Neointimal coverage of bare-metal and sirolimus-eluting stents evaluated with optical coherence tomography

Plaque burden is associated with minimal intimal coverage following drug-eluting stent implantation in an adult familial hypercholesterolemia swine model

Safety and efficacy of coronary drug-eluting stents (DES) are often preclinically tested using healthy or minimally diseased swine. These generally show significant fibrotic neointima at follow-up, while in patients, incomplete healing is often observed. The aim of this study was to investigate neointima responses to DES in swine with significant coronary atherosclerosis. Adult familial hypercholesterolemic swine (n = 6) received a high fat diet to develop atherosclerosis. Serial OCT was performed before, directly after, and 28 days after DES implantation (n = 14 stents). Lumen, stent and plaque area, uncovered struts, neointima thickness and neointima type were analyzed for each frame and averaged per stent. Histology was performed to show differences in coronary atherosclerosis. A range of plaque size and severity was found, from healthy segments to lipid-rich plaques. Accordingly, neointima responses ranged from uncovered struts, to minimal neointima, to fibrotic neointima. Lower plaque burden resulted in a fibrotic neointima at follow-up, reminiscent of minimally diseased swine coronary models. In contrast, higher plaque burden resulted in minimal neointima and more uncovered struts at follow-up, similarly to patients' responses. The presence of lipid-rich plaques resulted in more uncovered struts, which underscores the importance of advanced disease when performing safety and efficacy testing of DES.

Optical Coherence Tomography: An Eye Into the Coronary Artery

Optical coherence tomography (OCT) is slowly but surely gaining a foothold in the hands of interventional cardiologists. Intraluminal and transmural contents of the coronary arteries are no longer elusive to the cardiologist's probing eye. Although the graduation of an interventionalist in imaging techniques right from naked eye angiographies to ultrasound-based coronary sonographies to the modern light-based OCT has been slow, with the increasing regularity of complex coronary cases in practice, such a transition is inevitable. Although intravascular ultrasound (IVUS) due to its robust clinical data has been the preferred imaging modality in recent years, OCT provides a distinct upgrade over it in many imaging and procedural aspects. Better image resolution, accurate estimation of the calcified lesion, and better evaluation of acute and chronic stent failure are the distinct advantages of OCT over IVUS. Despite the obvious imaging advantages of OCT, its clinical impact remains subdued. However, upcoming newer trials and data have been encouraging for expanding the use of OCT to wider indications in clinical utility. During percutaneous coronary intervention (PCI), OCT provides the detailed information (dissection, tissue prolapse, thrombi, and incomplete stent apposition) required for optimal stent deployment, which is the key to successfully reducing the major adverse cardiovascular event (MACE) and stent-related morbidities. The increasing use of OCT in complex bifurcation stenting involving the left main (LM) is being studied. Also, the traditional pitfalls of OCT, such as additional contrast load for image acquisition and stenting involving the ostial and proximal LM, have also been overcome recently. In this review, we discuss the interpretation of OCT images and its clinical impact on the outcome of procedures along with current barriers to its use and newer paradigms in which OCT is starting to become a promising tool for the interventionalist and what can be expected for the immediate future in the imaging world.

Vascular Responses to First-Generation Sirolimus-Eluting Stents and Bare-Metal Stents Beyond 10 Years

Background: There are limited data regarding differences in vascular responses between first-generation sirolimus-eluting stents (1G-SES) and bare-metal stents (BMS) >10 years after implantation.

Methods and Results: We retrospectively investigated 223 stents (105 1G-SES, 118 BMS) from 131 patients examined by optical coherence tomography (OCT) >10 years after implantation. OCT analysis included determining the presence or absence of a lipid-laden neointima, calcified neointima, macrophage accumulation, malapposition, and strut coverage. Neoatherosclerosis was defined as having lipid-laden neointima. OCT findings were compared between the 1G-SES and BMS groups, and the predictors of neoatherosclerosis were determined. The median stent age at the time of OCT examinations was 12.3 years (interquartile range 11.0–13.2 years). There were no significant differences in patient characteristics between the 1G-SES and BMS groups. On OCT analysis, there was no difference in the prevalence of neoatherosclerosis and calcification between 1G-SES and BMS. Multivariable logistic regression analysis revealed that stent size, stent length, and angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use were significant predictors of neoatherosclerosis. In addition, uncovered and malapposed struts were more prevalent with 1G-SES than BMS.

Conclusions: After >10 years since implantation, the prevalence of neoatherosclerosis was no different between 1G-SES and BMS, whereas uncovered struts and malapposition were significantly more frequent with 1G-SESs.

Should We Still Have Bare-Metal Stents Available in Our Catheterization Laboratory?

The introduction of bare-metal stents (BMS) has represented a major advancement over plain old balloon angioplasty in the management of coronary artery disease. However, the high rates of target lesion revascularization associated with use of BMS have led to the development of drug-eluting stents, which require prolonged dual antiplatelet therapy due to the increased risk of late and very late stent thrombosis. The improvements in newer-generation drug-eluting stents have translated into better safety and efficacy compared with earlier generation and BMS, thus allowing shorter dual antiplatelet therapy duration. Here, we aim to provide reasons as to why we still need BMS in our cardiac catheterization laboratory.

Vascular response profiles following a nano polymer-free sirolimus-eluting stent implantation assessed by optical coherence tomography in a porcine model

Optical coherence tomography (OCT) is a high resolution imaging modality and has been considered as the ideal tool for the evaluation of neointimal tissue and vascular responses following stent implantation. However, vascular response profiles following the implantation of a novel nano polymer-free sirolimus-eluting stent (SES) assessed by OCT has not been fully investigated. Therefore, the aim of the present study was to determine the effects of a nano polymer-free SES on neointimal formation using OCT. A total of 16 nano polymer-free SESs were implanted in the coronary arteries of 8 pigs. At 3 (n=4) or 6 months (n=4), the animals were euthanized following OCT evaluation and the stented arterial segments were analyzed by histological analysis. Neointimal area, thickness and burden were evaluated by OCT. In addition, strut-associated inflammation, stent endothelialization and arterial injury were investigated by histomorphological analysis. OCT examination showed that at 6 months, neointimal thickness (193.3±109.5 vs. 167.2±119.7 µm, P=0.023) and neointimal burden (29.3±14.3 vs. 24.8±17.4%, P=0.006) significantly increased compared with at 3 months. Histomorphological analysis indicated that the endothelialization score was significantly greater at 6 months compared with at 3 months (2.85±0.36 vs. 2.52±0.60, P<0.001). However, at 3 months, nano polymer-free SES showed a significantly higher inflammatory score [0 (0, 1) vs. 0 (0, 0), P<0.001] compared with at 6 months. In conclusion, nano polymer-free SES achieves endothelialization at 3 months; however, neointimal proliferation is more significant at 6 months and may be attributed to strut-associated inflammation.

Automated detection of vessel lumen and stent struts in intravascular optical coherence tomography to evaluate stent apposition and neointimal coverage

PURPOSE

Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the microstructure of arterial walls in vivo. IV-OCT enables the clinician to clearly observe and accurately measure stent apposition and neointimal coverage of coronary stents, which are associated with side effects such as in-stent thrombosis. In this study, the authors present an algorithm for quantifying stent apposition and neointimal coverage by automatically detecting lumen contours and stent struts in IV-OCT images.

METHODS

The algorithm utilizes OCT intensity images and their first and second gradient images along the axial direction to detect lumen contours and stent strut candidates. These stent strut candidates are classified into true and false stent struts based on their features, using an artificial neural network with one hidden layer and ten nodes. After segmentation, either the protrusion distance (PD) or neointimal thickness (NT) for each strut is measured automatically. In randomly selected image sets covering a large variety of clinical scenarios, the results of the algorithm were compared to those of manual segmentation by IV-OCT readers.

RESULTS

Stent strut detection showed a 96.5% positive predictive value and a 92.9% true positive rate. In addition, case-by-case validation also showed comparable accuracy for most cases. High correlation coefficients (R > 0.99) were observed for PD and NT between the algorithmic and the manual results, showing little bias (0.20 and 0.46 μm, respectively) and a narrow range of limits of agreement (36 and 54 μm, respectively). In addition, the algorithm worked well in various clinical scenarios and even in cases with a low level of stent malapposition and neointimal coverage.

CONCLUSIONS

The presented automatic algorithm enables robust and fast detection of lumen contours and stent struts and provides quantitative measurements of PD and NT. In addition, the algorithm was validated using various clinical cases to demonstrate its reliability. Therefore, this technique can be effectively utilized for clinical trials on stent-related side effects, including in-stent thrombosis and in-stent restenosis.

Optical coherence tomography assessment of efficacy of thrombus aspiration in patients undergoing a primary percutaneous coronary intervention for acute ST-elevation myocardial infarction

OBJECTIVE

We used optical coherence tomography (OCT) to assess the impact of thrombus aspiration before angioplasty on poststenting tissue protrusions in patients undergoing a primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

A total of 188 patients with STEMI who underwent thrombus-aspiration PCI (n=113) or standard PCI (n=75) were examined in this study. OCT was performed immediately after primary PCI to assess lesion morphology in the stented segment. The minimum stent area was similar between the thrombus-aspiration PCI group and the standard PCI group [7.4 interquartile range (IQR): 5.8-9.4 vs. 7.4 IQR: 5.8-8.9 mm², P=0.788]. The maximum tissue protrusion area [0.6 (IQR: 0.3-1.1) vs. 1.2 (IQR: 0.8-1.9) mm², P<0.001], the mean tissue protrusion area [0.1 (IQR: 0.1-0.2) vs. 0.5 (IQR: 0.3-0.8) mm², P<0.001], and tissue protrusion volume [2.3 (IQR: 1.3-4.3) vs. 8.3 (IQR: 5.4-14.6) mm², P<0.001] were significantly smaller in the thrombus-aspiration PCI group compared with the standard PCI group. Minimum lumen area was significantly greater in the thrombus-aspiration PCI group compared with the standard PCI group [6.9 (IQR: 5.4-8.8) vs. 6.3 (IQR: 4.6-7.8) mm², P=0.033].

CONCLUSION

Thrombus aspiration before angioplasty in patients with STEMI was associated with significantly smaller tissue protrusion and larger lumen poststenting compared with standard PCI. Thrombus aspiration in primary PCI favorably influenced lesion morphologies in the stented segment.

Diagnostic imaging capabilities of the Ocelot -Optical Coherence Tomography System, ex-vivo evaluation and clinical relevance

BACKGROUND

Optical coherence tomography (OCT) is a high-resolution sub-surface imaging modality using near-infrared light to provide accurate and high contrast intra-vascular images. This enables accurate assessment of diseased arteries before and after intravascular intervention. This study was designed to corroborate diagnostic imaging equivalence between the Ocelot and the Dragonfly OCT systems with regards to the intravascular features that are most important in clinical management of patients with atherosclerotic vascular disease. These intravascular features were then corroborated in vivo during treatment of peripheral arterial disease (PAD) pathology using the Ocelot catheter.

METHODS

In order to compare the diagnostic information obtained by Ocelot (Avinger Inc., Redwood City, CA) and Dragonfly (St. Jude Medical, Minneapolis, MN) OCT systems, we utilized ex-vivo preparations of arterial segments. Ocelot and Dragonfly catheters were inserted into identical cadaveric femoral peripheral arteries for image acquisition and interpretation. Three independent physician interpreters assessed the images to establish accuracy and sensitivity of the diagnostic information. Histologic evaluation of the corresponding arterial segments provided the gold standard for image interpretation. In vivo clinical images were obtained during therapeutic interventions that included crossing of peripheral chronic total occlusions (CTOs) using the Ocelot catheter.

RESULTS

Strong concordance was demonstrated when matching image characteristics between both OCT systems and histology. The Dragonfly and Ocelot system's vessel features were interpreted with high sensitivity (91.1-100%) and specificity (86.7-100%). Inter-observer concordance was documented with excellent correlation across all vessel features. The clinical benefit that the Ocelot OCT system provided was demonstrated by comparable procedural images acquired at the point of therapy.

CONCLUSIONS

The study demonstrates equivalence of image acquisition and consistent physician interpretation of images acquired by the Ocelot and the Dragonfly OCT systems in-spite of distinct image processing algorithms and catheter configurations. This represents a dramatic shift away from both fluoroscopic imaging and diagnostic-only OCT imaging during peripheral arterial intervention towards therapeutic devices that incorporate real time diagnostic OCT imaging. In the clinical practice, these diagnostic capabilities have translated to best-in-class safety and efficacy for CTO crossing using the Ocelot catheter.

Histological validation of frequency domain optical coherence tomography for the evaluation of neointimal formation after a novel polymer-free sirolimus-eluting stent implantation

Novel polymer-free drug-eluting stents have been developed to reduce polymer-related adverse events. However, neointimal coverage after polymer-free DES implantation is unclear and validation between optical coherence tomography (OCT) and histology is required. Sixteen polymer-free sirolimus-eluting stents were randomly implanted into coronary arteries of 8 normal swine. OCT and histological measurement were conducted at 3 or 6 months after stent placement. For quantitative measures, lumen area, stent area, neointimal area and neointimal thickness were validated in every single OCT and histology matched cross-section. Moreover, for qualitative analysis, OCT signal patterns of neointimal tissue were classified as homogeneous, layered and heterogeneous patterns based on optical intensity and backscatter pattern and peri-strut inflammation was also determined by histology. In total, 70 OCT and histology matched cross-sections were analyzed. At quantitative analysis, good correlations and agreements were found in the measurement of lumen area (ICC = 0.67, P<0.001), neointimal area (ICC = 0.89, P<0.001) and neointimal thickness (ICC = 0.94, P<0.001) except for stent area (ICC 0.19, P = 0.13) between OCT and histology. At qualitative analysis, lymphocyte infiltrations of peri-strut were more frequently seen in heterogeneous sections than in homogeneous sections (10/14 sections, 71.4% vs. 12/50 sections, 24%; P = 0.003). In conclusion, OCT has proper correlation and agreement with histology in assessment of neointimal formation and heterogeneous neointima assessed by OCT may also be associated with peri-strut inflammation detected in histology after polymer-free sirolimus-eluting stents implantation, supporting the use of OCT to evaluate neointimal coverage after polymer-free stent implantation in clinical practice.

Local MicroRNA Modulation Using a Novel Anti-miR-21-Eluting Stent Effectively Prevents Experimental In-Stent Restenosis

OBJECTIVE

Despite advances in stent technology for vascular interventions, in-stent restenosis (ISR) because of myointimal hyperplasia remains a major complication.

APPROACH AND RESULTS

We investigated the regulatory role of microRNAs in myointimal hyperplasia/ISR, using a humanized animal model in which balloon-injured human internal mammary arteries with or without stenting were transplanted into Rowett nude rats, followed by microRNA profiling. miR-21 was the only significantly upregulated candidate. In addition, miR-21 expression was increased in human tissue samples from patients with ISR compared with coronary artery disease specimen. We systemically repressed miR-21 via intravenous fluorescein-tagged-locked nucleic acid-anti-miR-21 (anti-21) in our humanized myointimal hyperplasia model. As expected, suppression of vascular miR-21 correlated dose dependently with reduced luminal obliteration. Furthermore, anti-21 did not impede reendothelialization. However, systemic anti-miR-21 had substantial off-target effects, lowering miR-21 expression in liver, heart, lung, and kidney with concomitant increase in serum creatinine levels. We therefore assessed the feasibility of local miR-21 suppression using anti-21-coated stents. Compared with bare-metal stents, anti-21-coated stents effectively reduced ISR, whereas no significant off-target effects could be observed.

CONCLUSION

This study demonstrates the efficacy of an anti-miR-coated stent for the reduction of ISR.

Impact of drug-eluting balloon (pre- or post-) dilation on neointima formation in de novo lesions treated by bare-metal stent: the IN-PACT CORO trial

The efficacy of DEB in modifying the high restenosis risk associated with BMS implantation is doubtful. Optical coherence tomography (OCT) may allow precise assessment of neointimal formation after stent implantation. We performed a single-center, prospective, 1:2 randomized trial comparing BMS implantation alone (BMS group) vs. additional DEB (DEB group). DEB patients were further randomized 1:1 to DEB before stenting (pre-DEB group), or after stenting (post-DEB group). Primary endpoint was OCT-assessed neointimal hyperplasia (expressed both as mean in-stent neointimal area and as percentage obstruction of the mean stent area) at 6 months. Secondary endpoints were the percentage of uncovered and malapposed stent struts. Thirty patients were enrolled and randomized to BMS (n = 10), pre-DEB (n = 10), post-DEB (n = 10). At 6-month OCT follow-up, DEB significantly reduced neointimal area compared with BMS: mean neointimal area 2.01 ± 0.89 vs. 3.03 ± 1.07 mm(2) (p = 0.02), percentage area obstruction 24.56 ± 12.50 vs. 37.51 ± 12.26 % (p = 0.02). The percentage of uncovered and malapposed stent struts did not differ significantly between BMS and DEB. In the comparison between pre-DEB and post-DEB, no significant difference was observed for both primary and secondary endpoints. In de novo coronary lesions treated with BMS, DEB use could be associated with a mild reduction in neointimal hyperplasia at 6 months; this effect could be unrelated to the timing of DEB dilation (pre- or post-stenting).

CLINICAL TRIAL REGISTRATION INFORMATION

http://www.clinicaltrials.gov . Identifier: NCT01057563.

In Vivo Characterization of Carotid Neointimal Hyperplasia by use of Optical Coherence Tomography: Before and After Cutting Balloon Angioplasty

Optical coherence tomography (OCT) is a modern intravascular imaging modality that has the capability to provide detailed, in vivo characterization of the arterial wall and atherosclerotic plaque. The current understanding of the appearance of atherosclerotic plaque via OCT is largely based on coronary arterial studies where OCT information has been employed to guide therapeutic management and permits the immediate evaluation of percutaneous intervention. The clinical success of OCT in the coronary arteries has laid the foundation for investigation of the carotid artery and thus, stroke risk assessment. We report the novel use of OCT for tissue characterization of severe stenosis subsequent to carotid artery stenting (CAS), both before and after treatment with cutting balloon angioplasty.

Intracoronary optical coherence tomography: a review of clinical applications

Optical coherence tomography (OCT) is a light-based technology that provides very high spatial resolution images. OCT has been initially employed as a research tool to investigate plaque morphology and stent strut coverage. The introduction of frequency domain OCT allowing fast image acquisition during a prolonged contrast injection via the guiding catheter has made OCT applicable for guidance of coronary interventions. In this manuscript, the various applications of OCT are reviewed, from assessment of plaque vulnerability and severity to characteristics of unstable lesions and thrombus burden to stent optimization and evaluation of late results.

Mechanisms, pathophysiology, and clinical aspects of incomplete stent apposition

Incomplete stent apposition (ISA) is characterized by the lack of contact of at least 1 stent strut with the vessel wall in a segment not overlying a side branch; it is more commonly found in drug-eluting stents than bare-metal stents. The accurate diagnosis of ISA, initially only possible with intravascular ultrasound, can currently be performed with higher accuracy by optical coherence tomography, which also enables strut-level assessment due to its higher axial resolution. Different circumstances related both to the index procedure and to vascular healing might influence ISA occurrence. Although several histopathology and clinical studies linked ISA to stent thrombosis, potential selection bias precluded definitive conclusions. Initial studies usually performed single time point assessments comparing overall ISA percentage and magnitude in different groups (i.e., stent type), thus hampering a comprehensive understanding of its relationship with vascular healing. Serial intravascular imaging studies that evaluated vascular response heterogeneity recently helped fill this gap. Some particular clinical scenarios such as acute coronary syndromes, bifurcations, tapered vessels, overlapping stents, and chronic total occlusions might predispose to ISA. Interventional cardiologists should be committed to optimal stent choices and techniques of implantation and use intravascular imaging guidance when appropriate to aim at minimizing acute ISA. In addition, the active search for new stent platforms that could accommodate vessel remodeling over time (i.e., self-expandable stents) and for new polymers and/or eluting drugs that could induce less inflammation (hence, less positive remodeling) could ultimately reduce the occurrence of ISA and its potentially harmful consequences.

Clinical and angiographic outcomes following first-in-man implantation of a novel thin-strut low-profile fixed-wire stent: the Svelte Coronary Stent Integrated Delivery System first-in-man trial

AIMS

The Svelte Stent Integrated Delivery System (IDS) is a novel fixed-wire thin-strut cobalt-chromium stent characterised by a very low entry profile. The aim of the present study is to evaluate the safety and the feasibility of the Svelte stent IDS implantation in humans.

METHODS AND RESULTS

The present investigation is a prospective, multicentre non-randomised single-arm study. The primary endpoint was freedom from major adverse cardiac events (MACE) at 30 days post-procedure. Invasive follow-up was scheduled at six months post implantation. A total of 47 patients were enrolled and serial OCT imaging was performed in a subgroup of 18 patients. At the index procedure the lesion success rate was 97.9% (46 patients), the mean acute gain was 1.56 ± 0.43 mm with a mean minimum lumen diameter of 2.48 ± 0.43 mm. Post-implantation OCT imaging revealed a minimal mean prolapse area (0.10 ± 0.06 mm²), mean incomplete stent apposition area (0.12 ± 0.13 mm²) and mean intraluminal mass area (0.05 ± 0.03 mm²). Edge dissections were reported in eight cases (mean dissection width 0.17 ± 0.07 mm proximally and 0.25 ± 0.24 mm distally). At 30-day clinical follow-up, one case of myocardial infarction was reported. At six months, the angiographic mean in-stent late loss was 0.95 ± 0.76 mm. By OCT, a high percentage of struts was covered (97.6 ± 15.00 %) with a mean neointimal thickness of 0.31 ± 0.14 mm, all edge dissections were clinically silent and healed. Target lesion revascularisation (TLR) occurred in 11 patients (23.4%) and clinically driven TLR in three of these patients (6.4%). No cases of death or stent thrombosis were reported during the study.

CONCLUSIONS

Implantation of the Svelte stent IDS was observed to be safe, feasible and associated with a low acute vascular injury and a high percentage of strut coverage at 6-month follow-up.

MicroRNA-21 mediates the rapamycin-induced suppression of endothelial proliferation and migration

Rapamycin suppresses endothelial proliferation and migration, which leads to delayed re-endothelialization in the rapamycin-eluted stents that are used in coronary heart disease patients. Because microRNAs (miRs) play important roles in endothelial angiogenesis, we tested the hypothesis that rapamycin induces endothelial suppression, partly through pathways that involve miRs. Rapamycin treatment increased the expression of miR-21 in HUVECs. The downregulation of miR-21 by inhibitors abolished the negative effects of rapamycin on endothelial cell growth and mobility. RhoB was confirmed as a direct target gene of miR-21. Knockdown of Raptor by siRNA mimicked the effects of rapamycin on miR-21 expression. Our study provides a new explanation of the mechanism of rapamycin-mediated inhibition of endothelial proliferation and migration.

Optical Coherence Tomography: Potential Clinical Applications

Optical coherence tomography (OCT) is a novel intravascular imaging modality using near-infrared light. By OCT it is possible to obtain high-resolution cross-sectional images of the vascular wall structure and assess the acute and long-term effects of percutaneous coronary intervention. For the time being OCT has been mainly used in research providing new insights into the pathophysiology of the atheromatic plaque and of the vascular response to stenting, however, it seems that there is potential for clinical application of OCT in various fields, such as pre-interventional evaluation of coronary arteries, procedural guidance in coronary interventions, and follow-up assessment of vascular healing after stent implantation. This review will focus on the potential and advantages of OCT in the clinical practice of a catheterization laboratory.

Initial findings of impact of strut width on stent coverage and apposition of sirolimus-eluting stents assessed by optical coherence tomography

OBJECTIVES

We investigate the influence of stent design on stent coverage at 6-9 months after sirolimus eluting stent (SES) implantation using optical coherence tomography (OCT).

BACKGROUND

Although some reports suggest that stent design may correlate with stent coverage of stent struts, there were few detailed data whether stent design impact on stent coverage in the same drug-eluting stent.

METHODS

A total of 21 SESs (15 patients), who had implanted 2.5, 2.75, and 3.0 mm stents, underwent OCT at 6-9 months after stent implantation. SES is constructed by two different strut width-components; narrow strut width parts (59 μm) and wide strut width parts (115 μm). Thus, we divided stent struts of SESs into two groups: narrow strut width parts (narrow group) and wide ones (wide group). We compared the incidence of incomplete apposed struts, uncovered struts, and neointimal hyperplasia (NIH) thickness between the two groups.

RESULTS

We could detect 2,948 struts (narrow group consisted of 1,132 struts and wide group consisted of 1,816 struts). Incidence of uncovered struts in the narrow group was significantly lower than in the wide group (30.2% vs. 40.8%, P < 0.001), and NIH thickness in the narrow group was significantly greater than in the wide group (127.5 ± 93.4 μm vs. 118.6 ± 81.4 μm, P = 0.03).

CONCLUSIONS

Stent design, especially strut width, affects stent coverage of SES. The narrow strut may avoid the absence of stent coverage in SES, which correlates with stent thrombosis.

INtimal hyPerplasia evAluated by oCT in de novo COROnary lesions treated by drug-eluting balloon and bare-metal stent (IN-PACT CORO): study protocol for a randomized controlled trial

Background

Neointimal hyperplasia plays a pivotal role in the pathogenesis of in-stent restenosis in patients undergoing percutaneous coronary interventions. Drug-eluting balloons are a promising tool to prevent restenosis after coronary angioplasty. Moreover, an increased knowledge of the pathophysiology of restenosis my help improve therapeutic strategies.

Methods/Design

We present the design of an open-label, randomized three-arm clinical trial aimed to assess whether a strategy of bare-metal stent implantation with additional use of drug-eluting balloons, either before (pre-dilation) or after stenting (post-dilation), reduces the primary endpoint of in-stent neointimal hyperplasia area as compared with a strategy of bare-metal stent implantation alone. This primary endpoint will be assessed by optical coherence tomography at follow-up. Secondary endpoints will be the percentage of uncovered struts, and the percentage of struts with incomplete apposition. An ancillary study investigating the relation between systemic levels of endothelial progenitors cells and neointimal hyperplasia, and the interaction between endothelial progenitors cell levels and drug-eluting balloons has been planned. Thirty consecutive patients undergoing percutaneous coronary intervention will be randomized with a 1:1:1 design to bare-metal stent implantation alone (n = 10); bare-metal stent implantation after pre-dilation with a drug-eluting balloon (n = 10); or bare-metal stent implantation followed by post-dilation with a drug-eluting balloon (n = 10). Six-month follow-up coronary angiography with optical coherence tomography imaging of the stented segment will be performed in all patients. Blood samples for the assessment of endothelial progenitors cell levels will be collected on admission and at 6 months.

Discussion

Experimental and early clinical data showed that inhibition of neointimal hyperplasia may be obtained by local administration of antiproliferative drugs loaded on the surface of angioplasty balloons. The INtimal hyPerplasia evAluated by oCT in de novo COROnary lesions treated by drug-eluting balloon and bare-metal stent (IN-PACT CORO) trial was conceived to test the superiority of a strategy of bare-metal stent implantation with additional drug-eluting balloon use (either before or after stenting) versus a strategy of bare-metal stent implantation alone for the reduction of neointimal hyperplasia. We also planned an ancillary study to assess the role of endothelial progenitors cells in the pathophysiology of neointimal hyperplasia.

Trial registration

Clinicaltrials.gov NCT01057563.

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.

Stent thrombosis: incidence, predictors and new technologies

Some concerns have been raised regarding the risk of late and very late stent thrombosis (ST) following drug-eluting stent implantation. Despite remaining an uncommon complication of percutaneous coronary intervention, when ST occurs, it can be catastrophic to the individual, commonly presenting as acute ST elevation myocardial infarction or sudden cardiac death. The incidence and predictors of ST have been reported in the literature and the role of dual antiplatelet therapies in the avoidance of such a complication remains vital. Ongoing studies are assessing the role of these therapies including platelet reactivity testing, genetic testing and optimum duration of therapy. In addition, newer polymer-free and bioabsorbable stents are under investigation in the quest to potentially minimise the risk of ST.

Incomplete arterial healing 8 years after the implantation of sirolimus-eluting stent. In vivo visualization by optical coherence tomography

The time course of complete arterial healing after drug eluting stent implantation is unknown. We present a case of incomplete endothelialization and late stent malapposition identified by optical coherence tomography 8 years after a sirolimus-eluting stent implantation, which was not related with any adverse clinical event.

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.

Impact of platelet reactivity to adenosine diphosphate before implantation of drug-eluting stents on subsequent adverse cardiac events in patients with stable angina

BACKGROUND

Diverse pharmacological effects of anti-platelet thienopyridines due to individual differences in metabolism have been reported. However, an association between on-treatment platelet reactivity and adverse ischemic events after drug-eluting stent (DES) implantation in Japanese patients has not been fully elucidated.

METHODS AND RESULTS

A total of 450 consecutive patients on dual anti-platelet therapy (aspirin and ticlopidine) with stable angina who underwent DES implantation were enrolled. Adenosine diphosphate (ADP)-induced platelet aggregation was measured before DES implantation using the screen filtration pressure method. The ADP concentration necessary for 50% aggregation was designated as the platelet aggregation threshold index (PATI). A composite primary endpoint of cardiac death, myocardial infarction, target lesion revascularization (TLR), and stent thrombosis occurring within 1 year after stenting, was evaluated. A PATI value <4.8 µmol/L was defined as high on-treatment reactivity to ADP. The composite primary endpoint occurred in 55 patients (12.2%) in the 1-year-period after DES implantation, and the prevalence was 19.0% and 5.1% in groups with high and low on-treatment reactivity to ADP, respectively, showing a significantly higher prevalence in the high reactivity group (P<0.001). The main event was TLR (18.1% vs. 5.1%, P<0.001).

CONCLUSIONS

These data suggested that high on-treatment platelet reactivity to ADP and subsequent occurrence of adverse ischemic events (particularly TLR) were correlated in patients with stable angina who underwent DES implantation.

Optical coherence tomography for guidance in bifurcation lesion treatment

Optical coherence tomography (OCT) has higher resolution than IVUS (approximately 10 times), with the potential to precisely measure lumen diameters in the variable geometry of a bifurcational lesion and to identify superficial lipid laden plaques and calcium, relevant to confirm the severity of the lumen obstruction before treatment and guide location and diameter of the stent. In addition, OCT produces fewer strut-induced artifacts and offers precise evaluation of strut apposition in a real-life clinical setting. The increase in the speed of image acquisition consequent to the introduction of frequency domain OCT allows rapid pull-back at a speed of 2 cm/sec, minimising the amount of contrast required to clear blood during image acquisition, with an average injection of 10-18 ml required for the maximal length currently available of 5.6 cm. This allows serial OCT acquisitions, typically before treatment if the lesion is not very severe and flow is expected to be present around the OCT catheter, after predilatation and to assess and guide stent expansion. Repeated OCT examinations at follow-up may help to detect presence and characteristics of strut coverage, a potential predictor of late stent thrombosis. These applications are of particular interest in the context of bifurcational lesion treatment because this condition is still associated with a higher number of malapposed stent struts and frequent impairment of stent expansion, explaining the higher incidence of stent thrombosis and restenosis. In this article, all potential applications of OCT for bifurcational lesion treatment are explored. The use of OCT to characterise plaque components, and to optimise stent expansion and strut apposition are first discussed in detail. The conclusion of the article highlights some future research and technological developments that promise to expand the role of OCT further still.

Correlation of angiographic late loss with neointimal coverage of drug-eluting stent struts on follow-up optical coherence tomography

Minimal data have been published on the correlation between angiographic late loss (LL) and incomplete neointimal coverage of struts after drug-eluting stent (DES) implantation. Therefore, we evaluated the relationship between angiographic LL and the percentage of uncovered struts on follow-up optical coherence tomography (OCT) images, in all cross-sections of the lesions. From the OCT registry database, 219 lesions without restenosis after DES implantation were divided into tertiles based on angiographic LL: tertile I (LL ≤ 0.26 mm), tertile II (0.26 < LL < 0.59 mm), and tertile III (≥0.59 mm). Lesions with the percentage of uncovered struts in the highest quartile (≥75th percentile; >6.0%) were defined as highly uncovered; in an independent analysis, lesions without any uncovered strut(s) were defined as completely covered. Higher percentages of uncovered struts were observed in tertile I than in both tertile II and III (10.3 ± 12.8% vs. 4.2 ± 7.4% vs. 2.4 ± 5.1%, respectively; P < 0.001 for I vs. II and I vs. III). Angiographic LL correlated significantly with the percentage of uncovered struts on OCT (r = -0.340, P < 0.001). The best cut-off values of angiographic LL to predict highly uncovered and completely covered lesions were 0.29 mm (area under curves [AUC] = 0.723, P < 0.001) and 0.61 mm (AUC = 0.692, P < 0.001), respectively. Angiographic LL inversely and significantly correlated with the percentage of uncovered struts on OCT after DES implantation.

Head-to-head comparison of early vessel healing by optical coherence tomography after implantation of different stents in the same patient

OBJECTIVES

Strut coverage represents the most powerful morphometric predictor of stent thrombosis and the best surrogate indicator of endothelization. The aim of this study was to get new insights on temporal patterns of vessel healing after stenting with different types of stent.

METHODS

Optical coherence tomography (OCT) was used to investigate the early strut coverage of lesions treated with CATANIA (CAT) stent, drug-eluting stent (DES) or cobalt-chromium bare metal stent (BMS). Two cohorts of 10 and 24 patients underwent OCT follow-up at 7-10 and 28-32 days after stenting, respectively. In each cohort, patients were randomly assigned to receive a CAT stent in one lesion and a BMS or a DES in a separate lesion.

RESULTS

A total of 7975 and 8406 struts were analyzed for the comparisons of CAT stent vs. DES and CAT stent vs. BMS at 7-10 days, respectively. A total of 21 123 and 25 069 struts were analyzed for the comparisons of CAT stent vs. DES and CAT stent vs. BMS at 28-32 days, respectively. At 7-10 days, the CAT stent showed higher coverage rates compared with DES (90.0 vs. 85.9%, P < 0.0001) and BMS (90.2 vs. 83.6%, P < 0.0001). Similarly, at 28-32 days, the coverage rate was higher with CAT stent compared with DES (97.7 vs. 90.5%, P < 0.0001) and BMS (97.2 vs. 96.5%, P < 0.0001).

CONCLUSION

The CAT stent yields quicker and more complete strut coverage than DES and BMS in the early phases of vessel healing following stent implantation.

Major determinants for the uncovered stent struts on optical coherence tomography after drug-eluting stent implantation

There have been little data regarding major determinants for the uncovered stent struts after drug-eluting stent (DES) implantation on optical coherence tomography (OCT). We investigated the major determinants of incomplete neointimal coverage of DES struts on OCT after implantation in a large cohort of patients. A total of 261 patients with 279 lesions who were treated with various DESs were selected from the OCT registry database. The lesions were divided into two groups based on the ratio of uncovered struts to total struts in all OCT cross-sections; an uncovered group (highest quartile with % uncovered struts ≥5.4%, n = 70), and covered group (the remaining lower quartiles with % uncovered struts <5.4%, n = 209). The uncovered group was more likely to have complex lesions, smaller reference vessel and stent diameter, and longer stent, more use of sirolimus-eluting stents, and less use of zotarolimus-eluting stents compared with the covered group. Of these variables, the most significant determinant of uncovered stent struts was DES type (odds ratio [OR] = 2.75, 95% confidence interval [CI] = 1.94-3.89, P < 0.001). The use of sirolimus-eluting stents (OR = 2.44, 95% CI, 1.15-5.47, P = 0.023) and zotarolimus-eluting stents (OR = 0.02, 95% CI = 0.01-0.25, P = 0.002) were the only significant risk and protective factors for uncovered stent struts, respectively. This study demonstrated that DES type might be associated with the most important determinants of uncovered struts compared to any other clinical or angiographic factor.

Do patients with drug-eluting stent thrombosis have a similar prognosis to patients presenting with st-Elevation myocardial infarction of de novo lesions?

BACKGROUND

Despite significant advances in stent technology and pharmacotherapy, drug-eluting stent thrombosis (DES-ST) remains a major complication of percutaneous coronary intervention (PCI) and commonly presents as ST-elevation myocardial infarction (STEMI). There are currently little data comparing the in-hospital outcomes of patients presenting with STEMI due to DES-ST with those due to de novo coronary artery disease (CAD).

METHODS

Our study comprised 985 consecutive patients who underwent primary PCI for STEMI, 102 of whom were diagnosed as having a definite DES-ST. The primary end-point was the in-hospital composite of death or recurrent myocardial infarction (MI). The secondary end-point was the in-hospital maximum rise in creatine kinase (myocardial band [MB] fraction) and troponin I.

RESULTS

 The DES-ST group had a higher proportion of patients with diabetes mellitus, hypercholesterolemia, history of ischemic heart disease, coronary revascularization, and chronic renal impairment. The adjusted primary end-point was higher in the DES-ST cohort (12.7% vs. 7.4%; P = 0.05). The 2 cohorts did not differ in the secondary end-point. The independent predictors of the primary end-point were age (hazard ratio [HR]= 1.04; 95% confidence interval [CI]= 1.01 - 1.06; P = 0.005), cardiogenic shock (HR = 11.5; 95% CI = 6.38 - 20.07, P < 0.001), and lesions involving the left anterior descending coronary artery (HR = 1.8; 95% CI = 1.03 - 3.13, P = 0.04). DES-ST was not an independent predictor of the primary end-point (HR = 1.18; 95% CI = 0.53-2.63, P = 0.38).

CONCLUSIONS

Patients with STEMI secondary to DES-ST have a poorer in-hospital outcome than do patients in whom STEMI is due to de novo CAD. This difference may be predominantly driven by differences in the baseline characteristics between these cohorts. (J Interven Cardiol 2011;24:320-325).

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.