Background: Little is known about the direct effect of diabetes mellitus (DM) on medium-term to long-term lesion characteristics in patients treated with different types of stents.
Methods: A total of 261 stents enrolled in the multicenter study of intra-coronary angioscopy after stenting (MICASA) study were observed by coronary angioscopy about 1 year after percutaneous coronary intervention (PCI). There were 15 bare metal stents (BMS), 87 first-generation drug-eluting stents (1st-DES: 64 sirolimus-eluting stents [SES] and 23 paclitaxel-eluting stents [PES]), and 159 second-generation DES (2nd-DES: 73 everolimus-eluting stents [EES], 56 zotarolimus-eluting stents [ZES], and 30 biolimus-eluting stents [BES]). Neointimal coverage (NC) of the stents was classified into 4 grades from 0 (none) to 3 (complete). The maximum and minimum NC grades (Max-NC and Min-NC, respectively) were assessed for each stented segment, and the heterogeneity index was calculated by subtracting Min-NC from Max-NC. The color of plaques at stented segments was classified into four grades from 0 (white) to 3 (bright yellow). Thrombus was also investigated.
Results: In patients with DM, the yellow color grade was lower and the heterogeneity index was higher than in patients without DM for all stents (1.0 ± 0.8 vs. 1.2 ± 0.9, P = 0.050) and for BMS (2.0 ± 0.9 vs. 1.0 ± 0.9, P = 0.050), respectively. In addition, Min-NC was significantly higher and the plaque color grade was significantly lower in patients with DM than in those without DM for 1st-DES (Min-NC: 0.7 ± 0.6 vs. 0.4 ± 0.5, P = 0.009; color grade: 1.2 ± 0.9 vs. 1.7 ± 0.9, P = 0.006). Multivariate analysis revealed that DM was a significant negative predictor of yellow plaque (P = 0.048, OR: 0.600).
Conclusions: DM had the strongest influence on the chronic characteristics of coronary lesions, especially in patients treated with 1st-generation DES.
Progression of atheromatous plaque within neointima of coronary stents, which was termed neoatherosclerosis, has gained interest as a potential cause of very late stent failure. Pathologically, neoatherosclerosis was defined as the development of foamy macrophage clusters, fibroatheroma, thin-cap fibroatheroma, plaque rupture, and in-stent calcification within the stent. Following the pathological observations, a growing number of in vivo studies by using optical coherence tomography (OCT) and coronary angioscopy have been published to date. Those studies tried to clarify the features of neoatherosclerosis and have improved our knowledge substantially. Nevertheless, there still are missing information on natural history and clinical implications of neoatherosclerosis. The present review article summarized the definitions of neoatherosclerosis from the stands of view of pathology, OCT, and angioscopy. Moreover, what is known and what is not known regarding neoatherosclerosis were outlined for better understanding of pathophysiological consequences of coronary stents, which hopefully generates further ideas of clinical investigations.
Angioscopy is the only imaging modality that can directly evaluate the color of plaques. Therefore, nothing is more important to angioscopy than color. Plaque is classified into yellow plaque and white plaque according to their color. Yellow plaque has been considered to be vulnerable and high risk for the acute coronary syndromes, especially high-intense yellow plaque. Beta carotene is lipotorophic binding to lipid and coexisting with lipids in human atherosclerotic lesions and produces the yellow color of atherosclerotic plaque. Yellow plaque has several kinds of histopathology, such as a thin fibrous cap with lipid core, superficial or diffuse lipid deposition (cholesterol and cholesterol ester) with or without macrophage-foam cells and calcified plate. Therefore, all yellow plaques might not be vulnerable. Some pharmacological intervention and trans-catheter therapy decreased the intensity of yellow color. As angioscopic interpretation of color is usually subjective, objective computerized colorimetric evaluation is desirable.
The recent improvement of technical aspects of multimodality coronary imaging allow not only assessment of the degree of vessel luminal narrowing but also evaluation of the plaque characteristics and the useful prognostic information and accurate risk stratification. Among them, coronary angioscopy is the coronary imaging modality that enables direct visualization of internal surface of a vessel. Moreover it provides the detail information of plaque morphology, thrombus formation and neointimal coverage (NIC) after stent implantation. A lot of previous studies have shown that coronary angioscopy enabled not only the detection of vulnerable plaque but also prediction of cardiovascular events and percutaneous coronary intervention related complications. In this review, we discuss the role of coronary angioscopy for coronary plaque imaging, including in a comparison with other currently available imaging modalities used to examine atherosclerotic plaque.
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.
Intravascular optical coherence tomography (OCT) is an imaging modality uniquely characterized by its high resolution. OCT can visualize in vivo plaque characteristics and detect vulnerable plaque, such as thin-cap fibroatheroma, which has a large lipid pool with overlying thin fibrous cap. OCT can also help the clinicians to identify the underlying pathology of acute coronary syndrome: plaque rupture, plaque erosion, and calcified nodule. The OCT system enables automated measurement of the lumen diameter, lumen area, and lesion length, which is useful to determine appropriate reference sites, stent size and stent length during percutaneous coronary intervention (PCI). Evaluation of underlying plaque characteristics is helpful in predicting possible complications after PCI. OCT-guided PCI may acquire comparable angiographical and clinical outcomes to intravascular ultrasound-guided PCI. OCT can be used to evaluate characteristics of non-culprit plaque and efficacy of lipid-lowering therapy on plaque stabilization. OCT also clearly visualizes mechanical vessel injury after stent implantation. Notably, the presence of irregular tissue protrusion has been shown to be associated with the occurrence of device-oriented clinical events. Recent studies suggest that OCT is feasible for the selection of conservative management without stenting in patients with acute coronary syndrome caused by plaque erosion.