Modification of venous end of dialysis grafts: An attempt to reduce neointimal hyperplasia

Polytetrafluoroethylene (PTFE) grafts used for hemodialysis access are plag ued by the development of neointimal hyperplasia (NIH). This extracellular matrix of collagen and mucopolysaccharide acts like a tumor; its relentless growth causes obstruction of the venous ends of PTFE grafts, adversely imp acting the quality of dialysis and eventually leading to graft thrombosis. Researchers are divided over the etiology of NIH. Some attribute the proble m to mechanical factors, while others believe that the production of growth factors is responsible. Possibly both types of noxious stimuli adversely i mpact the microenvironment near the venotomy and the anastomosis site when PTFE grafts are sutured to veins in the conventional way. In an attempt to address the problem of NIH, a new anastomosis technique ha s been devised for the venous end of the PTFE arteriovenous graft, based on the concept of the old Scribner shunt being inserted into the vein. A graf t with plastic rings is cut at an angle and inserted about 3 cm into the ax illary vein, then secured with a purse-string suture around the venotomy, r einforced with vascular clips. In this way, the venotomy is everted and iso lated from the bloodstream. Any activated smooth muscle cells (SMCs) at the venotomy site are thus presented with a barrier if they attempt to migrate into the interior of the vein. The length of the graft inside the vein and the plastic rings constitute additional barriers to the potential migratio n of SMCs down the outside of the graft to the arterial blood exit site. In addition, the blood exiting the graft is more laminar in flow and is paral lel to the venous blood flow. The momentum vectors of the two streams are a ligned; thus, mixing is less of a problem. The maelstrom effect seen with c onventional end-to-side anastomosis is avoided. All of the grafts (n = 5) t hat have been inserted thus for using this new technique have worked well, without the need for revision and with no complications. The grafts are now between 10 and 20 months old. If these initial results are maintained, thi s technique could prove to be a useful addition to the vascular access surg eons' armamentarium.