Editorials
Coronary Angioscopy for the Evaluation of Vessel Response After Drug-Eluting Stent Implantation
2016 Volume 80 Issue 3 Pages 590-591
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2016 Volume 80 Issue 3 Pages 590-591
Drug-eluting stents (DES) have been widely used because they dramatically reduce the occurrence of restenosis and target lesion revascularization. However, late stent thrombosis has emerged as a major concern, because of excessive inhibition of neointimal formation and delayed arterial healing with insufficient endothelialization.1 Therefore, prolonged dual antiplatelet therapy (DAPT) is recommended after DES implantation. Second-generation DES have been designed to overcome the safety issues of the 1st-generation DES by using thinner stent strut and polymers with different properties.2 The Endeavor zotarolimus-eluting stent (E-ZES) is a cobalt chromium-based thin-strut stent that has a phosphorylcholine biocompatible polymer with shorter drug-eluting duration.3 Clinical investigation has shown that the E-ZES had nearly complete neointimal coverage at 3 months.4 Sufficient arterial repair characterized by less development of thrombus, and substantial neointima formation occurred by 4 months after E-ZES implantation.5 Such more rapid arterial repair than with other DES may contribute to neointimal stability. The ZEUS (Zotarolimus-eluting Endeavor sprint stent in Uncertain DES candidates) trial randomized uncertain DES candidates (high bleeding risk, high thrombotic risk or low restenosis risk) to receive E-ZES or bare metal stent (BMS).6 Despite short DAPT duration (median 32 days), E-ZES was associated with lower 1-year major adverse cardiac events than BMS. Recently, a new-generation ZES, the Resolute ZES (R-ZES), which has slower drug release kinetics, became available. Despite using the same platform and drug, clinical outcomes are different between E-ZES and R-ZES. In this issue of the Journal, Nishimoto et al performed coronary angioscopy (CAS) 1 year after R-ZES and E-ZES implantation and reported that E-ZES had better neointimal coverage with less yellow plaque and a lower heterogeneity score than R-ZES.7 These findings may explain the more stable long-term clinical outcomes of lesions treated with E-ZES.
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CAS allows direct visualization of the color and superficial morphology of the plaque and thrombus, using projected white light through thin, flexible glass fibers loaded into catheters. Several studies have shown that CAS can identify atherosclerosis as a yellow color, which has been regarded as high-risk plaques correlated with future coronary events.8 CAS has also been used to evaluate the vascular response to stent implantation. Serial CAS examinations have revealed that white neointima at the DES-implanted lesion rapidly becomes yellow. This phenomenon is pathologically confirmed as neoatherosclerosis after DES. Thrombus are frequently found at the site of yellow plaque, especially when neointimal coverage over the DES is poor.9 A prospective study has shown that yellow plaque at the DES-implanted lesion predicts late stent-related events.10 Thus, CAS has been used to compare vascular responses to different types of coronary stent.11
Such ability to visualize plaque color is one of the greatest advantages of CAS over other intravascular imaging techniques.12 Yellow neointima is generally considered to indicate vulnerable plaque. We previously reported an autopsy case after DES implantation.13 Histopathology revealed in-stent dark yellow plaque correlated with thin-cap fibroatheroma. Another autopsy case of ex-vivo CAS and histopathological examination also showed yellow plaque on CAS at the lesion previously treated with DES. Corresponding histopathological examination revealed a large fibroatheroma inside the stent (Figure 1). As we expected, yellow intima showed advanced in-stent atherosclerosis that could be the cause of late stent failure. However, it should be kept in mind that the yellow color may not always represent vulnerable plaque. Superficial calcium deposition without lipid pool also appears yellow in native coronary artery (Figure 2). Calcium deposition is usually observed by CAS as a yellow area with a clearly partitioned boundary.14 A histopathologic study reported that in-stent atherosclerosis included calcium deposition in the intima, even with 2nd-generation DES.15 Hence, in-stent calcification could appear yellow-colored. Combined use of CAS and other intravascular imaging modalities is useful to accurately detect fibroatheroma formation. Further consideration is warranted to determine whether yellow plaque definitely reflects in-stent atherosclerosis.
Histopathology and coronary angioscopy (CAS) images of fibroatheroma after drug-eluting stent implantation. (A) CAS image showing yellow plaque in the intima and no visible stent strut. (B) Corresponding histological image from the same section of the lesion in (A) shows large amount of necrotic debris underneath the fibrous cap inside the stent strut (elastica van Gieson stain, bar=500 μm).
Coronary angioscopy findings of superficial calcium deposition and comparison with optical coherence tomography and histopathology. (A) The color intensity of the angioscopic image is yellow with a clearly partitioned boundary. (B) Optical coherence tomography image of the plaque shows a low signal intensity area with a sharply delineated border. (C) Corresponding histological image of (A) shows superficial dense calcium without lipid deposition (H&E, bar=500 μm).
The authors gratefully acknowledge Drs Takahiro Imanaka, Kenji Kawai, Ten Saita, Rika Kawakami, Kenichi Fujii, and Hiroyuki Hao for their excellent assistance. The authors also thank the members of the cardiology and surgical pathology departments at Hyogo College of Medicine for their cooperation.
