Short- and long-term histopathologic evaluation of stenting using a self-expanding nitinol stent in pig carotid and iliac arteries

Stenting is increasingly being used to treat carotid artery disease. Howeve r, complications including distal embolization, stent thrombosis, stent col lapse from external compression, the need for high-pressure inflation with increased neointimal response, or balloon rupture during stent expansion an d stent loss are all potential problems and of concern. To address each of these specific concerns, a new stent was designed, which is self expandable , made of nitinol, with temperature dependent superelastic properties, and with high vessel wall surface coverage. Since this device has a number of n ovel characteristics, we aimed to assess the short- and long-term histopath ologic response in pig carotid and iliac arteries. Single stents were deplo yed in pig carotid and iliac arteries after overstretch balloon injury. Ang iograms were performed pre- and poststenting and prior to sacrifice. Intrav ascular ultrasound was used before implantation to determine vessel size. V essels were examined histologically at 1 month (n = 6) and 6 months(n = 6) for morphometric analysis, hemorrhage and thrombus, endothelialization, and inflammatory and fibrotic responses. There was a 100% angiographic success rate at implantation. In one case, it was determined histologically that a single stent was implanted in a dissection plane of a pig's left iliac art ery and was occluded by organized thrombus, with the true lumen being paten t. At 6-month follow-up, this was the only evidence of a single stent occlu sion, with flow adjacent to the stent in the true lumen. In the other vesse ls, the stents showed good vessel wall-stent apposition and the lumens were patent with a concentric and thin neointima. Inflammatory cells were rare and there were no mural thrombi. Coverage of the vessel wall by endothelial -like cells was complete at 1 month. The novel nitinol EndoStent appears to have favorable biocompatibility with minimal thrombus deposition or inflam matory response, and its use is feasible for clinical application in caroti d and iliac arteries. Cathet. Cardiovasc. Intervent. 48:316-323, 1999. a 19 99 Wiley-Liss, Inc.