Neoendothelialization of small-diameter polytetrafluoroethylene arterial grafts is not delayed by aspirin and dipyridamole.

The effect of aspirin and dipyridamole on neoendothelialization of polytetrafluoroethylene (PTFE) was studied in the rabbit aortic graft model. Forty-three New Zealand white rabbits were allocated to receive a combination of aspirin 10 mg/kg/day and dipyridamole 10 mg/kg/day (n = 23) or placebo (n = 20). Both regimens began 3 days before insertion of PTFE aortic grafts (10 mm long and 3 mm internal diameter). Serum thromboxane B2 concentration in the control group averaged 254 +/- 22 ng/ml (+/- standard error of the mean) and 40 +/- 23 ng/ml in the treatment group (p less than 0.001). Grafts and adjacent aorta were harvested at 2 weeks (n = 4), 4 weeks (n = 9), 8 weeks (n = 13), and 12 weeks (n = 17) after implantation. Morphologic techniques, including conventional light microscopy, immunoperoxidase staining for endothelial factor VIII-related antigen, and scanning electron microscopy (SEM) demonstrated that neointima was composed of endothelial cells arising by ingrowth at anastomotic site and as islands in the center of the graft. The percentage of graft neoendothelialization was measured by SEM. At 2 weeks 18% +/- 2% of the PTFE surface was covered with endothelium in the aspirin/dipyridamole group. The percentages of graft neoendothelialization for the treatment and control groups at 4 weeks were 44% +/- 13% (n = 5) and 46% +/- 10% (n = 4) (p = NS), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)