Percutaneous Transanastomotic Stent Graft Deployment to Salvage Dysfunctional Native Forearm Radiocephalic Fistulae: Feasibility and Primary Patency at 12 Months

Prospective, randomized, multicenter clinical study comparing a self-expanding covered stent to percutaneous transluminal angioplasty for treatment of upper extremity hemodialysis arteriovenous fistula stenosis

Use of a covered stent after percutaneous transluminal angioplasty (PTA) was compared to PTA alone for treatment of upper extremity hemodialysis patients with arteriovenous fistula (AVF) stenoses. Patients with AVF stenosis of 50% or more and evidence of AVF dysfunction underwent treatment with PTA followed by randomization of 142 patients to include a covered stent or 138 patients with PTA alone. Primary outcomes were 30-day safety, powered for noninferiority, and six-month target lesion primary patency (TLPP), powered to test whether TLPP after covered-stent placement was superior to PTA alone. Twelve-month TLPP and six-month access circuit primary patency (ACPP) were also hypothesis tested while additional clinical outcomes were observed through two years. Safety was significantly non-inferior while six- and 12-month TLPP were each superior for the covered stent group compared to PTA alone (six months: 78.7% versus 55.8%; 12 months: 47.9% versus 21.2%, respectively). ACPP was not statistically different between groups at six-months. Observed differences at 24 months favored the covered-stent group: 28.4% better TLPP, fewer target-lesion reinterventions (1.6 ± 1.6 versus 2.8 ± 2.0), and a longer mean time between target-lesion reinterventions (380.4 ± 249.5 versus 217.6 ± 158.4 days). Thus, our multicenter, prospective, randomized study of a covered stent used to treat AVF stenosis demonstrated noninferior safety with better TLPP and fewer target-lesion reinterventions than PTA alone through 24 months.

The role of stents in hemodialysis vascular access

Vascular access is the Achilles' heel of dialysis therapy among patient with end stage kidney disease. The development of neointimal hyperplasia and subsequent stenosis is common in vascular access and is associated with significant morbidity. Percutaneous transluminal angioplasty using balloon inflation was the standard therapy of these lesions. However, the balloon-based approaches were associated with poor vascular access patency rate necessitating new inventions. It is within this context that different types of stents were developed in order to improve the overall dialysis vascular access functionality. In this article, we review the available literature regarding the use of stents in treating dialysis vascular access stenotic lesions. Further, we review the major clinical trials of stent use in different anatomic locations and in different clinical scenarios.

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.

Advances in Endovascular Salvage

Endovascular salvage plays an important role in dialysis access care. Angioplasty using standard high- and ultrahigh-pressure balloon is the mainstay of therapy, while the use of cutting balloons and balloons designed to deliver pharmacologically active agents to the site of recurrent stenosis is demonstrating improved performance for specific targets that have to be further defined. Stents and stent grafts are additional tools for use at access segments predisposed for inward remodeling such as the cephalic arch or basilic swing point. The juxta-anastomotic segment has particular relevance in maturation of autogenous accesses as well as maintenance of access flow volume. Depending on the location of the access in the forearm or upper arm, and which artery is feeding into the access vein, any type of balloon angioplasty and stent or stent graft placement may be used to establish and maintain patency. Successful management of dialysis access options relies on preservation of venous real estate during the chronic kidney disease phase of kidney disease as well as on knowledgeable evaluation of arm veins and the access by physical examination, bed side ultrasound, and angiographic studies.

Interwoven Nitinol Stents to Treat Radiocephalic Anastomotic Arteriovenous Fistula Stenosis

Purpose: To determine the clinical outcomes in hemodialysis patients after implantation of a Supera stent to treat juxta-anastomotic stenosis in radiocephalic arteriovenous fistulas (AVF). Materials and Methods: A single-center retrospective study was conducted of 42 consecutive patients (mean age 66.7 years, range 40–84; 26 men) who had a failing AVF due to juxta-anastomotic stenosis treated with the interwoven Supera stent between February 2014 and February 2018. A third of the patients had previous juxta-anastomotic intervention (either balloon angioplasty or open surgical revision). Results: The stent was inserted successfully in all patients. Overall mean follow-up was 12.2±8.2 months (range 3.8–38.3). Juxta-anastomotic segment primary patency estimates at 6 and 12 months were 92.5% and 59.8%, respectively, with assisted primary patency rates of 97.5% and 92.9%. Reintervention (elective drug-coated balloon angioplasty) occurred at a rate of 0.31 procedures/year. Two AVFs thrombosed during the 1-year follow-up and were revascularized using balloon angioplasty. Ultrasound measurements of brachial artery flow rates increased significantly from 543.5±96.72 mL/min (range 430–644) before intervention to 919.2±355.9 mL/min (range 200–1600) after intervention (p=0.047). Arterial pressures on hemodialysis improved from −142.3±24.9 mm Hg (range −100 to −180) to −123.4±21.9 mm Hg (range −100 to −184; p=0.051). No AVFs were lost or abandoned during the follow-up period. Conclusion: The interwoven Supera stent is a promising treatment for failing AVFs with juxta-anastomotic stenosis. Encouraging 1-year primary and assisted primary patency was demonstrated, with a low reintervention rate. This treatment facilitates long-term maintenance of AVF vascular accesses.