Objectives: We sought to examine by angioscopy the neointima formation and thrombogenic potential of the neointima after deployment of a drug-eluting stent (DES).
Background: Late stent thrombosis after DES implantation, a major safety concern, has been associated with poor strut coverage by neointima. Intracoronary angioscopy provides a method for visual evaluation of stent coverage by neointima and detection of thrombus in the stented coronary segment.
Methods: Patients undergoing implantation of a sirolimus DES (n = 57) were serially examined by angioscopy immediately after (baseline) and again at 10 months (follow-up) after implantation. The angioscopic color grade of the neointima from white to yellow was assessed in a semiquantitative manner. Stent coverage was classified into not covered (Grade 0), covered by a thin layer (Grade 1), or buried under neointima (Grade 2). The thrombogenic potential of the neointima was evaluated by the prevalence of thrombus on the neointima.
Results: The maximum yellow color grade of the neointima within DES-implanted lesions increased significantly from baseline to follow-up (1.4 +/- 1.1 vs. 1.9 +/- 0.6, p = 0.0008). Even among lesions without yellow color at baseline, yellow color was detected in 94% (17 of 18) of lesions at follow-up. The prevalence of thrombus was significantly higher on the yellow than on the white neointimal areas. Thrombus was detected on yellow and/or Grade-0/1 neointima, but never on the white Grade-2 neointima.
Conclusions: Sirolimus DES promoted formation of atherosclerotic yellow neointima in the stent-implanted lesion at 10-month follow-up. Thrombus was detected more often on the yellow area than on the white area and was never detected where a stent was buried under white neointima. These data suggest that the increased potential risk of late stent thrombosis in DES lesions may be due to the newly formed yellow neotima and cholesterol-laden plaque.