Neointimal tissue component assessed by tissue characterization with 40 MHz intravascular ultrasound imaging: comparison of drug-eluting stents and bare-metal stents

Neointimal tissue characterization after implantation of drug-eluting stents by optical coherence tomography: quantitative analysis of optical density

Normalized optical density (NOD) measured by optical coherence tomography represents neointimal maturity after coronary stent implantation and is correlated with morphologic information provided by both light and electron microscopy. We aimed to test the hypothesis that even second generation drug-eluting stents (DESs) are problematic in terms of neointimal maturity. We implanted bare-metal stents (BMS: n = 14), everolimus-eluting stents (EESs: n = 15) or zotarolimus-eluting stents (ZESs: n = 12) at 41 sites in 32 patients with stable coronary artery disease. OCT was performed at up to 12 months of follow-up, and the average optical density of neointima covering struts was evaluated. NOD was calculated as the optical density of stent-strut covering tissue divided by the optical density of the struts. We also measured circulating CD34+ /CD133+ /CD45low cells, and serum levels of stromal cell-derived factor (SDF)-1, interleukin (IL)-8 and matrix metalloproteinase (MMP)-9 at baseline and follow-up. NOD was lower in the EES (0.70 ± 0.06) group than in the BMS (0.76 ± 0.07, P < 0.05) and ZES (0.76 ± 0.06, P < 0.05) groups. The mean neointimal area (R = 0.33, P < 0.05) and mean neointimal thickness (R = 0.37, P < 0.05) were correlated with NOD. Although NOD was not correlated with percent changes in circulating endothelial progenitor cells, and the levels of SDF-1 and IL-8, it was negatively correlated with the change in MMP-9 level (R = - 0.51, P < 0.01). Neointimal maturity might be lower at EES sites than BMS or ZES sites. This might lead to impaired neointimal tissue growth and matrix degradation. These results suggest a specific pathophysiology after DES implantation.

Neoatherosclerosis after Drug-Eluting Stent Implantation: Roles and Mechanisms

In-stent neoatherosclerosis (NA), characterized by a relatively thin fibrous cap and large volume of yellow-lipid accumulation after drug-eluting stents (DES) implantation, has attracted much attention owing to its close relationship with late complications, such as revascularization and late stent thrombosis (ST). Accumulating evidence has demonstrated that more than one-third of patients with first-generation DES present with NA. Even in the advent of second-generation DES, NA still occurs. It is indicated that endothelial dysfunction induced by DES plays a critical role in neoatherosclerotic development. Upregulation of reactive oxygen species (ROS) induced by DES implantation significantly affects endothelial cells healing and functioning, therefore rendering NA formation. In light of the role of ROS in suppression of endothelial healing, combining antioxidant therapies with stenting technology may facilitate reestablishing a functioning endothelium to improve clinical outcome for patients with stenting.

Coronary angioscopic imaging of in-stent restenosis after biolimus-eluting coronary stent implantation

A 69-year-old man underwent repeat percutaneous coronary intervention for in-stent restenosis in the obtuse marginal artery 8 months after biolimus-eluting stent (2.5 × 28 mm Nobori stent, Terumo, Tokyo, Japan) implantation. Coronary angiography showed focal stenosis in the distal part of the stent. Intravascular ultrasound revealed low echoic heterogeneous intimal tissue. Optical coherence tomography also revealed a heterogeneous finding classified as a layered pattern. Coronary angioscopy detected a white mass with a paste-like appearance at the stenosis extending around the in-stent restenosis as a thin membrane where stent strut could be seen transparently. A small part of the mass was swinging in the blood stream. Coronary angioscopic imaging was beneficial for the understanding of the suspected mechanism and feature of the in-stent restenosis after second-generation stent implantation, which was apparently different from neointimal hyperplasia after bare-metal stent implantation. <Learning objective: The learning objectives of this case report include understanding the mechanism of in-stent restenosis after second-generation drug-eluting stent implantation by showing the coronary angioscopic imaging beyond the other intravascular imaging. In particular, this case can make the general and interventional cardiologists learn that the mechanism of in-stent restenosis <1 year is different from that after bare-metal stent implantation.>.

In-vivo iMap IVUS comparison of in-stent neointima and native coronary atherosclerosis

PURPOSE

The purpose of this study was to compare plaque characteristics of native coronary atherosclerosis and in-stent neointima ten months after ST elevation myocardial infarction (STEMI) using iMap intravascular ultrasound (IVUS).

METHODS

In 49 patients in-stent neointima and the coronary segment proximal to the stent were analyzed with iMap intravascular ultrasound (IVUS) ten months after primary PCI for STEMI.

RESULTS

A higher percentage of necrotic tissue was observed in the proximal coronary segment compared to the in-stent neointima by iMap IVUS (25.5% ± 12.8% vs 12.3% ± 3.3%, p < 0.0001) ten months after STEMI. The proportion of fibrotic tissue in the proximal segment was lower (63.6% ± 14.8% vs 72.0% ± 5.7%, p = 0.002) and the proportion of the lipidic tissue was higher (8.8% ± 3.0% vs 5.9% ± 2.0%, p < 0.0001) than in-stent neointima.

CONCLUSIONS

In patients ten months after STEMI, in-stent neointima contained a higher proportion of fibrotic tissue and lower proportion of necrotic and lipidic tissue compared the native atherosclerotic lesion.

The wound healing response after implantation of a drug-eluting stent is impaired persistently in the long term

A 70-year-old man underwent stent implantation for right coronary artery (RCA) lesions with a bare metal stent (BMS) and two sirolimus-eluting stents (SES). However, as both the BMS and SES stented sites developed restenosis after 13 months, he underwent target lesion revascularization using directional coronary atherectomy (DCA). On histopathology, the restenosis lesion at the SES-deployed site showed greater inflammation and less re-endothelialization than that at the BMS-deployed site. Three months later, the SES-deployed site developed a second restenosis, in which paclitaxel-eluting stents (PES) were implanted (PES-in-SES), while the BMS-deployed site was restenosis free. Five years later, restenosis was absent in these RCA lesions. However, by optical coherence tomography and/or coronary angioscopy, the PES-in-SES site in the RCA showed poor neointimal coverage over the stent struts and yellowish neointima, suggesting lipid-rich neoatheroma formation, whereas at the BMS site appropriate white neointima formation was observed. Drug-eluting stents still have problems of persistent inflammation, inappropriate neointima formation, and neoatherosclerosis. Although we are now in the era of second generation DESs in which better stent performance would be promising, we should remember that we are obliged to continue to follow-up all patients in whom first generation DESs such as SES or PES have been placed.

Intravascular Ultrasound-based Imaging Modalities for Tissue Characterisation

Atherosclerosis is the leading cause of cardiovascular mortality and morbidity in the developed world. Intravascular ultrasound (IVUS) is a widely used imaging modality providing complementary diagnostic information to angiography regarding the vessel wall of the coronary arteries. IVUS has been used for assessment of ambiguous angiographic lesions, evaluation of new interventional devices and in atherosclerosis progression-regression trials. However, the standard gray-scale IVUS has limited value for the accurate identification of specific plaque components. This limitation has been partially over- come by introduction of new IVUS-based imaging methods such as: virtual histology IVUS, iMAP-IVUS and Integrated Backscatter IVUS. These methods utilise the ultrasound backscatter signal to enable a more detailed characterization of plaque morphology or tissue characterization and to provide insight on the features of vulnerable plaque.