Neointimal coverage of sirolimus-eluting stents 6 months and 12 months after implantation: evaluation by optical coherence tomography:

Exosomes secreted from mesenchymal stem cells mediate the regeneration of endothelial cells treated with rapamycin by delivering pro-angiogenic microRNAs

Delayed endothelial healing after drug eluting stent (DES) implantation is a critical clinical problem in treatment of coronary artery diseases. Exosomes exhibit proangiogenic potential in a variety of ischemic diseases. However, the association of exosomes with endothelial regeneration after DES implantation has been rarely reported. In this study, we aimed to investigate the therapeutic effects of mesenchymal stem cell (MSC)-derived exosomes on endothelial cells treated with rapamycin and explore the potential mechanisms of MSC-derived exosomes in promoting endothelial regeneration. Exosomes were isolated from MSCs by ultracentrifugation and identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blot assay. The in vitro effects of MSC-derived exosomes on the proliferation and migration of endothelial cells treated with rapamycin were evaluated by integrated experiment, cell counting kit-8, scratch, tube formation, and transwell assays. And the apoptosis of rapamycin-induced endothelial cells loaded with MSC-derived exosomes was detected using TUNEL and Annexin-V FITC and PI double-staining assays. The microRNA (miRNA) cargo of MSC-derived exosomes was identified by high-throughput RNA sequencing. Pro-angiogenic miRNAs and key pathways were further characterized. Our results indicated that MSC-derived exosomes could be ingested into umbilical vein endothelial cells (HUVECs) and significantly enhanced cell proliferation rate, migratory and tube-forming capabilities in vitro. MSC-derived exosomes also inhibited the apoptosis of HUVECs induced by rapamycin. A distinct class of exosomal miRNAs was further identified, including six miRNAs tightly related to neovasculogenesis. Silencing the expression of exosomal miRNA-21-5p and let-7c-5p attenuated the pro-proliferative and pro-migratory capacity of MSC-derived exosomes. Moreover, functional enrichment analysis indicated that metabolic pathways might contribute to reendothelialization. This study highlights a proregenerative effect of MSC-derived exosomes in vitro, which may be partly explained by the delivery of pro-angiogenic miRNAs to endothelial cells.

Invasive management without stents in selected acute coronary syndrome patients with a large thrombus burden: a prospective study of optical coherence tomography guided treatment decisions

AIMS

To assess whether a strategy of invasive management without stents in selected acute coronary syndrome (ACS) patients with a large thrombus burden (LTB) might be feasible and safe.

METHODS AND RESULTS

We performed a prospective non-randomised observational cohort study of invasive treatment decisions guided by optical coherence tomography (OCT) in selected ACS patients with LTB. Among 852 ACS patients who had undergone invasive coronary angiography, 101 (11.8%) patients with large thrombus burden on initial angiography underwent thrombectomy to restore TIMI 3 flow without stenting. All of these patients then had repeat angiography with OCT (days 0-2 [Group 1], days 3-6 [Group 2] or days 7-30 [Group 3]). No adverse events occurred between the initial and second angiograms. Residual thrombus was detected in 68% of patients with OCT (respectively, 94%, 79% and 32% in Group 1, Group 2 and Group 3), and 20% of cases with angiography. Plaque rupture was detected by OCT in 65% of cases. Minimal lumen area was 2.81 mm2, 3.40 mm2 and 4.89 mm2 in Group 1, Group 2 and Group 3, respectively. Sixty-two percent of patients were stented (respectively, 76%, 61% and 50%). During a minimum follow-up period of 12 months in all patients, one non-fatal MI occurred and one PCI was performed for angina.

CONCLUSIONS

Medical management without stents is safe and feasible in selected ACS patients with LTB. OCT revealed culprit lesion characteristics that were not disclosed by angiography and facilitated treatment decisions.

Intracoronary optical diagnostics current status, limitations, and potential

Optical coherence tomography (OCT), is a novel intravascular imaging modality analogous to intravascular ultrasound but uses light instead of sound. This review details the background, development, and status of current investigation using OCT, and discusses advantages, limitations, and likely future developments. It provides indications for possible future clinical use, and places OCT in the context of current intravascular imaging in what is a rapidly changing field of investigation.

Optical coherence tomography evaluation of drug-eluting stents: a systematic review

AIMS

We performed a systematic review of studies reporting stent strut coverage and malapposition post implantation of different drug-eluting stent (DES), as assessed by optical coherence tomography (OCT).

METHODS

A review of publications and online databases in May 2011 retrieved 33 published studies reporting stent strut coverage and malapposition post-DES implantation using OCT: 24 for sirolimus-eluting stents (SES), 13 for paclitaxel-eluting stents (PES), 10 for zotarolimus-eluting stents (ZES), and two for everolimus-eluting stents (EES). The follow-up duration ranged from 3 months to 4 years. Stent strut coverage and malapposition were compared between DES at various time intervals post implantation.

RESULTS

Significant differences in stent strut coverage and malapposition exist between various DES. The SES had the highest frequency of uncovered struts at 3, 6, 9, and 12 months (13.1%, 10.9%, 8.1%, and 7.5%, respectively), followed by PES (5.5%, 4.4%, and 5.7% at 6, 9, and 12 months, respectively) and ZES (0.7%, 0%, and 0.5% at 3, 6, and 9 months, respectively) (P < 0.001 for all comparisons between stents). Only two studies reported 3.1% uncovered struts at 9 months with the EES. Stent strut malapposition at 6, 9, and 12 months was highest with SES (3.2%, 2.2%, and 1.2%, respectively) followed by PES (1.6%, 1.3%, and 0.9%, respectively), EES (0.46% at 9 months), and ZES (0.7% and 0.1% at 6 and 9 months, respectively).

CONCLUSIONS

SES had the highest rates of uncovered struts and malapposition, followed by PES and ZES. Such differences may explain the different clinical outcomes between various DES. © 2012 Wiley Periodicals, Inc.

Optical coherence tomography: from research to practice

Optical coherence tomography (OCT) is a high-resolution imaging technique with great versatility of applications. In cardiology, OCT has remained hitherto as a research tool for characterization of vulnerable plaques and evaluation of neointimal healing after stenting. However, OCT is now successfully applied in different clinical scenarios, and the introduction of frequency domain analysis simplified its application to the point it can be considered a potential alternative to intravascular ultrasound for clinical decision-making in some cases. This article reviews the use of OCT for assessment of lesion severity, characterization of acute coronary syndromes, guidance of intracoronary stenting, and evaluation of long-term results.

Mechanical properties and in vivo performance of a novel sliding-lock bioabsorbable poly-p-dioxanone stent

A bioabsorbable poly-p-dioxanone (PPDO) stent with a novel sliding-lock structure was fabricated to treat stenotic peripheral vessels. The sliding-lock PPDO stents have greater radial strength (107 kPa) than PPDO stents with conventional net-tube structure (32 kPa). The sliding-lock PPDO stents were implanted into the iliac arteries of pigs, and implantation success rate was 90% indicating the feasibility of this design. Additionally, we found that sliding-lock PPDO stents kept vessels patent, although by 3 and 6 months post implantation, luminal diameter decreased slightly due to intimal hyperplasia. At 1 month post implantation, the stents were sparsely covered with endothelial cells, and by 6 months, the stents were mostly absorbed and inflammatory reaction gradually decreased as the stents were absorbed. This study shows favorable mechanical strength, degradability and efficacy for the sliding-lock PPDO stents, and supports further research and development of this unique design of polymer stents for applications in vascular devices.

Optical coherence tomography endpoints in stent clinical investigations: strut coverage

Late stent thrombosis (LST) and very LST (VLST) are infrequent complications after drug-eluting stent (DES) implantation, but they carry a significant risk for patients. Delayed healing, which may be represented by incomplete stent coverage, has been observed in necropsy vessel specimens treated with DES. As a result, in vivo assessment of stent coverage, as well as stent apposition using optical coherence tomography (OCT), have been recently used as surrogate safety endpoints in clinical trials testing DES platforms. By adopting strut coverage assessed by OCT, one can assess the safety profile of the new generation of DES in preregistration studies. This article focuses on stent strut coverage as a central predictor of late DES thrombosis from the histopathological point of view, discusses the limitations of the current imaging modalities and presents the technical characteristics of OCT for the detection of neointimal coverage after stent implantation. We also review the preclinical and clinical investigations using this novel imaging modality.

Optical coherence tomography: its value in intravascular diagnosis today

Optical coherence tomography is a recently developed high-resolution intravascular diagnostic technique. Initially, it was mainly used for characterizing atherosclerotic plaque because it served a number of functions, from identifying plaque with high lipid content to detecting macrophage accumulation, both of which are associated with plaque instability. Currently, there is growing interest in the value of optical coherence tomography in the area of coronary intervention, where the technique offers significant advantages over more widespread intravascular diagnostic techniques such as intravascular ultrasound: its higher resolution means that the vessel lumen diameter can be measured more precisely, periprocedural complications such microdissection of the coronary artery can be detected, stent apposition relative to the vessel wall can be optimized, neointimal hyperplasia can be detected after stent implantation, and neointimal thickness can be measured. It would therefore appear to be a very useful technique for interventional cardiologists. This review article considers the technical details of the technique and its applications, and compares it with other intravascular diagnostic techniques.

Neointimal coverage and stent strut apposition six months after implantation of a paclitaxel eluting stent in acute coronary syndromes: an optical coherence tomography study

OBJECTIVES

Prospective optical coherence tomography (OCT) study of strut apposition and neointimal hyperplasia thickness (NIH) of a paclitaxel eluting stent (PES), (Infinium, Sahajanand Medical Technologies Pvt Ltd.).

BACKGROUND

Few data exist concerning neointimal coverage of PES. Uncovered and malapposed struts are more common following stenting in acute coronary syndromes (ACS) than in non-ACS lesions.

METHODS

All consecutive patients with ACS, treated with the above PES for single native coronary lesions between August 2008 and January 2009, who consented to invasive follow-up with OCT at six months (N=13), were included.

RESULTS

At 6 months no patient demonstrated angiographic restenosis. 3180 struts from 20 stents were analyzed, and 91.3% were covered with neointima (NIH 204.8 ± 159.5 μm). Standard statistics and least squares estimates (LSE) derived from a hierarchical ANCOVA model to take into account clustering effects are presented. Rate of uncovered struts was 8.6%, LSE 7.39 (95% CI 3.05-11.73), malapposed struts 2.2%, LSE 1.76 (95% CI 0.05-3.58), and protruding struts 2.9%, LSE 2.8 (95% CI 1.35-4.65). The proportion of uncovered malapposed struts was significantly higher compared to uncovered embedded struts (55.7% vs. 6.8%, p<0.01). In total, 5 (25%) PES were fully covered by neointima. No intracoronary thrombus or clinical events were detected.

CONCLUSIONS

Six months after implantation of a specific PES in patients with ACS, most of the stents were only partially covered with neointima, especially at sites of strut malapposition or protrusion. These findings emphasize the need for optimal stent apposition during implantation and for prolonged dual antiplatelet therapy.

The fate of incomplete stent apposition with drug-eluting stents: an optical coherence tomography-based natural history study

AIMS

To assess the fate of incomplete stent apposition (ISA) after deployment of sirolimus-eluting stents (SESs).

METHODS AND RESULTS

Thirty-two patients having intravascular ultrasound (IVUS)-guided PCI with SESs underwent assessment of stent deployment with quantitative coronary angiography, IVUS, and optical coherence tomography (OCT) pre-procedure, post-procedure, and at 10 months follow-up. Incomplete stent apposition was defined as separation of a stent strut from the inner vessel wall by >160 microm. At follow-up, 4.67% of struts with ISA at deployment failed to heal and 7.59% which were well apposed did not develop neointimal hyperplasia even after 10 months. Lesion remodelling was responsible for the development of late ISA in only 0.37% of struts. Failure of adequate neointimal hyperplasia was quantitatively the most important mechanism responsible for persistent acute ISA, classified in previous studies, which relied only on follow-up OCT, as late ISA. Thrombus was visualized in 20.6% of struts with ISA at follow-up and in 2.0% of struts with a good apposition (P < 0.001).

CONCLUSION

In patients with SESs, ISA can fail to heal and even complete apposition can be associated with no neointimal hyperplasia. Incomplete stent apposition without neointimal hyperplasia was significantly associated with the presence of OCT-detected thrombus at follow-up, and may constitute a potent substrate for late stent thrombosis.

Different vascular healing patterns with various drug-eluting stents in primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: optical coherence tomographic findings

The introduction of optical coherence tomography has provided a new method for evaluating the vascular response to drug-eluting stents (DESs). We used optical coherence tomography to compare neointimal coverage and stent malapposition among DESs in patients with ST-segment elevation myocardial infarction. Optical coherence tomography was performed at 9 months after implantation of 3 types of DESs at the culprit lesions in 46 patients with ST-segment elevation myocardial infarction (16 sirolimus-eluting stents [SESs, Cypher Select], 11 paclitaxel-eluting stents [PESs, Taxus Liberte], and 19 zotarolimus-eluting stents [ZESs, Endeavor Sprint]). The neointimal thickness and apposition at each strut at each 1-mm interval and the presence of thrombi in each stent were evaluated. A total of 11,512 stent struts were analyzed. SESs had the thinnest neointimal thickness (SES 62 +/- 43 mum vs PES 244 +/- 142 mum vs ZES 271 +/- 128 mum, p <0.001). The incidence of uncovered struts and malapposed struts were significantly greater in SESs and PESs than in ZESs (SES vs PES vs ZES, 16.2 +/- 17.8% vs 4.7 +/- 7.4% vs 0.6 +/- 1.5%, respectively, p = 0.001; and 4.0 +/- 8.2% vs 2.1 +/- 4.5% vs 0 +/- 0%, respectively, p = 0.001). Thrombus was also detected more often in SESs and PESs than in ZESs (SES, 6 [38%] vs PES, 3 [27%] vs ZES, 1 [5%], p = 0.02). In conclusion, the rate of stent strut coverage and malapposition were significantly different among the DES types in ST-segment elevation myocardial infarction. In particular, most stent struts in ZESs were covered with neointima and well-apposed. These findings imply that the type of DES might affect the vascular response in thrombotic lesions of ST-segment elevation myocardial infarction.

In vivo supervised analysis of stent reendothelialization from optical coherence tomography

The aim of this study is to interactively assess reendothelialization of stents at an accuracy of down to a few micrometer by analyzing endovascular optical coherence tomography (OCT) sequences. Vessel wall and stent struts are automatically detected by using morphological, gradient, and symmetry operators coupled with active contour models; alerts are issued to ask for user supervision over some extreme irregular geometries caused by thrombotic lesions or dissections. A complete distance map is then computed from sparse distances measured between wall and struts. Missing values are interpolated by thin-plate spline (TPS) functions. Accuracy and robustness are increased by taking into account the inhomogeneity of data points and integrating in the same framework orthogonalized forward selection of support points, optimal selection of regularization parameters by generalized cross-validation, and rejection of detection outliers. Validation is performed on simulated data, phantom acquisitions and 11 typical in vivo OCT sequences. The comparison against manual expert measurements demonstrates a bias of the order of OCT resolution (less than 10 microm) and a standard deviation of the order of the strut width (less than 150 microm).

The role of optical coherence tomography in vascular medicine

Optical coherence tomography (OCT) is an emerging imaging modality that provides high-resolution, microstructural information on atherosclerotic plaques in biological systems. Intracoronary OCT can identify thin-cap fibroatheroma and other vulnerable plaques that may be responsible for acute coronary events. These characteristics make OCT helpful in guiding coronary management and interventions, including stent apposition and early identification of procedure-related complications. OCT is being assessed for its potential role in carotid plaque characterization and in the diagnosis of peripheral arterial atherosclerosis. Its current use in studying carotid and cerebral vasculature and in the diagnosis of peripheral arterial diseases is limited and ill defined, but it is finding increasing application in these areas. Its performance can be further improved by increasing the signal to noise ratio and by using dynamic focus tracking techniques. It can potentially be used to monitor the progression and regression of atherosclerosis in the coronary, cerebral and peripheral vasculature. New indications for its use in vascular medicine are emerging as its technology continues to improve over time.