EFFECTS OF BALLOON LENGTH AND COMPLIANCE ON VASCULAR STENT EXPANSION

Abstract

Vascular stents are used to dilate arteries that are narrowed or clogged by plaque. However, in-stent restenosis is still one of the major causes of the clinical failure. It is believed that vessel trauma imposed during stent deployment is closely correlated to restenosis. Clinical observations show that the longitudinal and axial geographic miss in pre/post-dilation are responsible for the vessel trauma. The interactions between the stent-strut and the artery are difficult to measure in vivo or clinically and reported results are very limited. A numerical approach that leverages on computing power can provide new insights into the stent implantation process. In this study, the effects of balloon length and compliance that play important roles during stent expansion were investigated. Areas in the vessels with high stress concentrations were identified as these were weaknesses that might have a high possibility of vascular injury. Two different types of numerical models were constructed: a simplified model that considered only the balloon and stent and a more comprehensive model that consisted of the balloon, stent, plaque, and artery. Virtual stent implantation trials were simulated and the phenomena of stent recoil, dogboning and foreshortening were observed and examined. It was found that balloons which were slightly longer than the stent and less compliance would be more likely to eliminate dogboning. Furthermore, a new parameter, namely the Ectropion angle, was introduced to describe the turning effect of the stent end in situations when dogboning could not adequately characterize this phenomenon. The present study could provide guidance for the placement of stents by clinical practitioners.