Problems with Using a Covered Stent for Pseudoaneurysms of Autogenous Fistula
Stephen L Hill, Jeffrey D Shay
Carilion Clinic, Roanoke, VA
We have recently treated two patients with complications associated with the use of a covered stent (Bard Fluency) for salvage of an autogenous fistula. Both patients were elderly white females with end stage renal disease requiring dialysis. They had successfully received brachial vein transpositions with elevation and had been on dialysis for two to six months. In both these individuals they had developed small pseudoaneurysms due to repetitive sticks in the same location. They presented with persistent bleeding which was intermittent from the pseudoaneurysms. Interventional techniques were used to place a covered stent in one, and two overlapping stents were placed in the other patient. This treatment was immediately successful. Both patients continued dialysis without incident. Over the course of several months, however it was noticed in both patients that a small scab appeared at the site of the pseudoaneurysm. In both patients these small scabs progressed to complete erosion of the covered metal stent through the skin. There was no bleeding associated with the erosion, just the appearance of the metal stents over the covered prosthetic. A surgical correction was then performed with a wide dissection and undermining the surrounding tissue to have a two layer closure over the exposed segment of the fistula/stent. Dialysis continued uninterrupted. It will require several months to determine if this approach is successful for this problem.
Interventional techniques with covered stents have become a mainstay of treatment for isolated arterial bleeding and have been quite successful. It would, therefore, only seem logical that this technology could be applied to arterial bleeding from an autogenous dialysis fistula. Stent placement has been used extensively for areas of stenosis in arteriovenous fistulae and grafts, however the areas are usually deep in the tissues and not in superficial areas. The problems with use of covered stents in these types of situation are twofold. One, when the bleeding has occurred secondary to needle sticks, with the development of a pseudoaneurysm, the area, by definition, is very superficial with limited overlying tissue to help with healing. The other issue which is probably more important is that the anatomy and histology of a vein, even an arterialized vein, is fundamentally different from an artery. They both have a tunica intima, a tunica media and a tunica adventitia but in the artery the walls are thicker and the tunica media is much larger. The thicker walls and tunica media of the arteries allow ingrowth and healing. The vein wall is very thin with less muscle fibers, collagen fibers and elastic fibers and if close to the skin as in both these instances the covered stent will erode through the injured thin walled vein and skin. It would appear from these case reports that an access related pseudoaneurysm of an autogenous fistula might best be served by a combined interventional approach with a surgical approach to help cover the area and bury the vessel/stent in deeper tissue.
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