Acute thrombogenicity and 4 weeks healing properties of a new stretch-ePTFE graft

Recently a new expanded polytetrafluoroethylene (ePTFE) graft with length compliant characteristics has been developed. The present study compared the acute thrombogenicity and 4 weeks healing characteristics of the stretch ePTFE graft to standard ePTFE grafts in vivo. Grafts of 6 cm length and 8 mm internal diameter were inserted end-to-side into the iliac arteries in pigs. Platelet adhesion was assessed by infusing indium-111-oxine (20 MBq) labelled autologous platelets and dynamically imaging the grafts. Explanted grafts (n = 14) were opened longitudinally and the thrombus-free surface (TFS) and segmental accumulation of platelets were determined. Stretch ePTFE grafts had significantly less platelet deposition when compared to standard ePTFE graft (p < 0.01). The dynamic increase of activity from 10 min after start of measurement was also significantly reduced (p < 0.05) for 170 min as compared to standard ePTFE grafts. TFS was 68 +/- 5% for stretch ePTFE and 37 +/- 5% for standard ePTFE grafts (p < 0.01). After explanation and fixation the grafts were investigated by light microscopy, scanning and transmission electron microscopy. At 1 week after surgery, both kind of grafts were covered by a fibrinous layer containing platelets and leukocytes. After 2 weeks a pseudoendothelial layer was found in the perianastomotic regions. After 4 weeks, two out of four standard ePTFE grafts were occluded due to intimal hyperplasia and subsequent thrombosis in the midportion of the grafts. All stretch ePTFE grafts were patent and covered by a smooth pseudointima. This study thus demonstrates a lower acute thrombogenicity in stretch ePTFE grafts compared to the standard graphs.