Assessment by Optical Coherence Tomography of Stent Struts Across Side Branch - Comparison of Bare-Metal Stents and Drug-Eluting Stents

Background: Late stent thrombosis (LST) after drug-eluting stent (DES) implantation is a major clinical problem that has not been fully explained. Incomplete neointimal coverage of stent struts is an important morphometric predictor of LST, which may be associated with impaired healing and the absence of full coverage of struts at branch-point ostia. Optical coherence tomography (OCT) was performed to compare 3 types of stents placed across side branches. Methods and Results: At 9-month follow-up, the neointimal coverage of the struts of 58 stents across a side branch was measured by OCT (bare metal (BMS), n=20; sirolimus-eluting (SES), n=23; paclitaxel-eluting (PES), n=15). According to the diameter ratio of side branch to main vessel, the side branches were classified as either large (ratio >0.33) or small (ratio <= 0.33). BMS had the lowest frequency of uncovered struts (29.4%) and the greatest neointimal thickness on the struts (123 +/- 33 mu M). Neointimal thickness on the struts was less for SES than for PES (72 +/- 16 vs. 91 +/- 22 mu rn, P=0.009), but there was no difference in the frequency of uncovered struts (66.1% VS. 58.6%, P=0.493). For large side branches, the frequency of uncovered struts was greater than in the small group for SES (87.5% vs. 40.7%, P=0.0002) and PES (83.3% vs. 18.2%; P=0.0013); there was no significant difference for BMS (43.8% vs. 16.7%, P=0.138). Conclusions: Neointimal coverage on struts across a side branch was less frequently observed in DES than in BMS, particularly in large side branches. (Circ J 2011; 75: 106-112)