Background: Late incomplete stent apposition (LISA) develops following implantation of conventional bare-metal stents (BMS) or drug-eluting stents, or after adjunctive intracoronary radiation (IR). However, no study has systematically compared the morphology of LISA seen with various treatment modalities.
Purpose: To compare the morphometric features of LISA accompanying BMS, IR or sirolimus-eluting stents (SES) using serial intravascular ultrasound (IVUS).
Methods: A query of Stanford University's IVUS database of the Cardiovascular Core Analysis Laboratory was performed to identify LISA cases. Dedicated software programs were used for volumetric IVUS analyses.
Results: In 30 LISA cases (12 BMS, 6 IR and 12 SES), there was no intertreatment difference in the degree of LISA (lumen area minus stent area at follow up). Serial analyses of LISA segments showed that vessel area of SES and IR showed significant increase at follow up as compared with post procedure, while there was no significant change in plaque area. In contrast, the BMS group showed no increase in vessel area, whereas plaque area revealed significant reduction. Eight of 12 BMS cases were treated by directional atherectomy before stenting; however, there was no difference in the area change between patients with or without pre-stent atherectomy. Post-procedure plaque thickness beneath the stent struts of LISA was thinner for SES as compared with BMS.
Conclusions: Plaque reduction primarily contributes to LISA after BMS, whereas vessel expansion is the predominant factor in LISA development for IR and SES. Thus, the mechanism of LISA may vary among different interventional treatments.