Effect of antithrombotic agents on the patency of PTFE-covered stents in the inferior vena cava: An experimental study

Purpose: To evaluate the efficacy of antithrombotic agents in the preventio n of stenosis of polytetrafluoroethylene (PTEE)-covered stents in the venou s system. Methods: Spiral Z stents covered with PTFE (PTFE-covered stents) were place d in the inferior vena cava (IVC) of 34 dogs. Nineteen dogs, used as a cont rol group, were sacrificed at 2, 4, and 12 weeks. Fifteen dogs, previously given antithrombotic agents [cilostazol (n = 5), warfarin potassium (n = 5) , cilostazol plus warfarin potassium (n = 5)] were sacrificed at 4 weeks, a nd then examined angiographically and histopathologically. The effect of th e antithrombotic agents was compared between groups. Results: The patency rate of the antithrombotic agent group was 93% (14/15) , which was higher than the control group rate of 63% (12/19). The mean ste nosis rate of the patent stent at both ends and at the midportion was lower at 4 weeks in the antithrombotic agent group than in the control group. In particular, the mean stenosis rate in the cilostazol plus warfarin potassi um group was significantly lower than the control group (Tukey's test, p < 0.05). The mean neointimal thickness of the patent stent at both ends and a t the midportion was thinner at 4 weeks in the antithrombotic agent group t han in the control group. In particular, the thickness of the neointima in the cilostazol plus warfarin potassium group was significantly decreased wh en compared with the control group (Tukey's test p < 0.05). At 4 weeks, end othelialization in the antithrombotic agent group tended to be almost ident ical to that in the control group. Conclusion: The present study suggests that administration of an antithromb otic agent is an effective way of preventing the stenosis induced by a neoi ntimal thickening of PTFE-covered stents in the venous system.