Infection of endovascular stents in a swine model

Percutaneous balloon angioplasty with intravascular metallic stent placement has rapidly gained popularity for the treatment of arterial occlusive disease. Although the incidence of vascular prosthetic infection is well described, the risk of infection following metallic stent placement is unknown. The purpose of this study was to determine if intravascular metallic stents could become infected following systemic bacterial challenge.

Balloon expandable metallic stents were implanted in the iliac arteries of 10 swine following balloon catheter angioplasty. A second angioplasty, without stent placement, was also performed in the contralateral iliac artery. A bacterial challenge with Staphylococcus aureus was then infused into the aorta immediately after stent placement. Group 1 (n = 5) was killed at 72 hours, and group 2 (n = 5) at 3 weeks. A third group (n = 5) underwent stent placement without bacterial challenge and was killed at 3 weeks. At the time of death, the stents were cultured, and both iliac arteries were submitted for pathologic examination. Arterial patency and evidence of systemic infection were also assessed.

In the animals sacrificed at 72 hours (group 1), 80% had stent cultures with significant growth of S aureus; while at 3 weeks (group 2), 60% of cultures were positive. Of the stents placed without bacterial challenge (group 3), none had a positive culture at 3 weeks. In group 2, 40% of the stented arteries remained patent, while 100% of group 3 remained patent until sacrifice at 3 weeks. All of the stented arteries which were patent at 3 weeks were culture negative, while all those which were thrombosed were culture positive for S aureus. When compared to angioplasty alone, the presence of a stent was strongly associated with pathologic evidence of inflammation [93% versus 7%]. The quality of inflammation in the stented groups also differed. Ninety percent of the stented arteries in groups 1 and 2 had acute inflammation, compared to only 20% in group 3. The remainder of the stented arteries in group 3 had chronic inflammation or were normal.

In the swine model, intravascular metallic stents have the potential to become infected. This is associated with acute inflammation of the arterial wall and vessel thrombosis. Further studies evaluating the incidence of stent infections in humans are needed.