A person with severely diseased arteries in one or both legs can experience pain on walking (intermittent claudication), pain at rest, or death of tissues in the leg. When the main thigh artery has a long blockage, the best option is to insert a bypass to carry the blood from an artery with good blood flow to the affected artery below the blockage. Bypass is intended to improve walking, or to save limbs that might otherwise require amputation. The different types of material available to create the bypass include the person’s own vein (autologous vein), human umbilical vein, and the prosthetic materials polytetrafluoroethylene (PTFE) or Dacron, alone or with the blood thinning agent heparin bonded to the inside of the graft. Bypass grafts extending to below the knee are not as effective at remaining patent (open) with good blood flow as those above the knee. The aim of this review was to determine the most effective type of material to use for above-knee and below-knee bypass grafts.
Study characteristics and key results
We identified 19 randomised controlled trials that included a total of 3123 people. Of these people, 2547 were given above-knee bypass grafts and 576 were given bypass grafts below the knee. The evidence in our review is current until 13 March 2017. From our analysis, we found that grafts made from a person’s own vein had a better primary patency (blood flow) rate than the prosthetic materials PTFE or Dacron for above-knee bypass grafts. Meanwhile, Dacron (and possibly also human umbilical vein) achieved better blood flow (patency) than PTFE. We also found that Dacron with supporting rings around it (designed to prevent external compression) showed worse patency than non-supported Dacron when used in grafts above the knee.
Adding a ‘cuff’ of vein did not improve the patency of PTFE for grafts extending to below the knee. The included trials provided few results on how long people’s limbs survived following the bypass procedure. There was not much consistency between the trials (and sometimes within the trials) with regards to people taking additional medications such as antiplatelets or anticoagulants, and this might have affected the results.
Quality of the evidence
The overall quality of the evidence ranged from very low to moderate. Issues which affected the quality of the evidence included differences in the design of the trials, and differences in the types of grafts they compared. These differences meant we were often only able to combine and analyse small numbers of participants and this resulted in uncertainty over the true effects of the graft type used.