Mismatch in elastic properties around anastomoses of interposition grafts for hemodialysis access

Abstract

Arteriovenous (AV) fistulas for hemodialysis access, constructed with the use of interposition grafts, are often complicated by intimai hyperplastic stenosis, mainly occurring at the venous anastomosis. In this study, mismatch in elastic properties around the arterial and venous anastomoses of graft AV fistulas in humans was quantified in order to find clues for the predisposition of intimai hyperplasia to develop at the venous anastomosis. The elastic properties of graft AV fistulas in 31 hemodialysis patients were investigated by the use of vessel wall Doppler tracking, 2 wk after construction. Nine saphenous vein grafts, 8 expanded polytetrafluoroethylene (ePTFE) grafts, and 14 stretch-PTFE (sPTFE) grafts were measured at the arterial inflow segment, the proximal graft segment, the distal graft segment, and the venous outflow segment. Area increase (Al), representing the capacity of the vessel wall to store blood volume, and relative distension, representing the intrinsic elastic properties, were calculated from diameter and distension. A decrease in Al was observed in the arterial anastomoses of all graft types. An increase in Al was found in the venous anastomosis of ePTFE and sPTFE grafts. Higher values for Al and relative distension were found at the proximal and distal graft segments of the saphenous vein grafts when compared with the prosthetic grafts. In the sPTFE grafts, the level of Al was maintained along the graft, whereas in the ePTFE grafts, a decrease in Al was found. In the arterial anastomoses of AV fistulas, a decline in the capacity to store blood volume was observed. By contrast, an increase in the capacity to store blood volume was found in the venous anastomoses. Because the latter condition is associated with flow disturbances, like enhanced particle residence time and low shear, it may contribute to the predisposition of intimai hyperplasia to develop at the venous site.