Characterization of edge effects with paclitaxel-eluting stents using serial intravascular ultrasound radiofrequency data analysis: the BETAX (BEside TAXus) Study.

INTRODUCTION AND OBJECTIVES At present, the effect of paclitaxel on tissue structure at the edges of Taxus(R) stents is unknown. The objective of this study was to investigate in vivo the temporal changes occurring at the edges of paclitaxel-eluting stents using intravascular ultrasound radiofrequency (IVUS-RF) data analysis. METHODS The study included 24 patients who had a total of 26 paclitaxel-eluting stented segments. In all patients, IVUS-RF imaging was performed 5 mm proximally and 5 mm distally to the stent edges 6 months after stent implantation. For subsequent analysis, proximal and distal segments were divided into five 1-mm subsegments. RESULTS In the first two subsegments adjacent to the proximal edge of the stent, the vessel wall had grown to compensate for plaque growth without affecting the vessel lumen, while in the remaining three subsegments there was overcompensation (i.e., the vessel wall increased to greater than the plaque size). Consequently, the lumen had increased in size. At the distal edge of the stent, overcompensation was observed in all five subsegments and the lumen had increased in size. In general, proximal and distal growth was due to an increase in fibrolipid plaque (P< .001 and P< .001, respectively) along with a decrease in the necrotic core (P=.014 and P< .001, respectively) and the presence of dense calcium (P< .001 and P< .001, respectively). CONCLUSIONS Serial expansive vascular remodeling was observed at proximal and distal stent edges. Remodeling occurred in response to tissue growth, which was mainly due to increased fibrofatty tissue.