Since the adoption of the “fistula first” initiative, greater attention has been given to creation and maintenance of arteriovenous vascular accesses, especially arteriovenous fistulae. These last few years, many new concepts and fascinating technologies have emerged in this field, write Raphaël Coscas and Eric Chemla.
First evolutions concern arteriovenous fistula creation. As arteriovenous fistulae can sometimes be the unintentional result of arterial or venous punctures, why should we continue to surgically create arteriovenous fistulae? Recently, percutaneous creation has been rendered possible by new specific devices. The ingenious system developed by TVA Medical uses radiofrequency cutting current to create an arteriovenous fistula between the proximal ulnar artery and the ulnar vein at the level of its connection to the median antecubital, cephalic, and basilic veins by deep perforating branches. Of note, coil embolisation of the brachial vein is necessary after arteriovenous fistula creation. Its feasibility has been demonstrated and trials are ongoing.
Since an important part of arteriovenous fistula stenosis occurs in the anastomotic area, novel devices have been studied to improve flow at the anastomosis site. The Optiflow (Bio-connect Systems) device is an implantable anastomotic connector used to standardise the creation of an arteriovenous fistula. It serves as a surgical template whereby the geometry and flow path of the anastomosis are predetermined. Its successful use has now been reported in several papers. The VasQ (Laminate Medical Technologies) is an external support device designed to avoid turbulent flow and reduce neointimal hyperplasia at the anastomotic site of arteriovenous fistulae. It is a nitinol implant, externally surrounding and supporting the vein and “hugging” the artery near the junction site without being in contact with the blood flow. A pilot study conducted in St George’s Vascular Institute (St George’s University Hospitals Foundation Trust, London, UK) in autogenous brachiocephalic arteriovenous fistulae demonstrated satisfactory unassisted maturation rates and high primary patency rates at six-month follow-up.
Adjuncts to arteriovenous fistula creation are also being investigated. A recent large multicentre randomised study conducted in the USA demonstrated promising results with intraoperative adjuncts of human type I pancreatic elastase on the anastomosis site regarding unassisted maturation rates. However, unassisted primary patency at 12 months did not differ from the placebo group. The Coll-R eluting gauze is a sirolimus-eluting collagen implant, which is positioned around the juxta-anastomotic segment following arteriovenous fistula creation to suppress neointimal hyperplasia. Results of pilot studies are promising but larger studies are waited.
Apart from arteriovenous fistula creation, techniques of fistula maintenance evolve. Drug-coated balloons clearly represent the most exciting technologies in this field. Their results in the superficial femoral artery have been reported to be excellent in several large prospective randomised trials. As arteriovenous fistula stenoses are generally due to intense neointimal hyperplasia, local delivery of paclitaxel should logically improve the results of arteriovenous fistula angioplasty and postpone reintervention.
Surprisingly, data to answer this question are currently lacking. In vitro results of arteriovenous grafts impregnated with paclitaxel decreased neointimal hyperplasia at anastomosis sites. A prospective randomised study demonstrated impressive improvement of arteriovenous fistula angioplasty results when drug-coated balloons were compared to placebo (Kitrou et al, J Vasc Interv Radiol 2015). However, several criticisms emerged due to the small size of the population (n=40), the absence of pre-dilatation before drug-coated balloon angioplasty and inclusion of arteriovenous fistula and arteriovenous grafts altogether. Other limited cohort studies showed promising results of drug-coated balloons and juxta-anastomotic and central vein stenoses.
Clearly, large randomised studies are needed to assess the efficiency of drug-coated balloons in arteriovenous fistulae. Several studies are already ongoing in North America and Europe. It will be critical to look at their designs, asking several questions: (1) Will they distinguish arteriovenous fistulae/grafts and stenosis/restenosis? (2) Will wrist and elbow fistulae be melted together? (3) Will a blind corelab evaluate for stenosis degree and fistula flow? (4) Will indications for interventions and reinterventions be strictly defined?
In France, we will conduct the multicentre double blind prospective trial ABISS (Angioplastie au ballon imprégné de paclitaxel versus angioplastie standard pour le traitement des sténoses sur fistule artério-veineuse). The study will start in mid-2016 with the goal to enrol 150 patients with stenosis on native arteriovenous fistulae and compare the results of drug-coated balloons and placebo balloons at 12 months. Results are hoped for 2018.
In conclusion, new technologies that are currently developed and evaluated will undoubtedly improve arteriovenous fistula results. The future of arteriovenous fistulae is bright with a tremendous hope for end-stage chronic kidney disease patients. And it is now.
Raphaël Coscas is a vascular surgeon, Department of Vascular Surgery, Ambroise Paré University Hospital, Assistance Publique – Hôpitaux de Paris (AP-HP), Boulogne-Billancourt, France, and Eric S Chemla is a consultant vascular surgeon, reader in Vascular Surgery at St George’s Vascular Institute, St George’s University Hospitals Foundation Trust, London, UK