Nitinol stent-assisted maturation of the dysfunctional cannulation zone in the immature arteriovenous fistula

Interwoven nitinol stent-assisted arteriovenous fistula maturation: 2 year-outcomes of a single center experience

OBJECTIVES

The aim of this study was to report 2-year outcomes of interwoven nitinol (SuperaTM) stent-assisted arteriovenous fistula (AVF) maturation in patients who presented with non-matured AVF.

METHODS

We reviewed the clinical data of 20 patients who presented with non-matured AVF (19 patients with brachiocephalic AVF and 1 patient with radiocephalic AVF) and underwent balloon angioplasty followed by SuperaTM stenting in the cephalic vein for long-term hemodialysis between January 2017 and January 2022. The outcomes were evaluated in these patients in terms of technical success, post-intervention complications, reintervention, and cumulative patency (6 months, 1 year, and 2 years).

RESULTS

The study included 20 patients who presented with non-matured AVF. The mean age of the patients was 65 years (range, 40-85). The SuperaTM stents of size 6.5 mm were used in 15 patients (75%), and those of 7.5 mm and 5.5 mm were used in 4 (20%) and 1 (5%) patient, respectively. The average stent length was 99.5 mm (range, 80-120). Technical success was achieved in all patients. Early use within 1 week by needling at the SuperaTM stent segment (cannulation zone) was successful in all patients without any complications. The mean follow-up time was 24.5 months. During the follow-up period, reinterventions to maintain the function of AVF were performed in 8 patients (40%) (7 patients with juxta-anastomotic stenosis, 1 patient with in-stent restenosis). The reintervention rate was 0.39 procedures per patient per year. The primary patency at 6 months, 1 year, and 2 years were 85.5%, 62.6%, and 54.2%, respectively. The assisted primary patency at 6 months, 1 year, and 2 years were 95%, 84.5%, and 78.8%, respectively.

CONCLUSIONS

The use of the SuperaTM stent to improve the AVF maturation rate was associated with acceptable outcomes at 2 years. Its benefit over other strategies was the early use of the access for hemodialysis.

Long-term Results of Interwoven Nitinol Stents to Treat the Radiocephalic Anastomotic Arteriovenous Fistula Stenosis

Introduction:

Juxta-anastomotic stenosis (JXAS) is a common problem afflicting the arteriovenous fistula (AVF). This study aimed to evaluate the safety and long-term efficacy of an interwoven nitinol stent (Supera, Abbott Vascular, Santa Clara, CA, USA) in the treatment of radiocephalic AVF JXAS.

Methods:

A single-center, retrospective, observational study was conducted of patients with failing AVF due to JXAS treated with an interwoven nitinol stent. End points included JXAS target lesion primary patency, access circuit primary patency, assisted access circuit primary patency, and endovascular intervention rate (EIR).

Results:

Sixty patients were treated with a Supera stent in the JXAS between February 2014 and March 2020. One patient was excluded (AVF used for illicit drug use), leaving 59 patients (67.8% male, mean age 66.9 ± 11.4 years [range: 40–84]) with typical medical comorbidities. Overall, 45.8% of patients had previous AVF intervention. The stent was inserted with a 100% technical success rate with a mean follow-up of 729.6 ± 456.0 days (range: 5–2182 days). Juxta-anastomotic stenosis target lesion primary patency was 68.2 ± 6.6%, 53.3 ± 7.5%, and 46.2 ± 8.1% at 12, 24, and 36 months, respectively. The EIR was .64 (0–3.29) procedures/patient/year, after which the assisted access circuit primary patency rate was 94.3 ± 3.2% at 12, 24, and 36 month time points. Three thrombosed circuits occurred which were all successfully salvaged with no difference in patency by indication for procedure and no AVFs lost/abandoned out to 3 years. Avoidance of stent post-dilatation and the presence of stent mal-apposition were associated with improved primary patency, and reduced EIR, which may suggest an importance in vessel preparation prior to stent implantation.

Conclusion:

Interwoven nitinol stent treatment of the failing AVF with JXAS results in promising 3 year JXAS patency, with a low rate of endovascular re-intervention for those circuits developing restenosis. All AVFs were maintained over 3 years, demonstrating this treatment allows for long-term radiocephalic AVF vascular access.

Arteriovenous Fistula Formation with Adjuvant Endovascular Maturation

INTRODUCTION

The clinical utility of the native arteriovenous fistula (AVF) is limited by a prolonged time to maturation, low overall maturation rate, and subsequent abandonment. Endovascular intervention is increasingly accepted as first line therapy to treat AVF stenosis. The objective of this study was to evaluate AVF formation outcomes when early endovascular intervention was selectively performed to bring about timely AVF maturation.

METHODS

A retrospective study (February 2014- February 2020) was performed on 82 AVF consecutive patients (mean age 62.5±13.5 (17-83); 58 male (70.7%)) with end-stage renal failure who had Vascular Access (VA) construction at a single institution. Four year AVF patency, vascular diameters, haemodialysis parameters, re-intervention rate, and mortality were analysed.

RESULTS

Radiocephalic AVF was the most common fistula constructed (71 patients; 88.6%). Post formation evaluation (46.2+/-56.0 days (5-343)) revealed 33 (40.2%) immature AVFs. Subsequently, 19 patients underwent endovascular procedures consisting of angioplasty/stenting of the juxta-anastomosis, cannulation and/or outflow segments to bring about timely maturation of the AVF. Hence 93.9% of AVFs had reached functional patency (maturation) by 6 months post formation, with a mean time to maturation of 67.8 +/- 65.9 (5-320) days. After reaching maturation, Primary Access Functional Patency was 82 +/- 4.3 % at 6 months, 58+/- 5.5% at 12 months and 34 +/- 6.8% at 48 months. Primary Assisted Access Functional Patency was 95 +/- 2.4% at 6 months, 90 +/-3.3 % at 12 months and 83 % +/- 4.7 % at 48 months. 121 endovascular interventions were performed to maintain patency, equating to an endovascular reintervention rate of .37 procedures/patient year. Mean arterial, venous and brachial flow rates did not change significantly after maturation with a mean fistula (primary assisted functional patency) survival time of 5.9 +/- 0.26 (5.33- 6.36) years from maturation. Only 12 thromboses occurred after the first post formation follow up review, which were all salvaged using endovascular techniques leading to 100% Total secondary functional patency at 4 years. 5 year estimated all-cause mortality was 45.6 +/-12.7%.

CONCLUSION

Arteriovenous fistula maturation rate and time to maturation can be improved when early endovascular intervention is selectively performed post formation. This allows for near universal maturation where, once matured, the use of ongoing endovascular re-intervention allows for a low re-intervention rate and long term patency providing for reliable long term renal vascular access.