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 x 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 microm; 316L, 155 microm). 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.