Evaluation of polymer-based comparator drug-eluting stents using a rabbit model of iliac artery atherosclerosis

Impact of baseline yellow plaque assessed by coronary angioscopy on vascular response after stent implantation

BACKGROUND

The relationship between baseline yellow plaque (YP) and vascular response after stent implantation has not been fully investigated.

METHODS

This was a sub-analysis of the Collaboration-1 study (multicenter, retrospective, observational study). A total of 88 lesions from 80 patients with chronic coronary syndrome who underwent percutaneous coronary intervention were analyzed. Optical coherence tomography (OCT) and coronary angioscopy (CAS) were serially performed immediately and 11 months after stent implantation. YP was defined as the stented segment with yellow or intensive yellow color assessed by CAS. Neoatherosclerosis was defined as a lipid or calcified neointima assessed by OCT. OCT and CAS findings at 11 months were compared between lesions with baseline YP (YP group) and lesions without baseline YP (Non-YP group).

RESULTS

Baseline YP was detected in 37 lesions (42 %). OCT findings at 11 months showed that the incidence of neoatherosclerosis was significantly higher in the YP group (11 % versus 0 %, p = 0.028) and mean neointimal thickness tended to be lower (104 ± 43 μm versus 120 ± 48 μm, p = 0.098). CAS findings at 11 months demonstrated that the dominant and minimum neointimal coverage grades were significantly lower (p = 0.049 and P = 0.026) and maximum yellow color grade was significantly higher (p < 0.001) in the YP group.

CONCLUSIONS

Baseline YP affected the incidence of neoatherosclerosis as well as poor neointimal coverage at 11 months after stent implantation.

Development of a Rabbit Iliac Arterial Stenosis Model Using a Controlled Cholesterol Diet and Pullover Balloon Injury

Purpose

This study aimed to develop a rabbit iliac stenosis model and evaluate the effects of different mechanical injury techniques on the degree of arterial stenosis.

Materials and Methods

Eighteen rabbits were divided into three groups: cholesterol-fed with pullover balloon injury (group A; n = 6), cholesterol-fed with localized balloon dilatation (group B; n = 6), and chow-diet with pullover balloon injury (group C; n = 6). After baseline angiography, the left iliac arteries of all rabbits were injured with a 3 × 10 mm noncompliant balloon using either a wide pullover technique (groups A and C) or a localized balloon dilatation technique (group B). A nine-week follow-up angiography was performed, and the angiographic late lumen loss and percentage of stenosis were compared.

Results

Group A exhibited the most severe late lumen loss (A vs. B, 0.67 ± 0.13 vs. 0.04 ± 0.13 mm, p < 0.0001; A vs. C, 0.67 ± 0.13 vs. 0.26 ± 0.29 mm, p < 0.05; stenosis percentage 32.02% ± 6.54%). In contrast, group B showed a minimal percentage of stenosis (1.75% ± 6.55%).

Conclusion

Pullover-balloon injury can lead to significant iliac artery stenosis in rabbits with controlled hypercholesterolemia. This model may be useful for elucidating the pathogenesis of atherosclerosis and for evaluating the efficacy of novel therapeutic interventions.

In-Stent Restenosis

In-stent restenosis (ISR) remains a potential complication after percutaneous coronary intervention, even in the era of drug-eluting stents, and its treatment remains suboptimal. Neoatherosclerosis is an important component of the pathology of ISR and is accelerated in drug-eluting stents compared with bare-metal stents. Coronary angiography is the gold standard for evaluating the morphology of ISR, although computed tomography angiography is emerging as an alternative noninvasive modality to evaluate the presence of ISR. Drug-coated balloons and stent reimplantation are the current mainstays of treatment for ISR, and the choice of treatment should be based on clinical background and lesion morphology.

The Residual Lipid-Rich Coronary Atheroma Behind the Implanted Newer-Generation Drug-Eluting Stent and Future Stent-Related Event Risks

BACKGROUND

Lipid-rich plaque is an important substrate that causes future coronary events. However, the clinical implications of underlying plaque characteristics in coronary lesions after newer-generation drug-eluting stent (DES) implantation remain unknown.

METHODS

The current study analyzed 445 target lesions after newer-generation DES implantation in 416 patients with coronary artery disease (CAD) (chronic coronary syndrome/acute coronary syndrome = 264/181) from the REASSURE-NIRS multicentre registry. Near-infrared spectroscopy (NIRS) imaging was used to evaluate maximum lipid core burden index after stent implantation in target lesions (residual maxLCBI4mm). The primary and secondary outcomes were 3-year lesion-oriented clinical outcomes (LOCO): cardiac death, nonfatal target-lesion-related myocardial infarction (MI), or ischemia-driven target-lesion revascularization (ID-TLR) and patient-oriented clinical outcomes (POCO): all-cause death, nonfatal MI, or ID unplanned revascularization. Outcomes were compared by residual maxLCBI4mm tertile.

RESULTS

Median residual maxLCBI4mm was 183; 16% of lesions had residual maxLCBI4mm > 400. Higher residual maxLCBI4mm was not associated with a greater likelihood of LOCO or POCO during the observational period (LOCO, log-rank P = 0.76; POCO, log-rank P = 0.84). Mixed-effects logistic regression demonstrated that residual maxLCBI4mm does not predict LOCO (odds ratio [OR], 1.000; 95% confidence interval [CI], 0.997-1.003; P = 0.95). There was no significant relationship between residual maxLCBI4mm and POCO (OR, 1.001; 95% CI, 0.999-1.002; P = 0.30).

CONCLUSIONS

Residual maxLCBI4mm is not associated with LOCO or POCO in patients with CAD after newer-generation DES implantation. Our findings suggest that NIRS-derived underlying lipid-rich plaque is not associated with the risk of stent-related events and patient-based outcomes in patients with CAD who have received newer-generation DESs.

Noninvasive assessment of foot perfusion in cholesterol-fed rabbits using dynamic volume perfusion CT with an upslope method

To evaluate the feasibility of dynamic foot volume CT with the upslope method and to demonstrate macrovascular reactivity and microvascular perfusion during cuff-induced reactive hyperemia state in cholesterol-fed rabbits. 30 New Zealand male rabbits were divided into 2 groups: dietary hypercholesterolemia (n = 10) and normal diet control (n = 20). To measure for macrovascular reactivity, perfusion parameters of the left posterior tibial artery was measured at baseline and at reactive hyperemia state. For the evaluation of microvascular perfusion, color-coded perfusion map of the plantar dermis was generated for perfusion CT scan by an in-house developed dedicated analysis software based on upslope method. Dermal perfusion values were measured and analyzed before and after cuff-induced reactive hyperemia. Foot dynamic volume CT with the upslope method demonstrated significant impairment of both macrovascular reactivity and microvascular perfusion in cholesterol-fed rabbits without significant macrovascular lesions during cuff-induced reactive hyperemia (CRH) state. Arterial time-to-peak of cholesterol-fed rabbits failed to show acceleration while chow-fed rabbits showed significant decrease in time. Microvascular perfusion calculated by perfusion value (P < 0.01) and perfusion ratio (P = .014) showed decreased microvascular perfusion in cholesterol-fed rabbits compared to chow-fed rabbits during CRH state. Post-CT pathologic examination revealed decreased endothelial cell density in cholesterol-fed rabbits (P < 0.001). Foot perfusion CT using upslope method provides perfusion parameters for large arteries and a perfusion map of the foot during cuff-induced reactive hyperemia in cholesterol-fed rabbits. It may be a useful tool to assess microvascular reactivity in patients with peripheral artery disease but no apparent macrovascular lesions.

In Stent Neo-Atherosclerosis: Pathophysiology, Clinical Implications, Prevention, and Therapeutic Approaches

Despite the dramatic improvements of revascularization therapies occurring in the past decades, a relevant percentage of patients treated with percutaneous coronary intervention (PCI) still develops stent failure due to neo-atherosclerosis (NA). This histopathological phenomenon following stent implantation represents the substrate for late in-stent restenosis (ISR) and late stent thrombosis (ST), with a significant impact on patient’s long-term clinical outcomes. This appears even more remarkable in the setting of drug-eluting stent implantation, where the substantial delay in vascular healing because of the released anti-proliferative agents might increase the occurrence of this complication. Since the underlying pathophysiological mechanisms of NA diverge from native atherosclerosis and early ISR, intra-coronary imaging techniques are crucial for its early detection, providing a proper in vivo assessment of both neo-intimal plaque composition and peri-strut structures. Furthermore, different strategies for NA prevention and treatment have been proposed, including tailored pharmacological therapies as well as specific invasive tools. Considering the increasing population undergoing PCI with drug-eluting stents (DES), this review aims to provide an updated overview of the most recent evidence regarding NA, discussing pathophysiology, contemporary intravascular imaging techniques, and well-established and experimental invasive and pharmacological treatment strategies.

Overcoming challenges in refining the current generation of coronary stents

INTRODUCTION

Late stent thrombosis caused by delayed vascular healing and prolonged local inflammation were major drawbacks of 1^st generation drug-eluting stents (DES). Strut design, biocompatibility of polymer, and drug-release profiles were improved in 2^nd and 3rdgeneration DES. Accordingly, the indications for percutaneous coronary intervention with DES have been expanded to more complex patients and lesions. Despite these improvements, significant barriers such as greater flexibility in the duration of dual-antiplatelet therapy (DAPT) as well as reducing long-term stent-related events remain. To achieve ideal short- and long-term results, these existing limitations need to be overcome.

AREAS COVERED

We will discuss the current limitations of coronary DES and how they might be overcome from pathological and clinical viewpoints.

EXPERT OPINION

Optimizing DAPT duration after stent implantation and prevention of in-stent neoatherosclerosis are two major issues in current DES. Overcoming these drawbacks is a prerequisite toward achieving better short- and long-term clinical outcomes. New technologies including platform design, polymer types, and anti-proliferative agent itself might lead to further improvements. Although the initial experience with bioresorbable scaffold/stents (BRS) was disappointing, positive results of clinical studies regarding novel BRS are raising expectations. Overall, further device innovation is desired for overcoming the limitations of current DES.

[Morphological and Molecular-Biological Changes in the Coronary Arteries after Stenting]

This review addresses morphological changes in coronary arteries following stenting, which result from damage to the vascular wall. These changes include 1) formation of a thrombus in the site of intimal injury; 2) inflammation; 3) proliferation and migration of smooth muscle cells; 4) formation of extracellular matrix. Each of these pathological processes has specific morpho-biological features. The review shows the role of von Willebrand factor in development of early thrombosis after intimal injury, which provokes activation of the inflammatory response followed by proliferation of smooth muscle cell that synthetize the extracellular matrix. These cellular and intercellular changes are based on overexpression of TGF-β1 protein, which facilitates modulation of various types of smooth muscle cells, including contractile and secretory ones. Issues of fine regulation of cellular and intercellular interactions by apoptosis, activation of mTOR signaling molecules, and microRNA are still understudied. Dynamic changes in drug-coated stents during development of neoatherosclerosis and late thrombosis remain not elucidated. Current reports show that initial mechanisms triggering pathological regenerative and hyperplastic processes that result in coronary restenosis in the area of implanted stents may form early (first hours or days) after stenting. Most studies were performed on experimental rather than on autopsy material, which does not allow fully unbiased interpretation of obtained data. Studying dynamics of morphological and molecular changes in coronary arteries after stenting, including on autopsy material, will allow one to express an opinion on the risk of postoperative thrombosis and restenosis.

Vascular Response of a Polymer-Free Paclitaxel-Coated Stent (Zilver PTX) versus a Polymer-Coated Paclitaxel-Eluting Stent (Eluvia) in Healthy Swine Femoropopliteal Arteries

PURPOSE

To compare the long-term vascular healing responses of healthy swine iliofemoral arteries treated with a polymer-free paclitaxel-eluting stent (Z-PES, Zilver PTX) or a fluoropolymer-based paclitaxel-eluting stent (FP-PES, Eluvia).

MATERIALS AND METHODS

Bilateral iliofemoral arteries in 20 swine were treated with a Z-PES (n = 16) or a FP-PES (n = 24) and were examined histologically at 1, 3, 6, and 12 months.

RESULTS

Morphometric analysis revealed larger external and internal elastic lamina, stent expansion, and lumen area in the FP-PES than in the Z-PES at all timepoints. Luminal narrowing was similar in the 2 groups at 1 month; however, greater stenosis was observed in the Z-PES group at 3 months, with significant regression thereafter, resulting in equivalent stenosis at 6 and 12 months. Greater drug effect and less complete vessel healing were found in the FP-PES group at all timepoints, including greater numbers of malapposed struts with excessive fibrin deposition at 1 and 3 months, than in the Z-PES group. Three of 12 FP-PESs from the 6- and 12-month cohorts also showed circumferential medial disruption with peri-strut inflammation, whereas no abnormal findings were observed in contralateral Z-PESs.

CONCLUSIONS

Prolonged paclitaxel release with the presence of a permanent polymer may contribute to the differential vascular responses seen for the Z-PES and FP-PES groups, including medial layer disruption and aneurysmal vessel degeneration that was sometimes observed in the FP-PES group. These distinct features should be confirmed by pathology and in vivo imaging of human superficial femoral arteries to determine their clinical significance.

Risk prediction of in-stent restenosis among patients with coronary drug-eluting stents: current clinical approaches and challenges

Introduction: In-stent restenosis (ISR) has been one of the biggest limitations to the success of percutaneous coronary intervention for the treatment of coronary artery disease (CAD). The introduction of drug-eluting stent (DES) was a revolution in the treatment of CAD because these devices drastically reduced ISR to very low levels (<5%). Subsequently, newer generation DES treatments have overcome the drawbacks of first-generation DES, i.e. delayed endothelialization, and late stent thrombosis. However, the issue of late ISR, including neoatherosclerosis after DES implantation especially in high-risk patients and complex lesions, still exists as a challenge to be overcome.Areas covered: We discuss the mechanisms of ISR development including neoatherosclerosis, past and current clinical status of ISR, and methods to predict and overcome this issue from pathological and clinical points of view.Expert opinion: The initial drawbacks of first-generation DES, such as delayed endothelial healing and subsequent risk of late stent thrombosis, have been improved upon by the current generation DES. To achieve better long-term clinical outcomes, further titration of drug-release and polymer degradation profile, strut thickness as well as material innovation are needed.

Final 5-Year Results in Randomized Japanese Patients Implanted With a Thin-Strut, Bioabsorbable, Polymer-Coated, Everolimus-Eluting SYNERGY Stent (From the EVOLVE II Study)

Background: SYNERGY is a thin-strut, platinum-chromium metal alloy stent with an ultrathin abluminal everolimus-eluting bioabsorbable polymer. EVOLVE II was a global randomized controlled trial that enrolled 1,684 patients treated with either a SYNERGY or durable polymer PROMUS Element Plus (PE+) everolimus-eluting stent, including 155 patients from Japanese sites. This substudy analyzed 5-year clinical outcomes in the Japanese and non-Japanese cohorts.

Methods and Results: Patients aged ≥18 years with ≤3 native coronary artery lesions (reference vessel diameter ≥2.25–≤4.00 mm; length ≤34 mm) in ≤2 major vessels were randomized 1 : 1 to receive either SYNERGY (n=74 patients in Japan) or PE+ (n=81 patients in Japan). Five-year target lesion failure (TLF) was observed in 8.3% SYNERGY- and 11.2% PE+-treated patients (P=0.54). There were no cardiac deaths, and rates of target lesion revascularization and myocardial infarction were comparable between treatment arms. One patient in the SYNERGY arm experienced a very late definite stent thrombosis (ST); no ST occurred in the PE+ arm (P=0.30). Despite differences in baseline clinical and lesion characteristics, the 5-year TLF rates were not significantly different in SYNERGY-treated patients either in (8.3%) or outside (14.8%) Japan (P=0.14).

Conclusions: In Japanese patients with coronary artery disease, SYNERGY showed comparable efficacy to PE+, with low rates of adverse events over 5 years. Similarly, 5-year clinical outcomes were favorable in Japanese vs. non-Japanese patients implanted with SYNERGY.

Incidence and Predictors of Neoatherosclerosis in Patients with Early In-Stent Restenosis Determined Using Optical Coherence Tomography

In-stent restenosis (ISR) still exists after drug-eluting stent (DES) implantation, even up to one year. The incidence and risk factors for neoatherosclerosis in patients with early ISR have not yet been elucidated. Here, we used optical coherence tomography (OCT) to evaluate the incidence and predictors of neoatherosclerosis in patients with early ISRs.OCT was performed on ISR lesions in 185 patients in order to detect neoatherosclerosis. The median follow-up was 180 days, and neoatherosclerosis was detected in 37% of early ISR lesions. According to the presence of neoatherosclerosis, patients with ISR were divided into two groups: neoatherosclerosis (group A, n = 69) and non-neoatherosclerosis (group B, n = 116) groups.The risk factors were similar, except for hypercholesterolemia. Moreover, the tissue characteristics were not significantly different between patients with and without neoatherosclerosis. Follow-up low-density lipoprotein-cholesterol (LDL-C) levels were divided into three grades (LDL < 70 mg/dL, 70 mg/dL≤ LDL < 100 mg/dL, and LDL ≥ 100 mg/dL). The incidence of neoatherosclerosis was significantly lower (23% versus 57%, P < 0.0001) in the LDL < 70 mg/dL group. There was no significant difference in the incidence of neoatherosclerosis in patients with lipid levels between 70 and 100 mg/dL (P = 0.53). However, neoatherosclerosis was significantly more common in patients with a follow-up LDL-C level > 100 mg/dL (45% versus 15%, P < 0.0001).In patients with early ISR lesions, the LDL-C levels may be related to the formation and progression of early neoatherosclerosis, and poor LDL-C control may be a risk factor for the occurrence of early-stage neoatherosclerosis following DES implantation.

A preclinical animal model for evaluating the sealing capacity of covered stent grafts in acute vessel perforation

Background

Percutaneous coronary intervention is among the most common therapeutic interventions in cardiology. This procedure may, however, be associated with a rare, though life-threatening complication: acute coronary perforation (CP). CP is primarily treated using covered stents, which are made of bare metal stents with a polytetrafluoroethylene (PTFE) or polyurethane coating. These stents’ major limitations include higher rates of thrombus formation and restenosis. Hence, there is a still unmet need for new stents regarding their design and composition. Or, to test new covered stent designs, the rabbit iliac artery has become the best-established animal model. This study sought to present a preclinical animal approach designed to test covered stents that are utilized following vessel perforation.

Methods

The animal experiments were performed using New Zealand white rabbits, each weighting 3.5–4.5 kg. The animal models described herein relied on the three most common clinical causes for CP, such as guidewire-induced, balloon catheter bursting, and device oversizing. Moreover, the sealing capacity of covered stent grafts was assessed for each of these models by means of angiography.

Results

We herein report a rabbit iliac artery perforation model using three different types of vessel perforation that closely mimic the clinical setting, such as guidewire-induced, balloon catheter rupture, and device oversizing. Using the same rabbit iliac perforation model, we additionally assessed the sealing capacity of a covered stent graft for each model.

Conclusions

The novel rabbit iliac artery perforation models, as described in this report, represent promising animal testing approaches. While their setting is very similar to the real-life context encountered in humans, all three models are based on an animal model that is ideally suited for evaluating the sealing capacity and performance of new medical devices for humans.

The Cre8 amphilimus-eluting stent for the treatment of coronary artery disease: safety and efficacy profile

Introduction: Polymer-free drug-eluting stents are designed with stent surface modifications and drug-matrix formulations in order to release antiproliferative agents without the need of a polymer coating. Polymer-free technologies have the potential to overcome complications due to polymer persistence over time, such as local inflammatory reactions, delayed arterial healing, neoatherosclerosis, and subsequent ischemic adverse events.Areas covered: The Cre8 polymer-free amphilimus-eluting stent received CE mark in 2011 and was conceived with the aim of addressing the safety and efficacy limitations of early generation drug-eluting stents based on permanent polymer coatings. Besides the absence of polymer, the main features of the Cre8 stent include the abluminal reservoirs, the passive carbon film coating, and the antiproliferative agent formulation based on sirolimus mixed with free-fatty acid chain - namely amphilimus. This review will focus on the Cre8 development, technical characteristics, preclinical evidence, clinical efficacy and safety, and future perspectives.Expert opinion: The Cre8 stent has shown favorable angiographic and clinical outcomes at short and medium-term follow-up. This technology might provide a benefit in patients with diabetes. Further randomized evidence is required to provide an adequate clinical evaluation of this promising technology in patients with and without diabetes.

Vascular responses to coronary calcification following implantation of newer-generation drug-eluting stents in humans: impact on healing

AIMS

Vascular calcification is routinely encountered in percutaneous coronary intervention (PCI) and severe coronary calcification is a known predictor of in-stent restenosis and stent thrombosis. However, the histopathologic mechanisms behind such events have not been systematically described.

METHODS AND RESULTS

From our registry of 1211 stents, a total of 134 newer-generation drug-eluting stents (DES) (Xience, Resolute-Integrity, PROMUS-Element, and Synergy) with duration of implant ≥30 days were histologically analysed. The extent of calcification of the stented lesions was evaluated radiographically and divided into severe (SC, n = 46) and non-severely calcified lesions (NC, n = 88). The percent-uncovered struts per section {SC vs. NC; median 2.4 [interquartile range (IQR) 0.0-19.0] % vs. 0.0 (IQR 0.0-4.6) %, P = 0.02} and the presence of severe medial tears (MTs) (59% vs. 44%, respectively, P = 0.03) were greater in SC than NC. In addition, SC had a higher prevalence of ≥3 consecutive struts lying directly in contact with surface calcified area (3SC) (52% vs. 8%, respectively, P < 0.0001). Multivariate analysis demonstrated that sections with duration of implantation ≤6 months [odds ratio (OR): 7.7, P < 0.0001], 3SC (OR: 6.5, P < 0.0001), strut malapposition (OR: 5.0, P < 0.0001), and lack of MTs (OR: 2.5, P = 0.0005) were independent predictors of uncovered struts. Prevalence of neoatherosclerosis was significantly lower in SC than that of NC (24% vs. 44%, P = 0.02).

CONCLUSION

Severe calcification, especially surface calcified area is an independent predictor of uncovered struts and delayed healing after newer-generation DES implantation. These data expand of knowledge of the vascular responses of stenting of calcified arteries and suggests further understand of how best to deal with calcification in patients undergoing PCI.

Occurrence and predictive factors of restenosis in coronary heart disease patients underwent sirolimus-eluting stent implantation

BACKGROUND

This study aimed to investigate the occurrence and predictive factors of restenosis in coronary heart disease (CHD) patients underwent percutaneous coronary intervention (PCI) with sirolimus-eluting stent (SES).

METHODS

Demographic data, clinical features, and laboratory tests of 398 CHD patients underwent PCI with SES were retrospectively reviewed. Coronary angiography was performed to evaluate coronary stenosis before PCI and in-stent restenosis at 1-year follow-up.

RESULTS

There were 37 (9.3%) patients suffered restenosis, but 361 (90.7%) patients did not develop restenosis at 1-year follow-up. Demographic characteristic (age), cardiovascular risk factors (hypertension and hyperuricemia), biochemical indexes (fasting blood-glucose, total cholesterol, low density lipoprotein cholesterol (LDL-C) and high-sensitivity C-reactive protein (HsCRP)), cardiac function index (cardiac troponin I), lesion features (multivessel artery lesions, target lesion at left circumflex artery (LCX), two target lesions and length of target lesion), and operation procedure (length of stent) were correlated with higher restenosis risk. Moreover, age, hypertension, diabetes mellitus, LDL-C, HsCRP, and target lesion at LCX were independent predictive factors for raised restenosis risk. Based on these independent predictive factors, we established a restenosis risk prediction model, and receiver-operating characteristic curves displayed that this model exhibited an excellent predictive value for higher restenosis risk (areas under the curve 0.953 (95% CI 0.926-0.981)).

CONCLUSION

Our findings provide a new insight into the prediction for restenosis in CHD patients underwent PCI with SES.

Biodegradable polymer-coated thin strut sirolimus- -eluting stent versus durable polymer-coated everolimus-eluting stent in the diabetic population

BACKGROUND

The number of patients with diabetes mellitus (DM) presenting with coronary artery disease is increasing and accounts for more than 30% of patients undergoing percutaneous coronary interventions (PCI). The biodegradable polymer drug-eluting stents were developed to improve vascular healing. It was sought herein, to determine 1-year clinical follow-up in patients with DM treated with the thin strut biodegradable polymer-coated sirolimus-eluting stent (BP-SES) versus durable coating everolimus-eluting stent (DP-EES).

METHODS

Patients were retrospectively analyzed with DM were treated with either a BP-SES (ALEX™, Balton, Poland, n = 670) or a DP-EES (XIENCE™, Abbott, USA, n = 884) with available 1 year clinical follow-up using propensity score matching. Outcomes included target vessel revascularization (TVR) as efficacy outcome and all-cause death, myocardial infarction, and definite/probable stent thrombosis as safety outcomes.

RESULTS

After propensity score matching 527 patients treated with BP-SES and 527 patients treated with DP-EES were selected. Procedural and clinical characteristics were similar between both groups. In-hospital mortality was 3.23% in BP-SES vs. 2.09% in DP-EES group (p = 0.25). One-year followup demonstrated comparable efficacy outcome TVR (BP-SES 6.64% vs. DP-EES 5.88%; p = 0.611), as well as similar safety outcomes of all-cause death (BP-SES 10.06% vs. DP-EES 7.59%; p = 0.158), myocardial infarction (BP-SES 7.959% vs. DP-EES 6.83%; p = 0.813), and definite/probable stent thrombosis (BP-SES 1.14% vs. DP-EES 0.76%; p = 0.525).

CONCLUSIONS

The thin-strut biodegradable polymer coated, sirolimus-eluting stent demonstrated comparable clinical outcomes at 1-year after implantation to DP-EES. These data support the relative safety and efficacy of BP-SES in diabetic patients undergoing PCI.

Fas ligand and nitric oxide combination to control smooth muscle growth while sparing endothelium

Metallic stents cause vascular wall damage with subsequent smooth muscle cell (SMC) proliferation, neointimal hyperplasia, and treatment failure. To combat in-stent restenosis, drug-eluting stents (DES) delivering mTOR inhibitors such as sirolimus or everolimus have become standard for coronary stenting. However, the relatively non-specific action of mTOR inhibitors prevents efficient endothelium recovery and mandates dual antiplatelet therapy to prevent thrombosis. Unfortunately, long-term dual antiplatelet therapy leads to increased risk of bleeding/stroke and, paradoxically, myocardial infarction. Here, we took advantage of the fact that nitric oxide (NO) increases Fas receptors on the SMC surface. Fas forms a death-inducing complex upon binding to Fas ligand (FasL), while endothelial cells (ECs) are relatively resistant to this pathway. Selected doses of FasL and NO donor synergistically increased SMC apoptosis and inhibited SMC growth more potently than did everolimus or sirolimus, while having no significant effect on EC viability and proliferation. This differential effect was corroborated in ex vivo pig coronaries, where the neointimal formation was inhibited by the drug combination, but endothelial viability was retained. We also deployed FasL-NO donor-releasing ethylene-vinyl acetate copolymer (EVAc)-coated stents into pig coronary arteries, and cultured them in perfusion bioreactors for one week. FasL and NO donor, released from the stent coating, killed SMCs close to the stent struts, even in the presence of flow rates mimicking those of native arteries. Thus, the FasL-NO donor-combination has a potential to prevent intimal hyperplasia and in-stent restenosis, without harming endothelial restoration, and hence may be a superior drug delivery strategy for DES.

Balloons and Stents and Scaffolds: Preclinical Evaluation of Interventional Devices for Occlusive Arterial Disease

Atherosclerosis places a significant burden on humankind; it is the leading cause of mortality globally, and for those living with atherosclerosis, it can significantly impact quality of life. Fortunately, treatment advances have effectively reduced the morbidity and mortality related to atherosclerosis, with one such modality being percutaneous intervention (PCI) to open occluded arteries. Over the 40-year history of PCI, preclinical models have played a critical role in demonstrating proof of concept, characterizing the in vivo behavior (pharmacokinetics, degradation) and providing a reasonable assurance of biologic safety of interventional devices before entering into clinical trials. Further, preclinical models may provide insight into the potential efficacy of these devices with the appropriate study design and end points. While several species have been used in the evaluation of interventional devices, the porcine model has been the principal model used in the evaluation of safety of devices for both coronary and endovascular treatments. This article reviews the fundamentals of permanent stents, transient scaffolds, and drug-coated balloons and the models, objectives, and methods used in their preclinical evaluation.

Endothelial Function: A Short Guide for the Interventional Cardiologist

An impaired function of the coronary endothelium is an important determinant of all stages of atherosclerosis, from initiation, to mediation of functional phenomena—such as spasm and plaque erosion, to atherothrombotic complications. Endothelial function is modified by therapies, including stent implantation. Finally, endothelial function changes over time, in response to physical stimuli and pharmocotherapies, and its assessment might provide information on how individual patients respond to specific therapies. In this review, we describe the role of the endothelium in the continuum of coronary atherosclerosis, from the perspective of the interventional cardiologist. In the first part, we review the current knowledge of the role of endothelial (dys)function on atherosclerotic plaque progression/instabilization and on the mechanisms of ischemia, in the absence of coronary artery stenosis. In the second part of this review, we describe the impact of coronary artery stenting on endothelial function, platelet aggregation, and inflammation.

The effects of stenting on coronary endothelium from a molecular biological view: Time for improvement?

Coronary artery stenting following balloon angioplasty represents the gold standard in revascularization of coronary artery stenoses. However, stent deployment as well as percutaneous transluminal coronary angioplasty (PTCA) alone causes severe injury of vascular endothelium. The damaged endothelium is intrinsically repaired by locally derived endothelial cells and by circulating endothelial progenitor cells from the blood, leading to re‐population of the denuded regions within several weeks to months. However, the process of re‐endothelialization is often incomplete or dysfunctional, promoting in‐stent thrombosis and restenosis. The molecular and biomechanical mechanisms that influence the process of re‐endothelialization in stented segments are incompletely understood. Once the endothelium is restored, endothelial function might still be impaired. Several strategies have been followed to improve endothelial function after coronary stenting. In this review, the effects of stenting on coronary endothelium are outlined and current and future strategies to improve endothelial function after stent deployment are discussed.

40 Years of Percutaneous Coronary Intervention: History and Future Directions

The field of interventional cardiology has evolved significantly since the first percutaneous transluminal coronary angioplasty was performed 40 years ago. This evolution began with a balloon catheter mounted on a fixed wire and has progressed into bare-metal stents (BMS), first-generation drug-eluting stents (DES), second- and third-generation biodegradable polymer-based DES, and culminates with the advent of bioabsorbable stents, which are currently under development. Each step in technological advancement has improved outcomes, while new persisting challenges arise, caused by the stent scaffolds, the polymers employed, and the non-selective cytostatic and cytotoxic drugs eluted from the stents. Despite the promising technological advances made in stent technology, managing the balance between reductions in target lesion revascularization, stent thrombosis, and bleeding remain highly complex issues. This review summarizes the evolution of percutaneous coronary intervention with a focus on vascular dysfunction triggered by the non-selective drugs eluted from various stents. It also provides an overview of the mechanism of action of the drugs currently used in DES. We also discuss the efforts made in developing novel cell-selective drugs capable of inhibiting vascular smooth muscle cell (VSMC) proliferation, migration, and infiltration of inflammatory cells while allowing for complete reendothelialization. Lastly, in the era of precision medicine, considerations of patients’ genetic variance associated with myocardial infarction and in-stent restenosis are discussed. The combination of personalized medicine and improved stent platform with cell-selective drugs has the potential to solve the remaining challenges and improve the care of coronary artery disease patients.

Early-Phase Vascular Healing of Bioabsorbable vs. Durable Polymer-Coated Everolimus-Eluting Stents in Patients With ST-Elevation Myocardial Infarction - 2-Week and 4-Month Analyses With Optical Coherence Tomography

BACKGROUND

Despite the revolution of coronary stents, there remain concerns about the risk of stent thrombosis, especially in patients with ST-elevation myocardial infarction (STEMI). The present study compared early vascular healing as a contributing factor to reducing stent thrombosis between Xience everolimus-eluting stents (X-EES) and Synergy everolimus-eluting stents (S-EES) in patients with STEMI.

METHODS AND RESULTS

The present study included 47 patients with STEMI requiring primary percutaneous coronary intervention with X-EES (n=25) or S-EES (n=22). Optical coherence tomography (OCT) assessments of the stented lesions were performed 2 weeks and 4 months after stent implantation. Neointimal strut coverage, malapposition and the frequency of thrombus formation were evaluated. In the 2-week OCT analysis, the proportion of covered struts in S-EES (42.4±15.4%) was significantly higher than in X-EES (26.3±10.1%, P<0.001). In the 4-month OCT analysis, the proportion of covered struts in S-EES (72.2±17.9%) was still significantly higher than in X-EES (62.0±14.9%, P=0.04).

CONCLUSIONS

Compared with X-EES, S-EES showed a higher proportion of covered struts in the early phase after stent implantation for STEMI patients.

Fracture in drug-eluting stents increases focal intimal hyperplasia in the atherosclerosed rabbit iliac artery

OBJECTIVES

Drug-eluting stent (DES) strut fracture (SF) is associated with higher incidence of In-stent restenosis (ISR)-return of blockage in a diseased artery post stenting-than seen with bare metal stents (BMS). We hypothesize that concomitance of drug and SF leads to greater neointimal response.

BACKGROUND

Controlled release of therapeutic agents, such as sirolimus and its analogs, or paclitaxel from has reduced tissue based DES failure modes compared to BMS. ISR is dramatically reduced and yet the implications of mechanical device failure is magnified.

METHODS

Bilateral Xience Everolimus-eluting stents (EES) were implanted in 20 New Zealand White rabbits on normal (n = 7) or high fat (HF)/high cholesterol (HC) (n = 13) diets. Implanted stents were intact or mechanically fractured. Everolimus concentration was as packaged or pre-eluted. After 21 days, stented vessels were explanted, resin embedded, MicroCT scanned, and analyzed histomorphometrically.

RESULTS

Fractured EES were associated with significant (P < 0.05) increases in arterial stenosis and neointimal formation and lower lumen-to-artery area ratios compared to intact EES. Hyperlipidemic animals receiving pre-eluted EES revealed no significant difference between intact and fracture groups.

CONCLUSIONS

SF increases intimal hyperplasia, post EES implant, and worse with more advanced disease. Pre-eluted groups, reflective of BMS, did not show significant differences, suggesting a synergistic effect of everolimus and mechanical injury, potentially explaining the lack of SF reports for BMS. Here, we report that ISR has a higher incidence with SF in EES, the clinical implication is that patients with SF after DES implantation merit careful follow-up.

Incidence and predictors of target lesion failure in a multiethnic Asian population receiving the SYNERGY coronary stent: A prospective all-comers registry

OBJECTIVES

To evaluate the target lesion failure (TLF) rate of the SYNERGY stent in all-comers, multiethnic Asian population.

BACKGROUND

Currently, most drug eluting stents deliver anti-proliferative drugs from a durable polymer which is associated with a risk of late stent thrombosis. The novel everolimus-eluting, platinum chromium SYNERGY stent is coated with a bioabsorbable abluminal polymer that resolves within 4 months.

METHODS

This was a prospective, single center registry of consecutive patients treated with the SYNERGY stent between December 2012 and April 2015. The primary outcome was the incidence of TLF, defined as the combination of cardiac death, target vessel myocardial infarction, or clinically driven target lesion revascularization (TLR) at 1 year.

RESULTS

A total of 807 patients received the SYNERGY stent during the study period. One-year clinical outcome data was available for 765 patients (94.8%) and were considered for statistical analysis. The mean age was 60.7 ± 10.8 years, and 83.4% were males. Patients with acute myocardial infarction consisted of 50.3% (ST-segment elevation myocardial infarction: 23.0%, Non-ST-segment elevation myocardial infarction: 27.3%) of the study population. The treated lesions were complex (ACC/AHA type B2/C: 72.7%). The primary end point of TLF at 1 year was 5.8%. Rates of cardiac mortality, target vessel myocardial infarction, and TLR were 4.2, 1.0, and 1.3%, respectively, at 1 year. Predictors of the incidence and time to early TLF were female gender, Malay ethnicity, diabetes mellitus, acute myocardial infarction at presentation, a prior history of coronary artery bypass surgery and the presence of lesion calcification. The incidence of definite stent thrombosis was 0.4% at 1 year.

CONCLUSIONS

In this registry, the use of the SYNERGY stent was associated with low rates of TLF at 1 year.

Endothelial Barrier Protein Expression in Biodegradable Polymer Sirolimus-Eluting Versus Durable Polymer Everolimus-Eluting Metallic Stents

OBJECTIVES

This study sought to investigate endothelial coverage and barrier protein expression following stent implantation.

BACKGROUND

Biodegradable polymer drug-eluting stents (BP-DES) have been purported to have biological advantages in vessel healing versus durable polymer DES (DP-DES), although clinical trial data suggest equipoise.

METHODS

Biodegradable polymer-sirolimus-eluting stents (BP-SES), durable polymer-everolimus-eluting stents (DP-EES), and bare-metal stents (BMS) were compared. In the rabbit model (28, 45, and 120 days), stented arteries underwent light microscopic analysis and immunostaining for the presence of vascular endothelium (VE)-cadherin, an endothelial barrier protein, and were subjected to confocal microscopy and scanning electron microscopy. A cell culture study in stented silicone tubes was performed to assess cell proliferation.

RESULTS

Light microscopic assessments were similar between BP-SES and DP-EES. BMS showed nearly complete expression of VE-cadherin at 28 days, whereas both DES showed significantly less with results favoring BP-SES versus DP-EES (39% coverage in BP-SES, 22% in DP-EES, 95% in BMS). Endothelial cell morphologic patterns differed according to stent type with BMS showing a spindle-like shape, DP-EES a cobblestone pattern, and BP-SES a shape in between. VE-cadherin-negative areas showed greater surface monocytes regardless of type of stent. Cell proliferation was suppressed in both DES with numerically less suppression in BP-SES versus DP-EES.

CONCLUSIONS

This is the first study to examine VE-cadherin expression after DES. All DES demonstrated deficient barrier expression relative to BMS with results favoring BP-SES versus DP-EES. These findings may have important implications for the development of neoatherosclerosis in different stent types.

The Rabbit Model of Accelerated Atherosclerosis: A Methodological Perspective of the Iliac Artery Balloon Injury

Acute coronary syndrome resulting from coronary occlusion following atherosclerotic plaque development and rupture is the leading cause of death in the industrialized world. New Zealand White (NZW) rabbits are widely used as an animal model for the study of atherosclerosis. They develop spontaneous lesions when fed with atherogenic diet; however, this requires long time of 4 - 8 months. To further enhance and accelerate atherogenesis, a combination of atherogenic diet and mechanical endothelial injury is often employed. The presented procedure for inducing atherosclerotic plaques in rabbits uses a balloon catheter to disrupt the endothelium in the left iliac artery of NZW rabbits fed with atherogenic diet. Such mechanical damage caused by the balloon catheter induces a chain of inflammatory reactions initiating neointimal lipid accumulation in a time dependent fashion. Atherosclerotic plaque following balloon injury show neointimal thickening with extensive lipid infiltration, high smooth muscle cell content and presence of macrophage derived foam cells. This technique is simple, reproducible and produces plaque of controlled length within the iliac artery. The whole procedure is completed within 20 - 30 min. The procedure is safe with low mortality and also offers high success in obtaining substantial intimal lesions. The procedure of balloon catheter induced arterial injury results in atherosclerosis within two weeks. This model can be used for investigating the disease pathology, diagnostic imaging and to evaluate new therapeutic strategies.

Clinical Implication of Optical Coherence Tomography-Based Neoatherosclerosis

Recent research has indicated neoatherosclerosis (NA), the de novo development of atherosclerosis within the neointimal region of the stented segment after coronary stent implantation, as a mechanism of late/very late stent thrombosis (VLST) and restenosis. This research is based on histologic and intravascular imaging studies. Optical coherence tomography (OCT) is an imaging tool that is superior with regard to resolution capacity, and can be used to visualize detailed information about distinct morphological characteristics of the restenotic tissue. Thus, OCT is a valuable imaging tool for examining NA, such as macrophage infiltration, lipid accumulation, in-stent calcification, or neointimal rupture. This article discusses the prevalence, predictors, and clinical implications of NA that can be observed by OCT.

Bioresorbable Scaffolds versus Metallic Stents in Routine PCI

BACKGROUND

Bioresorbable vascular scaffolds were developed to overcome the shortcomings of drug-eluting stents in percutaneous coronary intervention (PCI). We performed an investigator-initiated, randomized trial to compare an everolimus-eluting bioresorbable scaffold with an everolimus-eluting metallic stent in the context of routine clinical practice.

METHODS

We randomly assigned 1845 patients undergoing PCI to receive either a bioresorbable vascular scaffold (924 patients) or a metallic stent (921 patients). The primary end point was target-vessel failure (a composite of cardiac death, target-vessel myocardial infarction, or target-vessel revascularization). The data and safety monitoring board recommended early reporting of the study results because of safety concerns. This report provides descriptive information on end-point events.

RESULTS

The median follow-up was 707 days. Target-vessel failure occurred in 105 patients in the scaffold group and in 94 patients in the stent group (2-year cumulative event rates, 11.7% and 10.7%, respectively; hazard ratio, 1.12; 95% confidence interval [CI], 0.85 to 1.48; P=0.43); event rates were based on Kaplan-Meier estimates in time-to-event analyses. Cardiac death occurred in 18 patients in the scaffold group and in 23 patients in the stent group (2-year cumulative event rates, 2.0% and 2.7%, respectively), target-vessel myocardial infarction occurred in 48 patients in the scaffold group and in 30 patients in the stent group (2-year cumulative event rates, 5.5% and 3.2%), and target-vessel revascularization occurred in 76 patients in the scaffold group and in 65 patients in the stent group (2-year cumulative event rates, 8.7% and 7.5%). Definite or probable device thrombosis occurred in 31 patients in the scaffold group as compared with 8 patients in the stent group (2-year cumulative event rates, 3.5% vs. 0.9%; hazard ratio, 3.87; 95% CI, 1.78 to 8.42; P<0.001).

CONCLUSIONS

In this preliminary report of a trial involving patients undergoing PCI, there was no significant difference in the rate of target-vessel failure between the patients who received a bioresorbable scaffold and the patients who received a metallic stent. The bioresorbable scaffold was associated with a higher incidence of device thrombosis than the metallic stent through 2 years of follow-up. (Funded by Abbott Vascular; AIDA ClinicalTrials.gov number, NCT01858077 .).

Comparison of a Drug-Free Early Programmed Dismantling PDLLA Bioresorbable Scaffold and a Metallic Stent in a Porcine Coronary Artery Model at 3-Year Follow-Up

BACKGROUND

Arterial Remodeling Technologies bioresorbable scaffold (ART-BRS), composed of l- and d-lactyl units without drug, has shown its safety in a porcine coronary model at 6 months. However, long-term performance remains unknown. The aim of this study was to evaluate the ART-BRS compared to a bare metal stent (BMS) in a healthy porcine coronary model for up to 3 years.

METHODS AND RESULTS

Eighty-two ART-BRS and 66 BMS were implanted in 64 Yucatan swine, and animals were euthanatized at intervals of 1, 3, 6, 9, 12, 18, 24, and 36 months to determine the vascular response using quantitative coronary angiography, optical coherence tomography, light and scanning electron microscopy, and molecular weight analysis. Lumen enlargement was observed in ART-BRS as early as 3 months, which progressively increased up to 18 months, whereas BMS showed no significant difference over time. Percentage area stenosis by optical coherence tomography was greater in ART-BRS than in BMS at 1 and 3 months, but this relationship reversed beyond 3 months. Inflammation peaked at 6 months and thereafter continued to decrease up to 36 months. Complete re-endothelialization was observed at 1 month following implantation in both ART-BRS and BMS. Scaffold dismantling started at 3 months, which allowed early vessel enlargement, and bioresorption was complete by 24 months.

CONCLUSIONS

ART-BRS has the unique quality of early programmed dismantling accompanied by vessel lumen enlargement with mild to moderate inflammation. The main distinguishing feature of the ART-BRS from other scaffolds made from poly-l-lactic acid may result in early and long-term vascular restoration.

Intravascular fibrin molecular imaging improves the detection of unhealed stents assessed by optical coherence tomography in vivo

AIMS

Fibrin deposition and absent endothelium characterize unhealed stents that are at heightened risk of stent thrombosis. Optical coherence tomography (OCT) is increasingly used for assessing stent tissue coverage as a measure of healed stents, but cannot precisely identify whether overlying tissue represents physiological neointima. Here we assessed and compared fibrin deposition and persistence on bare metal stent (BMS) and drug-eluting stent (DES) using near-infrared fluorescence (NIRF) molecular imaging in vivo, in combination with simultaneous OCT stent coverage.

METHODS AND RESULTS

Rabbits underwent implantation of one BMS and one DES without overlap in the infrarenal aorta (N = 20 3.5 × 12 mm). At Days 7 and/or 28, intravascular NIRF-OCT was performed following the injection of fibrin-targeted NIRF molecular imaging agent FTP11-CyAm7. Intravascular NIRF-OCT enabled high-resolution imaging of fibrin overlying stent struts in vivo, as validated by histopathology. Compared with BMS, DES showed greater fibrin deposition and fibrin persistence at Days 7 and 28 (P < 0.01 vs. BMS). Notably, for edge stent struts identified as covered by OCT on Day 7, 92.8 ± 9.5% of DES and 55.8 ± 23.6% of BMS struts were NIRF fibrin positive (P < 0.001). At Day 28, 18.6 ± 10.6% (DES) and 5.1 ± 8.7% (BMS) of OCT-covered struts remained fibrin positive (P < 0.001).

CONCLUSION

Intravascular NIRF fibrin molecular imaging improves the detection of unhealed stents, using clinically translatable technology that complements OCT. A sizeable percentage of struts deemed covered by OCT are actually covered by fibrin, particularly in DES, and therefore such stents might remain prothrombotic. These findings have implications for the specificity of standalone clinical OCT assessments of stent healing.

Current State of Bioabsorbable Polymer-Coated Drug-Eluting Stents

Drug-eluting stents (DES) have been shown to significantly reduce clinical and angiographic restenosis compared to bare metal stents (BMS). The polymer coatings on DES elute antiproliferative drugs to inhibit intimal proliferation and prevent restenosis after stent implantation. Permanent polymers which do not degrade in vivo may increase the likelihood of stent-related delayed arterial healing or polymer hypersensitivity. In turn, these limitations may contribute to an increased risk of late clinical events. Intuitively, a polymer which degrades after completion of drug release, leaving an inert metal scaffold in place, may improve arterial healing by removing a chronic source of inflammation, neoatherosclerosis, and/or late thrombosis. In this way, a biodegradable polymer may reduce late ischemic events. Additionally, improved healing after stent implantation could reduce the requirement for long-term dual antiplatelet therapy and the associated risk of bleeding and cost. This review will focus on bioabsorbable polymer-coated DES currently being evaluated in clinical trials.

Comparison of Vascular Responses Following New-Generation Biodegradable and Durable Polymer-Based Drug-Eluting Stent Implantation in an Atherosclerotic Rabbit Iliac Artery Model

Background

Incomplete endothelialization is the primary substrate of late stent thrombosis; however, recent reports have revealed that abnormal vascular responses are also responsible for the occurrence of late stent failure. The aim of the current study was to assess vascular response following deployment of biodegradable polymer‐based Synergy (Boston Scientific) and Nobori (Terumo) drug‐eluting stents and the durable polymer‐based Resolute Integrity stent (Medtronic) in an atherosclerotic rabbit iliac artery model.

Methods and Results

A total of 24 rabbits were fed an atherogenic diet, and then a balloon injury was used to induce atheroma formation. Synergy, Nobori, and Resolute Integrity stents were randomly implanted in iliac arteries. Animals were euthanized at 28 days for scanning electron microscopic evaluation and at 90 days for histological analysis. The percentage of uncovered strut area at 28 days was lowest with Synergy, followed by Resolute Integrity, and was significantly higher with Nobori stents (Synergy 1.1±2.2%, Resolute Integrity 2.0±3.9%, Nobori 4.6±3.0%; P<0.001). At 90 days, inflammation score was lowest for Synergy (0.27±0.45), followed by Nobori (0.62±0.59), and was highest for Resolute Integrity (0.89±0.46, P<0.001). Foamy macrophage infiltration within neointima (ie, neoatherosclerosis) was significantly less with Synergy (0.62±0.82) compared with Nobori (0.85±0.74) and Resolute Integrity (1.39±1.32; P=0.034).

Conclusions

The biodegradable polymer‐coated thin‐strut Synergy drug‐eluting stent showed the fastest stent strut neointimal coverage and the lowest incidence of neoatherosclerosis in the current animal model.

Neoatherosclerosis after Drug-Eluting Stent Implantation: Roles and Mechanisms

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

A novel polymer-free ciglitazone-coated vascular stent: in vivo and ex vivo analysis of stent endothelialization in a rabbit iliac artery model

AIM

Peroxisome proliferator-activated receptor-gamma (PPARg) agonists have known pleiotropic cardiovascular effects with favourable properties in vascular remodeling, and specifically in suppression of vascular smooth muscle cell proliferation. A novel vascular stent coating using the PPARg ligand ciglitazone (CCS) was investigated regarding its effects on endothelialization after 7 and 28 days.

METHODS

Microporous bare metal stents (BMS) were coated with ciglitazone by ultrasonic flux with a load of 255 μg ciglitazone/stent. SixteenNew Zealand white rabbits, fed a with high cholesterol diet, underwent stent implantation in both iliac arteries. Everolimus-eluting stents (EES) and BMS were comparators. Histology (CD 31 immunostaining, confocal and scanning electron microscopy, morphometry) was performed after 7 and 28 days and by OCT (optical coherence tomography) in vivo after 28 days.

RESULTS

Microscopy showed comparable results with near complete endothelialization in CCS and BMS (%CD31 above stent struts after 7 days: 67.92±36.35 vs. 84.48±23.86; p = 0.55; endothel % above stent struts: 77.22±27.9 vs. 83.89±27.91; p = 0.78). EES were less endothelialized with minimal fibrin deposition, not found in BMS and CCS (% CD 31 above struts after 28 days, BMS: 100.0±0.0 vs. EES: 95.9±3.57 vs. CCS: 100.0±0.0; p = 0.0292). OCT revealed no uncovered struts in all stents after 28 days.

CONCLUSIONS

Polymer-free coating with ciglitazone, a PPARg agonist is feasible and stable over time. Our data prove unimpaired endothelial coverage of a ciglitazone-coated vascular stent system by histology and OCT. Thus, this PPARg agonist coating deserves further investigation to evaluate its potency on local neointimal suppression.

Preserved endothelial vasomotor function after everolimus-eluting stent implantation

AIMS

To compare the degree of endothelial dysfunction (ED) in patients treated with everolimus-eluting stent (EES) versus bare metal stent (BMS) implantation.

METHODS AND RESULTS

This is an observational study. A total of 30 elective patients (15 treated with EES and 15 with BMS) were recruited. All patients underwent coronary angiography and intracoronary acetylcholine (Ach) test at different doses at six months after stent implantation. Quantitative coronary angiography analysis was performed to evaluate the changes in mean luminal diameter (MLD) of the segments distal to the distal stent edge after increasing doses of Ach. Both EES and BMS groups had similar baseline characteristics except for stent length (18.6±2.5 vs. 16.5±2.5 mm; p=0.033) and diameter (3.1±0.2 vs. 3.4±0.3 mm; p=0.007). The vasomotion test showed that EES had 3.14% of MLD decrease after Ach infusion and BMS had 2.35% of vasoconstriction (p=0.62). After adjustment for baseline characteristics, no statistical difference was observed between groups.

CONCLUSIONS

In our study EES implantation was associated with a low degree of ED and had a similar vasomotion response as compared to BMS. Prospective randomised investigations are warranted to confirm these findings.

Influence of the coating with extracellular matrix and the number of cell passages on the endothelialization of a polystyrene surface

The proper morphology and function of the vascular endothelium are prerequisites for a sufficient supply of the tissues. Endothelial cell (EC) dysfunction can lead to circulatory disorders and the development of cardiovascular diseases. The endothelialization of cardiovascular implants is a sophisticated task since EC miss their natural environment and physiological stimuli in vitro. In addition, different studies revealed that the EC behavior and morphology depended on the substrate and the passage number of the EC. Therefore, the comparison of endothelialization studies is very difficult, when passage and substrate are unknown.The aim of this study was to investigate the growth potential and cell morphology of human venous endothelial cells (HUVEC) as a function of different cell passages and different substrates (pristine polystyrene, tissue-typical ECM-coated polystyrene). The study revealed that HUVEC morphology and growth potential were significantly different on pristine polystyrene compared to the basal lamina-like ECM-coated polystyrene surface. Furthermore, it became obvious that the passage of the cells affected the endothelialization of the polystyrene surface significantly. In conclusion, this study emphasized the need for a critical consideration of EC data whereas a simple comparison of results is not possible if EC age and passage is unknown.

CYP2C19 loss-of-function alleles are not associated with clinical outcome of clopidogrel therapy in patients treated with newer-generation drug-eluting stents

CYP2C19 loss-of-function (LOF) alleles adversely affect clinical outcome of clopidogrel therapy. Recent introduction of a newer-generation drug-eluting stent (DES) has significantly reduced the occurrence of stent thrombosis.The aim of this study was to evaluate the impact of CYP2C19 LOF alleles on clinical outcome in patients treated with the newer-generation DES.The effects of CYP2C19 genotypes were evaluated on clinical outcome of clopidogrel therapy in 2062 patients treated with percutaneous coronary intervention using either first-generation DES (sirolimus- and paclitaxel-eluting stent, n = 1349) or newer-generation DES (everolimus- and zotarolimus-eluting stent, n = 713). The primary clinical outcome was major cardiac and cerebrovascular event (MACCE) including cardiac death, nonfatal myocardial infarction, stroke, and stent thrombosis during 1 year of follow-up.CYP2C19 LOF alleles were significantly associated with a higher risk of MACCE in patients treated with first-generation DES (hazard ratio [HR] 2.599, 95% confidence interval [CI] 1.047-6.453; P = 0.034). In contrast, CYP2C19 LOF alleles were not associated with primary outcome in newer-generation DES (HR 0.716, 95% CI 0.316-1.622; P = 0.522). In the further multivariate analysis, CYP2C19 LOF alleles were not associated with MACCE in patients receiving newer-generation DES (adjusted HR 0.540, 95% CI 0.226-1.291; P = 0.166), whereas they were demonstrated to be an independent risk factor for MACCE in those implanted with first-generation DES (adjusted HR 3.501, 95% CI 1.194-10.262; P = 0.022).In contradiction to their clinical impact in first-generation DES era, CYP2C19 LOF alleles may not affect clinical outcome of clopidogrel therapy in patients treated with newer-generation DES.

Efficacy and safety of a novel bioabsorbable polymer-coated, everolimus-eluting coronary stent: the EVOLVE II Randomized Trial

BACKGROUND

Drug eluting stents with durable polymers may be associated with hypersensitivity, delayed healing, and incomplete endothelialization, which may contribute to late/very late stent thrombosis and the need for prolonged dual antiplatelet therapy. Bioabsorbable polymers may facilitate stent healing, thus enhancing clinical safety. The SYNERGY stent is a thin-strut, platinum chromium metal alloy platform with an ultrathin bioabsorbable Poly(D,L-lactide-co-glycolide) abluminal everolimus-eluting polymer. We performed a multicenter, randomized controlled trial for regulatory approval to determine noninferiority of the SYNERGY stent to the durable polymer PROMUS Element Plus everolimus-eluting stent.

METHODS AND RESULTS

Patients (n=1684) scheduled to undergo percutaneous coronary intervention for non-ST-segment-elevation acute coronary syndrome or stable coronary artery disease were randomized to receive either the SYNERGY stent or the PROMUS Element Plus stent. The primary end point of 12-month target lesion failure was observed in 6.7% of SYNERGY and 6.5% PROMUS Element Plus treated subjects by intention-to-treat (P=0.83 for difference; P=0.0005 for noninferiority), and 6.4% in both the groups by per-protocol analysis (P=0.0003 for noninferiority). Clinically indicated revascularization of the target lesion or definite/probable stent thrombosis were observed in 2.6% versus 1.7% (P=0.21) and 0.4% versus 0.6% (P=0.50) of SYNERGY versus PROMUS Element Plus-treated subjects, respectively.

CONCLUSIONS

In this randomized trial, the SYNERGY bioabsorbable polymer everolimus-eluting stent was noninferior to the PROMUS Element Plus everolimus-eluting stent with respect to 1-year target lesion failure. These data support the relative safety and efficacy of SYNERGY in a broad range of patients undergoing percutaneous coronary intervention.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01665053.

Modelling the Impact of Atherosclerosis on Drug Release and Distribution from Coronary Stents

Although drug-eluting stents (DES) are now widely used for the treatment of coronary heart disease, there remains considerable scope for the development of enhanced designs which address some of the limitations of existing devices. The drug release profile is a key element governing the overall performance of DES. The use of in vitro, in vivo, ex vivo, in silico and mathematical models has enhanced understanding of the factors which govern drug uptake and distribution from DES. Such work has identified the physical phenomena determining the transport of drug from the stent and through tissue, and has highlighted the importance of stent coatings and drug physical properties to this process. However, there is limited information regarding the precise role that the atherosclerotic lesion has in determining the uptake and distribution of drug. In this review, we start by discussing the various models that have been used in this research area, highlighting the different types of information they can provide. We then go on to describe more recent methods that incorporate the impact of atherosclerotic lesions.

Effect of anti-ApoA-I antibody-coating of stents on neointima formation in a rabbit balloon-injury model

Background and Aims

Since high-density lipoprotein (HDL) has pro-endothelial and anti-thrombotic effects, a HDL recruiting stent may prevent restenosis. In the present study we address the functional characteristics of an apolipoprotein A-I (ApoA-I) antibody coating in vitro. Subsequently, we tested its biological performance applied on stents in vivo in rabbits.

Materials and Methods

The impact of anti ApoA-I- versus apoB-antibody coated stainless steel discs were evaluated in vitro for endothelial cell adhesion, thrombin generation and platelet adhesion. In vivo, response to injury in the iliac artery of New Zealand white rabbits was used as read out comparing apoA-I-coated versus bare metal stents.

Results

ApoA-I antibody coated metal discs showed increased endothelial cell adhesion and proliferation and decreased thrombin generation and platelet adhesion, compared to control discs. In vivo, no difference was observed between ApoA-I and BMS stents in lumen stenosis (23.3±13.8% versus 23.3±11.3%, p=0.77) or intima surface area (0.81±0.62 mm² vs 0.84±0.55 mm², p=0.85). Immunohistochemistry also revealed no differences in cell proliferation, fibrin deposition, inflammation and endothelialization.

Conclusion

ApoA-I antibody coating has potent pro-endothelial and anti-thrombotic effects in vitro, but failed to enhance stent performance in a balloon injury rabbit model in vivo.

Long-term safety of an everolimus-eluting bioresorbable vascular scaffold and the cobalt-chromium XIENCE V stent in a porcine coronary artery model

BACKGROUND

The Absorb everolimus-eluting bioresorbable vascular scaffold (Absorb) has shown promising clinical results; however, only limited preclinical data have been published. We sought to investigate detailed pathological responses to the Absorb versus XIENCE V (XV) in a porcine coronary model with duration of implant extending from 1 to 42 months.

METHODS AND RESULTS

A total of 335 devices (263 Absorb and 72 XV) were implanted in 2 or 3 main coronary arteries of 136 nonatherosclerotic swine and examined by light microscopy, scanning electron microscopy, pharmacokinetics, and gel permeation chromatography analyses at various time points. Vascular responses to Absorb and XV were largely comparable at all time points, with struts being sequestered within the neointima. Inflammation was mild to moderate (with absence of inflammation at 1 month) for both devices, although the scores were greater in Absorb at 6 to 36 months. Percent area stenosis was significantly greater in Absorb than XV at all time points except at 3 months. The extent of fibrin deposition was similar between Absorb and XV, which peaked at 1 month and decreased rapidly thereafter. Histomorphometry showed expansile remodeling of Absorb-implanted arteries starting after 12 months, and lumen area was significantly greater in Absorb than XV at 36 and 42 months. These changes correlated with dismantling of Absorb seen after 12 months. Gel permeation chromatography analysis confirmed that degradation of Absorb was complete by 36 months.

CONCLUSIONS

Absorb demonstrates comparable long-term safety to XV in porcine coronary arteries with mild to moderate inflammation. Although Absorb was associated with greater percent stenosis relative to XV, expansile remodeling was observed after 12 months in Absorb with significantly greater lumen area at ≥ 36 months. Resorption is considered complete at 36 months.

Effects of everolimus on macrophage-derived foam cell behavior

PURPOSE

The purpose of this study was to investigate the effects of everolimus on foam cell (FC) viability, mRNA levels, and inflammatory cytokine production to better understand its potential inhibitory effects on atheroma progression.

METHODS AND MATERIALS

Human THP1 macrophage-derived FC were formed using acetylated LDL (acLDL, 100 μg/mL) for 72 hours, followed by everolimus treatment (10(-5)-10(-11) M) for 24 hours. FC viability was quantified using fluorescent calcein AM/DAPI staining. FC lysates and media supernatants were analyzed for apoptosis and necrosis using a Cell Death ELISA(PLUS) assay. FC lysates and media supernatants were also analyzed for inflammatory cytokine (IL1β, IL8, MCP1, TNFα) mRNA levels and protein expression using quantitative reverse transcription real-time polymerase chain reaction (QPCR) and a Procarta® immunoassay, respectively. mRNA levels of autophagy (MAP1LC3), apoptosis (survivin, clusterin), and matrix degradation (MMP1, MMP9) markers were evaluated by Quantigene® Plex assay and verified with QPCR. Additionally, hypercholesterolemic rabbits received everolimus-eluting stents (EES) for 28 or 60 days. RAM-11 immunohistochemical staining was performed to compare %RAM-11 positive area between stented sections and unstented proximal sections. Statistical significance was calculated using one-way ANOVA (p≤0.05).

RESULTS

Calcein AM/DAPI staining showed that FC exposed to everolimus (10(-5) M) had significantly decreased viability compared to control. FC apoptosis was significantly increased at a high dose of everolimus (10(-5)M), with no necrotic effects at any dose tested. Everolimus did not affect endothelial (HUVEC) and smooth muscle (HCASMC) cell apoptosis or necrosis. Everolimus (10(-5)M) significantly increased MAP1LC3, caused an increased trend in clusterin (p=0.10), and significantly decreased survivin and MMP1 mRNA levels in FC. MCP1 cytokine mRNA levels and secreted protein expression was significantly decreased by everolimus (10(-5) M) in FC. Percentage of RAM-11 positive area exhibited a reduction trend within sections stented with EES compared to unstented proximal sections at 60 days (p=0.09).

CONCLUSION

Everolimus, a potent anti-proliferative agent used in drug-eluting stents and bioresorbable vascular scaffolds, may inhibit atheroma progression and/or promote atheroma stabilization through diminished viability of FC, decreased matrix degradation, and reduced pro-inflammatory cytokine secretion.

EXECUTIVE SUMMARY

We explored the effects of everolimus on the behavior of human THP1 macrophage-derived foam cells in culture, including cell viability, mRNA levels, and pro-inflammatory cytokine production. We conclude that everolimus, a potent anti-proliferative agent used in drug-eluting stents/bioresorbable vascular scaffolds, may potentially inhibit atheroma progression and/or promote atheroma stabilization through diminished viability of foam cells, decreased matrix degradation, and reduced pro-inflammatory cytokine secretion.

Long-term vascular responses to Resolute® and Xience V® polymer-based drug-eluting stents in a rabbit model of atherosclerosis

OBJECTIVES

To assess the late postinterventional response to iliac stenting in atheromatous rabbits using the Xience V everolimus-eluting stent (Xience V EES; Abbott Vascular) and the Resolute zotarolimus-eluting stent (Resolute ZES; Medtronic Vascular) with the MultiLink Vision bare metal stent (BMS; Abbott Vascular) as a reference.

BACKGROUND

Xience V EES and Resolute ZES were developed to overcome shortcomings of first-generation DES.

METHODS

Functional and microscopic changes were assessed by organ bath experiments and histopathologic examination. Gene expression was investigated using RT-PCR.

RESULTS

After 91 days, re-endothelialization was nearly complete (BMS: 93 ± 3%; Resolute ZES: 92 ± 2%; Xience V EES: 94 ± 3%; P = 0.10). Neointima thickness was similar in Resolute ZES (0.17 ± 0.08 mm) and BMS (0.17 ± 0.09 mm), and reduced in Xience V EES (0.03 ± 0.01 mm; P < 0.0001). Xience V EES had less peri-strut inflammation compared with BMS (P = 0.001) and Resolute ZES (P = 0.0001), while arterial segments distal to Xience V EES were more sensitive to acetylcholine than those distal to BMS and Resolute ZES (P = 0.02). Lectin-like oxidized receptor-1 was overexpressed in stented arteries (P < 0.001), whereas thrombomodulin was downregulated in Resolute ZES (P = 0.01) and BMS (P = 0.02) compared to unstented arteries of rabbits on regular chow. No significant changes were seen for vascular cell adhesion molecule-1, nitric oxide synthase 3, or endothelin-1.

CONCLUSIONS

At 3-month follow-up, nearly complete re-endothelialization was achieved for all stent groups. Xience V EES induced greater suppression of neointimal growth and peri-strut inflammation, higher vasorelaxation to acetylcholine, and expression of thrombomodulin at the level of unstented controls.