Recent advances in coronary angioscopy

Angioscopy enables macroscopic pathological diagnosis of cardiovascular diseases from the inside. This imaging modality has been intensively directed to characterizing vulnerable coronary plaques. Scoring of plaque color was developed, and based on prospective studies; dark yellow or glistening yellow plaques were proposed as vulnerable ones. Colorimetry apparatus was developed to assess the yellow color of the plaques quantitatively. The effects of lipid-lowering therapies on coronary plaques were confirmed by angioscopy. However, since observation is limited to surface color and morphology, pitfalls of this imaging technology became evident. Dye-staining angioscopy and near-infrared fluorescence angioscopy were developed for molecular imaging, and the latter method was successfully applied to patients. Color fluorescence angioscopy was also established for molecular and chemical basis characterization of vulnerable coronary plaques in both in vitro and in vivo. Drug-eluting stents (DES) reduce coronary restenosis significantly, however, late stent thrombosis (LST) occurs, which requires long-term antiplatelet therapy. Angioscopic grading of neointimal coverage of coronary stent struts was established, and it was revealed that neointimal formation is incomplete and prevalence of LST is higher in DES when compared to bare-metal stent. Many new stents were devised and they are now under experimental or clinical investigations to overcome the shortcomings of the stents that have been employed clinically. Endothelial cells are highly anti-thrombotic. Neoendothelial cell damage is considered to be caused by friction between the cells and stent struts due to the thin neointima between them that might act as a cushion. Therefore, development of a DES that causes an appropriate thickness (around 100 μm) of the neointima is a potential option with which to prevent neoendothelial cell damage and consequent LST while preventing restenosis.