THERMAL TREATMENT EFFECTS ON A PLLA BIORESORBABLE STENT

摘要

Stent navigation and expansion may injure vascular endothelium, including vulnerable plaque lesions. Balloon expansion and deployment of a stent can lead to injury or the endothelial lining and stretching of the arterial wall [1]. Understanding the traction forces an expanding stent imparts on the vascular wall at the endothelial surface, the underlying plaque lesions and other tissue components during expansion is an important step in improving short-term stent-wall mechanics. More importantly, the long-term influence of stent-vascular wall mechanical interactions in restenosis remains unknown, and this analysis may shed light on the process. The pressure-diameter response curve of a stent is commonly used as the first indicator of its overall mechanical characteristics. It can be used to predict the progressive contact between an expanding stent and the vascular wall. At a given diameter, we could infer the magnitude and direction of the traction forces a stent exerts at the vascular wall and any underlying plaque lesion. It helps us to predict the degree of additional luminal expansion at increasing pressure from balloon catheter. Thermal treatment has been known to affect the mechanical properties of polymers [3]. Lendlein et al [4] showed the effects of light and temperature on the mechanical behavior of shape-memory polymers. We are studying the effect of thermal treatment on a PLLA polymer fiber stent developed at our institution [5] and expect to modulate and optimize the mechanical characteristics through thermal treatment. In this work, we study the effect of fiber's thermal treatment on the resulting pressure-diameter mechanical characteristic of the stent. Using SEM we measured the differences in twist of the fiber after balloon expansion up to 12 atm. We also compared the differences in the stiffness of the stent and elastic energy stored.