A heparin-coated endovascular prosthesis has received approval from the US Food and Drug Administration (FDA) for treatment of stenosis or thrombotic occlusions at the venous anastomosis of synthetic arteriovenous (AV) access grafts in hemodialysis patients. 

The Viabahn endoprosthesis (WL Gore and Associates, Flagstaff, AZ), which has long been approved for treatment of iliac and SFA lesions, consists of a self-expanding nitinol stent that supports an inner polytetrafluoroethylene lining and is coated with a bioactive heparin surface to provide sustained resistance to thrombosis.

According to a Gore press release, in the randomized REVISE study, the Viabahn device demonstrated superiority to balloon angioplasty with regard to the primary outcome of target lesion primary patency (P = 0.008).

In the press statement, Thomas Vesely, MD, of the Vascular Access Center of Frontenac Grove (Frontenac, MO), expressed confidence in the Viabahn endoprosthesis. “The device can be precisely deployed and its flexibility allows placement across the elbow and other challenging venous anastomotic locations,” he said. “I can rapidly and accurately deploy [the stent graft] in an emergent situation, and it will provide effective treatment for stenosis at the venous anastomosis of AV access grafts.”

In a telephone interview with TCTMD, Dheeraj Rajan, MD, of the University of Toronto (Toronto, Canada), said the availability of the Viabahn device is “a positive step forward” in the management of failing AV access grafts.

Prior studies, such as the randomized RENOVA trial, have shown improved primary patency compared with angioplasty for a similar stent graft (Flair, Bard Peripheral Vascular, Tempe, AZ), he noted, and these results appear to be replicated with the Viabahn device. However, he cautioned, because the REVISE study has not been published, the duration of the benefit and other details remain unknown.

Conformability a Key Advantage

Viabahn’s heparin coating is an attractive feature, Dr. Rajan commented, but whether it actually reduces thrombosis as intended remains unclear. Currently, he added, there is no evidence to support the use of systemic anticoagulation after stent graft placement.

Dr. Rajan identified Viabahn’s conformability as its most obvious advantage. “This stent graft follows the anatomy much better than the Flair device,” for example, and that makes it employable in a wider dialysis population, he observed.

Overall, however, stent grafts should not be used in AV grafts that are known or suspected to be infected, Dr. Rajan said. And even in healthy grafts, stent grafts’ potential susceptibility to infection is an ongoing concern. He added, another relative contraindication to stent graft use is a scenario in which implantation would entail sacrificing normal vein segments that could later have been harvested for creation of autogenous dialysis access, he added.

Despite the availability of several stent grafts, many physicians in the field still prefer angioplasty, Dr. Rajan reported, because even though stent devices are more effective in the short run in terms of opening AV stenosis, “the overall cumulative circuit [graft] patency doesn’t seem to be any different between a stent graft and angioplasty.” Until data show that long-term patency offsets the added cost of stent grafts, their use is unlikely to grow, he predicted.

Moreover, although results with the current stent graft technology are encouraging, there is much room for improvement, Dr. Rajan noted, especially since the approved devices are carryovers from PAD indications and were not developed specifically for dialysis access sites.

Nonetheless, the approval of Viabahn “adds another tool within a rapidly growing space” where many previous technologies have failed, he concluded, adding that he looks forward to scrutinizing the REVISE data to assess the device’s clinical efficacy more fully.

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