The role of venous diameter in predicting arteriovenous fistula maturation: when not to expect an AVF to mature according to pre-operative vein diameter measurements? A best evidence topic

Computational fluid-structure interaction analysis of the end-to-side radio-cephalic arteriovenous fistula

BACKGROUND AND OBJECTIVE

In the current work, we present a descriptive fluid-structure interaction computational study of the end-to-side radio-cephalic arteriovenous fistula. This allows us to account for the different thicknesses and elastic properties of the radial artery and cephalic vein.

METHODS

The core of the work consists in simulating different arteriovenous fistula configurations obtained by virtually varying the anastomosis angle, i.e. the angle between the end of the cephalic vein and the side of the radial artery. Since the aim of the work is to understand the blood dynamics in the very first days after the surgical intervention, the radial artery is considered stiffer and thicker than the cephalic vein.

RESULTS

Our results demonstrate that both the diameter of the cephalic vein and the anastomosis angle play a crucial role to obtain a blood dynamics without re-circulation regions that could prevent fistula failure.

CONCLUSIONS

When an anastomosis angle close to the perpendicular direction with respect to the radial artery is combined with a large diameter of the cephalic vein, the recirculation regions and the low Wall Shear Stress (WSS) zones are reduced. Conversely, from a structural point of view, a low anastomosis angle with a large diameter of the cephalic vein reduces the mechanical stress acting on the vessel walls.

The role of glomerular filtration rate in AVF success: Should we intervene earlier?

INTRODUCTION

End-stage kidney disease (ESKD) patients require life-sustaining kidney replacement therapies, with the natural arteriovenous fistula (AVF) being the preferred vascular access due to its low infection risk, high patency, and fewer complications. Factors like vessel diameter, gender, diabetes, age, and surgical technique influence AVF maturation.

METHOD

Our study focused on short-term AVF creation success, specifically examining estimated glomerular filtration rate (eGFR) levels using the CKD-EPI formula. Patients were categorized according to their eGFR levels to observe the effects of fistula timing and the severity of kidney disease.

RESULTS

No significant demographic or outcome differences between eGFR groups have been observed except for gender. AVF maturation was notably associated with distal vein diameter (>2 mm), while other factors did not significantly impact maturation rates. As a secondary outcome, it was concluded that the recording of patients' blood pressure values at preoperative and perioperative levels led to the conclusion that blood pressure levels may have an impact on fistula maturation.

CONCLUSION

To ensure vascular access effectiveness, optimizing blood pressure, determining vein diameter, strategic AVF timing, and reducing catheter usage are crucial. Our study aimed to identify eGFR levels conducive to optimal AVF outcomes. Although significant results could not be obtained in this regard, it is considered worthwhile to re-examine the effect of blood pressure in secondary outcomes. Additionally, prospective studies may be appropriate for reevaluating the effect of GFR.

Effectiveness of a native vein arteriovenous fistula tracking system

OBJECTIVE

This study aims to evaluate the effectiveness of a tracking program on the functional maturation rate of arteriovenous fistula (AVF).

METHODS

Two major clinical outcomes (commencement of cannulation and functional maturation) of created AVFs were compared between two cohorts. (i) Cohort 1: historical cohort; (ii) Cohort 2: AVFs created after implementation of the tracking project. Multivariable Cox regression models were used to assess the association between cohort allocation and the two major clinical outcomes.

RESULTS

Data of 114 and 141 patients were analyzed respectively from Cohorts 1 (historical data) and 2 (with AVF tracking). After adjustment of covariates in the multivariable analysis, the AVFs created in Cohort 2 were more likely to be cannulated earlier (adjusted HR: 2.82; 95% CI: 1.97-4.05; p < 0.001), compared to those in Cohort 1. Similarly, the AVFs of Cohort 2 patients had significantly higher probability of functional maturation (adjusted HR: 1.81; 95% CI: 1.31-2.48; p < 0.001) than fistulas in Cohort 1. Cannulation was commenced for half of the AVFs by 4.1 months post-creation in the historical cohort (Cohort 1), whereas in the post-tracking cohort, 50% of the AVFs were cannulated by 2.3 months after creation (p < 0.001). It took 5.5 and 4.3 months for 50% of the AVFs created in Cohort 1 and Cohort 2 patients to achieve catheter-free functional maturation, respectively (p = 0.06).

CONCLUSION

An AVF tracking program with maturation target for the access surgeons, together with a standardized tracking, feedback, and clinical strategy adjustment system is able to improve the AVF functional maturation rate.

Small Arteriovenous Anastomosis in Fistula Creation: Establishing a Functional Vascular Access while Minimizing Steal Syndrome

BACKGROUND

The size selection of the arteriovenous (AV) anastomosis in dialysis access creation requires a careful balance: the diameter must be large enough to accommodate sufficient flow for hemodialysis but small enough to minimize the complication of steal syndrome. Steal syndrome affects up to 10% of patients after creation of dialysis access with sometimes devastating consequences. Conventional teaching recommends a 7-10 mm anastomosis. We sought to assess the efficacy of using a smaller (5-6 mm) anastomosis in new arteriovenous fistula (AVF) creation.

METHODS

We conducted a comparative retrospective analysis of patients who underwent fistula creation with a small versus regular size anastomosis at any upper extremity anatomic site between March 2019 and October 2020 at our institution. Anatomic sites included radiocephalic, brachiocephalic, and brachiobasilic. All AV anastomoses were measured intraoperatively to be 5-6 mm in diameter for the small size groups and 8-10 mm for the regular size group. Endpoints included steal syndrome, functional patency, primary patency, and secondary patency.

RESULTS

Out of 110 patients who underwent an AVF creation, 59.1% received a 5-6 mm anastomosis with a median follow-up time of 10 ± 6 months. Patients' demographics and comorbidities were relatively similar between the 2 groups except for a higher rate of hyperlipidemia (55.4% vs. 28.9%, P = 0.008) in the small size group. Patients in the small size group were more likely to undergo a radiocephalic fistula (40% vs. 4.5%, P < 0.001) and to have a smaller mean vein diameter on preoperative duplex ultrasound (3.2±1 mm vs. 3.9±1 mm, P = 0.0016) when compared to their regular size counterparts. During follow-up, none of the patients in the small group developed steal syndrome (0% vs. 9%, P = 0.015). At 1 year, patients in the regular size group achieved higher rates of primary patency (67.9% vs. 46.9%, P = 0.02); however, no difference was seen in 1-year primary-assisted patency (84.9% vs. 73.6%, P = 0.3), secondary patency (89.6% vs. 79.5%, P = 0.3), or functional patency (87.7% vs. 82.2%, P = 0.64) between the small and regular size groups, respectively.

CONCLUSIONS

The use of a 5-6 mm anastomosis in the creation of new AVFs of the upper extremities appears to be a technically safe option for dialysis access. Our experience suggests that smaller anastomosis still creates enough flow to maintain a functional AV access while minimizing the incidence of steal syndrome. Additionally, even with smaller vein sizes preoperative, adequate dialysis access can be created via a small sized anastomosis, including distal arm access. Larger studies with longer follow-up are needed to evaluate long-term outcomes of small anastomosis fistulas.

Risk factors for arteriovenous fistula dysfunction in hemodialysis patients: a retrospective study

Arteriovenous fistula (AVF) is the first choice of vascular access in hemodialysis (HD) patients. However, the correlations between patient factors and the arteriovenous fistula patency remain unclear. Therefore, our study investigates the risk factors associated with AVF dysfunction in HD patients. A total of 233 end-stage renal disease (ESDR) patients who met the study inclusion criteria in the Nephrology Department of Hunan Provincial People's Hospital between December 2020 and June 2022 were included in this study. The baseline demographic, clinical and laboratory parameters were collected at the time of AVF creation and analyzed. Of the 233 ESRD patients, 146 (62.7%) were male and the mean age was 56.11 ± 12.14 (21-82) years. The patients were followed for a median time of 14 months. Kaplan-Meier analysis showed a 6-, 12- and 24-month post-placement survival of 87.1%, 82.8% and 80.7%, respectively. Univariate Cox regression analysis revealed weight (HR, 1.03; P = 0.03) as a predictor for the loss of vascular access functionality. In addition, multivariate Cox regression analysis further demonstrated that sex (HR, 3.41; P = 0.03), weight (HR 1.08; P < 0.01) and phosphorus level (HR: 3.03; P = 0.01) are independent risk factors for AVF dysfunction. AVF dysfunction is highly associated with several risk factors including weight, phosphorus level, and sex. Positive intervention strategies targeting these potential factors, such as weight loss or oral phosphate binders could improve the long-term success of AVF.

Long-term efficacy and risk factors of balloon-assisted maturation for radial-cephalic arteriovenous fistula with small-caliber veins

INTRODUCTION

Balloon angioplasty maturation (BAM) is a salvage method for autologous arteriovenous fistula (AVF) maturation failure. AVF creation using small-diameter veins is considered to have poor outcomes. Therefore, this study aimed to explore the long-term patency of small-diameter veins (≤3 mm) using BAM.

METHODS

BAM was performed if the fistula failed to mature and function adequately to provide prescribed dialysis.

FINDINGS

Out of 61 AVFs, 22 AVFs successfully matured without further intervention (AVF group) and 39 AVFs failed to mature. Except for 1 patient who required peritoneal dialysis, the remaining 38 patients received salvage BAM, and 36 of those successful matured (BAM group). Kaplan-Meier analysis revealed no significant differences between the AVF and BAM groups in terms of primary functional patency (p = 0.503) and assisted functional patency (p = 0.499). Compared with the AVF group, the BAM group had similar assisted primary functional patency (1-year: 94.7% vs. 93.1%; 3-year: 88.0% vs. 93.1%; 5-year: 79.2% vs. 88.3%). In addition, there were no significant difference between groups in the duration of primary functional patency and assisted primary functional patency (p > 0.05). Multivariate analyses showed that vein diameter and number of BAM procedures were independent predictors of primary functional patency in the AVF group and BAM group, respectively. Patient with 1 mm increase in vein size had 0.13-fold probability of having decreased duration of patency (HR = 0.13, 95% CI: 0.02-0.99, p = 0.049), while patients who received two times of BAM procedures were 2.885 as likely to have decreased duration of primary functional patency (HR = 2.885, 95% CI: 1.09-7.63, p = 0.033) than patients who received one BAM procedure.

DISCUSSION

BAM is a relatively effective salvage management option with an acceptable long-term patency rate, even for small cephalic veins.

Does the balloon-assisted maturation procedure offer comparable results for AVF created with a smaller vein?

BACKGROUND

Traditionally, a venous diameter of less than 3 mm was not considered for creation of AVF. Some studies have reported smaller venous size could be used for operation. AVF created with a smaller vein may have a lower maturation rate. Currently, percutaneous angioplasty is also used to enhance the maturation of AVF. This study aimed to establish whether the BAM procedure could offer comparable results for AVF created with a smaller vein.

METHODS

From January 2016 to July 2021, 290 patients who received native AVF operation were enrolled in this study. All of the preoperative venous sizes were measured by Duplex ultrasonography under tourniquet enhancement. The study cohort was categorized into two groups based on the pre-operative venous diameter: smaller vein group (SVG, 2.5 < size < 3 mm, 53.1%) and normal vein group (NVG, size ⩾ 3 mm, 46.9%).

RESULTS

The mean age was 64 ± 12.9 years, and 58.6% of patients were male. Hypertension and DM were the most common comorbidities. Most patients underwent operation of radio-cephalic fistula (71.4%). The overall primary maturation rate was 79%. The primary maturation rate was significantly higher in the NVG (86% vs 72.7%, p = 0.009). However, after the BAM procedure, the secondary maturation rate was similar in both groups (94.1% vs 90.3%, p = 0.319).

CONCLUSIONS

According to our study, the BAM procedure can significantly increase the maturation rate, and the secondary maturation rate was similar in both groups. Thus, more patients can be given the opportunity to undergo creation of an AVF for long-term hemodialysis.

Intraoperative vascular mapping improves patient eligibility for arteriovenous fistula creation

BACKGROUND

We assessed the utility of intraoperative vein mapping performed by the operating surgeon for evaluating vessel suitability for arteriovenous fistula (AVF) creation.

METHODS

In a retrospective review of 222 AVFs, vein diameter measurements were compared between intraoperative and preoperative mapping in the same anatomical location. AVF creation was based on intraoperative vein diameter ≥2 mm, using a distal to proximal and superficial veins first approach. Potential selection of access type based on preoperative findings alone was analyzed.

RESULTS

The mean diameter of the veins used for AVF creation measured 3.6 ± 0.8 mm on intraoperative duplex versus 2.5 ± 0.9 mm when the same veins were measured on preoperative duplex. Based on preoperative mapping alone, 23% of patients would have received a more proximal AVF and 5% would have needed a graft. AVFs created more distally based on intraoperative findings had similar maturation rates compared to the rest of the cohort, 79% versus 84% (p = 0.2).

CONCLUSIONS

Intraoperative vein mapping can be used to evaluate vessel suitability for AVF and compared to pre-operative vein mapping may increase the eligibility of distal veins for fistula creation while reducing the need for AV grafts.

Venous Evaluation

The vascular lab (VL) provides unequalled information regarding venous disease especially in the depiction and characterization of venous waveforms. This article provides the indications, protocol, and diagnostic criteria for peripheral and central venous disease and venous mapping. Venous evaluation is one of the most common studies performed at vascular labs (VL). Patient may present with swelling for evaluation of thrombosis, central obstruction, or venous insufficiency, or may need preoperative planning prior to a bypass or dialysis access creation. It is my hope that the added value a VL brings to the sonographic evaluation of veins, beyond the compressibility of the veins, is the utmost respect and attention to the depiction and characterization of the venous waveform.

Ultrasound Measurement of Vascular Distensibility Based on Edge Detection and Speckle Tracking Using Ultrasound DICOM Data

This study presents an edge detection and speckle tracking (EDST) based algorithm to calculate distensibility as percentage of change of vessel diameter during cardiac cycles. Canny edge detector, Vandermonde matrix representation, Kanade Lucas Tomasi algorithm with pyramidal segmentation, and penalized least squares technique identifies the vessel lumen edge, track the vessel diameter, detrend the signal and find peaks and valleys when the vessel is fully distended or contracted. An upper extremity artery from 10 patients underwent an ultrasound examination as part of preoperative evaluation before arteriovenous fistula surgery. Three studies were performed to evaluate EDST with automatic peak and valley selection versus manual speckle selection of expert users using manual peak and valley selection. Results demonstrate the effectiveness of the proposed methodology, to obtain comparable results as those obtained by expert-users, and considerably reducing the variability associated with external factors such as excessive motion, fluctuations in stroke volume, beat-to-beat blood pressure changes, breathing cycles, and arm-transducer pressure.

Maturation and survival of arteriovenous fistula: The challenge starts from the preoperative assessment stage

BACKGROUND

It is necessary to assess the association between the preoperative indicators and the maturation and survival of arteriovenous fistula (AVF).

METHODS

We retrospectively identified 236 patients with a new AVF created between 2016 and 2018 in our Dialysis Center.

RESULTS

Multivariate Logistic regression showed that preoperative arterial diameter (odds ratio [OR] = 1.452, 95% confidence interval [CI] [1.233, 1.710], p < 0.001), preoperative venous diameter (OR = 1.296, 95% CI [1.166, 1.477], p < 0.001), left ventricular ejection fraction (LVEF) (OR = 1.187, 95% CI [1.103, 1.277], p < 0.001), and diabetes mellitus (OR = 0.245, 95% CI [0.107, 0.560], p = 0.01) were independent influential factors for AVF maturation. Two years after the AVF surgery follow-up, multivariate Cox proportional-hazards model showed that the preoperative arterial diameter (OR = 0.510, 95% CI [0.320, 0.813], p = 0.005), preoperative venous diameter (OR = 0.940, 95% CI [0.897, 0.985], p = 0.010) and diabetes mellitus (OR = 1.785, 95% CI [1.117, 2.855], p = 0.016) was prognostic factors of AVF survival. The Kaplan-Meier method showed that the primary survival of AVF in patients with different preoperative arterial diameter was statistically significant (log-rank χ²  = 15.415, p < 0.001), while the secondary survival was not statistically significant (log-rank χ²  = 0.131, p = 0.717).

CONCLUSION

In our cohort, the preoperative arterial and venous diameter and diabetes mellitus were independent influential factors for AVF maturation and prognostic factors of AVF survival. However, the preoperative LVEF only associated with the maturation of AVF. Meanwhile, smaller arterial diameter (≤2.15 mm) was associated with AVF maturation failure, but did not impact secondary survival of AVF.

Effect of cilostazol on arteriovenous fistula in hemodialysis patients

BACKGROUND

The maturation and patency of permanent vascular access are critical in patients requiring hemodialysis. Although numerus trials have been attempted to achieve permanently patent vascular access, little have been noticeable. Cilostazol, a phosphodiesterase-3 inhibitor, has been shown to be effective in peripheral arterial disease including vascular injury-induced intimal hyperplasia. We therefore aimed to determine the effect of cilostazol on the patency and maturation of permanent vascular access.

METHODS

This single-center, retrospective study included 194 patients who underwent arteriovenous fistula surgery to compare vascular complications between the cilostazol (n=107) and control (n=87) groups.

RESULTS

The rate of vascular complications was lower in the cilostazol group than in the control group (36.4% vs. 51.7%; p=0.033), including maturation failure (2.8% vs. 11.5%; p=0.016). The rate of reoperation due to vascular injury after hemodialysis initiation following fistula maturation was also significantly lower in the cilostazol group than in the control group (7.5% vs. 28.7%; p<0.001). However, there were no significant differences in the requirement for percutaneous transluminal angioplasty (PTA), rate of PTA, and the interval from arteriovenous fistula surgery to PTA between the cilostazol and control groups.

CONCLUSION

Cilostazol might be beneficial for the maturation of permanent vascular access in patients requiring hemodialysis.

Association of preoperative vein mapping with hemodialysis access characteristics and outcomes in the Vascular Quality Initiative

BACKGROUND

Preoperative vein mapping before arteriovenous fistula (AVF) or arteriovenous graft (AVG) placement has been debated as a possible method of improving hemodialysis access outcomes for patients. However, high-quality national studies that have addressed this relationship are lacking. Thus, we assessed the association of preoperative vein mapping with hemodialysis access configuration and outcomes.

METHODS

In the present cohort study, we analyzed all patients who had undergone AVF or AVG placement with data captured in the Vascular Quality Initiative hemodialysis access dataset from August 2011 to September 2019. The patients were stratified by whether they had undergone preoperative vein mapping. The primary (configuration) outcomes were access type (AVF vs AVG) and location (upper arm vs forearm). The secondary (longitudinal) outcomes were the successful initiation of hemodialysis, maintenance of secondary patency, and the need for reintervention 1 year after the index operation.

RESULTS

Overall, 85.6% of the 46,010 included patients had undergone preoperative vein mapping. Of the 46,010 patients, 76.1% and 23.9% had undergone AVF and AVG creation, respectively. AVF creation (77.6% vs 67.3%) and forearm location (54.6% vs 47.3%) were more frequent for the patients who had undergone preoperative vein mapping than for those who had not (P < .001). After adjusting for baseline differences between the groups, preoperative vein mapping was associated with increased odds of receiving an AVF vs AVG (adjusted odds ratio, 1.64; 95% confidence interval [CI], 1.55-1.75) and forearm vs upper arm access (adjusted odds ratio, 1.22; 95% CI, 1.16-1.30). The incidence of the loss of secondary patency was lower for patients with preoperative vein mapping (P < .001), and persisted after risk adjustment (adjusted hazard ratio, 0.81; 95% CI, 0.75-0.88).

CONCLUSIONS

Preoperative vein mapping was associated with favorable hemodialysis access configurations and outcomes in real-world practice. These data suggest that the use of preoperative vein mapping could improve the likelihood of favorable outcomes for patients requiring hemodialysis access.

Artery to vein configuration of arteriovenous fistula improves hemodynamics to increase maturation and patency

Arteriovenous fistulae (AVF) are the preferred mode of hemodialysis access, but 60% of conventional [vein-to-artery (V-A)] AVF fail to mature, and only 50% remain patent at 1 year. We previously showed improved maturation and patency in a pilot study of the radial artery deviation and reimplantation (RADAR) technique that uses an artery-to-vein (A-V) configuration. Here, we show that RADAR exhibits higher rates of maturation, as well as increased primary and secondary long-term patencies. RADAR is also protective in female patients, where it is associated with decreased reintervention rates and improved secondary patency. RADAR and conventional geometries were compared further in a rat bilateral carotid artery-internal jugular vein fistula model. There was decreased cell proliferation and neointimal hyperplasia in the A-V configuration in male and female animals, but no difference in hypoxia between the A-V and V-A configurations. Similar trends were seen in uremic male rats. The A-V configuration also associated with increased peak systolic velocity and expression of Kruppel-like factor 2 and phosphorylated endothelial nitric oxide synthase, consistent with improved hemodynamics. Computed tomography and ultrasound-informed computational modeling showed different hemodynamics in the A-V and V-A configurations, and improving the hemodynamics in the V-A configuration was protective against neointimal hyperplasia. These findings collectively demonstrate that RADAR is a durable surgical option for patients requiring radial-cephalic AVF for hemodialysis access.

Effect of cilostazol on arteriovenous fistula in hemodialysis patients

BACKGROUND

The maturation and patency of permanent vascular access are critical in patients requiring hemodialysis. Although numerus trials have been attempted to achieve permanently patent vascular access, little have been noticeable. Cilostazol, a phosphodiesterase-3 inhibitor, has been shown to be effective in peripheral arterial disease including vascular injury-induced intimal hyperplasia. We therefore aimed to determine the effect of cilostazol on the patency and maturation of permanent vascular access.

METHODS

This single-center, retrospective study included 194 patients who underwent arteriovenous fistula surgery to compare vascular complications between the cilostazol (n=107) and control (n=87) groups.

RESULTS

The rate of vascular complications was lower in the cilostazol group than in the control group (36.4% vs. 51.7%; p=0.033), including maturation failure (2.8% vs. 11.5%; p=0.016). The rate of reoperation due to vascular injury after hemodialysis initiation following fistula maturation was also significantly lower in the cilostazol group than in the control group (7.5% vs. 28.7%; p<0.001). However, there were no significant differences in the requirement for percutaneous transluminal angioplasty (PTA), rate of PTA, and the interval from arteriovenous fistula surgery to PTA between the cilostazol and control groups.

CONCLUSION

Cilostazol might be beneficial for the maturation of permanent vascular access in patients requiring hemodialysis.

Reliability of preoperative venous mapping ultrasonography in predicting for autogenous arteriovenous fistula maturation

BACKGROUND

Autogenous arteriovenous fistula creation is the preferred route for vascular access for hemodialysis. Although preoperative venous mapping ultrasonography has been advocated as an operative planning adjunct and recently incorporated into the Society for Vascular Surgery clinical guidelines, controversy remains regarding its usefulness for predicting access success. The purpose of the present retrospective clinical study was to test the hypothesis that vein size measured on routine preoperative venous mapping is a poor predictor of primary fistula maturation.

METHODS

Consecutive upper extremity autogenous arteriovenous fistulas created by three dedicated vascular surgeons were retrospectively reviewed. The demographic characteristics, preoperative venous mapping, functional maturation, and patency were analyzed. The clinically relevant variables were tested for predictive significance using a logistic regression model.

RESULTS

A total of 199 upper extremity autogenous arteriovenous fistulas had been created during a 5-year period. Patients were aged 70 ± 16 years (range, 20-96 years), and 62% were men. Most had already been undergoing dialysis before fistula creation (83%), usually via a tunneled central venous catheter (62%). Radial-cephalic, brachial-cephalic, and brachial-basilic arteriovenous fistulas had been created in 82 patients (41%), 76 patients (38%), and 10 patients (5%), respectively. Fistula maturation, defined as a palpable thrill and/or successful cannulation of the fistula with the ability to deliver a flow rate of 400 mL/min, was achieved in 67% of the patients. A higher body mass index was associated with nonmaturation on both univariate and multivariate analyses (success, 28.6 ± 7.7 kg/m²; vs failed, 31.6 ± 9.4 kg/m²; P = .029; odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02-1.10; P < .01). On univariate analysis, the maximum target vein diameter assessed by preoperative venous mapping was slightly larger in the group achieving successful maturation (2.9 ± 1.1 mm vs 2.6 ± 0.9 mm; P = .014). However, neither the maximum target vein diameter nor a target vein size >3 mm was significantly predictive of maturation on multivariate analysis (maximum vein diameter: OR, 0.65; 95% CI, 0.35-1.22; P = .176; vein size >3 mm: OR, 0.91; 95% CI, 0.32-2.60; P = .857). After a median follow-up of 15 months (interquartile range, 26 months), the primary functional patency, primary-assisted patency, and secondary patency rates were 39.1% ± 0.6%, 94.5% ± 0.6%, and 97.9% ± 0.5%. No association of vein diameter with long-term patency was found.

CONCLUSIONS

Despite the national fistula-first initiatives, most patients still undergo access via catheter at the initiation of hemodialysis. The use of routine preoperative venous mapping does not predict successful primary maturation. Also, no clinically useful predictor of fistula maturation was identified in the present study.

Transit Time Flowmetry and Vein Size Are Predictive of Arteriovenous Fistula Maturation

Background

This study aimed to assess the effect of vessel size and flow characteristics on the maturation of autogenous radiocephalic arteriovenous fistulae (RCAVFs).

Methods

We retrospectively reviewed records of patients undergoing RCAVF creation at a single medical center from January 2013 to December 2019. Operative variables were compared between patients whose fistulae matured and those whose fistulae failed to mature.

Results

Overall, 152 patients (33 of whom were women) with a mean age of 62.6±13.6 years underwent RCAVF creation; functional maturation was achieved in 123. No statistically significant differences were observed between patients in whom maturation was or was not achieved in terms of the following variables: female sex (20.3% vs. 25.0%), radial artery size (2.5 vs. 2.4 mm), and pulsatility index (0.69 vs. 0.62). Low intraoperative transit time flowmetry (TTF; 150.4 vs. 98.1 mL/min) and small vein size (2.4 vs. 2.0 mm) were associated with failure of maturation. The best cutoff diameter for RCAVF TTF and cephalic vein size were 105 mL/min and 2.45 mm, respectively.

Conclusion

In patients who undergo RCAVF creation, vein diameter on preoperative ultrasonography and intraoperative TTF are predictors of functional maturation. We identified an intraoperative TTF cutoff value that can be used for intraoperative decision-making.

Preoperative color Doppler ultrasound parameters for surgical decision-making in upper arm arteriovenous fistula maturation

OBJECTIVE

Current scientific evidence is insufficient to determine the best vascular access for each patient. It is an unmet clinical need because vascular access dysfunction accounts for 20% to 30% of hospital admissions. Our aim was to evaluate preoperative color flow Doppler ultrasound (CDUS)-derived parameters (vein diameter and brachial artery flow and diameter) and their effect interaction with comorbidities as predictors of brachiocephalic (BC) and brachiobasilic (BB) arteriovenous fistula (AVF) maturation.

METHODS

A prospective analysis was performed of patients who underwent BC and BB AVF as primary definitive vascular access between January 2016 and May 2017. Variables included patients' demographics, comorbidities, medication, preoperative blood pressure, and CDUS-derived parameters. Outcomes were patency 48 hours after surgery and fistula maturation at 6 and 12 weeks. Nonparametric descriptive and univariate statistics were used. Logistic regression models and receiver operating characteristic curve analyses were performed.

RESULTS

There were 132 patients (91 with BC AVF and 41 with BB AVF) included. The 48-hour patency was 91.7%. AVF maturation at 6 weeks was observed in 71.3%, and AVF maturation at 12 weeks was observed in 66.3%. There were no associations in univariate and multivariate logistic regression analysis between AVF maturation and comorbidities. Systolic blood pressure was an independent predictor of 48-hour patency with an optimized cutoff of 154 mm Hg (area under the curve, 0.73; P = .013; Youden index, 0.40). Vein diameter with tourniquet was an independent predictor of AVF maturation at 6 and 12 weeks with an optimized cutoff of 3.9 mm (area under the curve, 0.74; P < .001; Youden index, 0.38).

CONCLUSIONS

AVF maturation was independent of comorbidities. Systolic blood pressure ≥154 mm Hg and vein diameter with tourniquet ≥3.9 mm were the associated conditions that better predicted BC and BB AVF maturation. There were no effect interactions between CDUS-derived parameters and associated comorbidities.

Early Predictors of Arteriovenous Fistula Maturation: A Novel Perspective on an Enduring Problem

BACKGROUND

Preoperative ultrasound mapping is routinely used to select vessels meeting minimal threshold diameters for surgical arteriovenous fistula (AVF) creation but fails to improve AVF maturation rates. This suggests a need to reassess the preoperative ultrasound criteria used to optimize AVF maturation.

METHODS

We retrospectively identified 300 catheter-dependent patients on hemodialysis with a new AVF created between 2010 and 2016. We then evaluated the associations of preoperative vascular measurements and hemodynamic factors with unassisted AVF maturation (successful use for dialysis without prior intervention) and overall maturation (successful use with or without prior intervention). Multivariable logistic regression was used to identify preoperative factors associated with unassisted and overall AVF maturation.

RESULTS

Unassisted AVF maturation associated with preoperative arterial diameter (adjusted odds ratio [aOR], 1.50 per 1-mm increase; 95% confidence interval [95% CI], 1.23 to 1.83), preoperative systolic BP (aOR, 1.16 per 10-mm Hg increase; 95% CI, 1.05 to 1.28), and left ventricular ejection fraction (aOR, 1.07 per 5% increase; 95% CI, 1.01 to 1.13). Overall AVF maturation associated with preoperative arterial diameter (aOR, 1.36 per 1-mm increase; 95% CI, 1.10 to 1.66) and preoperative systolic BP (aOR, 1.17; 95% CI, 1.06 to 1.30). Using receiver operating curves, the combination of preoperative arterial diameter, systolic BP, and left ventricular ejection fraction was fairly predictive of unassisted maturation (area under the curve, 0.69). Patient age, sex, race, diabetes, vascular disease, obesity, and AVF location were not associated with maturation.

CONCLUSIONS

Preoperative arterial diameter may be an under-recognized predictor of AVF maturation. Further study evaluating the effect of preoperative arterial diameter and other hemodynamic factors on AVF maturation is needed.

Stimulation of Caveolin-1 Signaling Improves Arteriovenous Fistula Patency

Objective- Arteriovenous fistulae (AVF) are the most common access created for hemodialysis; however, many AVF fail to mature and require repeated intervention, suggesting a need to improve AVF maturation. Eph-B4 (ephrin type-B receptor 4) is the embryonic venous determinant that is functional in adult veins and can regulate AVF maturation. Cav-1 (caveolin-1) is the major scaffolding protein of caveolae-a distinct microdomain that serves as a mechanosensor at the endothelial cell membrane. We hypothesized that Cav-1 function is critical for Eph-B4-mediated AVF maturation. Approach and Results- In a mouse aortocaval fistula model, both Cav-1 mRNA and protein were increased in the AVF compared with control veins. Cav-1 KO (knockout) mice showed increased fistula wall thickening ( P=0.0005) and outward remodeling ( P<0.0001), with increased eNOS (endothelial NO synthase) activity compared with WT (wild type) mice. Ephrin-B2/Fc inhibited AVF outward remodeling in WT mice but not in Cav-1 KO mice and was maintained in Cav-1 RC (Cav-1 endothelial reconstituted) mice (WT, P=0.0001; Cav-1 KO, P=0.7552; Cav-1 RC, P=0.0002). Cavtratin-a Cav-1 scaffolding domain peptide-decreased AVF wall thickness in WT mice and in Eph-B4 het mice compared with vehicle alone (WT, P=0.0235; Eph-B4 het, P=0.0431); cavtratin also increased AVF patency (day 42) in WT mice ( P=0.0275). Conclusions- Endothelial Cav-1 mediates Eph-B4-mediated AVF maturation. The Eph-B4-Cav-1 axis regulates adaptive remodeling during venous adaptation to the fistula environment. Manipulation of Cav-1 function may be a translational strategy to enhance AVF patency.

Influence of cephalic vein dilation on arteriovenous fistula maturation in patients with small cephalic veins

A substantial limitation of dialysis fistulas is their high primary failure rate due to nonmaturation. Various studies have documented that patients with larger vein diameters exhibit reduced risks for nonmaturation. Nevertheless, some patients have small veins. Few studies have focused on patients with small veins. We hypothesize that sufficient venous dilation contributes to fistula maturation. Therefore, we studied the influence of cephalic vein dilation on fistula maturation in patients with small veins.Patients with small cephalic veins (diameter <2 mm) undergoing initial arteriovenous fistulae (AVF) operation were included. A total of 72 patients were enrolled in this study. A prospective study was performed, and the patients were followed for 6 weeks after surgery. Preoperative and postoperative duplex ultrasound mapping of veins was performed, and dilation of the cephalic vein was evaluated.The fistula maturation rate was 44.44%. Multivariate logistic regression analysis revealed a significant relationship between fistula maturation and preoperative cephalic vein dilation. Based on the results of ROC analysis, the fistula maturation rate in patients with vein dilation greater than or equal to the cut-off was 57.14% in the training data set and 54.55% in the testing data set. The independent influencing factors for fistula maturation were used to establish a combined index with logistic regression analysis. The fistula maturation rate in patients with combined indexes greater than or equal to the cut-off was 80.95% in the training data set and 77.78% in the testing data set.Our results demonstrated that preoperative venous dilation was associated with AVF maturation. For patients with small veins, venous distensibility needs to be carefully assessed before surgery, as it may be a better predictor of AVF maturation than venous diameter.

Study protocol for a prospective observational study to investigate the role of luminal pressure on arteriovenous fistula maturation

INTRODUCTION

Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis due to its higher patency and lower infection rate. However, its suboptimal maturation rate is a major weakness. Although substantial risk factors for AVF maturation failure have been disclosed, modifiable risk factors remain unknown. During the AVF maturation process, an elevated luminal pressure is required for outward remodeling; however, excessively high luminal pressure may also be detrimental to AVF maturation, which remains to be defined. We hypothesized that higher AVF luminal pressure is harmful to its maturation, and investigate its potential as a modifiable factor to improve AVF maturation.

METHODS AND ANALYSIS

This prospective study includes patients undergoing surgical creation for a native AVF. The exclusion criteria were as follows: age <20 years, inability to sign an informed consent, and failure to create a native AVF due to technical difficulties. Demographic and laboratory profiles will be collected before AVF surgery. Vascular sonography will be performed within 1 week of AVF creation to measure the diameters, flow rates, and flow volumes of AVF and its branched veins. The pressure gradient within AVF will be estimated from the blood flow rates using the modified Bernoulli equation. The primary outcome is spontaneous AVF maturation defined as provision of sufficient blood flow for hemodialysis within 2 months of its creation without any interventional procedures. The secondary outcome is assisted AVF maturation, which is defined as AVF maturation within 2 months from its creation aided by any interventional procedure before the successful use of AVF.

DISCUSSION

While contemporary theory for AVF maturation failure focuses on disturbed wall shear stress, complicate assumptions and measurement preclude its clinical applicability. AVF luminal pressure, which may be manipulated pharmaceutically and surgically, may be a target to improve the outcome of AVF maturation.

TRIAL REGISTRATION

This study has been registered at the protocol registration and results system. The Protocol ID: NCT04017806.

Effect of local papaverine on arteriovenous fistula maturation in patients with end-stage renal disease

BACKGROUND

Arteriovenous fistula (AVF) maturation is one of the main concerns in patients with end-stage renal disease (ESRD) and finding a strategy for increasing success rate and accelerating fistula maturation is valuable. The aim of this study was to evaluate the effects of papaverine injection on AVF maturation and success rate.

METHOD

This study was a randomized clinical trial that involved 110 patients with ESRD that were referred for AVF construction. Patients were allocated in papaverine group and control group with block randomization according to age and sex. In the case group, papaverine (0.1 or 0.2 cc) was injected locally within the subadventitia of artery and vein after proximal and distal control during AVF construction and in the control group, AVF construction was done routinely without papaverine injection.

RESULTS

Maturation time in case and control groups was 37.94 ± 11.49 and 44.23 ± 9.57 days, respectively (p=0.004). Hematoma was not seen in the case group but occurred in one patient in the control group. One patient of the case group developed venous hypertension. Four functional fistulas, 1 (1.8%) in the case group and 3 (5.5%) in the control group, failed to mature (p=0.618). Maturation rate did not differ between the two groups statistically (p=0.101).

CONCLUSION

Local papaverine injection increased vessel diameter and blood flow, increasing shearing stress in both arterial and venous segment of recently created AVF. In this way, papaverine probably can decrease AVF maturation time without an increase in complications.

Inhibition of the Akt1-mTORC1 Axis Alters Venous Remodeling to Improve Arteriovenous Fistula Patency

Arteriovenous fistulae (AVF) are the most common access created for hemodialysis, but up to 60% do not sustain dialysis within a year, suggesting a need to improve AVF maturation and patency. In a mouse AVF model, Akt1 regulates fistula wall thickness and diameter. We hypothesized that inhibition of the Akt1-mTORC1 axis alters venous remodeling to improve AVF patency. Daily intraperitoneal injections of rapamycin reduced AVF wall thickness with no change in diameter. Rapamycin decreased smooth muscle cell (SMC) and macrophage proliferation; rapamycin also reduced both M1 and M2 type macrophages. AVF in mice treated with rapamycin had reduced Akt1 and mTORC1 but not mTORC2 phosphorylation. Depletion of macrophages with clodronate-containing liposomes was also associated with reduced AVF wall thickness and both M1- and M2-type macrophages; however, AVF patency was reduced. Rapamycin was associated with improved long-term patency, enhanced early AVF remodeling and sustained reduction of SMC proliferation. These results suggest that rapamycin improves AVF patency by reducing early inflammation and wall thickening while attenuating the Akt1-mTORC1 signaling pathway in SMC and macrophages. Macrophages are associated with AVF wall thickening and M2-type macrophages may play a mechanistic role in AVF maturation. Rapamycin is a potential translational strategy to improve AVF patency.

Baseline characteristics of arm vessels by preoperative duplex ultrasonography in Korean patients for hemodialysis vascular access

BACKGROUND

Preoperative mapping with duplex ultrasonography is crucial for successful vascular access creation for hemodialysis. The aims of this study are to assess the baseline characteristics of arm vessels by preoperative duplex ultrasonography in Korean patients, to find out a preoperative duplex ultrasonography parameter precluding distal arteriovenous fistula creation, to assess the maturation failure rate of arteriovenous fistulas, and to identify associated risk factors.

METHODS

Preoperative duplex ultrasonography mapping for vascular access creation was done in all patients with end-stage renal diseases during the year 2015. The baseline data of duplex ultrasonography were retrospectively analyzed with follow-up clinical data.

RESULTS

A total of 299 end-stage renal disease patients (mean age = 62 years, 62% male) were included. On preoperative duplex ultrasonography, mean diameters of radial artery and cephalic vein at wrist were 2.03 and 2.40 mm in the non-dominant arm and 2.10 and 2.26 mm in the dominant arm, respectively. The most common reason for precluding radial-cephalic arteriovenous fistula at wrist was small-sized cephalic vein. Multivariate logistic regression analysis revealed that the risk factors for inadequate vessels were warfarin treatment, old age (⩾75 years), and peripheral arterial occlusive disease. The rate of arteriovenous fistula maturation failure was 21% and vein diameter <2.5 mm was the only risk factor for arteriovenous fistula maturation failure by multivariate logistic regression analysis.

CONCLUSION

Preoperative duplex ultrasonography evaluation is important to find out inadequate vessels for native arteriovenous fistula and to determine the location of vascular access.

Influence of intraoperative findings on immediate flow through radial-cephalic arteriovenous wrist fistulas for hemodialysis access

Background

Adequate flow through a newly created arteriovenous fistula depends on multiple characteristics of the vessels and patient comorbidities. Several studies have related preoperative findings to failure, but few have analyzed the influence of intraoperative findings.

Objectives

To evaluate the predictive value of intraoperative findings on the immediate outcome of radial-cephalic arteriovenous wrist fistulas (RCAVF) by collecting data that are easily measured intraoperatively.

Methods

We designed a cross-sectional study, in which a single surgeon performed 101 RCAVF in 100 patients at a single center. We analyzed the immediate postoperative flow, assessed by thrill intensity immediately after fistula creation, against patient demographics and intraoperative data. The following variables were analyzed: age, sex, comorbidities, length of vein visible at preoperative examination, macroscopic arterial calcification, maximum vein diameter, and length of stenosis-free vein, measured by cannulation with a urethral catheter during the procedure. The chi-square test was used both to eliminate possible bias introduced by side of venous access (left or right), and to determine predictive values of immediate thrill.

Results

Side of access was not associated with any significant differences in variables. Absence of macroscopic arterial calcification, successful venous catheterization using a 6 French catheter or larger, and ability to advance it more than 10 centimeters along the lumen of the proximal vein were correlated with adequate immediate postoperative thrill (p = 0.004, p < 0.001, and p = 0.005, respectively).

Conclusions

In this series of 101 RCAVF, both the diameter of the catheter and its progress through the proximal vein and also absence of arterial calcification had positive predictive value for achieving adequate immediate thrill after vascular access construction.

Association of Preoperative Mean Arterial Pressure With the Primary Failure of Brescia-Cimino Arteriovenous Fistula Within the First 7 Days Following Surgery in Hemodialysis Patients

This retrospective study included 1051 patients with end-stage kidney disease and Brescia-Cimino arteriovenous fistula (AVF) (excluding pre-dialysis patients), and aimed to investigate the role of blood pressure in AVF primary failure. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured twice daily for 3 days before surgery. The success (N = 1010) and failure (N = 41) groups were based on AVF primary failure within 7 days of surgery. The cephalic vein was larger and the preoperative mean arterial pressure (MAP) was higher in the success group compared with the failure group (P < 0.05). Cephalic vein diameter and preoperative MAP independently predicted AVF primary failure within 7 days after surgery. In conclusion, small cephalic vein diameter and low preoperative MAP were associated with AVF primary failure within 7 days of surgery.

End-To-Side versus Side-To-Side Anastomosis in Upper Limb Arteriovenous Fistula for Dialysis Access: A Systematic Review and a Meta-Analysis

BACKGROUND

An arteriovenous fistula (AVF) is the best modality for hemodialysis access. The end-to-side (ETS) technique has been suggested in the literature to produce superior results to the side-to-side (STS) approach; however, in the absence of a systematic review, this practice remains debatable.

METHODS

Online search for randomized controlled trials and observational studies that compared the ETS versus the STS anastomosis techniques in creating an upper limb AVF. Aims were to systematically assess the difference between both procedures in terms of access maturation, patency, and postoperative complications.

RESULTS

Seven studies were included with 463 patients in the ETS group and 523 in the STS group. The difference between the 2 techniques was not significant in relation to patency rates at 3, 6, 12, and 24 months (P values: 0.28, 0.82, 0.54, and 0.21, respectively). There were fewer cases of postoperative hematoma in the ETS group; however, the difference was not significant (P = 0.09). Arterial steal syndrome was found to be significantly associated with the STS configuration in pooled analysis (pooled risk ratio = 0.11 [0.01-0.88], 95% CI, P = 0.04).

CONCLUSIONS

Similar maturation rates between ETS and STS fistula configuration, however, arterial steal syndrome was significantly associated with the STS technique. ETS will likely remain as the preferred AVF configuration as it is less technically demanding.

Arteriovenous fistula in dialysis patients: Factors implicated in early and late AVF maturation failure

Increasing numbers of patients are being diagnosed with end-stage renal disease (ESRD), and the demand for on haemodialysis (HD) is rising. Arteriovenous fistulae (AVFs) remain the best conduit for adequate HD, with fewer complications associated with long-term use compared to bypass grafts and central venous catheters. However, it is known that many newly formed fistulae do not mature to provide useful HD access. The paper provides a narrative overview of factors influencing the process of AVF maturation failure.