Patency and blood flow in gas denucleated arterial prostheses.

Biomaterials exposed to blood often fail due to thrombosis. Gas nuclei (air) in the material are thrombogenic and a potential cause of failure. The effects of gas nuclei on patency and blood flow were studied in 4 mm diameter arterial grafts (Gore ePTFE; Johnson and Johnson Vitagraft ePTFE; Bard ACG EXS) in the femoropopliteal position of dogs. Control and denucleated (air-free) grafts were implanted bilaterally. Grafts were denucleated by immersion in degassed saline and exposure to 4 torr vacuum and 3,000-20,000 psig pressure. Graft patency was determined at harvest in 46 dogs. Blood flow was measured with acoustic flow probes in eight dogs. Denucleated graft patency was 60% after 2 days of implant while control patency was 22% (P < .05). Measured blood flow was higher in denucleated grafts than in control grafts (P < .02) in 4 of 5 dogs which had significantly different flows. Patency and flow decreased to zero for both control and denucleated grafts over periods of up to 80 days. Air in the control grafts may have been absorbed within several days, leading to late similarity with the denucleated grafts. Thus, removing the air from 4 mm ePTFE grafts decreased acute thrombosis and increased the patency.