Endovascular Proximal Forearm Arteriovenous Fistula for Hemodialysis Access: Results of the Prospective, Multicenter Novel Endovascular Access Trial (NEAT)

BACKGROUND

Hemodialysis arteriovenous fistulas (AVFs) are suboptimally used primarily due to problems with maturation, early thrombosis, and patient nonacceptance. An endovascular approach to fistula creation without open surgery offers another hemodialysis vascular access option.

STUDY DESIGN

Prospective, single-arm, multicenter study (Novel Endovascular Access Trial [NEAT]).

SETTINGS & PARTICIPANTS

Consecutive adult non-dialysis-dependent and dialysis-dependent patients referred for vascular access creation at 9 centers in Canada, Australia, and New Zealand.

INTERVENTION

Using catheter-based endovascular technology and radiofrequency energy, an anastomosis was created between target vessels, resulting in an endovascular AVF (endoAVF).

OUTCOMES

Safety, efficacy, functional usability, and patency end points.

MEASUREMENTS

Safety as percentage of device-related serious adverse events; efficacy as percentage of endoAVFs physiologically suitable (brachial artery flow ≥ 500mL/min, vein diameter ≥ 4mm) for dialysis within 3 months; functional usability of endoAVFs to provide prescribed dialysis via 2-needle cannulation; primary and cumulative endoAVF patencies per standardized definitions.

RESULTS

80 patients were enrolled (20 roll-in and 60 participants in the full analysis set; the latter are reported). EndoAVFs were created in 98% of participants; 8% had a serious procedure-related adverse event (2% device related). 87% were physiologically suitable for dialysis (eg, mean brachial artery flow, 918mL/min; endoAVF vein diameter, 5.2mm [cephalic vein]). EndoAVF functional usability was 64% in participants who received dialysis. 12-month primary and cumulative patencies were 69% and 84%, respectively.

LIMITATIONS

Due to the unique anatomy and vessels used to create endoAVFs, this was a single-arm study without a surgical comparator.

CONCLUSIONS

An endoAVF can be reliably created using a radiofrequency magnetic catheter-based system, without open surgery and with minimal complications. The endoAVF can be successfully used for hemodialysis and demonstrated high 12-month cumulative patencies. It may be a viable alternative option for achieving AVFs for hemodialysis patients in need of vascular access.

Transcriptomics of Human Arteriovenous Fistula Failure: Genes Associated With Nonmaturation

RATIONALE & OBJECTIVE

Improving arteriovenous fistula (AVF) outcomes requires better understanding of the biology underlying maturation or failure. Our current knowledge of maturation relies on extrapolation from other vascular pathologies, which does not incorporate unique aspects of AVF remodeling. This study compares the RNA expression of pre-access (native) veins and AVFs with distinct maturation outcomes.

STUDY DESIGN

Case-control study.

SETTING & PARTICIPANTS

64 patients undergoing 2-stage AVF surgeries at a single center. 19 native veins and 19 AVF samples were analyzed using RNA sequencing (RNA-seq). 58 native veins were studied using real-time polymerase chain reaction; 45, using immunohistochemistry; and 19, using Western blot analysis.

PREDICTOR

RNA expression in native veins and AVFs.

OUTCOME

Anatomic nonmaturation, defined as an AVF that never achieved an internal diameter ≥ 6mm.

ANALYTICAL APPROACH

Pre-access native veins and AVF samples were obtained from patients undergoing 2-stage AVF creation. Veins that subsequently matured or failed after access creation were analyzed using RNA-seq to search for genes associated with maturation failure. Genes associated with nonmaturation were confirmed using real-time polymerase chain reaction, immunohistochemistry, and Western blot analysis. In addition, the association between pre-access gene expression and postoperative morphology was evaluated. RNA-seq was also performed on AVFs to search for transcriptional differences between AVFs that matured and those that failed at the time of transposition.

RESULTS

Pro-inflammatory genes (CSF3R, FPR1, S100A8, S100A9, and VNN2) were upregulated in pre-access veins that failed (false discovery rate < 0.05), and their expression colocalized to smooth muscle cells. Expression of S100A8 and S100A9 correlated with postoperative intimal hyperplasia and the product of medial fibrosis and intimal hyperplasia (r=0.32-0.38; P < 0.05). AVFs that matured or failed were transcriptionally similar at the time of transposition.

LIMITATIONS

Small sample size, analysis of only upper-arm veins and transposed fistulas.

CONCLUSIONS

Increased expression of proinflammatory genes in pre-access veins appears to be associated with greater risk for AVF nonmaturation.

Efficacy of ultrasonography and color-Doppler for early prediction of hemodialysis arteriovenous fistula unassisted maturation

BACKGROUND

Arteriovenous fistula (AVF) failure is a prevalent concern for patients with end-stage kidney disease on hemodialysis. Recognizing the efficacy of ultrasound Doppler in post-operative AVF evaluation, this study sought to discern the predictive capabilities of various ultrasonographic and color-Doppler metrics for early AVF outcomes.

METHODS

This single-center, prospective cohort study spanned 1 year and, post ethical clearance, included all patients who underwent native AVF creation surgery and were subsequently referred for standard post-operative ultrasound Doppler assessment. Parameters such as fistula size, cephalic vein area and diameter, and AVF flow velocity and rates were assessed on post-operative day 2, week 2, and week 6. These initial findings were juxtaposed with later outcomes to determine unassisted AVF results.

RESULTS

Of the initial cohort of 40 patients, 75% encountered AVF failure, whereas 25% realized successful unassisted AVF maturation. A notable observation was the significant variance in AVF flow rates as early as post-operative day 2. A threshold of >246 ml/min was indicative of successful unassisted AVF maturation, leading to a sensitivity of 80% and a specificity of 70%. Although the cephalic vein diameter on post-operative day 2 lacked a robust association with AVF outcomes, a cut-off of >3.4 mm, when combined with flow rate testing, augmented the cumulative sensitivity to 92%.

CONCLUSION

Ultrasound Doppler stands out as a valuable quantitative imaging modality, adept at prognosticating AVF outcomes from as early as post-operative day 2. In particular, a flow rate exceeding 246 ml/min and a cephalic vein diameter surpassing 3.4 mm are salient indicators for the early prediction of successful AVF outcomes.

Pathohistomorphometric and Immuno-Histologic Changes in Early Arteriovenous Fistula Failure in Patients with Chronic Kidney Disease

BACKGROUND

Hemodialysis is a prevalent treatment for the end-stage chronic kidney disease (CKD) worldwide. The primary arteriovenous fistula (AVF), widely considered the optimal hemodialysis access method, fails to mature in up to two-thirds of the cases. The etiology of the early AVF failure, defined as thrombosis or inability to use within three months post-creation remains less understood, and is influenced by various factors including patient demographics, surgical techniques, and genetic predispositions. Neointimal hyperplasia is a primary histological finding in stenotic lesions leading to the AVF failure. However, there are insufficient data on the cellular phenotypes and the impact of the preexisting CKD-related factors. This study aims to investigate the histological, morphometric, and immunohistochemical alterations in the fistula vein, pre-, peri-, and post-early failure.

MATERIALS AND METHODS

Eighty-nine stage 4-5 CKD patients underwent standard preoperative assessment, including the Doppler ultrasound, before a typical radio-cephalic AVF creation. Post-failure, a new AVF was created proximally. The vein specimens were collected during the surgery, processed, and analyzed for morphometric analyses and various cellular markers, including Vimentin, TGF, and Ki 67.

RESULTS

The study enrolled 89 CKD patients, analyzing various aspects of their condition and AVF failures. The histomorphometric analysis revealed substantial venous luminal stenosis and varied endothelial changes. The immunohistologic analysis showed differential marker expressions pre- and post-AVF creation.

CONCLUSION

This study highlights the complexity of the early AVF failures in CKD patients. The medial hypertrophy emerged as a significant preexisting lesion, while the postoperative analyses indicated a shift towards neointimal hyperplasia. The research underscores the nuanced interplay of vascular remodeling, endothelial damage, and cellular proliferation in the AVF outcomes.