Kotani J et al. (2006) Incomplete neointimal coverage of sirolimus-eluting stents: angioscopic findings. J Am Coll Cardiol 47: 2108–2111

Sirolimus-eluting stents (SESs) inhibit neointimal hyperplasia, and are therefore associated with a lower risk of restenosis than bare-metal stents (BMSs). SES implantation might, however, increase the rate of late thrombosis, possibly because of impaired healing (incomplete neointimal coverage). Kotani et al. have compared neointimal coverage after SES implantation with that after BMS implantation.

Angioscopy was used to evaluate 37 consecutive stented coronary artery lesions in 25 patients (22 BMSs and 15 SESs). A new grading system was used to classify neointimal coverage, ranging from grade 0 (fully visible stent struts) to grade 3 (stent struts not visible by angioscopy).

Baseline demographics and lesion characteristics were similar in the two groups and the patients all received dual-antiplatelet therapy for a similar duration. Before and immediately after stent implantation, coronary angiographic findings did not differ between groups. At follow-up, 3–6 months after stent implantation, minimum lumen diameter was larger in the SES group than in the BMS group (P = 0.0255). Thrombi were identified in five SESs (33%) and in three BMSs (14%; P = 0.14). Neointimal coverage was significantly more complete with BMSs than with SESs: all 22 (100%) BMSs had complete intimal coverage (grades 2 or 3), whereas only 2 of 15 (13.3%) SESs had complete coverage (P <0.0001). In an analysis including all 37 lesions, incomplete neointimal coverage was correlated with thrombus formation (P = 0.09).

The authors conclude that SES implantation appears to be associated with incomplete neointimal coverage and thrombus formation. They recommend that patients treated with SESs receive long-term dual antiplatelet therapy.