The treatment of vascular access graft dysfunction: a nephrologist's view and experience.

Chronic hemodialysis, as it is practiced today, is heavily dependent on the use of the expanded polytetrafluoroethylene graft for vascular access, although it is prone to the problem of venous stenosis and its sequela, thrombosis. The natural history of untreated venous stenosis is to decrease the efficiency of dialysis and to limit the life expectancy of the graft. Prospective treatment of venous stenosis has been advocated and percutaneous transluminal angioplasty (PTA) has been shown to be safe and reasonably effective for this purpose. Because there is no optimum screening test for venous stenosis, patient selection for PTA is particularly important. The use of a group of clinical indicators that serve to indicate a significant degree of graft dysfunction has been recommended for this purpose. Long-term patency may be better when venous stenosis is surgically revised; however, PTA has a number of advantages, especially the preservation of potential vascular access sites. Endovascular metallic stents have been used to preserve patency following PTA with disappointing results except in selected cases with central lesions. Three types of percutaneous thrombolysis have been studied for the treatment of thrombosed access grafts. The technique of pharmacological thrombolysis in which a lytic enzyme is infused into the clotted graft has proven to be unsatisfactory. The more recently developed technique of pharmacomechanical thrombolysis (PMT) has proven to be practical for use in the dialysis patient. This procedure consists of two components, a pharmacological phase in which lytic enzyme is administered and a mechanical phase in which the residual clot is macerated and removed to restore flow. This technique offers the benefits of being quick, effective, and safe. Additionally, it combines angiographic evaluation of the access, thrombolysis, and angioplasty of stenotic lesions. Mechanical thrombolysis, performed in a manner identical to PMT except that saline is used in place of the lytic enzyme, has been shown to be equally effective and safe.