The influence of competitive flow on graft patency.

To evaluate the effects of competitive flow, bilateral aorto-iliac ePTFE grafts, 10 cm in length and with an internal diameter of 6 mm, were placed in ten mongrel dogs. On one side the external iliac artery was ligated (the control side); on the opposite side (the experimental side) flow continued through the native aorto-iliac system, as well as the graft, to allow a situation of competitive flow. Flow measurements showed the experimental graft carried 38.6% of the total blood flow going to the ipsilateral external iliac artery. After 30 days the grafts were exposed and patency and flow were evaluated by Doppler ultrasound. The control side showed 60% patency; all of the grafts on the experimental side were occluded. In addition, complete endothelial healing was observed at the occluded ostia of all experimental grafts. We conclude that competitive flow does influence graft patency and that graft thrombosis appears to be a relatively early phenomenon, as evidenced by the endothelial healing which occurred.

Comparison of immediate seeding of endothelial cells with culture lining of small diameter ePTFE carotid interposition grafts.

This study is the first to compare chronic healing characteristics of immediately seeded grafts with those of grafts lined by autogenous venous endothelial cells in tissue culture prior to implantation. Ten mongrel dogs had a segment of external jugular vein excised for enzymatic harvest of endothelial cells. After approximately 21 days growth in tissue culture, 4 X 10(6) cells/ml were inoculated into a 6-cm length of 4 mm i.d. ePTFE for formation of a confluent lining in culture media. The remaining external jugular vein had its endothelial cells enzymatically harvested for immediate seeding of an identical length of preclotted ePTFE. Both grafts were implanted end-to-end in the carotid position and excised after 30 days. In 6 of the 10 dogs, grafts were patent bilaterally; all others were occluded. Planimetric measurements on patent grafts with immediate seeding showed a thrombus-free surface area of 56 +/- 39% compared to 86 +/- 15% for culture-lined grafts (P = 0.046). Endothelial coverage was 70 +/- 24% for immediately seeded grafts and 29 +/- 21% for culture-lined grafts (P = 0.016). We conclude that immediate seeding and culture lining of autogenous endothelial cells in small diameter ePTFE grafts produce equivalent short-term patency. While culture-lined grafts have an initially less thrombogenic luminal surface, subsequent development of a confluent endothelial lining is slower than that with an immediate seeding preparation, and thus would appear to offer no significant clinical benefit, especially in light of the complexity culture lining adds to the procedure.