The most distinctive feature of coronary angioscopy is its ability to directly visualize the vessel. This allows direct observation of plaque natural history, including progression, rupture, and subsequent thrombus formation, in living patients. To date, coronary angioscopy has resulted in numerous discoveries, and we expect to find additional new phenomena using this technique. We introduced coronary angioscopy in 2002 and observed many surprising things. These included our observations of old saphenous vein grafts wherein dense, yellow plaques with numerous thrombi were observed in normal lesions. During the drug-eluting stent era, the healing process was observed to be absolutely different than after bare metal stent implantation. Following bare metal stent implantation, the stented site was covered with thick, white, smooth neointima; after implanting a first-generation drug-eluting stent, neointima formation was poor and the neointima was yellow, in some cases. This phenomenon, now called "neoatherosclerosis" was first observed using angioscopy. The cause of the yellow plaque formation was proven to be due to inflammation caused by the poor biocompatibility of the stent polymer. Developments in drug-eluting stent technology were clearly observed using angioscopy. Adequate healing after the implantation of second-generation drug-eluting stents was observed in stable coronary stenotic lesions; however, inadequate healing was observed in vulnerable lesions. Additional new technologies will be required to heal vulnerable lesions. In the near future, biodegradable vascular scaffolding will be available. Angioscopic observation of the healing process will be important to assess the safety of this new technology. Optical coherence tomography can also be used to observe and measure neointimal thickness after drug-eluting stent implantation. However, the layered thrombi attached to vessel walls cannot be assessed using this technology; angioscopy can clearly detect these thrombi. The hazy angiographic appearance of the lotus-root structures, sometimes seen using optical coherence tomography, were thought to be recanalized channels that formed after thrombosis. Angioscopy clearly showed these lotus-root observations to be due to fibrin nets. The characteristics of plaques, after stent implantation involving tissue protrusion, were also unclear; however, angioscopy identified the exact tissue characteristics and allowed the suggestion of further therapies. Recently, the angioscopic observation of the aorta has been a focus. Various thrombi and plaques may be observed on the surface of the aorta. Understanding these structures may elucidate the mechanism of acute aortic syndrome. Angioscopy is the only tool that allows the direct observation of the intravascular world and has a high potential for allowing new discoveries in living people.
