Infectibility of endovascular stents following antibiotic prophylaxis or after arterial wall incorporation

BACKGROUND: Case reports of endovascular stent infection have been accumula ting in the last several years. We sought to determine if prophylactic anti biotics would prevent stent/artery complex infections in a swine model if g iven before a bacterial challenge at the time of stent placement and 4 week s following deployment. We also investigated whether arterial wall incorpor ation protected the stent against infection without antibiotic prophylaxis. METHODS: Balloon expandable Palmaz stents were placed in the iliac arteries of 42 swine. At the same time, angioplasty was performed on the contralate ral iliac artery as a control. In group A, prophylactic cefazolin was given to 12 swine at the time of stent deployment followed by an intraaortic bac terial challenge of Staphylococcus aureus. In group B, 10 swine received pr ophylactic cefazolin followed by intravenous S aureus 4 weeks after iliac s tenting and angioplasty. In group C, 3 months following iliac stent placeme nt and angioplasty an intravenous bacterial challenge was administered with S aureus, All swine were euthanized, and the iliac stent/artery complex an d the contralateral angioplastied iliac artery were harvested and sent for culture and pathology. Experimental groups were compared with results from our previously published swine infection model using the Fisher's exact tes t. P values were considered significant if less than 0.05, RESULTS: Group A: Two of the 12 (17%) stent/artery complexes in the antibio tic treatment group had positive cultures. This compares with 7 of 10 (70%) in the control group (P = 0.016). In addition, there was one infection in an angioplastied vessel contralateral to one of the two stent infections. M olecular strain typing verified that the positive cultures were the same st rain that was used to challenge the animals. No vessel thrombosis occurred in the stented arteries even in the presence of infection. Group B: One of 10 (10%) stented iliac arteries had a culture positive infection. This comp ares with 7 of 14 (50%) positive cultures in the control group (P = 0.04), In addition, one angioplastied vessel did have mild S aureus growth on cult ure. Both positive cultures were verified to be the same as the injected st rain by molecular strain typing. There were no thrombosed or occluded vesse ls. Group C: One of 15 patent stents had growth of S aureus on culture and evidence of acute inflammation on histopathologic examination. The stent in fection late of 1 of 15 (7%) patent stents in this study was significantly less than the infection rates with bacterial challenge at placement (7 of 1 0, 70%; P < 0.01) and at 1 month postplacement (7 of 14, 50%; P = 0.0142). Five stents occluded without evidence of infectious cause. CONCLUSIONS: The results of this study support a recommendation that antibi otic prophylaxis should be used at the time of arterial stent placement and early after placement at times of anticipated bacteremia, but indefinite p rophylaxis may be unnecessary due to arterial wall incorporation of the ste nt. (C) 1999 by Excerpta Medics, Inc.