A Randomized Optical Coherence Tomography Study of Coronary Stent Strut Coverage and Luminal Protrusion With Rapamycin-Eluting Stents

Non-linear shrinkage of Batson's #17 resin during vascular corrosion casting

Many studies of cardiovascular function require a realistic representation of vascular geometry. Corrosion casting has been used to acquire such geometries for many decades. However, the fidelity with which this method reproduces vascular anatomy has not been completely determined. Here we report on the non-linear shrinkage characteristics and exothermic properties of Batson's #17, a widely used casting resin, in model systems and in aortas of rats and rabbits. The setting process was captured using high-resolution photography. Shrinkage ranged from 3.4 ± 1.5% of the diameter in 1 ml plastic syringes (inner diameter 4.8 mm) to 19.6 ± 5.6% in the aorta of rats (diameter 1.5-2.6 mm). In addition, aortic curvature and branching angles changed during setting. These effects should be determined and corrected in studies of vascular geometry where high accuracy is required.

Impact of diabetes mellitus on vascular healing process after everolimus-eluting stent implantation: An optical coherence tomography study

BACKGROUND/PURPOSE

To study the impact of diabetes mellitus (DM) on vascular healing process after implantation of everolimus-eluting stent (EES).

METHODS/MATERIALS

Data from 3 prospective studies (HEAL-EES, REVER, and RESERVOIR), including patients with EES implantation and OCT follow-up, were merged. Differences in vascular healing process assessed by OCT were compared between DM and non-DM using generalized estimating equations. Neointimal proliferation, neointimal signal pattern (high, low, and layered), and uncovered/malapposed struts were evaluated.

RESULTS

A total of 96 lesions (61 DM lesions and 35 non-DM lesions) were included. Mean OCT follow-up time was 8.9 ± 1.5 months and comparable between groups. DM were older, high frequently female and acute coronary syndrome, and received smaller stent than non-DM. No differences were observed in quantitative vascular healing process between groups. However, DM exhibited higher low and layered signal pattern neointima compared to non-DM at lesion level (p = 0.030) and cross-section level (p < 0.001). Uncovered/malapposed struts were comparable between groups.

CONCLUSIONS

Quantitative vascular healing process was comparable between groups. However, DM was significantly associated with low signal pattern, which is characteristic of focal inflammation, after EES implantation. Further study might be required to study relationship between neointimal signal pattern and clinical events.

Vulnerable struts with CRE8, Biomatrix and Xience stents assessed with OCT and their correlation with clinical variables at 6-month follow-up: the CREBX-OCT study

First-generation drug eluting stents (DES) reduced the incidence of restenosis and need for repeated target lesion revascularization but, in autoptic studies, frequently resulted in incomplete endothelial coverage, which is an important predictor of late adverse events and increased mortality after stent implantation. More recently, not only uncovered, but also malapposed or protruding struts have been considered vulnerable structures, as they are deemed to perturb blood flow, whereas only struts well embedded into the vessel wall are considered stable. We compared the number of uncovered and of other vulnerable (protruding or malapposed) struts among three different second-generation drug-eluting stents (DES) (Cre8, Biomatrix, Xience), using optical coherence tomography (OCT) 6 months after implantation. Moreover, we analyzed the relationship between the percentage of vulnerable struts and the clinical characteristics of patients. 60 patients with stable angina or non-ST-Elevation acute coronary syndrome and indication to percutaneous angioplasty were randomly assigned to receive one of the three DES. After 6 months, OCT images were obtained. After 6 months, OCT images were obtained (1289 cross sections; 10,728 struts). None of the three DES showed non-coated struts or areas of stent thrombosis. Significant differences in the average number of protruding struts (Cre8: 33.9 ± 12.6; Biomatrix: 26.2 ± 18.1; Xience: 13.2 ± 8.5; p < 0.001) and in the proportion of malapposed struts (Cre8: 0.7%; Biomatrix: 0.9%; Xience: 0.0%; p = 0.040) and of incomplete stent apposition area (Cre8: 10.4%; Biomatrix: 4.7%; Xience: 0.7%; p < 0.001) were observed. No significant difference was found in neointimal hyperplasia area with a not significant tendency toward greater minimal and maximal struts thickness for Biomatrix. In comparison with Cre8 and Biomatrix, Xience showed a significantly lower proportion of vulnerable struts in all clinical sub-groups considered. In the group of 60 patients a significant relation was found between age and number of vulnerable struts (p = 0.014). The three second-generation DES were similarly effective in permitting neo-intimal formation and complete struts coating 6 months after implantation, but Cre8 and Biomatrix showed a greater proportion of protruding and malapposed struts.Trail Registry: Clinical Trials.gov Identifier: NCT02850497.

Study protocol for a randomised controlled trial: harmonising optimal strategy for treatment of coronary artery stenosis - coronary intervention with next-generation drug-eluting stent platforms and abbreviated dual antiplatelet therapy (HOST-IDEA) trial

INTRODUCTION

We have recently seen the introduction of newer generation drug-eluting stents with ultrathin struts that use advanced polymer technologies. However, the efficacy and safety of these newest stents have not yet been fully explored. In addition, there are still controversies over the optimal duration of dual antiplatelet therapy (DAPT) after stent implantation, particularly for ultrathin stents with the newest polymer technologies.

METHODS AND ANALYSIS

The HOST-IDEA trial is a randomised, open-label, multicentre, non-inferiority trial and the first study to directly compare two of these ultrathin sirolimus-eluting stents: Orsiro stent with biodegradable polymer, and polymer-free Coroflex ISAR (CX-ISAR) stent. This study has a scheme of 2×2 factorial design according to the stent type and DAPT duration (3 vs 12 months). A total of 2152 patients will be randomised and stratified to demonstrate the non-inferiority of CX-ISAR to Orsiro, or of the abbreviated DAPT duration to the conventional 12 months (both in 1:1 ratio). For the comparison of stent type, the primary endpoint is target lesion failure (TLF), which is a composite of cardiac death, target vessel-related myocardial infarction and clinically driven target lesion revascularisation. For the comparison of DAPT duration, the net adverse clinical event is the coprimary endpoint, which is defined as a composite of TLF, definite/probable stent thrombosis and major bleeding.

ETHIC APPROVAL AND DISSEMINATION

All the institutions involved in this study are required to have ethical approval prior to patient enrolment. This multicentre study will recruit patients through competitive registration, but institutions that have not yet obtained ethical approvals have made it impossible to enrol patients in a centralised web database. The final results will be presented at relevant international conferences and will be materialised in the form of papers.

TRIAL REGISTRATION NUMBER

NCT02601157; Pre-results.

Utility of adjunctive modalities in Coronary chronic total occlusion intervention

Coronary chronic total occlusion (CTO) intervention remains one of the most challenging domains in interventional cardiology. Due to the technical challenges involved and potential procedural complications, CTO percutaneous coronary intervention (PCI) attempt and success rates remain less than standard PCI. However, the use of several adjunctive tools such as intravascular ultrasound, optical coherence tomography, rotational atherectomy, orbital atherectomy, excimer laser coronary atherectomy and percutaneous left ventricular assist device may contribute to improved CTO PCI success rates or provide better hemodynamic assessment of CTO lesion (i.e., using fractional flow reserve). In this review we present the current literature describing the utility and efficacy of these adjunctive modalities in CTO intervention.

Difference in vascular response between sirolimus-eluting- and everolimus-eluting stents in ostial left circumflex artery after unprotected left main as observed by optical coherence tomography

BACKGROUND

Kissing-balloon technique (KBT) is commonly performed during percutaneous coronary intervention of distal unprotected left main coronary artery (ULM) aiming at obtaining optimal opening of the side branch (left circumflex artery; LCX) ostium. Nonetheless, detailed evaluation of vascular response to stents in LCX ostium is lacking. We therefore evaluated the vascular response to different drug-eluting stents (DES) in ostial LCX after ULM by means of optical coherence tomography (OCT).

METHODS

We prospectively enrolled 38 consecutive patients with ULM disease, who were treated with single-stent procedure using DES, crossover the ULM-left anterior descending artery (LAD) followed by KBT. Twelve patients were treated with sirolimus-eluting stents (SES) and 26 patients were treated with everolimus-eluting stents (EES). OCT was conducted at post-PCI and 9-month follow-up. We evaluated the DES-vessel interactions and number of stent struts at the side branch (LCX) ostium (SO) at post-PCI, and compared the narrowing of ostial area at LCX between SES and EES.

RESULTS

Post-procedure, the number of stent struts at SO was significantly higher in SES compared to EES (median 14.47% vs 0.19%, p<0.001). The narrowing of LCX ostial area at follow-up was more pronounced in SES compared with EES (29.16% vs 2.46%, respectively, p<0.001). Linear regression analysis showed a high correlation between the number of stent struts in LCX ostium and ostial area narrowing (r=0.771, p<0.001).

CONCLUSIONS

OCT showed differences between EES- and SES-vessel interactions at ULM bifurcation PCI. Number of LCX ostium struts at post-PCI impacted the narrowing of ostial area at 9-month follow-up.

Enhancing Stent Effectiveness with Nanofeatures

Drug-eluting stents are an effective therapy for symptomatic arterial obstructions, substantially reducing the incidence of restenosis by suppressing the migration and proliferation of vascular smooth muscle cells into the intima. However, current drug-eluting stents also inhibit the growth of endothelial cells, which are required to cover the vascular stent to reduce an excessive inflammatory response. As a result, the endothelial lining of the lumen is not regenerated. Since the loss of this homeostatic monolayer increases the risk of thrombosis, patients with drug-eluting stents require long-term antithrombotic therapy. Thus, there is a need for improved devices with enhanced effectiveness and physiological compatibility towards endothelial cells. Current developments in nanomaterials may enhance the function of commercially available vascular devices. In particular, modified design schemes might incorporate nanopatterns or nanoparticle-eluting features that reduce restenosis and enhance re-endothelialization. The intent of this review is to discuss emerging nanotechnologies that will improve the performance of vascular stents.

Vessel healings after stenting with different polymers in STEMI patients

BACKGROUND

Different stents implantation in ST-segment elevation myocardial infarction (STEMI) patients may influence the long term prognosis by affecting vessel healings after stenting. The aim of this study was to evaluate the vessel healings after implantation of drug eluting stents (DES) with biodegradable or durable polymer or of bare-metal stents (BMS) in patients with acute STEMI.

METHODS

This study included 50 patients, who underwent follow up angiogram and optical coherence tomography (OCT) assessment about one year after percutaneous coronary intervention (PCI) for STEMI. According to the initial stents types, these patients were classified to durable (n = 19) or biodegradable polymer sirolimus-eluting stents (n = 15), or BMS (n = 16) groups. The conditions of stent struts coverage and malapposition were analyzed with OCT technique.

RESULTS

A total of 9003 struts were analyzed: 3299, 3202 and 2502 from durable or biodegradable polymer DES, or BMS, respectively. Strut coverage rate (89.0%, 94.9% and 99.3%, respectively), malapposition presence (1.7%, 0.03% and 0 of struts, respectively) and average intimal thickness over struts (76 ± 12 µm, 161 ± 30 µm and 292 ± 29 µm, respectively) were significantly different among different stent groups (all P < 0.001).

CONCLUSIONS

Vessel healing status in STEMI patients is superior after implantation of biodegradable polymer DES than durable polymer DES, while both are inferior to BMS.

Large platelets but not putative endothelial progenitor cells are associated with low strut coverage after drug-eluting stent implantation

OBJECTIVES

This study assessed whether different subsets of circulating endothelial and putative endothelial progenitor cells (CEC and EPC) correlate with stent strut coverage (SSC) using second generation optical coherence tomography (OCT).

BACKGROUND

Due to the lack of imaging modalities with a resolution down to the magnitude of a few cells, the influence of EPC on endothelialisation of drug-eluting stents has not been assessed in patients.

METHODS

In 37 patients, SSC of everolimus-eluting stents was assessed by OCT 5-7months after stent implantation. Different subsets of EPC (CD34(+)KDR(+), CD34(+)KDR(+)CD45(dim), CD133(+), CD3(+)CD31(+)), CEC (CD31(+)CD45(-)CD146(+)), and CD31(+)CD45(-)CD146(-) representing large platelets were analysed by flow cytometry, including viability analyses with 7-AAD. Statistical analysis comprised univariate regression analysis and multivariable models integrating OCT and flow cytometry data as well as clinical variables.

RESULTS

SSC and frequency of different cell types were highly comparable with previously published data. EPC defined in part by KDR expression were mostly non-viable. On univariate and in multivariable models, no association between EPC counts and strut coverage was detected. For CD31(+)CD45(-)CD146(-) counts, representing large platelets, an inverse relationship with strut coverage was identified by a multivariable regression model adjusting for age, sex, diabetes mellitus, NYHA and CCS class, CRP, serum triglycerides, glucose and creatinine (beta=-9.42, p=0.006).

CONCLUSIONS

There was no significant association between EPC or CEC and healing after drug-eluting stent implantation. Yet, CD31(+)CD45(-)CD146(-) cells were associated with low SSC. These data suggest that large platelets may represent a more important mediator of late stent endothelialisation than EPC.

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.

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.

Evaluation neointimal coverage in patients with coronary artery aneurysm formation after drug-eluting stent implantation by optical coherence tomography

The neointimal coverage in patients with coronary artery aneurysms (CAA) formation after drug eluting stent (DES) implantation is not clear. Total of 175 patients who had been implanted DES were identified. Patients were divided into the CAA group (n = 31) and non-CAA group (n = 144) based on the results of the coronary angiography. The cardiac events including angina and acute myocardial infarction were noted, in addition, the neointimal thickness and the frequence of strut malapposition and strut uncoverage were noted. A greater proportion of incomplete neointimal coverage (17.17 vs. 1.9 %, P < 0.001) and malapposition struts (18.2 vs. 1.38%, P < 0.001) were observed in the CAA group. 8 patients in CAA group underwent OCT examination twice in the period of follow-up. The proportion of incomplete neointimal coverage increased significantly as compared the second OCT results with the first examination (18.45 vs. 2.66 %, P < 0.001). Hyperplasia neointimal desquamated from struts and acquired struts incomplete neointimal coverage were detected. Patients with CAA had a higher frequency of cardiac events including angina pectoris (25.81 vs. 6.25 %, P = 0.001) and acute myocardial infarction (9.68 vs. 0.13 %, P = 0.002) and thrombosis (16.13 vs. 0.69 %, P < 0.001). The longitudinal length of CAA in cardiac event group was significantly longer than no cardiac event group (20.0 ± 9.07 vs. 12.05 ± 5.38 mm, P = 0.005). CAA formation after DES implantation frequently associated with cardiac events as a result of stent malapposition and incomplete neointimal coverage. Acquired incomplete neointimal coverage associated with CAA formation.

First report of a novel polymer-free dual-drug eluting stent in de novo coronary artery disease: results of the first in human BICARE trial

BACKGROUND

Persistence of stent polymer coating has been associated with incomplete endothelialization, expansive vessel remodeling, neoatherosclerosis, and delayed healing associated with inflammation that may contribute to late adverse events.

METHODS

The BICARE (Lepu Medical, Beijing, China) stent is a novel polymer-free, nanotechnology-based stent eluting sirolimus and probucol. As a first in human feasibility study, patients with a single de novo native coronary stenosis <30 mm in length and with reference vessel diameter from 2.5 to 4.0 mm underwent revascularization with the BICARE stent. The primary endpoint of target lesion failure (TLF) was assessed at 30 days. Secondary endpoints included in-stent late lumen loss and proportion of uncovered or malapposed stent struts by optical coherence tomography at 4-month angiographic surveillance.

RESULTS

Among 32 consecutive patients (age, 55.7 ± 8.7 years; men, 62.5%; diabetes, 18.8%), the average baseline reference vessel diameter and lesion length were 2.85 ± 0.48 mm and 15.0 ± 5.6 mm, respectively. At 30 days there was no occurrence of TLF. At 4 months (angiographic follow-up, N=32), angiographic in-stent late loss was 0.14 ± 0.19 mm, and the in-stent binary restenosis rate was 3.1%. Complete strut coverage was 98.2% with 0.2% malapposition among 16,751 analyzed struts. At 18 months, TLF occurred in 3 (9.4%) patients related to repeat revascularization with no adverse safety events identified.

CONCLUSIONS

The preliminary feasibility and safety of a polymer-free, dual-drug eluting stent are demonstrated by absence of early adverse safety events and favorable angiographic suppression of neointimal hyperplasia. Stent imaging suggests favorable healing with extensive stent strut coverage and very low malapposition. These findings further inform comparison with biopermanent polymer DES.

Optical coherence tomographic observations of polytetrafluoroethylene-covered sirolimus-eluting coronary arterial stent

The aim of this study was to evaluate neointimal coverage obtained using a new method of polytetrafluoroethylene-covered stent (PCS) implantation combined with underlying longer sirolimus-eluting stent (SES) implantation using optical coherence tomography. Nine patients were enrolled in this study, including patients with coronary artery perforations, original coronary aneurysms, and acquired coronary aneurysms after drug-eluting stent implantation. All patients were first treated with long SES implantation and then with focal PCS implantation. Postprocedural and follow-up angiographic and optical coherence tomographic examinations were performed in all patients, and intravascular ultrasound was performed in 5 patients. All patients were asymptomatic during follow-up, without recurrent angina. There was no stent-edge or stent-segment binary restenosis. Values of late loss for proximal SES segments, PCS segments, and distal SES segments were similar (0.09, 0.07, and 0.04 mm, respectively, p = 0.8113). The mean neointimal thickness of PCS was less than that of proximal and distal SES. However, no malapposed cross sections or uncovered cross sections were found in PCS segments compared with SES segments (p = 0.0011). In conclusion, the combination of PCS and underlying longer SES implantation can offer better angiographic follow-up results. High-resolution optical coherence tomography provided convincing proof of full neointimal coverage of PCS. This new method of combined PCS and SES implantation may be a better choice compared with direct PCS implantation in certain clinical settings.

Comparison of early strut coverage between zotarolimus- and everolimus-eluting stents using optical coherence tomography

There have been no optical coherence tomographic (OCT) data directly comparing the pattern of strut coverage between the 2 second-generation drug-eluting stents in the early period. The aim of this prospective study was to evaluate early strut coverage using optical coherence tomography 3 months after Resolute zotarolimus-eluting stent (ZES-R) or everolimus-eluting stent (EES) implantation in de novo coronary artery lesions. A total of 40 patients who were suitable for the OCT procedure and consented to the study protocol were randomized 1:1 to receive either ZES-R or EES. Among these patients, 35 stented lesions (18 ZES-R, 17 EES) in 34 patients were evaluated by optical coherence tomography immediately and 3 months after stent implantation. Neointimal hyperplasia thickness, percentage of uncovered struts, and the proportion of malapposed struts were measured at 1-mm intervals. An uncovered strut was defined as having a neointimal hyperplasia thickness of 0 μm. At the 3-month OCT evaluation, mean neointimal hyperplasia thickness (ZES-R vs EES 74 ± 41 vs 75 ± 35 μm, p = 0.89) and mean percentage of uncovered struts (ZES-R vs EES 6.2 ± 6.9 vs 4.7 ± 5.1%, p = 0.62) were not significantly different between the groups. The percentage of malapposed struts was also similar between the groups (0.7 ± 2.2% for ZES-R and 0.7 ± 1.7% for EES, p = 0.64). Thrombi were documented in 3 stents (1 [5.6%] in a ZES-R vs 2 [11.8%] in EES, p = 0.60). In conclusion, early stent strut coverage on the basis of serial OCT evaluation was comparable between ZES-R and EES 3 months after stent implantation.

Biodegradable versus durable polymer drug eluting stents in coronary artery disease: insights from a meta-analysis of 5,834 patients

BACKGROUND

Biodegradable polymer drug eluting stents (BP-DES) have been developed to overcome the limitations of first generation durable polymer DES (DP-DES) but the clinical results of different BP-DES are not consistent. We performed a meta-analysis to compare the outcomes of BP-DES and DP-DES in the treatment of coronary artery disease (CAD).

METHODS AND RESULTS

Online databases including MEDLINE were searched for studies comparing BP-DES and DP-DES for obstructive CAD that reported rates for overall mortality, myocardial infarction (MI), late stent thrombosis (LST), target lesion revascularization (TLR) and late lumen loss (LLL) with a follow-up of ≥ 6 months. Ten studies (5834 patients) with a 1-year median follow-up were included in the meta-analysis. When comparing patients treated with DP-DES and BP-DES those treated with BP-DES had lower LLL (in-stent: weighted mean difference (WMD) -0.10 mm, 95% CI = -0.17 to -0.03 mm, p = 0.004; in-segment: WMD -0.06 mm, 95% CI = -0.10 to -0.01 mm, p = 0.01) with lower TLR rates (OR 0.67, 95% CI = 0.47 to 0.98, p = 0.04). However, BP-DES did not improve mortality (OR 0.97, 95% CI = 0.73 to 1.29, p = 0.83), MI (OR 1.13, 95% CI = 0.87 to 1.46, p = 0.36) or LST rates (OR 0.64, 95% CI = 0.36 to 1.16, p = 0.14). A pre-specified subgroup analysis of Biolimus BP-DES confirmed significant LLL reduction without differences in other clinical endpoints. Meta-regression analysis demonstrated a strong significant inverse correlation between LLL and reference coronary diameter (p < 0.001).

CONCLUSIONS

Our present meta-analysis showed that BP-DES when compared with DP-DES significantly reduced LLL and TVR but without clear benefits on mortality, MI and LST rates. (Clinicaltrials.gov identifier: NCT01466634).

Optical coherence tomography: from physical principles to clinical applications

Optical coherence tomography is a new endocoronary imaging modality employing near infrared light, with very high axial resolution. We will review the physical principles, including the old time domain and newer Fourier domain generations, clinical applications, controversies and perspectives of optical coherence tomography.

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.

Optical Coherence Tomography Imaging: Novel Insights into the Vascular Response After Coronary Stent Implantation

Optical coherence tomography (OCT) is a high-resolution imaging technique that is increasingly used for intracoronary imaging to characterize coronary atherosclerotic plaques and vascular responses after coronary stent implantation. Introduction of optical frequency-domain imaging (OFDI; second generation OCT) has simplified practical use of this novel imaging modality resulting in a more widespread availability in interventional cardiology. Here we highlight recent insights into the acute and chronic vascular response after coronary stent implantation by OCT imaging. OCT provides cross-sectional images with approximately 10-fold higher resolution as compared to intravascular-ultrasound (IVUS), allowing for precise evaluation of tissue coverage and malapposition of coronary stent struts. More than 30 studies using OCT to compare vascular responses to different stents have now been reported. Recent studies have examined the relation between OCT-image characteristics and tissue composition around stent struts. OCT is used for evaluation of novel stent concepts, such as bioengineered stents and bioabsorbable stents, where it provides more accurate information than IVUS. While intracoronary OCT imaging is further developed, including faster 3D-OCT-image-reconstruction, larger OCT studies/registries with standardized analysis will provide more insights into clinical implications of observations from OCT-imaging after coronary stent implantation.

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.

New strategies in the treatment of coronary bifurcations

Despite major improvements in stent technology (i.e., drug-eluting stents, DES), treatment of coronary bifurcations is an ever occurring problem of the interventional cardiology. While stenting the main branch with provisional side branch stenting seems to be the prevailing approach, in the era of DES various two-stent techniques emerged (crush) or were re-introduced (V or simultaneous kissing stents, crush, T, culottes, etc.) to allow stenting in the side branch when needed. New techniques in imaging like optical coherence tomography help in better understanding bifurcation anatomy and, thus, have the potential to help us better treat this challenging subset of lesions. In addition, new dedicated bifurcation stents have been proposed in an attempt to overcome limitations associated with current approaches, and they showed promising results in early studies; however, the safety and the efficacy of these devices remain to be seen in the ongoing and upcoming trials. This review focuses on the current approaches and the development of new techniques employed for the treatment of bifurcation disease.

Randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus: the LIPSIA Yukon trial

OBJECTIVES

The objective of the study was to assess noninferiority of the polymer-free sirolimus-eluting Yukon Choice stent (Translumina GmbH, Hechingen, Germany) compared with the polymer-based Taxus Liberté stent (Boston Scientific, Natick, Massachusetts) with regard to the primary endpoint, in-stent late lumen loss, at 9 months in patients with diabetes mellitus.

BACKGROUND

The Yukon Choice stent has been evaluated in several randomized controlled trials before, albeit to date, there has been no trial that exclusively enrolled patients with diabetes mellitus.

METHODS

Patients with diabetes mellitus undergoing percutaneous coronary intervention for clinically significant de novo coronary artery stenosis were randomized 1:1 to receive either the polymer-free sirolimus-eluting Yukon Choice stent or the polymer-based paclitaxel-eluting Taxus Liberté stent.

RESULTS

A total of 240 patients were randomized. Quantitative coronary angiography was available for 79% of patients. Mean in-stent late lumen loss was 0.63 ± 0.62 mm for the Yukon Choice stent and 0.45 ± 0.60 mm for the Taxus Liberté stent. Based on the pre-specified margin, the Yukon Choice stent failed to show noninferiority for the primary endpoint. During follow-up, there were no significant differences between groups regarding death, myocardial infarction, stent thrombosis, target lesion revascularization, target vessel revascularization, or nontarget vessel revascularization.

CONCLUSIONS

Compared with the Taxus Liberté stent, the polymer-free sirolimus-eluting Yukon Choice stent failed to show noninferiority with regard to the primary endpoint, in-stent late lumen loss, in patients with diabetes mellitus after 9-month follow-up. Both stents showed comparable clinical efficacy and safety. (Yukon Choice Versus Taxus Liberté in Diabetes Mellitus; NCT00368953).

A novel polymer-free paclitaxel-eluting stent with a nanoporous surface for rapid endothelialization and inhibition of intimal hyperplasia: Comparison with a polymer-based sirolimus-eluting stent and bare metal stent in a porcine model

Hypersensitivity and inflammatory responses to polymers may be responsible for late stent thrombosis after implantation of a drug-eluting stent (DES). Polymer-free DES may reduce the prevalence of these adverse reactions in vessels. We evaluated a polymer-free paclitaxel-eluting-stent with a nanoporous surface (nano-PES) for endothelialization and inhibition of neointimal hyperplasia by optical coherence tomography (OCT) and pathology in a porcine model. Nano-PES with high-dose (HD) and low-dose (LD) paclitaxel (1.0 μg/mm(2) and 0.4 μg/mm(2), respectively) was compared with a sirolimus-eluting stent (SES) and bare-metal stent (BMS) in a porcine model. Fifty-three stents (14 HD, 14 LD, 14 SES, 11 BMS) were implanted in 18 minipigs. At 14 days, nano-PES with HD and LD showed more complete endothelialization compared with SES. BMS had 100% endothelial coverage. At 28 days, a significant reduction in neointimal hyperplasia was detected by OCT in the nano-PES HD group compared with BMS. No benefit in prevention of the neointimal hyperplasia was observed in the nano-PES LD group. Nano-PES stents showed decreased deposition of fibrin and inflammation compared with SES. Pharmacokinetic studies revealed that nano-PES could effectively deliver the drug to the local coronary artery and it released the drug more rapidly than SES. Such a release profile was favorable for rapid endothelialization of nano-PES. The present study showed the nano-PES to be a new drug-delivery technology; that it used a nanoporous stent surface; that it offered desirable drug-elution properties without the use of polymers; that it may translate into an improved safety profile for next-generation DES.

Possible role of damaged neoendothelial cells in the genesis of coronary stent thrombus in chronic phase. A dye staining angioscopic study

The mechanism(s) underlying formation of coronary stent thrombus (ST) in chronic phase is yet unclear. Endothelial cells are highly antithrombotic, therefore, it is conceivable that neoendothelial cells (NECs) covering stent struts are damaged and cause ST. This study was performed to examine the role of damaged NECs covering coronary stent struts in the genesis of occlusive or nonocclusive ST in chronic phase.(1) Forty-four patients with acute coronary syndrome (17 females and 27 males) underwent dye-staining coronary angioscopy, using Evans blue which selectively stains damaged endothelial cells, 6 months after bare-metal stent (BMS) deployment. Neointimal coverage was classified into not covered (grade 0), covered by a thin layer (grade 1), and buried under neointima (grade 2) groups. (2) In 7 beagles, the relationships between neointimal thickness and ST were examined 6 months after BMS deployment. (3) The NECs on the struts were stained blue in 4 of 25 patients with grade 2 and in 11 of 20 patients with grade 0/1 (P < 0.05). ST was observed in none of the former and in 5 of the latter (P < 0.05). (4) In beagles, neointimal coverage was grade 0/1 when neointimal thickness was 80.2 ± 40.0 µm, whereas grade 2 when thickness was 184 ± 59.4 µm. ST was observed in 9 of 15 struts with neointimal thickness within 100 µm and in one of 17 struts with thickness over 100 µm (P < 0.05). ST arose from damaged NECs covering the stent struts. NECs may have been damaged due to friction between them and struts due to thin interposed neointima which might have acted as a cushion, resulting in ST.

Different patterns of vascular response between patients with or without diabetes mellitus after drug-eluting stent implantation: optical coherence tomographic analysis

OBJECTIVES

We performed this study to investigate with optical coherence tomography (OCT) the vascular response after sirolimus-eluting stent (SES) implantation between patients with and those without diabetes mellitus (DM).

BACKGROUND

The difference in vascular response after SES implantation between patients with and those without DM has not been fully evaluated with OCT.

METHODS

Optical coherence tomography was performed to examine 74 nonrestenotic SES implanted in 63 patients (32 with DM and 31 without DM) at 9 months after SES implantation. For struts showing neointimal coverage, the neointimal thickness on the luminal side of each strut section was measured, and neointimal characteristics were classified into high, low, and layered signal pattern.

RESULTS

Baseline patient characteristics and lesion and procedural characteristics data were similar between the 2 groups. In total, 11,422 struts were analyzed. High signal neointima was observed in 90.2 ± 13.9%, low signal neointima in 7.3 ± 10.0%, and layered neointima in 2.7 ± 5.8%/stents. There was higher incidence of low signal neointima (10.5 ± 10.3% vs. 4.5 ± 5.6%, p = 0.003), neointimal thickness was larger (median: 106.8 μm, interquartile range: 79.3 to 130.4 μm vs. median: 83.5 μm, interquartile range: 62.3 to 89.3 μm; p < 0.0001), and neointimal coverage of stent struts was higher (92.1 ± 6.2% vs. 87.2 ± 11.9%; p = 0.03) in DM patients.

CONCLUSIONS

High signal neointimal pattern was predominantly observed, and low or layered signal pattern was observed in some cases. In DM patients, low signal neointima was observed with high frequency. Neointimal coverage and neointimal thickness was also higher in DM patients as compared with non-DM patients.

Coronary stents: looking forward

Despite all the benefits of drug-eluting stents (DES), concerns have been raised over their long-term safety, with particular reference to stent thrombosis. In an effort to address these concerns, newer stents have been developed that include: DES with biodegradable polymers, DES that are polymer free, stents with novel coatings, and completely biodegradable stents. Many of these stents are currently undergoing pre-clinical and clinical trials; however, early results seem promising. This paper reviews the current status of this new technology, together with other new coronary devices such as bifurcation stents and drug-eluting balloons, as efforts continue to design the ideal coronary stent.

Angioscopic Evaluation of Neointimal Coverage of Coronary Stents

Drug-eluting stents (DES) reduce coronary restenosis significantly; however, late stent thrombosis (LST) occurs, which requires long-term antiplatelet therapy. Angioscopic grading of neointimal coverage of coronary stent struts was established, and it was revealed that neointimal formation is incomplete and prevalence of LST is higher in DES when compared to bare-metal stents. It was also observed that the neointima is thicker and LST is less frequent in paclitaxel-eluting and zotarolimus-eluting stents than in sirolimus-eluting stents. Many new stents were devised and they are now under experimental or clinical investigations to overcome the shortcomings of the stents that have been employed clinically. Endothelial cells are highly anti-thrombotic. Neo-endothelial cell damage is considered to be caused by friction between the cells and stent struts due to the thin neointima between them which might act as a cushion. Therefore, development of a DES that causes an appropriate thickness (around 100 μm) of the neointima is a potential option with which to prevent neo-endothelial cell damage and consequent LST while preventing restenosis.

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.

In-stent restenosis associated with stent malapposition: seven year optical coherence tomography findings

Stent thrombosis and in-stent restenosis remain significant issues in post-coronary angioplasty care despite advances in anti-platelet therapy and stent technology. Angiographic predictors of stent failure have been proposed, but its precise mechanism has been difficult to elucidate on conventional coronary angiography and intravascular ultrasound due to the low resolution of either approach. Optical coherence tomography (OCT) as a high-resolution intracoronary imaging modality has enabled more detailed insight into the interaction between implanted stent and underlying endothelium, the evolution of unstable plaque, and the pathogenesis of late lumen loss, affirming its place as an essential tool in the modern-day cardiac catheterisation laboratory. We present a case of in-stent restenosis seven years after bare-metal stent insertion, the mechanism of which was gross stent malapposition as clearly demonstrated on OCT examination.