Bare Metal Stent Thrombosis and In-Stent Neoatherosclerosis

Detection of Cholesterol Crystals Using the Filter Paper Rinse Method in Very Late Stent Thrombosis Cases

Very late stent thrombosis (VLST) is a rare but critical complication of stent placement. In this report, we present 2 VLST cases diagnosed with neoatherosclerosis by detecting cholesterol crystals (CCs) via the filter paper rinse method. In terms of differentiating between neoatherosclerosis and stent thrombosis. There was no visible thrombus observed on thrombus aspiration. Examination of the blood sample obtained from the thrombus aspiration using the filter paper rinse method showed the presence of CCs under polarized light microscopy, thus, diagnosing VLST caused by neoatherosclerosis. Diagnosis of neoatherosclerosis would provide a rationale for intensive lipid-lowering therapy.

Two-Staged Technology for CoCr Stent Production by SLM

Additive manufacturing of porous materials with a specific macrostructure and tunable mechanical properties is a state-of-the-art area of material science. Additive technologies are widely used in industry due to numerous advantages, including automation, reproducibility, and freedom of design. Selective laser melting (SLM) is one of the advanced techniques among 3D fabrication methods. It is widely used to produce various medical implants and devices including stents. It should be noticed that there is a lack of information on its application in stent production. The paper presents the technological aspects of CoCr stent SLM fabrication, including design of stents and development of regimes for their manufacturing. Physical, chemical, and technological properties of CoCr powder were initially determined. Parametric design of mesh stent models was adopted. A two-stage approach was developed to ensure dimensional accuracy and quality of stents. The first stage involves a development of the single-track fusion process. The second stage includes the stent manufacturing according to determined technological regimes. The single-track fusion process was simulated to assign laser synthesis parameters for stent fabrication. Melting bath temperature and laser regimes providing such conditions were determined. Twenty-seven SLM manufacturing regimes were realized. Dependence of single-tracks width and height on the laser power, exposition time, and point distance was revealed. The qualitative characteristics of tracks imitating the geometry of the stent struts as well as favorable and unfavorable fusion regimes were determined. The results of surface roughness regulating of the stents' structural elements by various methods were analyzed. Thus, this two-staged approach can be considered as a fundamental approach for CoCr stent SLM fabrication.

Neoatherosclerosis prediction using plaque markers in intravascular optical coherence tomography images

Introduction

In-stent neoatherosclerosis has emerged as a crucial factor in post-stent complications including late in-stent restenosis and very late stent thrombosis. In this study, we investigated the ability of quantitative plaque characteristics from intravascular optical coherence tomography (IVOCT) images taken just prior to stent implantation to predict neoatherosclerosis after implantation.

Methods

This was a sub-study of the TRiple Assessment of Neointima Stent FOrmation to Reabsorbable polyMer with Optical Coherence Tomography (TRANSFORM-OCT) trial. Images were obtained before and 18 months after stent implantation. Final analysis included images of 180 lesions from 90 patients; each patient had images of two lesions in different coronary arteries. A total of 17 IVOCT plaque features, including lesion length, lumen (e.g., area and diameter); calcium (e.g., angle and thickness); and fibrous cap (FC) features (e.g., thickness, surface area, and burden), were automatically extracted from the baseline IVOCT images before stenting using dedicated software developed by our group (OCTOPUS). The predictive value of baseline IVOCT plaque features for neoatherosclerosis development after stent implantation was assessed using univariate/multivariate logistic regression and receiver operating characteristic (ROC) analyses.

Results

Follow-up IVOCT identified stents with (n = 19) and without (n = 161) neoatherosclerosis. Greater lesion length and maximum calcium angle and features related to FC were associated with a higher prevalence of neoatherosclerosis after stent implantation (p < 0.05). Hierarchical clustering identified six clusters with the best prediction p-values. In univariate logistic regression analysis, maximum calcium angle, minimum calcium thickness, maximum FC angle, maximum FC area, FC surface area, and FC burden were significant predictors of neoatherosclerosis. Lesion length and features related to the lumen were not significantly different between the two groups. In multivariate logistic regression analysis, only larger FC surface area was strongly associated with neoatherosclerosis (odds ratio 1.38, 95% confidence interval [CI] 1.05-1.80, p < 0.05). The area under the ROC curve was 0.901 (95% CI 0.859-0.946, p < 0.05) for FC surface area.

Conclusion

Post-stent neoatherosclerosis can be predicted by quantitative IVOCT imaging of plaque characteristics prior to stent implantation. Our findings highlight the additional clinical benefits of utilizing IVOCT imaging in the catheterization laboratory to inform treatment decision-making and improve outcomes.

Pathological evaluation 18 years after bare-metal stent implantation in the superficial femoral artery

Bare-metal stents (BMSs) have been generally applied for the treatment of peripheral artery disease in patients with femoropopliteal disease. However, very long-term pathological findings after BMS implantation have not been elucidated to date. We experienced an autopsy case in which we performed a pathological evaluation 18 years after BMS implantation in the right superficial femoral artery. The BMS was totally occluded and filled with remarkable neointima formation. Neointima was mainly composed of a lot of rather atrophic smooth muscles and intercellular spaces containing dense collagenous fibers. Furthermore, regional fatty infiltration was also observed, but inflammatory cell infiltration, such as macrophages and lymphocytes, was not recognized obviously even around the struts. Judging from the pathological findings, the main mechanism of the very long-term in-stent restenosis in the patients with femoropopliteal disease was continuous proliferation of smooth muscle cells that led to the totally occlusive disease. This observation leads us to speculate that continuous elution of an anti-proliferating drug over a longer duration, at least beyond 1 year, would be effective to prevent chronic-phase restenosis. Further development of devices that can be used in the femoropopliteal artery is needed in light of this speculation. <Learning objective: Very long-term pathological findings after bare-metal stent (BMS) implantation in the femoropopliteal (FP) artery have not been elucidated to date. The BMS which was implanted in the FP artery 18 years before was totally occluded and filled with remarkable neointima formation due to smooth muscle cell (SMC) proliferation without any infiltration of inflammatory cells around the struts. The main mechanism of the very long-term in-stent restenosis of FP disease was continuous proliferation of SMC.>.

Very late intrastent thrombotic occlusion caused by neoatherosclerosis after bare-metal stent implantation in the superficial femoral artery: Insight from histopathological findings

A 58-year-old male with gangrene in his left 1st digit due to critical limb ischemia had undergone endovascular therapy for chronic total occlusion of the left superficial femoral artery using bare-metal stents (BMSs). Angiography revealed in-stent occlusion of the BMS site when he was referred to our hospital with a recurrent ulcer at 7 years after stent implantation. As catheter-directed thrombolysis with urokinase was not effective, surgical thrombectomy was performed. His ankle-brachial index improved, and the ulcer was completely healed after thrombectomy. Pathological evaluation of the retrieved thrombi showed that it consisted of a massive erythrocyte, abundant fibrin precipitation, and fragments of atherosclerotic plaques, such as foamy macrophages and ghost images thought to be cholesterol crystals. These findings suggested that the neoatherosclerotic changes in the neointima gradually occurred in the stented segment, and neointimal disruption potentially caused the intrastent thrombotic occlusion. .

Different Neoatherosclerosis Patterns in Drug-Eluting- and Bare-Metal Stent Restenosis - Optical Coherence Tomography Study

BACKGROUND

There are few reports about the differences between drug-eluting stents (DES) and bare metal stents (BMS) in neoatherosclerosis associated with in-stent restenosis (ISR), so we compared the frequency and characteristics of neoatherosclerosis with ISR evaluated by optical coherence tomography (OCT) in the present study.

METHODS AND RESULTS

Between March 2009 and November 2016, 98 consecutive patients with ISR who underwent diagnostic OCT were enrolled: 34 patients had a BMS, 34 had a 1st-generation DES, and 30 had a 2nd-generation DES. Neoatherosclerosis was defined as a lipid neointima (including a thin-cap fibroatheroma [TCFA] neointima, defined as a fibroatheroma with a fibrous cap <65 µm) or calcified neointima. As a result, lipid neointima, TCFA neointima and calcified neointima were detected in 39.8%, 14.3%, and 5.1%, respectively, of all patients. The frequency of neoatherosclerosis was significantly greater with DES than BMS (48.4% vs. 23.5%, P=0.018). The minimum fibrous cap thickness was significantly thicker with DES than BMS (110.3±41.1 µm vs. 62.5±17.1 µm, P<0.001). In addition, longitudinal extension of neoatherosclerosis in the stented segment was less with DES than BMS (20.2±15.1% vs. 71.8±27.1%, respectively, P=0.001).

CONCLUSIONS

OCT imaging demonstrated that neoatherosclerosis with ISR was more frequent with DES than BMS and its pattern exhibited a more focal and thick fibrous cap as compared with BMS.

Five-year clinical outcomes of everolimus-eluting stents from the post marketing study of CoCr-EES (XIENCE V/PROMUS) in Japan

The Cobalt Chromium Everolimus-Eluting Stent (CoCr-EES) Post Marketing Surveillance (PMS) Japan study is a prospective multicenter registry designed to evaluate the safety and efficacy of XIENCE V/PROMUS everolimus-eluting stents in routine clinical practice at 47 centers representative of the clinical environment in Japan. We enrolled 2010 consecutive patients (2649 lesions) who underwent percutaneous coronary intervention using CoCr-EES. Clinical outcomes were evaluated through 5 years. Mean age was 68.8 years, 41.9% had diabetes, 4.9% received hemodialysis. Five-year clinical follow up was available for 1704 (84.8%) patients. Major adverse cardiovascular events (MACE) occurred in 10.7% of patients, including cardiac death (3.8%), myocardial infarction (1.8%), and clinically driven target lesion revascularization (TLR) (6.0%). Beyond 1 year, annual incidence of clinically driven TLR was 0.5-0.8%. Definite or probable stent thrombosis occurred in 9 (0.5%) patients at 5 years. After 1 year, definite stent thrombosis occurred in only 1 patient. Significant predictors for MACE were dialysis (ODDs ratio 4.58, 95% CI 2.75-7.64), prior cardiac intervention (ODDs ratio 2.47, 95% CI 1.75-3.49), total stent length (ODDs ratio 1.01, 95% CI 1.01-1.02), and number of diseased vessels (ODDs ratio 1.66, 95% CI 1.08-2.55). Five-year clinical outcomes from the CoCr-EES PMS Japan study demonstrated a low incidence of clinical events in the daily practice up to 5 years.Clinical Trial Registration Information: https://clinicaltrials.gov/ct2/show/NCT01086228 .

Failure Mechanisms and Neoatherosclerosis Patterns in Very Late Drug-Eluting and Bare-Metal Stent Thrombosis

BACKGROUND

There are few clinical studies on the pathophysiological mechanisms of very late stent thrombosis (VLST). We report optical coherence tomography findings in patients with VLST and compare the findings between bare-metal stents (BMS) and drug-eluting stents (DES).

METHODS AND RESULTS

We conducted a registry of stent thrombosis at 4 North American centers with optical coherence tomography imaging programs SAFE registry (The Study of Late Stent Failure Evaluated by OCT). Images were acquired in 61 patients (42 DES and 19 BMS) presenting with definite VLST. The median duration from implantation to VLST presentation was 51.4 months in the DES and 69.9 months in the BMS group (P=0.011). Uncovered and malapposed struts were observed in 70.5% (43/61) and 62.3% (38/61) of patients, respectively, whereas neoatherosclerosis was revealed in 49.2% (30/61). Stent underexpansion was observed in 42.4% of patients. Malapposed struts and stent underexpansion were more frequently demonstrated in DES than in BMS patients, whereas neoatherosclerosis was frequently observed in BMS (40.5% in DES and 68.4% in BMS; P=0.056). The percentage of frames with neoatherosclerosis was lower in DES than in BMS (15.56% [12.24-28.57] versus, 56.41% [40.74-70.00], respectively; P<0.001). Maximum consecutive lipid neointima length was shorter in DES than in BMS (2.4 [1.2-3.6] and 5.3 [3.0-7.0] mm; P=0.011).

CONCLUSIONS

Optical coherence tomography imaging demonstrated that VLST in DES and BMS had a wide variety of abnormal findings, such as neoatherosclerosis, uncovered strut, and malapposed strut. Neoatherosclerosis and lipid neointima were more frequently observed and had more longitudinal extension in BMS compared with DES.

Case Report: INTRAPROCEDURAL STENT THROMBOSIS IN PERCUTANEOUS CORONARY ANGIOPLASTY

Stent thrombosis is a rare complication of PCI but associated with STEMI and sudden cardiac death. Intra procedural stent thrombosis (IPST) was defined new or increasing (compared with baseline) thrombus within or adjacent to a deployed stent occurring the index PCI procedure whether occlusive or nonocclusive. We describe a case with double vessel disease who has complication cardiac arrest and intra procedural stent thrombosis in LAD and Left Main coronary artery after deployed stent in bifurcation LAD-D1. Thrombectomy and rescucitation were performed, and the patient completed her hospital course without complications.

Utility of near-infrared spectroscopy for detection of thin-cap neoatherosclerosis

Aims

Near-infrared spectroscopy (NIRS) has been employed to assess the composition of the atherosclerotic plaques in native coronary arteries. However, little is known about the detection of neoatherosclerosis by NIRS in in-stent restenosis (ISR). The aim of the study was to assess the relationship between the distribution of lipid determined by NIRS and morphology of ISR on optical coherence tomography (OCT).

Methods and results

We performed both NIRS and OCT in 39 drug-eluting stents with ISR. Values of lipid-core burden index (LCBI) derived by NIRS were compared with the OCT-derived thickness of the fibrous cap covering neoatherosclerotic lesions. A total of 22 (49%) in-stent neointimas were identified as lipid rich by both NIRS and OCT. There was good agreement between OCT and NIRS in identifying lipid within in-stent neointima (kappa = 0.60, 95% CI: 0.34-0.86). OCT identified thin-cap neoatheromas (TCNA) (<65 µm) in 12 stents (23%). The minimal cap thickness of in-stent neoatherosclerotic plaque measured by OCT correlated with the maxLCBI4mm (maximal LCBI per 4 mm) within the stent (r = -0.77, P< 0.01). Moreover, maxLCBI4mm was able to accurately predict TCNA with a cut-off value of >144.

Conclusion

NIRS correlates with OCT identification of lipids in stented vessels and is able to predict the presence of thin fibrous cap neoatheroma.

Impact of optical coherence tomography- and coronary angioscopy-assessed neointimal tissue characteristics on occurrence of periprocedural myonecrosis in patients with in-stent restenosis

Several characteristics of neointimal tissues, including neoatherosclerotic progression, have been reported in lesions with in-stent restenosis (ISR). However, the effects of these characteristics on outcomes after percutaneous coronary intervention (PCI) for ISR lesions remain unclear. We assessed the relationships between neointimal tissue characteristics and the occurrence of periprocedural myonecrosis (PMN) after PCI in ISR lesions. We investigated 72 ISR lesions in 72 patients with stable angina pectoris (SAP) who underwent pre- and post-revascularization optical coherence tomography (OCT) and coronary angioscopy (CAS). All lesions were classified as with PMN, defined by an elevated peak high-sensitivity cardiac troponin-T level during the 24-h post-PCI period, and without PMN. PMN was observed in 23 (31.9 %) lesions. PMN lesions had higher frequencies of OCT-derived thin-cap fibroatheroma (26.1 vs. 6.1 %, P = 0.03), CAS-derived intensive yellow neointima (30.4 vs. 10.2 %, P = 0.04), neointima with complex surface (60.9 vs. 28.6 %, P = 0.01), and CAS-derived atheromatous appearance (CAS-AAP), defined as yellow plaque including complex thrombi underneath disrupted neointimal coverage after ballooning (47.8 vs. 16.3 %, P = 0.008) at the most stenotic sites inside stents, compared to lesions without PMN. Multivariate logistic regression analysis identified CAS-AAP (odds ratio: 3.568, 95 % confidence interval: 1.109-11.475, P = 0.033) as an independent predictor of PMN. For ISR lesions in SAP patients, an OCT- and CAS-based assessment of neointimal tissue characteristics might help to predict the occurrence of PMN.

Use of intravascular ultrasound vs. optical coherence tomography for mechanism and patterns of in-stent restenosis among bare metal stents and drug eluting stents

This article is a perspective responses to the "Mechanisms and Patterns of Intravascular Ultrasound In-Stent Restenosis Among Bare Metal Stents and First- and Second-Generation Drug-Eluting Stents" by Goto et al., The above mentioned article outlines the use of intravascular ultrasound (IVUS) in visualizing the patterns and mechanisms of in-stent restenosis (ISR) post percutaneous coronary intervention (PCI). Although IVUS is an appropriate method of choice for this scenario, IVUS has certain limitations which can be overcome by using optical coherent tomography (OCT). OCT is not only able to overcome IVUS's limitations but is also able to provide additional information to enhance the understanding of in-stent restenotic lesions. This article also outlines the future directions for OCT both in clinical and investigation settings.

Multilayered electrospun fibrous meshes for restenosis-suppressing metallic stents

Nanofiber is a flexible and highly porous mesh that is advantageous for coating bare metal stent and local drug delivery. Herein, we developed drug-eluting stent coated with PCL/PU blending coaxial nanofiber for controlling drug release manner and suppressing in-stent restenosis, which is a representative side effect of stenting surgery. The shell of coaxial electrospun nanofibrous are composed of poly (ε-caprolactone) (PCL) and polyurethane (PU) for biodegradability and elasticity to the polymeric coating of stent. Paclitaxel (PTX) is loaded into both the core and shell through electrospinning using coaxial nozzle with different weight ratio. The morphology of nanofiber-coated stent, expansion state, and core/shell structure of nanofiber were visualized by scanning electron microscope and transmission electron microscope. As more amount of PCL/PU was infused from the outer nozzle, PTX release speed from the nanofiber was increased. And PTX suppressed L6 cell proliferation in vitro expecting potential possibility of PTX-loaded coaxial nanofiber as a drug-eluting stent coating material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 628-635, 2017.

OCT demonstrating neoatherosclerosis as part of the continuous process of coronary artery disease

Although the advent of drug-eluting stents has reduced the rates of target vessel revascularization, there are observations of ongoing stent failure occurring very late after stent implantation and presenting as very late restenosis or as very late stent thrombosis. The de novo development of atherosclerosis within the neointimal region, called neoatherosclerosis, has been identified as one of the pathomechanisms of these observed late stent failures. The mechanisms of neoatherosclerosis development and its association with stent failure are currently the subject of intensive research. Optical coherence tomography (OCT) is an invasive imaging modality that allows us to visualize the micromorphology of coronary arteries with near-histological resolution, thus providing detailed assessment of the morphological characteristics of the neointima after stent implantation, including neoatherosclerosis. Several OCT studies have tried to provide in vivo insights in the mechanisms of neoatherosclerosis development and its association with late stent failure. This review summarizes the current insights into neoatherosclerosis obtained with OCT and discusses the association of neoatherosclerosis with late stent failure.

Stent thrombosis caused by metal allergy complicated by protein S deficiency and heparin-induced thrombocytopenia: a case report and review of the literature

A 43-year-old woman recipient of a bare metal coronary stent during an acute anterior myocardial infarction was repeatedly hospitalized with recurrent stent thrombosis (ST) over the following 3 years. Emergent coronary angiography showed a thrombus in the in-stent segment of the proximal left anterior descending artery. We repeatedly aspirated the thrombus, which immediately reformed multiple times. The discontinuation of heparin and administration of thrombolytics and argatroban, followed by repeated balloon dilatations, ended the formation of new thrombi. The patient was found to be allergic to nickel, protein S deficient and carrier of heparin-induced thrombocytopenia antibody. We discuss this case in the context of a) literature pertaining to acute coronary syndromes in the young, and b) the detailed investigations needed to identify thrombotic risk factors. Steroids may be effective to prevent recurrent ST caused by stent allergy.

Association of localized hypersensitivity and in-stent neoatherosclerosis with the very late drug-eluting stent thrombosis

BACKGROUND

Localized hypersensitivity reaction, delayed arterial healing, and neoatherosclerosis inside the stent have been suggested as the underlying pathologic mechanisms of very late stent thrombosis (VLST) of drug-eluting stent (DES). The present study sought to explore the prevalence of inflammatory cell infiltrates and evidence for fragments of atherosclerotic plaques in the aspirated thrombi in patients with DES VLST.

METHODS AND RESULTS

From April 2004 to September 2012, 48 patients with stent thrombosis (ST) of DES underwent thrombus aspiration with retrieved material sufficient for the histopathologic analysis; early ST (EST, within 30 days): N = 17, late ST (LST, between 31 and 365 days): N = 7, and very late ST (VLST, >1 year): N = 24. Eosinophil fraction in the aspirated thrombi was significantly higher in patients with VLST (8.2±5.7%) as compared with those with EST (4.3±3.0%) and LST (5.5±3.8%) (P = 0.03). Eosinophil fraction in the aspirated thrombi was significantly higher in 12 VLST patients with angiographic peri-stent contrast staining (PSS) and/or incomplete stent apposition (ISA) by intravascular ultrasound than in 12 VLST patients without PSS or ISA (10.6±6.1% versus 5.8±4.1%, P = 0.03). Evidences for fragments of atherosclerotic plaques in the aspirated thrombi were observed only in 3 (13%) out of 24 patients with DES VLST.

CONCLUSIONS

Eosinophil fraction in the aspirated thrombi was significantly higher in patients with DES VLST as compared with those with EST and LST. Evidences for fragments of atherosclerotic plaques were relatively uncommon in patients with DES VLST.

Current treatment of in-stent restenosis

Management of patients with in-stent restenosis (ISR) remains an important clinical problem. Although drug-eluting stents (DES) have drastically reduced the incidence of ISR, treatment of DES-ISR is particularly challenging. ISR mainly results from aggressive neointimal proliferation, but recent data also suggest that neoatherosclerosis may play an important pathophysiological role. Intracoronary imaging provides unique insights to unravel the underlying substrate of ISR and may be used to guide repeated interventions. In this paper, we systematically reviewed clinical trial data with currently available therapeutic modalities, including DES and drug-coated balloons, in patients presenting with ISR within bare-metal stents or DES.

Clinical utility of intravascular imaging and physiology in coronary artery disease

Intravascular imaging and physiology techniques and technologies are moving beyond the framework of research to inform clinical decision making. Currently available technologies and techniques include fractional flow reserve; grayscale intravascular ultrasound (IVUS); IVUS radiofrequency tissue characterization; optical coherence tomography, the light analogue of IVUS; and near-infrared spectroscopy that detects lipid within the vessel wall and that has recently been combined with grayscale IVUS in a single catheter as the first combined imaging device. These tools can be used to answer questions that occur during daily practice, including: Is this stenosis significant? Where is the culprit lesion? Is this a vulnerable plaque? What is the likelihood of distal embolization or periprocedural myocardial infarction during stent implantation? How do I optimize acute stent results? Why did thrombosis or restenosis occur in this stent? One of the legacies of coronary angiography is to presume that one technique will answer all of these questions; however, that often has been proved inaccurate in contemporary practice.

Intra-stent tissue evaluation within bare metal and drug-eluting stents > 3 years since implantation in patients with mild to moderate neointimal proliferation using optical coherence tomography and virtual histology intravascular ultrasound

OBJECTIVE

We aimed to compare neointimal tissue characteristics between bare-metal stents (BMS) and drug-eluting stents (DES) at long-term follow-up using optical coherence tomography (OCT) and virtual histology intravascular ultrasound (VH-IVUS).

BACKGROUND

Neoatherosclerosis in neointima has been reported in BMS and in DES.

METHODS

Thirty patients with 36 stented lesions [BMS (n=17) or DES (n=19)] >3years after implantation were prospectively enrolled. OCT and VH-IVUS were performed and analyzed independently. Stents with ≥70% diameter stenosis were excluded.

RESULTS

The median duration from implantation was 126.0months in the BMS group and 60.0months in the DES group (p <0.001). Lipid-laden intima (58.8% vs. 42.1%, p=0.317), thrombus (17.6% vs. 5.3%, p=0.326), and calcification (35.3% vs. 26.3%, p=0.559) did not show significant differences between BMS and DES. When divided into 3 time periods, the cumulative incidence of lipid-laden neointima from >3years to <9years was similar between BMS and DES (42.9% vs. 42.1%, p=1.000). Furthermore, it continued to gradually increase over time in both groups. OCT-derived thin-cap fibroatheroma (TCFA) was observed in 17.6% of BMS- and 5.3% of DES-treated lesions (p=0.326). No stents had evidence of intimal disruption. The percentage volume of necrotic core (16.1% [9.7, 20.3] vs. 9.7% [7.0, 16.5], p=0.062) and dense calcium (9.5% [3.8, 13.6] vs. 2.7% [0.4, 4.9], p=0.080) in neointima tended to be greater in BMS-treated lesions. Intra-stent VH-TCFA (BMS vs. DES 45.5% vs. 18.2%, p=0.361) did not differ significantly.

CONCLUSION

At long-term follow-up beyond 3 years after implantation, the intra-stent neointimal tissue characteristics appeared similar for both BMS and DES.

Causes of very late stent thrombosis investigated using optical coherence tomography

OBJECTIVE

Very late stent thrombosis (VLST) remains an unresolved problem, and recent reports have indicated that VLST onset can occur in patients treated with both drug-eluting stents (DES) and bare metal stents (BMS). We evaluated the causes of VLST using optical coherence tomography (OCT).

METHODS

OCT was performed in 22 patients (12 DES-treated patients, 10 BMS-treated patients). Because two instances of VLST occurred simultaneously in one case in the DES group, the DES group comprised 13 lesions, while the BMS group comprised 10 lesions. All struts were counted in each frame, and the proportion of uncovered or malapposed struts was calculated based on the overall number of struts in the stent.

RESULTS

The interval from stent implantation to VLST onset was significantly longer in the BMS group. The proportion of uncovered struts and the ratio of malapposed struts were significantly higher in the DES group than in the BMS group. The OCT analysis demonstrated intimal hyperplasia or intimal disruption in all patients in the BMS group. However, in the DES group, severe hyperplasia and/or neoatherosclerosis was observed in only eight lesions (61.5%), while uncovered and malapposed struts were involved in the other lesions.

CONCLUSION

In most BMS-treated lesions, it appeared that VLST was caused by the occurrence of neoatherosclerosis after stent implantation. The causes of VLST in DES-treated lesions are more various and complicated than those observed for BMS-treated lesions.

Stent-related defects in patients presenting with stent thrombosis: differences at optical coherence tomography between subacute and late/very late thrombosis in the Mechanism Of Stent Thrombosis (MOST) study

AIMS

Subacute, late, and very late stent thrombosis (ST) may occur after stent implantation, but they are characterised by different underlying pathophysiological mechanisms. We sought to appraise differences between subacute and late/very late ST at the thrombus site by optical coherence tomography (OCT). The Mechanism Of Stent Thrombosis (MOST) study was a prospective multicentre non-randomised registry which enrolled six subacute ST and six controls (subacute ST study), and 17 late/very late ST and 17 controls (late/very late ST study).

METHODS AND RESULTS

Patients with subacute ST had a minimum stent area at the thrombus site of 2.1 mm² (1st-3rd quartile 1.3-4.5) vs. 2.9 mm² (2.4-5.0) in the matched control (p=0.05). Uncovered struts were 26.2% (16.5-35.9) vs. 13.9% (8.9-18.9), p=0.001. Malapposed struts were 18.8% (13.1-24.5) vs. 15.2% (12.8-17.6), p=0.001. In patients with late/very late ST, uncovered struts were 23.6% (13.9-33.3) vs. 5.2% (0.5-10.2), p=0.001. Malapposed struts were 12.1% (6.4-17.8) vs. 2.8% (0.4-5.2), p=0.001, and maximum malapposition distance was 0.45 mm (0.32-0.62) vs. 0.12 mm (0-0.25), p=0.01. Notably, all patients with ST had previously discontinued dual antiplatelet therapy (n=14) or showed high residual platelet reactivity on clopidogrel therapy.

CONCLUSIONS

Subacute ST had a significant stent underexpansion while late/very late ST had a greater stent strut malapposition distance at the thrombus site. These findings explain how procedure-related complications and vessel remodelling have a specific impact on the segment characterised by thrombus. High platelet reactivity also seems a necessary cofactor for both subacute and late/very late ST.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov unique identifier NCT01410539.

A case of in-stent neoatherosclerosis 10 years after carotid artery stent implantation: observation with optical coherence tomography and plaque histological findings

We report a patient's case of slow progressive in-stent restenosis 10 years after bare-metal stent implantation to his carotid artery. We treated the patient with an additional stent placement under a distal filter protection device. Optical coherence tomographic assessment and plaque histology during the carotid artery stenting (CAS) revealed atheromatous change at in-stent neointima, which contained lipid-rich plaque and calcification deposits. These findings suggest that in-stent neoatherosclerosis may play an important role in the pathogenesis of very late stent restenosis after CAS.

Stent malapposition, as a potential mechanism of very late stent thrombosis after bare-metal stent implantation: a case report

A 90-year-old man was admitted to our hospital with acute ST-segment elevation myocardial infarction. He had a history of post-infarction angina pectoris 79months ago and had a bare-metal stent (BMS) implanted in the proximal left anterior descending artery at our hospital. Emergent coronary angiography demonstrated thrombotic occlusion in the previously stented segment. After catheter thrombectomy, antegrade flow was restored, but 90% stenosis with haziness persisted in the proximal and distal portions of the previously stented segment. Intravascular ultrasound imaging showed interstrut cavities or stent malapposition at the proximal and distal sites of stented segment. In close proximity to the sites, residual thrombi were also observed. Optical coherence tomography (OCT) demonstrated neither lipid-laden neointimal tissue nor rupture but clearly demonstrated residual thrombus adjacent to the malapposed region in addition to the stent malapposition. PCI with balloon was successfully performed and stent apposition was confirmed by OCT. Stent malapposition is an unusual mechanism of very late stent thrombosis after BMS implantation. OCT can clearly reveal the etiology of stent thrombosis.

Pathological analyses of very long-term sirolimus-eluting stent implantation in human coronary artery

A 73-year-old man underwent sirolimus-eluting stent (SES) implantation for chest pain on exertion with left anterior descending coronary artery (LAD) and left circumflex coronary artery (LCX). The patient died due to non-obstructive mesenteric ischemia after 57 months of SES implantation. An autopsy demonstrated that the lesions of stented site at LAD and LCX were histopathologicaly similar images. In short, only mild neointimal formation with enough patent lumen was observed in all stented sites with no evidence of restenosis. In addition, complete coverage of endothelial cells in the surface of neointima was visible. Furthermore, necrotic core formation with a lot of circumferential cholesterol clefts was evident around the struts. In spite of these findings, observations of neointimal rupture and stent thrombosis were not found in this very late period autopsy study. In this histopathological examination, although neointimal coverage with enough lumen was observed, accumulation of extracellular lipid and cholesterol crystal was shaping necrotizing core, in short neoatherosclerosis. In the future, biocompatible drug-eluting stents which do not induce inflammation to the arterial wall post stenting should be appropriately addressed by the future development of improved coronary stents. <Learning objective: This manuscript contains original materials from pathological analysis of very long-term SES implantation. The current case report is the first one with very long-term course after SES implantation over 4 years and 9 months. In this pathological examination, although neointimal coverage with enough lumen was observed, neoatherosclerotic change around stent struts was evident. We should observe close clinical follow up after SES implantation.>.

Increased thin-cap neoatheroma and periprocedural myocardial infarction in drug-eluting stent restenosis: multimodality intravascular imaging of drug-eluting and bare-metal stents

BACKGROUND

Re-endothelialization is delayed after drug-eluting stent (DES) implantation. In this setting, neointima is more prone to become lipid laden and develop neoatherosclerosis (NA), potentially increasing plaque vulnerability.

METHODS AND RESULTS

Optical coherence tomography and near-infrared spectroscopy with intravascular ultrasound were used to characterize NA in 65 (51 DES and 14 bare-metal stents) consecutive symptomatic patients with in-stent restenosis. Median duration poststent implantation was 33 months. Optical coherence tomography-verified NA was observed in 40 stents with in-stent restenosis (62%), was more prevalent in DES than bare-metal stents (68% versus 36%; P=0.02), and demonstrated significantly higher prevalence of thin-cap neoatheroma (47% versus 7%; P=0.01) in DES. Near-infrared spectroscopy assessment demonstrated that the total lipid core burden index (34 [interquartile range, 12-92] versus 9 [interquartile range, 0-32]; P<0.001) and the density of lipid core burden index (lipid core burden index/4 mm, 144 [interquartile range, 60-285] versus 26 [interquartile range, 0-86]; P<0.001) were higher in DES compared with bare-metal stents. Topographically, NA was classified as I (thin-cap NA), II (thick-cap NA), and III (peri-strut NA). Type I thin-cap neoatheroma was more common in DES (20% versus 3%; P=0.01) and in areas of the stented segment without significant in-stent restenosis (71%). Periprocedural myocardial infarction occurred only in DES (11 versus 0; P=0.05), of which 6 (55%) could be attributed to segments with >70% in-stent restenosis. By logistic regression, prior DES was the only independent predictor of both NA (odds ratio, 7.0; 95% confidence interval, 1.7-27; P=0.006) and periprocedural myocardial infarction (odds ratio, 1.8; 95% confidence interval, 1.1-2.4; P=0.05).

CONCLUSIONS

In-stent thin-cap neoatheroma is more prevalent, is distributed more diffusely across the stented segment, and is associated with increased periprocedural myocardial infarction in DES compared with bare-metal stents. These findings support NA as a mechanism for late DES failure.

Very late bare metal stent thrombosis

Very late stent thrombosis is a rare and not-well-understood complication after bare metal stent implantation. It usually presents as an ST elevation acute coronary syndrome and it is associated with high rates of morbidity and mortality. Pathophysiologic mechanisms are not well defined; nevertheless, recent studies have proposed a neoatherosclerotic process as the triggering mechanism. We present the case of a patient with bare metal very late stent thrombosis 12 years after implantation.

A rare mechanism of very late bare metal stent thrombosis--role of optical coherence imaging in its evaluation and management

Very late stent thrombosis is an uncommon event following implantation with bare metal stents (BMS) in coronary arteries. Long term follow up studies have shown that a small number of BMS develop very late thrombosis following years of stability. Atherosclerotic transformation of neointimal tissue is increasingly being recognised as the cause of these adverse events. A 49 year-old male presented with acute inferior wall myocardial infarction resulting from thrombosis of the BMS implanted in his right coronary artery five years earlier. He was successfully thrombolysed and his coronary angiogram showed mild diffuse instent restenosis. The intravascular optical coherence tomography revealed instent neoatherosclerotic plaque rupture without any flow limiting stenosis as the likely culprit event.

Very late stent thrombosis related to incomplete neointimal coverage or neoatherosclerotic plaque rupture identified by optical coherence tomography imaging

AIMS

Recent data have reported that neoatherosclerosis could develop long after stent implantation and lead to subsequent rupture and acute coronary syndrome (ACS). We sought to identify the presence of in-stent neoatheroma (ISNA) in patients with very late stent thrombosis (VLST) using optical coherence tomography (OCT).

METHODS AND RESULTS

All patients from two catheterization centres who presented with ACS related to VLST underwent a standard coronary angiography and intra-coronary OCT. ISNA was defined as the combination of diffuse neointimal proliferation, lipid-laden intima with plaque organization, and fibrous cap rupture with no evidence of an uncovered strut. Out of 2139 ACS patients, 20 presented with definite VLST, including 10 with evidence of ISNA lesions, detected using OCT. The mean delay between initial percutaneous coronary intervention and VLST was longer in the ISNA patients compared with non-ISNA patients (10.5 ± 1.6 vs. 4.0 ± 0.6 years, P = 0.003). The mean LDL-cholesterol tended to be higher in ISNA patients compared with non-ISNA patients. OCT analysis revealed significantly thicker neointimal coverage as well as a lower number of uncovered struts in ISNA lesions compared with the other patients. LDL-cholesterol levels were correlated with the average neointima thickness (Spearman's rho = 0.46, P = 0.04). All the ISNA lesions were treated through initial thrombectomy followed by redo stenting in nine patients.

CONCLUSION

Our data show that ISNA is frequent in patients with VLST. These results suggest that OCT imaging is helpful in identifying the underlying mechanisms of VLST and, therefore, in the clinical decision-making process.

OCT analysis in patients with very late stent thrombosis

OBJECTIVES

We report optical coherence tomography (OCT) findings in 33 patients who presented with very late stent thrombosis (VLST) after either drug-eluting stent (DES) or bare-metal stent (BMS) implantation.

BACKGROUND

VLST is a potentially life-threatening complication, but the underlying mechanisms remain unclear.

METHODS

In 33 patients (27 DES- and 6 BMS-treated lesions) with definite VLST, OCT images were acquired before either thrombus aspiration or intravascular ultrasonography (IVUS) imaging.

RESULTS

The median duration from implantation was 61.5 months in the DES group and 109.1 months in the BMS group. In the overall cohort, combining DES and BMS, 94% showed intraluminal thrombi. VLST was associated with in-stent neointimal rupture in 23 patients (70%); 22 had thrombi near the site of neointimal rupture. Stent malapposition was observed in 14 (42%) lesions, but only 9 of them showed thrombi at the site of stent malapposition; moreover, 6 (18%) stented segments with malapposition also had neointimal rupture. Only 2 (6%) lesions had no evidence of neointimal rupture or malapposition. Stent fracture was detected in 3 DES-treated lesions, all with concomitant neointimal rupture. Compared with lesions without neointimal rupture, lesions with neointimal rupture showed a higher frequency of ST-segment elevation myocardial infarction (65% vs. 20%, respectively, p = 0.040) as well as a higher peak creatine kinase-myocardial band level (163.1 ng/ml vs. 15.7 ng/ml, respectively, p = 0.017).

CONCLUSIONS

OCT imaging indicated that advanced neoatherosclerosis with neointimal rupture and thrombosis was the most common mechanism of definite VLST and was associated with a high frequency of ST-segment elevation myocardial infarction.