Polytetrafluoroethylene-covered stents in the venous and arterial system: angiographic and pathologic findings in a swine model.

BACKGROUND: Although polytetrafluoroethylene (PTFE) is now used as a covering in a wide variety of vascular stents, little is known about the resultant pathologic and angiographic changes in the arterial and venous system after stent deployment.
METHODS: Atrium PTFE-covered stents were deployed in the abdominal aorta and the inferior vena cava (IVC) of two Yorkshire pigs. Angiograms were performed after deployment and at recatheterization. A complete histopathological exam was performed after sacrifice, and angiographic and histology findings were then compared between the two types of blood vessels.
RESULTS: The arterial stents demonstrated no stenosis on angiography and minimal in-stent intimal proliferation by histopathology. A uniform layer of neointima coated the inside of the stent by 1 month with no obvious thrombus formation. In contrast, the venous stents demonstrated angiographic evidence of significant in-stent stenosis of variable degrees and the histology showed increased intimal hyperplasia with fibrin deposition. PTFE from both the arterial and venous stents had variable amounts of tissue ingrowth with cells observed to be growing into and through the PTFE fibers.
CONCLUSIONS: Atrium PTFE-covered stents have excellent short-term angiography and histopathology in the arterial system, while stents in the venous system developed rapid in-stent intimal hyperplasia. PTFE fibers from both types of vasculature permitted cells to grow through and within them.