Vas Q – An Innovative External Support Device Improves Functionality of Arteriovenous Fistulas: Pilot Study Results

Abstract

Introduction: Patients in need of dialysis treatment depend on vascular access. Arteriovenous fistula (AVF), is the gold standard for access, however, while superior to other access methods, it is associated with high early failure rates which necessitates frequent interventions intended to maintain AVF functionality. Large series have shown that although native AVFs have a low rate of complications and improved longevity of use when functional, they suffer from relatively poor early patency rates with more than half being unsuitable for dialysis use by one year. The precise reasons for these early failures remain to be fully elucidated, although it is clear that inability to increase inflow often results from perianastomotic stenosis and venous neointimal hyperplasia. Turbulent flow has been identified as a driver for neointimal hyperplasia and as a cause of stenosis. VasQ, is a new external support device, implanted over the arteriovenous fistula. Targeting the juxta-anastomotic area, the VasQ adjusts anastomosis geometry, regulates flow patterns, and supports the venous wall thereby facilitating fistula maturation and longevity. We present results of a Pilot prospective study, enrolling 20 patients with a follow up period of 6 months. Study objectives included assessment of the implantation procedure and fistula maturation and patency rates. Methods: The trial was conducted as a prospective, single-arm study design so as to determine device safety and initial efficacy. The study was conducted at St. George's Vascular Institute, St. George's University Hospitals Foundation Trust, London, UK. 20 patients were enrolled. Patients were eligible if they were referred for creation of a new brachiocephalic fistula with non-stenotic vein and artery diameter ≥3 mm, and free of significant co-morbidities which can prevent study completion. The VasQ device was threaded proximally on the vein prior to anastomosis suturing and subsequently lowered distally onto the anastomosis after completion. Patients were followed for 6 months post-procedure, with Doppler ultrasound examinations performed at 1, 3, and 6 months. Fistula was considered matured if Doppler measurements showed venous outflow ≥500 ml/min and vein diameter ≥5 mm. Results: Between June 2014 and January 2015, two surgeons implanted VasQ in 20 patients. Device implantation easily integrated with the routine fistula procedure. All patients were free from any device related complications. One patient died following a myocardial infarction. At 1, and 3 months fistula maturation rate were 75% and 79%, Primary patency rates at 1, 3 and 6 months were 95%, 79% and 79%. mean outflow rates at 1, 3 and 6 months were 1130 ml/min and 1426 ml/min, and 1304 ml/min. mean vein diameters were 6.6 mm, 8.4 mm and 10 mm at 1,3 and 6 months respectively. Conclusion: The VasQ used in autogenous brachiocephalic AVFs is associated with higher short- and medium-term maturation and patency rates for externally supported AVFs than previously reported. Larger, longer-term prospective studies are required in order to confirm these promising results. VasQ may obviate some of the problems implicated in early AVF failure providing a fixed outflow diameter and shielding the anastomosis from adhesions and inflammatory reaction. Disclosure of Interest: None Declared.