isolated human veins and found that veins can tolerate up to 66% overstretch without notable histological damage.
Project description:Vascular access dysfunction remains a major cause of morbidity and mortality in hemodialysis patients. At present there are few effective therapies for this clinical problem. The poor understanding of the pathobiology that leads to arteriovenous fistula (AVF) and graft (AVG) dysfunction remains a critical barrier to development of novel and effective therapies. However, in recent years we have made substantial progress in our understanding of the mechanisms of vascular access dysfunction. This article presents recent advances and new insights into the pathobiology of AVF and AVG dysfunction and highlights potential therapeutic targets to improve vascular access outcomes.
Project description:For end-stage kidney disease (ESKD) patients, hemodialysis requires durable vascular access which is often surgically created using an arteriovenous fistula (AVF). However, some ESKD patients that undergo AVF placement develop access-related hand dysfunction (ARHD) through unknown mechanisms. In this study, we sought to determine if changes in the serum metabolome could distinguish ESKD patients that develop ARHD from those that have normal hand function following AVF creation. Forty-five ESKD patients that underwent first-time AVF creation were included in this study. Blood samples were obtained pre-operatively and 6-weeks post-operatively and metabolites were extracted and analyzed using nuclear magnetic resonance spectroscopy. Patients underwent thorough examination of hand function at both timepoints using the following assessments: grip strength manometry, dexterity, sensation, motor and sensory nerve conduction testing, hemodynamics, and the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. Nineteen of the forty-five patients displayed overt weakness using grip strength manometry (P < 0.0001). Unfortunately, the serum metabolome was indistinguishable between patients with and without weakness following AVF surgery. However, a significant correlation was found between the change in tryptophan levels and the change in grip strength suggesting a possible role of tryptophan-derived uremic metabolites in post-AVF hand-associated weakness. Compared to grip strength, changes in dexterity and sensation were smaller than those observed in grip strength, however, post-operative decreases in phenylalanine, glycine, and alanine were unique to patients that developed signs of motor or sensory disability following AVF creation.
Project description:To assess the anatomic development of native arteriovenous fistula (AVF) during the first 6 weeks after creation by using ultrasonographic (US) measurements in a multicenter hemodialysis fistula maturation study.Each institutional review board approved the prospective study protocol, and written informed consent was obtained. Six hundred and two participants (180 women and 422 men, 459 with upper-arm AVF and 143 with forearm AVF) from seven clinical centers underwent preoperative artery and vein US mapping. AVF draining vein diameter and blood flow rate were assessed postoperatively after 1 day, 2 weeks, and 6 weeks. Relationships among US measurements were summarized after using multiple imputation for missing measurements.In 55% of forearm AVFs (68 of 124) and 83% of upper-arm AVFs (341 of 411) in surviving patients without thrombosis or AVF intervention prior to 6 weeks, at least 50% of their 6-week blood flow rate measurement was achieved at 1 day. Among surviving patients without thrombosis or AVF intervention prior to week 2, 70% with upper-arm AVFs (302 of 433) and 77% with forearm AVFs (99 of 128) maintained at least 85% of their week 2 flow rate at week 6. Mean AVF diameters of at least 0.40 cm were seen in 85% (389 of 459), 91% (419 of 459), and 87% (401 of 459) of upper-arm AVFs and in 40% (58 of 143), 73% (104 of 143), and 77% (110 of 143) of forearm AVFs at 1 day, 2 weeks, and 6 weeks, respectively. One-day and 2-week AVF flow rates and diameters were used to predict 6-week levels, with 2-week prediction of 6-week measures more accurate than those of 1 day (flow rates, R(2) = 0.47 and 0.61, respectively; diameters, R(2) = 0.49 and 0.82, respectively).AVF blood flow rate at 1 day is usually more than 50% of the 6-week blood flow rate. Two-week measurements are more predictive of 6-week diameter and blood flow than those of 1 day. US measurements at 2 weeks may be of value in the early identification of fistulas that are unlikely to develop optimally.
Project description:Stenosis from venous neointimal hyperplasia is common in native arteriovenous fistulas (AVFs). However, the preexisting histologic characteristics of veins at fistula creation, and associations thereof with baseline patient factors, have not been well characterized. In this study, we conducted histologic analysis of a segment of the vein used for anastomosis creation, obtained during AVF creation from 554 of the 602 participants in the multicenter Hemodialysis Fistula Maturation Cohort Study. We quantified intimal and medial areas and lengths of the internal and external elastic lamina by morphometry and assessed venous wall cells by immunohistochemistry, extracellular matrix with Movat stain, and calcium deposition by alizarin red stain. We also studied a representative subset of veins for markers of monocyte/macrophage content, cell proliferation, apoptosis, and neoangiogenesis. Neointima occupied >20% of the lumen in 57% of fully circumferential vein samples, and neointimal hyperplasia associated positively with age and inversely with black race. The neointima was usually irregularly thickened, sometimes concentric, and contained α-smooth muscle actin-expressing cells of smooth muscle or myofibroblast origin. Proteoglycans admixed with lesser amounts of collagen constituted the predominant matrix in the neointima. In 82% of vein samples, the media of vessel walls contained large aggregates of collagen. A minority of veins expressed markers of inflammation, cell proliferation, cell death, calcification, or neoangiogenesis. In conclusion, we observed preexisting abnormalities, including neointimal hyperplasia and prominent accumulation of extracellular matrix, in veins used for AVF creation from a substantial proportion of this cohort.
Project description:IntroductionLocal inflammation is an important regulator of vascular remodeling. We hypothesized that adipose tissue adjacent to hemodialysis arteriovenous fistulae modulates maturation.MethodsDuring fistula creation, perivenous adipose was collected from 111 participants in the Hemodialysis Fistula Maturation Study. Nine adipose-associated mediators were measured. Duplex ultrasound was performed at 4 time points postoperatively from 1 day to first cannulation (10-26 weeks). Associations between logarithmically transformed biomarker levels and fistula remodeling were evaluated using mixed effects regression.ResultsElevated interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 were associated with a reduction in the fractional vein diameter during the early time frame of 1 day to 2 weeks (diameter change of 26.6% and 20.4% at the 25th and 75th percentile for IL-6, P = 0.01; 27.8% and 21.1% at the 25th and 75th percentile for MCP-1, P = 0.02), but not in later stages of remodeling. Local leptin levels showed a significant negative correlation with fractional venous flow increase between 2 and 6 weeks (percent flow change 31.4% and 11.3% at the 25th and 75th percentile for leptin, P = 0.03).ConclusionThus, impaired fistula vein dilation and reduced capacity for flow augmentation associate with specific local adipose phenotypic signatures in a time-dependent manner. In view of adipose tissue plasticity, these findings raise the possibility of novel adipose-based strategies to facilitate fistula maturation.
Project description:An endovascular arteriovenous fistula is a recent technological advancement in hemodialysis vascular access. This systematic review and meta-analysis aimed to investigate the efficacy and safety of endovascular arteriovenous fistula (eAVF) creation compared with surgical arteriovenous fistula (sAVF) creation among patients with chronic kidney disease. We searched Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Clinical Trials.gov, and the WHO International Clinical Trials Registry Platform until May 2021 to perform meta-analyses using random-effects models. Pre-specified primary outcomes were fistula maturation, procedure-related complications, and patient satisfaction. Secondary outcomes were procedural technical success, procedure time, all adverse events, and medical expenditure. The risk of bias in non-randomized studies of the interventions assessment tool, and the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) approach were used to assess the quality of individual studies and the body of evidence, respectively. In seven studies including 860 patients, endovascular arteriovenous fistula creation had little to no effect on fistula maturation (odds ratio, 0.58; 95% confidence intervals, 0.05 to 6.91). Meta-analysis could not be performed for procedure-related complications and patient satisfaction due to insufficient data. For secondary outcomes, endovascular arteriovenous fistula resulted in a slight to no difference in procedural technical success (odds ratio, 0.69: 95% confidence intervals, 0.04 to 11.98) and all adverse events (odds ratio, 6.31; 95% confidence intervals, 0.64 to 62.22). Endovascular fistula creation incurred less medical expenditure than sAVF (mean difference, USD 12760; 95% confidence intervals, -19710 to -5820). Meta-analysis for procedure time was not performed because one of the studies had a critical risk of bias. All of these outcomes were of low certainty of evidence or very low certainty of evidence. There was limited evidence for supporting endovascular arteriovenous fistula creation over conventional surgical arteriovenous fistula creation for patients with chronic kidney disease. Multicenter randomized controlled trials are needed to confirm the efficacy and safety of eAVFs in selected populations.