Different Vascular Responses to a Bare Nitinol Stent in Porcine Femoral and Femoropopliteal Arteries.

Nitinol stents are widely used for the treatment of peripheral arterial diseases in lower extremity arteries and have shown different clinical outcomes depending on implanted arterial segments. We aimed to compare histopathological responses to nitinol stents in femoral artery (FA) with those in femoropopliteal artery (FPA), which is markedly bended during knee flexion. A single nitinol stent was implanted in FA and FPA of 21 domestic swine. The stented vessels were angiographically assessed and then harvested for histopathology at 1 and 3 months after implantation. Angiographic late lumen loss was significantly greater in FPA than in FA at 3 months. Neointimal area decreased in FA and increased in FPA from 1 to 3 months. Compared with FA, peri-strut area of FPA showed more pronounced hemorrhage and fibrin deposition at 1 month and angiogenesis and inflammation at 1 and 3 months. Injury to internal elastic lamina or media was minimal in both FA and FPA at both time points. In conclusion, vascular responses to nitinol stents were different between FA and FPA with respect to time course of neointimal formation and progress of healing, suggesting that repetitive interaction between stent and vessel wall during dynamic vessel motion affected vascular responses.

Vascular responses to a biodegradable polymer (polylactic acid) based biolimus A9-eluting stent in porcine models.

AIMS: The time-dependent changes in endothelial and healing properties of coronary arteries implanted with a biodegradable polymer-based biolimus A9-eluting stent (BioPol-BES) have not been investigated. We evaluated the short-term and the long-term in vivo response of BioPol-BES, as compared to a permanent polymer-based sirolimus-eluting stent (PermPol-SES), and a bare metal stent (BMS). METHODS AND RESULTS: Overlapping stents were placed in 33 swine (n=11 for BES, SES, and BMS, respectively) for two and four weeks and single stents in 30 miniature pigs (n=18 for BES, n=9 for SES, n=3 for BMS) for three, nine and 15-month evaluations. The vessel patency, arterial healing and endothelialisation were assessed by angiography, histopathology and scanning electron microscopy. At four weeks, the endothelialisation at overlapping stent regions was greater with BioPol-BES (87.8±3.7%) and BMSs (98.0±0.4%) than with PermPol-SES (66.4±3.2%). The inflammation score in vessels implanted with single BioPol-BES increased slightly from three to 15 months (0.00±0.00 to 0.28±0.14), while this increase was more pronounced with PermPol-SES (0.11±0.07 to 1.56±0.68). Compared to BMS moderate lymphocyte infiltration was seen with BioPol-BES, and marked granulomatous formation with PermPol-SES. CONCLUSIONS: The level of endothelial coverage in BioPol-BES was comparable to BMS at four weeks, with no significant increase of inflammatory reaction up to 15 months.