[Implications of late expansion of self-expanding stents on neointimal response: a serial study with intravascular ultrasound].

INTRODUCTION AND OBJECTIVES A unique property of self-expanding stents is the continuous force exerted against the vessel wall, which may induce additional arterial damage with implications on restenosis. The main purpose of this study is to evaluate the consequences of late self-expansion of coronary Wallstents. METHODS Eleven patients with Wallstents implanted in native coronary arteries, in whom baseline, post-stenting, after high pressure balloon inflation and at 6-month follow-up intravascular ultrasound were performed. The stented segments were divided in 2-mm cross-sections, that were analyzed independently and carefully matched at each situation using anatomic landmarks. Multiple regression analysis was performed. RESULTS Late expansion was present in 93% of the studied sections (mean increase in stent area of 2.0 1.9 mm2) and was clearly related to stent oversizing (r = 0.45; p < 0,0001). Although late expansion was a significant positive predictor of neointimal growth (r = 0.63; p < 0.0001), it showed a negative correlation with late luminal loss (r = 0.33; p < 0.0001). No significant correlation was found between optimization of angiographic results with high pressure inflations and late luminal loss. CONCLUSIONS Late expansion is a common phenomenon after Wallstent implantation and is mainly determined by stent oversizing. Despite the fact that this phenomenon is associated with greater neointimal proliferation, it seems to have a net beneficial effect on late luminal loss.