Sirolimus-Eluting Biodegradable Poly-l-Lactide Stent for Peripheral Vascular Application: A Preliminary Study in Porcine Carotid Arteries

Background: To assess technical feasibility and biocompatibility of a new Sirolimus (SIR)-eluting biodegradable poly-l-lactide (PLLA) stent for peripheral vascular application. Material and methods: In 15 pigs, both common carotid arteries (CCA) were surgically exposed and clamped in the proximal segment. After transverse incision, 12 316L stents, 12 unloaded and 6 SIR-loaded PLLA stents mounted on 6.0 × 40-mm balloon catheters were randomly implanted into the CCA and inflated to 8 bar. Angiographic equipment was not available. Stented CCA were explanted after 1 week (6 pigs; 316L versus PLLA) and 6 weeks (9 pigs; 316L versus PLLA versus SIR-PLLA), and processed for quantitative histomorphometry and estimation of vascular inflammation and injury scores. Results: No animals were lost during follow-up. All stents were patent on histological analysis without any signs of excessive recoiling or collapse. Unloaded PLLA stents showed decreased residual lumen area and increased neointimal area after 1 week (13.16 ± 0.34, 1.94 ± 0.26) and 6 weeks (11.57 ± 0.30, 2.85 ± 0.24) as compared with 316L stents (15.26 ± 0.13, 1.27 ± 0.41 and 13.99 ± 0.51, 1.54 ± 0.59). SIR-eluting stents demonstrated comparable neointimal area (1.75 ± 0.38) and 50% lower intimal thickness as compared with 316L stents after 6 weeks, but a slightly decreased residual lumen (13.06 ± 0.32) in the consequence of differences in strut thickness (PLLA, 270 μm; 316L, 155 μm). The vascular inflammation score against PLLA-stents could be reduced by Sirolimus. The vascular injury scores were low and similar in all groups. Conclusions: PLLA stents showed sufficient mechanical stability after porcine CCA stenting. By incorporation of Sirolimus, a significant reduction of the inflammatory and neointimal response to the PLLA stent was seen without systemic toxicity or thrombotic complications. These findings need to be assessed with longer follow-up to confirm maintenance of efficacy. The greater strut height of PLLA stents is a major limitation and requires modification. [Copyright &y& Elsevier]