Small-caliber polyurethane and polytetrafluoroethylene grafts: a comparative study in a canine aortoiliac model.

In vivo stability of a new small-caliber polyurethane graft (n8) was assessed in a canine aortoiliac model and compared to that of a conventional expanded polytetrafluoroethylene (ePTFE) graft (n8). Six months following implantation, marked aneurysmal dilatation to 230 +/- 80% (mean +/- SD) of the original diameter occurred in polyurethane grafts, while dilatation to 110 +/- 8% of the original diameter occurred in ePTFE grafts (p less than 0.005). Interval patency was 75% for each graft type. Luminal thrombus affected 59% of polyurethane graft surfaces compared to 22% of ePTFE graft surfaces (p less than 0.01). Qualitative examination of representative sections of polyurethane conduits demonstrated thick inner capsules with numerous small islands of graft material surrounded by macrophages and bands of mature fibrous tissue, in contrast to the thinner neointima and limited anastomotic pannus ingrowth observed in ePTFE grafts.