Differential Response of Delayed Healing and Persistent Inflammation at Sites of Overlapping Sirolimus- or Paclitaxel-Eluting Stents

Second- and third-generation drug-eluting coronary stents: progress and safety

Drug-eluting stents (DES) have revolutionized the treatment of coronary artery disease by reducing the rate of in-stent restenosis from 20-40% with bare-metal stent (BMS) to 6-8% with DES. However, with widespread use of DES, safety concerns have risen due to the observation of late stent thrombosis. With this in mind and better understanding of mechanism and pathophysiology of stent thrombosis, the technological platform, especially innovative anti-restenotic agents, polymeric coatings, and stent platforms, improved with newer DES. Two second-generation DES, the Endeavor zotarolimus-eluting stent (ZES) and the Xience-V everolimus-eluting stent (EES), have provided promising results in both randomized controlled trials (SPIRIT and ENDEAVOR) and registries (E-Five, COMPARE) compared with bare-metal stents (BMS) and first-generation DES. Newer third-generation stent technology, especially biodegradable polymers, polymer-free stents, and biodegradable stents on the basis of poly-L-lactide (PLLA) or magnesium, has been evaluated in preclinical and initial clinical trials. However, despite encouraging initial results, long-term data of large-scale randomized trials as well as registries comparing them to currently approved first- and second-generation DES are still lacking.

Effects of ramiprilat-coated stents on neointimal hyperplasia, inflammation, and arterial healing in a porcine coronary restenosis model

Background and Objectives

The renin-angiotensin-aldosterone system has been implicated in the pathogenesis of neointimal hyperplasia, and a role for angiotensin II in the migration and proliferation of vascular smooth muscle cells in restenotic lesions has been proposed. The aim of this study was to determine the anti-proliferative and anti-inflammatory effects of ramiprilat-coated stents in a porcine coronary overstretch restenosis model.

Subjects and Methods

Pigs were randomized into two groups in which the coronary arteries {16 pigs (16 coronaries in each group)} had a 3.0×17 mm ramiprilat-coated MAC stent or a 3.0×17 mm control MAC stent (AMG, Munich, Germany) implanted with oversizing (stent-to-artery ratio, 1.3 : 1) in porcine coronary arteries, and histopathologic analysis was assessed 28 days after stenting.

Results

There were no significant differences in the injury and inflammation scores between the two groups (1.20±0.43 vs. 1.23±0.57, p=0.8; and 1.21±0.39 vs. 1.25±0.49, p=0.6, respectively). Within the neointima, most inflammatory cells were lymphohistiocytes. Significant positive correlations existed between inflammatory cell counts and the neointima areas (r=0.567, p<0.001), and between inflammatory cell counts and the percent area stenosis (r=0.478, p<0.001). There was no significant difference in the inflammatory cell counts normalized to the injury (110±89 vs. 123±83, p=0.4) and fibrin scores (0.15±0.06 vs. 0.17±0.07, p=0.8) between the 2 groups. There were trends toward a smaller neointima area (1.06±0.51 mm² vs. 1.28±0.35 mm², p=0.083) and a smaller percent area stenosis (18.9±8.7% vs. 21.8±7.2%, p=0.088) in the ramiprilat-coated stent group.

Conclusion

Although the ramiprilat-coated stent did not show significant inhibitory effects on neointimal hyperplasia, the ramiprilat-coated stent showed good effects on the inflammatory reaction and arterial healing similar to the control stent in a porcine coronary restenosis model.

Vascular response to zotarolimus-coated balloons in injured superficial femoral arteries of the familial hypercholesterolemic Swine

BACKGROUND

Drug-coated balloons are rapidly emerging as a therapeutic alternative for the interventional treatment of peripheral vascular disease. The purpose of this study was to test the hypothesis that an angioplasty balloon coated with the mTOR inhibitor zotarolimus (ZCB) would inhibit neointimal hyperplasia in a novel injury-based superficial femoral artery model in the familial hypercholesterolemic swine.

METHODS AND RESULTS

A total of 44 familial hypercholesterolemic swine were included (12 designated to study tissue pharmacokinetics and 32 to study safety and efficacy). Fogarty balloon denudation was performed in all superficial femoral artery segments, followed by balloon angioplasty. In the pharmacokinetic study, a total of 24 ZCBs (300 μg/cm(2)) were used. Zotarolimus was detected in arterial tissue at 5 minutes (162 ng/mg of tissue), 24 hours (5.9 ng/mg of tissue), and 28 days (0.007 ng/mg of tissue) after ZCB inflation. In the safety and efficacy study, superficial femoral artery segments were randomized to either high-dose (600 μg/cm(2), n=16), low-dose (300 μg/cm(2), n=16), or paired uncoated balloons (high-dose ZCB control, n=16; low-dose ZCB control, n=16). At 28 days, the percentage of angiographic stenosis was similar among all tested groups. Histological analysis demonstrated a reduction in neointimal formation in both ZCB groups compared with controls (high-dose ZCB 44% reduction, P=0.007; low-dose ZCB 22% reduction, P=0.08). There was no evidence of delayed arterial healing or vascular toxicity in any of the ZCB groups.

CONCLUSIONS

The single delivery of zotarolimus via coated balloon is feasible, and therapeutic levels are maintained up to 28 days. The ZCB technology appears to be effective in the reduction of neointimal proliferation in the superficial femoral artery of the familial hypercholesterolemic swine.

Propensity-matched patient-level comparison of the TAXUS Liberté and TAXUS element (ION) paclitaxel-eluting stents

Stent design, metal alloy composition, and strut thickness may influence late lumen loss and clinical outcomes after bare metal stent deployment; however, their impact on outcomes after drug-eluting stent deployment is unknown. Although the TAXUS Liberté and ION paclitaxel-eluting stents use similar polymer and drug, the ION stent incorporates a novel thin-strut platinum chromium metal alloy and cell design. We therefore compared patient-level data from 2,298 subjects enrolled into the TAXUS ATLAS (TAXUS Liberté) and PERSEUS (ION) clinical trials. Propensity-score (1:1) matching was performed to adjust for covariate imbalance between stent types. Twelve-month major adverse cardiac events were less frequent after use of the ION compared to the TAXUS Liberté (12.7% vs 8.3%, p <0.001, unadjusted; 12.0% vs 7.5%, p = 0.007, propensity matched) largely because of decreased non-Q-wave myocardial infarction (MI; 2.9% vs 1.4%, p = 0.01, unadjusted; 3.2% vs 0.9%, p = 0.004, propensity matched). The MI difference was predominantly periprocedural and in patients treated with a single stent. In conclusion, this exploratory post hoc analysis demonstrated that the ION was associated with fewer adverse clinical events than the TAXUS Liberté because of decreased non-Q-wave MI. Stent platform-related variables may influence clinical outcomes after drug-eluting stent use despite similar polymer and drug elution. Differences in adjunctive pharmacotherapy and/or stenting technique may also be contributory.

In vivo assessment of optimal viewing angles from X-ray coronary angiography

AIMS

To propose and validate a novel approach to determine the optimal angiographic viewing angles for a selected coronary (target) segment from X-ray coronary angiography, without the need to reconstruct the entire coronary tree in three-dimensions (3D), such that subsequent interventions are carried out from the best view.

METHODS AND RESULTS

The approach starts with standard quantitative coronary angiography (QCA) of the target vessel in two angiographic views. Next, the target vessel is reconstructed in 3D, and in a very simple and intuitive manner, the possible overlap of the target vessel and other vessel segments can be assessed, resulting in the best view with minimum foreshortening and overlap. A retrospective study including 67 patients was set up for the validation. The overlap prediction result was compared with the true overlap on the available angiographic views (TEST views). The foreshortening for the views proposed by the new approach software viewing angle (SVA) and the views used during the stent deployment software viewing angle (EVA) were compared. Two experienced interventional cardiologists visually evaluated the success of SVA with respect to EVA. The evaluation results were graded into five values ranging from -2 to 2. The overlap prediction algorithm successfully predicted the overlap condition for all 235 TEST views. EVA was associated with more foreshortening than SVA (8.9% ± 8.2% vs. 1.6% ± 1.5%, p<0.001). The average evaluated point for the success of SVA was 0.94 ± 0.80 (p <0.001), indicating that the evaluators were in favor of the optimal views determined by the proposed approach versus the views used during the actual intervention.

CONCLUSIONS

The proposed approach is able to accurately and quickly determine the optimal viewing angles for the online support of coronary interventions.

Comparison of chronic-stage histopathological findings among 3 coronary stents implanted in the same patient

A 73-year-old woman suffering from anterior thoracic pain on exertion presented to our hospital. We performed coronary angiography and noted three stenotic legions in each coronary artery. For each angiographic finding, we implanted a bare metal stent (BMS), sirolimus-eluting stent (SES) and paclitaxel-eluting stent (PES) into the right coronary artery, left anterior descending and left circumflex coronary arteries, respectively. Nine months later, she died of lung disease, and we could compare the histopathological findings among the three coronary stents. In the drug-eluting stents, very thin intima, infiltration of inflammatory cells, and fibrin deposition were observed, while thick intima and no inflammatory findings were observed in the BMS. Fibrin deposition was more marked in the PES than in the SES. This report shows marked differences in the subsequent pathological course among three stents in the same patient.

Eosinophilic responses to stent implantation and the risk of Kounis hypersensitivity associated coronary syndrome

The use of drug eluting stents constitutes a major breakthrough in current interventional cardiology because it is more than halves the need of repeat interventions. It is incontrovertible that coronary stents, in general, have been beneficial for the vast majority of patients. A small increase in thrombosis, following DES implantation, is offset by a diminished risk of complications associated with repeat vascularization. However, late and, especially, very late stent thrombosis is a much feared complication because it is associated with myocardial infarction with increased mortality. Despite that stent thrombosis is thought to be multifactorial, so far clinical reports and reported pathology findings in patients died from coronary stent thrombosis as well as animal studies and experiments, point toward a hypersensitivity inflammation. The stented and thrombotic areas are infiltrated by interacting, via bidirectional stimuli inflammatory cells including eosinophils, macrophages, T-cells and mast cells. Stented regions constitute an ideal surrounding for endothelial damage and dysfunction, together with hemorheologic changes and turbulence as well as platelet dysfunction, coagulation and fibrinolytic disturbances. Drug eluting stent components include the metal strut which contains nickel, chromium, manganese, titanium, molybdenum, the polymer coating and the impregnated drugs which for the first generation stents are: the antimicrotubule antineoplastic agent paclitaxel and the anti-inflammatory, immunosuppressive and antiproliferative agent sirolimus. The newer stents which are called cobalt-chromiun stents and elute the sirolimus analogs everolimus and zotarolimus both contain nickel and other metals. All these components constitute an antigenic complex inside the coronary arteries which apply chronic, continuous, repetitive and persistent inflammatory action capable to induced Kounis syndrome and stent thrombosis. Allergic inflammation goes through three phases, the early phase, the late phase and the chronic phase and these three phases correspond temporally with early (acute and sub acute), late and very late stent thrombosis. Bioabsorbable allergy free poly lactic acid self expanding stents, nickel free stainless steel materials, stent coverage with nitric oxide donors and antibodies with endothelial progenitor cell capturing abilities as well as stents eluting anti-inflammatory and anti-allergic agents might be the solution of this so feared and devastating stent complication.

Evaluation of neointimal coverage and apposition with various drug-eluting stents over 12 months after implantation by optical coherence tomography

BACKGROUND

Optical coherence tomography (OCT) is an imaging technology with high resolution which provides new opportunities for evaluating the vascular healing reaction after stent implantation. We used OCT to compare neointimal coverage and stent strut apposition with different types of drug-eluting stent (DES) at more than 12 months follow-up.

METHODS

Fifty five patients who accepted 72 DESs (19 sirolimus-eluting stents [SES, Cypher Select], 27 paclitaxel-eluting stents [PES, Taxus Liberte], 26 zotarolimus-eluting stents [ZES, Endeavor]) were enrolled in our study. OCT was performed at 12-18 months after stent implantation. The neointimal hyperplasia (NIH) thickness and stent strut apposition at 1-mm interval and the presence of thrombus in each stent were observed.

RESULTS

The average NIH thickness (0.1806 ± 0.1726 mm in SES vs. 0.2558 ± 0.2187 mm in PES vs. 0.2983 ± 0.2567 mm in ZES, p<0.001) and percentage of NIH area (17.21 ± 14.05% in SES vs. 23.09 ± 14.53% in PES vs. 28.73 ± 20.47% in ZES, p=0.002) were significantly greater in ZES than in other DESs. The prevalence of uncovered struts (8.96% in SES vs. 6.19% in PES vs. 2.98% in ZES, p<0.01) and malapposed struts (6.36% in SES vs. 2.32% in PES vs. 1.69% in ZES, p<0.01) was significantly lower in ZES than in other DESs. Thrombus was less frequently observed in ZES than in other DESs (SES 1.70% vs. PES 0.83% vs. ZES 0.17%, p<0.01).

CONCLUSIONS

Compared with SES and PES, ZES showed lower prevalence of uncovered struts and malapposed struts at more than 12 months follow-up.

Comparison of sirolimus- and paclitaxel-eluting stents in patients undergoing primary percutaneous coronary intervention for ST-elevation myocardial infarction: a meta-analysis of randomized trials

BACKGROUND

It has been reported that sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) have been more effective than bare-metal stents in reducing restenosis and cardiac events in a broad range of patients with coronary artery disease. However, it is unknown whether there might be differences between these two drug-eluting stents in terms of efficacy and safety in the setting of acute ST-segment elevation myocardial infarction (STEMI).

HYPOTHESIS

The aim of the present study was to compare SES with PES in patients with acute STEMI undergoing primary percutaneous coronary intervention (PCI).

METHODS

The published research was scanned by formal searches of electronic databases (PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials) from January 2001 to February 2010. Internet-based sources of information on the results of clinical trials in cardiology were also searched.

RESULTS

A total of 4 randomized trials were included in the present meta-analysis, involving 1105 patients (550 in the SES group, 555 in the PES group). SES were significantly more effective in the reduction of angiographic binary (≥50%) restenosis (4.0% vs 9.6%, odds ratio 0.38, 95% confidence interval 0.19 to 0.74, P = 0.004) compared to PES. The differences between SES and PES were not statistically significant with respect to target vessel revascularization (TVR), stent thrombosis, cardiac death, and myocardial infarction.

CONCLUSIONS

SES are superior to PES in reducing the incidence of restenosis in patients undergoing primary PCI for STEMI, with nonsignificant differences in terms of TVR, cardiac death, myocardial infarction, and stent thrombosis.

Restenosis after implantation of sirolimus-eluting stent begins suddenly, shows short term progression, and stops suddenly

BACKGROUND AND PURPOSE

The peak of restenosis in patients implanted with bare metal stents (BMS) is thought to be 6 months after BMS implantation, but the development of restenosis with respect to time and the peak of restenosis in patients implanted with drug-eluting stents (DES) is not known. This study aims to reveal the rate of development of restenosis with respect to time in patients implanted with DES.

METHODS

A total of 282 patients who underwent sirolimus-eluting stent (SES) implantation in native coronary arteries at our hospital were evaluated by serial quantitative angiography at 3 and 6 months, and based on the latter results, at 1 and 2 years after SES implantation. Clinical data were collected for up to 3 years.

RESULTS

Three-year follow-up data were obtained for 261 patients. The 3-year incidence of clinically driven target-lesion revascularization (TLR) was 6.1% (16/261); of the 16 cases, 5 occurred at 3-month follow-up, 7 at 6-month angiographic follow-up, and 1 at 1-year follow up, respectively. While minimum lumen diameter (MLD) of these vessels that underwent TLR at 6 months decreased rapidly after the 3-month angiographic follow-up, MLD of the vessels with 50-70% stenosis at 6-month angiographic follow-up was almost unchanged at 1-year angiographic follow-up; however, 3 lesions required late (i.e. beyond 1 year) revascularization.

CONCLUSIONS

It is difficult to predict SES restenosis by angiography. SES restenosis begins suddenly, shows short-term progression, and stops suddenly. However, treatment of de novo coronary stenosis with SES is associated with a sustained clinical benefit and a very low incidence of TLR.

Comparison of bare metal stent and paclitaxel-eluting stent using a novel rat aorta stent model

The purpose of our study was to create a novel rat aorta stent implantation model. Stainless steel bare metal stents (BMS) or paclitaxel-eluting stents (PES) were implanted in male Sprague-Dawley rats (BW 400 ± 20 g). Two and four weeks after stent implantation, the aorta were collected, fixed with 2% glutaraldehyde, and cut into two segments. One segment was used for scanning electron microscopy analysis to evaluate re-endothelialization, and the other segment was used to calculate the neointimal area. At 2 weeks after stenting, the appearance of neointimal hyperplasia was less in the PES group than in the BMS group. At 4 weeks after stenting, no significant difference in neointimal hyperplasia was observed between two groups. On the other hand, the PES group showed more thrombus formation and less re-endothelialization compared to the BMS group. This study demonstrated the ability of a novel rat model of aorta stenting via a common carotid artery to measure the efficacy and safety of commercially available drug-eluting stents.

Polymeric coating of surface modified nitinol stent with POSS-nanocomposite polymer

Stent angioplasty is a successful treatment for arterial occlusion, particularly in coronary artery disease. The clinical communities were enthusiastic about the use of drug-eluting stents; however, these stents have a tendency to be a contributory factor towards late stage thrombosis, leading to mortality in a significant number of patients per year. This work presents an innovative approach in self-expanding coronary stents preparation. We developed a new nanocomposite polymer based on polyhedral oligomeric silsesquioxanes (POSS) and poly(carbonate-urea)urethane (PCU), which is an antithrombogenic and a non-biodegradable polymer with in situ endothelialization properties. The aim of this work is to coat a NiTi stent alloy with POSS-PCU. In prolonged applications in the human body, the corrosion of the NiTi alloy can result in the release of deleterious ions which leads to unwanted biological reactions. Coating the nitinol (NiTi) surface with POSS-PCU can enhance surface resistance and improve biocompatibility. Electrohydrodynamic spraying was used as the polymer deposition process and thus a few experiments were carried out to compare this process with casting. Prior to deposition the NiTi has been surface modified. The peel strength of the deposit was studied before and after degradation of the coating. It is shown that the surface modification enhances the peel strength by 300%. It is also indicated how the adhesion strength of the POSS-PCU coating changes post-exposure to physiological solutions comprised of hydrolytic, oxidative, peroxidative and biological media. This part of the study shows that the modified NiTi presents far greater resistance to decay in peel strength compared to the non-modified NiTi.

Advantages and disadvantages of biodegradable platforms in drug eluting stents

Coronary angioplasty with drug-eluting stent (DES) implantation is currently the most common stent procedure worldwide. Since the introduction of DES, coronary restenosis as well as the incidence of target vessel and target lesion revascularization have been significantly reduced. However, the incidence of very late stent thrombosis beyond the first year after stent deployment has more commonly been linked to DES than to bare-metal stent (BMS) implantation. Several factors have been associated with very late stent thrombosis after DES implantation, such as delayed healing, inflammation, stent mal-apposition and endothelial dysfunction. Some of these adverse events were associated with the presence of durable polymers, which were essential to allow the elution of the immunosuppressive drug in the first DES designs. The introduction of erodable polymers in DES technology has provided the potential to complete the degradation of the polymer simultaneously or immediately after the release of the immunosuppressive drug, after which a BMS remains in place. Several DES designs with biodegradable (BIO) polymers have been introduced in preclinical and clinical studies, including randomized trials. In this review, we analyze the clinical results from 6 observational and randomized studies with BIO polymers and discuss advantages and disadvantages of this new technology.

Time course of reendothelialization of stents in a normal coronary swine model: characterization and quantification

Late thrombosis of coronary drug-eluting stents is an infrequent but serious complication of percutaneous transluminal coronary angioplasty. The best predictor of this event is the lack of endothelialization of stent struts. The objective of this study is to characterize and quantify the time course of endothelialization of different stents implanted in nonatherosclerotic swine coronary arteries. Thirty-three Carbofilm-coated stents were implanted percutaneously in 11 anesthetized domestic, crossbred pigs (weight 25 ± 3 kg, 2 months old). Each animal received 1 stainless steel stent (SS), 1 cobalt-chromium stent (CCS), and 1 tacrolimus-eluting stent (TES) in each coronary artery. Follow-up periods were 1 day (n = 9 stents), 3 days (n = 9 stents), and 7 days (n = 15 stents). Longitudinal sections of the stented vessels were examined using scanning electron microscopy. At 1 day, there was scarce, patchy endothelialization with areas of fibrin; the endothelialization rate was similar for all the stents (SS, 29% ± 23%; CCS, 29% ± 24%; TES, 31% ± 25%; P = .9). At 3 days, there were more endothelial cells but with immature features and giant cells over fibrin; the endothelialization was greater in SS and CCS than in TES (SS, 79% ± 14%; CCS, 81% ± 17%; TES, 46% ± 9%; P = .007). At 7 days, arteries showed better endothelialization with few giant cells; the endothelialization was greater in SS and CCS than in TES (SS, 95% ± 4%; CCS, 98% ± 4%; TES, 79% ± 9%; P = .01). In conclusion, the described model is useful for the analysis of endothelialization of coronary stents and facilitates measurement of its rate of formation and characterization of the involved cell types.

Coronary responses and differential mechanisms of late stent thrombosis attributed to first-generation sirolimus- and paclitaxel-eluting stents

OBJECTIVES

The purpose of this study was to assess the mechanism(s) of late stent thrombosis (LST) and vascular healing responses in first-generation polymeric drug-eluting stents (DES).

BACKGROUND

Recent clinical trials have reported variations in late lumen loss between first-generation sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). Little is known, however, about the vascular responses, time course of healing, and underlying mechanism(s) of complications of LST between platforms in human coronary implants.

METHODS

The overall analysis included 174 cases (230 DES lesions) from the CVPath Institute's stent registry. Histomorphometry was performed on coronary stents from 127 patients (171 lesions) who died ≥ 30 days after receiving stent implants in which fibrin deposition, endothelial strut coverage, inflammatory response, and mechanism(s) of in-stent thrombosis were assessed.

RESULTS

Both platforms demonstrated increased neointimal thickness over time where values were greater in PES (mean 0.13 mm; range 0.03 to 0.20 mm) than SES (mean 0.10 mm; range 0.04 to 0.15 mm; p = 0.04). The percentage of uncovered struts was similar between SES and PES including stents with LST (SES = 21% vs. PES = 27%; p = 0.47). The underlying mechanism(s) of LST, however, was strikingly different between platforms; localized strut hypersensitivity was exclusive to SES, whereas malapposition secondary to excessive fibrin deposition was the underlying cause in PES. Moreover, although both PES and SES showed nearly complete strut coverage after 12 months for on-label use, the majority of stents placed for off-label indications remained unhealed after 12 months in both types of DES.

CONCLUSIONS

Differential mechanisms of LST involving either hypersensitivity or excessive fibrin were identified between first-generation DES in which overall stent healing was further delayed in DES placed for off-label indications.

Outcomes of stenting with overlapping drug-eluting stents versus overlapping drug-eluting and bare-metal stents for the treatment of diffuse coronary lesions

INTRODUCTION

we investigated the outcomes of stenting with overlapping drug-eluting stents (DES) versus overlapping stenting with a combination of drug-eluting and bare metal stents (BMS) in very long coronary lesions (≥ 25 mm).

METHODS AND RESULTS

fifty-two patients treated with either overlapping DES-DES (n = 22) or DES-BMS (n = 30) were selected from a registry of 588 patients with very long coronary lesions. Patients with acute myocardial infarction (MI) within the preceding 48 hours were excluded. The DES-DES combination was more frequently used for longer lesions compared with the DES-BMS group (47.95 ± 9.25 vs 39.98 ± 9.15 mm, p = 0.003). Left anterior descending artery lesions were also more frequently treated with the DES-DES combination (95.5 vs 66.7%, p = 0.02). In four patients in the DES-BMS group, overlapping stents were used for the coverage of dissections. Peri-procedural non-Q-wave MI occurred in one patient in the DES-BMS group. On follow up, only one case of non-fatal MI occurred in a patient with overlapping DES-DES.

CONCLUSION

overlapping a BMS in the proximal part of a long DES instead of exclusive deployment of two or more overlapped DES seems to be a safe and feasible therapeutic strategy in our practice.

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

BACKGROUND

Although atherosclerotic models, especially in the rabbit, have existed for a long time, a comparative study of various drug-eluting stent (DES) implantations in atherosclerotic arteries have not been systematically studied.

METHODS AND RESULTS

New Zealand White rabbits (n=44) with induced atheroma received bilateral iliac artery stents: bare metal stent (BMS) (Driver) or a stent eluting zotarolimus (ZES) (Endeavor), sirolimus (SES) (Cypher), or everolimus (EES) (Xience V). After 28 days, tissues were harvested for histomorphometric analyses, en face analysis of endothelial coverage, and expression of endothelial nitric oxide synthase (eNOS). Area measurements of external elastic lamina and stent area were similar. Neointimal area was significantly less in all DES versus BMS, which was least in SES and EES; similar trends were noted for cell proliferation. Uncovered struts were greater for SES and EES and least in BMS, whereas ZES were in between and associated with the least fibrin. Macrophages of the neointima were significantly less for all DES relative to BMS. Plaque calcification underneath stents, however, was significantly greater in SES and ZES than in BMS. Although endothelial coverage in between struts was comparable between BMS and DES, there was significantly greater expression of eNOS in BMS and ZES relative to EES and SES.

CONCLUSIONS

The rabbit atherosclerotic model of stenting showed delayed healing and significantly greater reduction of neointima following implantation of SES and EES; however, delayed healing was less in ZES with greater neointima (but less than BMS), endothelial regrowth, and eNOS expression.

The representative porcine model for human cardiovascular disease

To improve human health, scientific discoveries must be translated into practical applications. Inherent in the development of these technologies is the role of preclinical testing using animal models. Although significant insight into the molecular and cellular basis has come from small animal models, significant differences exist with regard to cardiovascular characteristics between these models and humans. Therefore, large animal models are essential to develop the discoveries from murine models into clinical therapies and interventions. This paper will provide an overview of the more frequently used large animal models, especially porcine models for preclinical studies.

Sirolimus- vs. paclitaxel-eluting stents in patients undergoing off-label percutaneous coronary intervention

Studies of percutaneous coronary intervention (PCI) with drug-eluting stents in high-risk scenarios are often limited by short follow up and use definitions of "off-label" PCI which do not entirely mirror insert packages recommendations. We analyzed the incidence of cardiovascular events in 1050 consecutive patients undergoing off-label PCI with sirolimus- (n=581) or paclitaxel- (n=469) eluting stents. At 3 years, there were no differences between groups in terms of major cardiovascular events (adjusted hazard ratio 0.991; 95% CI, 0.758 to 1.295; p=0.945), despite slightly higher rates of myocardial infarction and late stent thrombosis seen among patients who received paclitaxel-eluting stents.

A novel three-dimensional quantitative coronary angiography system: In-vivo comparison with intravascular ultrasound for assessing arterial segment length

BACKGROUND

Accurate on-line assessments of vessel dimensions are of utmost importance for selecting the appropriate stent size in coronary interventions. Recently a new three-dimensional quantitative coronary angiography (3D QCA) analytical software package was developed to accurately assess the vessel dimensions for the planning and guidance of such coronary interventions. This study aimed to validate the 3D QCA software package for assessing arterial segment length by comparing with intravascular ultrasound (IVUS). In addition, the difference in the two measurements from 3D QCA and IVUS for curved segments was studied.

METHODS

A retrospective study including 20 patients undergoing both coronary angiography and IVUS examinations of the left coronary artery was set up for the validation. The same vessel segments of interest between proximal and distal markers were identified and measured on both angiographic and IVUS images, by the 3D QCA software and by a quantitative IVUS software package, respectively. In addition, the curvature of each of the segments of interest was assessed and the correlation between the accumulated curvature of the segment and the difference in segment lengths measured from the two imaging modalities was analyzed.

RESULTS

37 vessel segments of interest were identified from both angiographic and IVUS images. The 3D QCA segment length was slightly longer than the IVUS segment length (15.42 +/- 6.02 mm vs. 15.12 +/- 5.81 mm, P = 0.040). The linear correlation of the two measurements was: 3D QCA Length = -0.09 + 1.03 x IVUS Length (r(2) = 0.98, P < 0.001). Bland-Altman plot showed that the difference in the two measurements was not correlated with the average of the two measurements (P = 0.141), but with the accumulated curvature of the segment (P = 0.015). After refining the difference by the correlation, the average difference of the two measurements decreased from 0.30 +/- 0.86 mm (P = 0.040) to 0.00 +/- 0.78 mm (P = 0.977).

CONCLUSIONS

The 3D QCA software package can accurately assess the actual arterial segment length. The difference in segment lengths measured from 3D QCA and IVUS was correlated with the accumulated curvature of the segment.

A retrospective analysis of consecutive patients undergoing nonurgent percutaneous coronary intervention comparing bare metal stents with drug-eluting stents using the National Institute for Clinical Excellence criteria

OBJECTIVE

In the National Institute for Clinical Excellence (NICE) guidelines, lesions with a reference vessel diameter of less than 3.0 mm or lesions with a length of greater than 15 mm are considered carrying a high risk of restenosis. In contrast, lesions with a reference vessel diameter of at least 3.0 mm or a lesion length of 15 mm or less are considered at low risk of restenosis. We performed a retrospective analysis of consecutive patients undergoing nonurgent percutaneous coronary intervention (PCI) comparing bare metal stent (BMS) with drug-eluting stent (DES) using the NICE guidelines.

METHODS AND RESULTS

Between 2003 and 2007, a total of 3883 patients underwent a nonurgent PCI for a de-novo coronary lesion; 2050 patients were considered to be at low risk and 1833 patients were considered at high risk of restenosis according to the NICE criteria. In the low-risk group, the 1-year composite of cardiac death, myocardial infarction, and target vessel revascularization was 10.5% in the BMS group and 11.1% in the DES group (P=0.85). Target lesion revascularization (TLR) was 5.3% by PCI and 1.6% by coronary artery bypass grafting (CABG) in the BMS group and 4.0 and 3.0% in the DES group (P=0.59 and P=0.24). In the high-risk group, the composite of cardiac death, myocardial infarction, and target vessel revascularization was 12.1 and 11.0% in the BMS and DES groups (P=0.48). TLR was 6.7% by PCI and 1.3% by CABG in the BMS group and 3.9 and 2.8% in the DES group (P=0.01; P=0.02). Definite stent thrombosis (ST) was 0.8% in the BMS-treated patients and 1.7% in the DES-treated patients (P=0.09).

CONCLUSION

In patients with lesions carrying a low risk of restenosis, no differences were observed between BMS and DES in composite end points, TLR, or ST at 1-year follow-up. In patients with lesions carrying a high risk of restenosis, patients treated with BMS had a significantly higher rate of TLR by PCI, but a significantly lower rate of TLR by CABG compared with patients treated with DES. A nonsignificant lower rate of definite ST was observed in the BMS group compared with the DES group.

The pre-clinical animal model in the translational research of interventional cardiology

Scientific discoveries for improvement of human health must be translated into practical applications. Such discoveries typically begin at "the bench" with basic research, then progress to the clinical level. In particular, in the field of interventional cardiology, percutaneous cardiovascular intervention has rapidly evolved from an experimental procedure to a therapeutic clinical setting. Pre-clinical studies using animal models play a very important role in the evaluation of efficacy and safety of new medical devices before their use in human clinical studies. This review provides an overview of the emerging role, results of pre-clinical studies and development, and evaluation of animal models for percutaneous cardiovascular intervention technologies for patients with symptomatic cardiovascular disease.

Local determinants of thrombus formation following sirolimus-eluting stent implantation assessed by optical coherence tomography

OBJECTIVES

We conducted this study to assess the prevalence and determinants of subclinical thrombus after sirolimus-eluting stent (SES) implantation.

BACKGROUND

Angioscopic analyses have demonstrated the presence of thrombus is more common than the clinical incidence of SES thrombosis.

METHODS

Fifty-three patients (53 lesions) underwent 6-month follow-up optical coherence tomography. A stent eccentricity index ([SEI] minimum/maximum stent diameter) was determined in each cross section. To evaluate unevenness of neointimal thickness, a neointimal unevenness score ([NUS] maximum neointimal thickness in the cross section/average neointimal thickness of the same cross section) was calculated for each cross section. Average SEI and NUS were calculated for each stent. Major adverse cardiac events were defined as a composite of death, myocardial infarction, and target vessel revascularization.

RESULTS

Fourteen cases of thrombus (26%) were detected by optical coherence tomography (thrombus: n = 14 vs. nonthrombus: n = 39). The percentage of thrombus was associated with longer stents (36.4 +/- 20.2 mm vs. 25.1 +/- 9.8 mm; p = 0.008), a larger number of uncovered struts (17 +/- 16 vs. 8 +/- 11; p = 0.03), smaller average SEI (0.89 +/- 0.04 vs. 0.92 +/- 0.03; p = 0.001), and greater average NUS (2.22 +/- 0.24 vs. 2.00 +/- 0.33; p = 0.03). A significant relationship existed between average SEI and average NUS (p < 0.0001, R = 0.68), and between average SEI and the number of uncovered struts (p < 0.0006, R = 0.46). There was no significant difference in major adverse cardiac events during follow-up (median: 485 days, 7.1% vs. 12.8%; p > 0.99).

CONCLUSIONS

Longer stents and greater asymmetric stent expansion may be important determinants of thrombus formation after SES implantation. In this small cohort, the presence of thrombus did not increase the risk of major adverse cardiac events.

Repeated sirolimus-eluting stent implantation to treat sirolimus-eluting stent and bare-metal stent restenosis

BACKGROUND

In-stent restenosis (ISR) remains a persistent, unresolved issue even in the era of percutaneous coronary intervention (PCI) using drug-eluting stents. The present study compares the clinical and angiographic outcomes of using sirolimus-eluting stents (SES) for re-intervention against ISR that was originally treated with sirolimus-eluting or bare-metal (BMS) stents.

METHODS AND RESULTS

This prospective single-center registry investigated 179 ISR lesions in 158 consecutive patients (53 lesions in 49, and 126 in 109 patients originally treated with SES and BMS, respectively), who had undergone re-intervention with SES. The patients were clinically and angiographically followed up at 8 months after re-PCI. The incidence of re-restenosis (29 vs 12%, P<0.01), ischemia-driven target lesion revascularization (TLR; 21 vs 8%, P<0.05) and major adverse cardiac events (MACE; 21 vs 9%, P<0.05) were significantly greater in ISR lesions originally treated with SES than in those originally treated with BMS at 8 months after re-PCI. Moreover, late luminal loss was significantly greater in the group with post-SES restenosis (P<0.05). Even after adjustment, post-SES restenosis was the only independent predictor of re-restenosis and MACE (P<0.05, each).

CONCLUSIONS

Although the re-restenosis rate is acceptable, the incidence rates of late restenosis, ischemia-driven TLR and MACE are higher after repeated SES implantation to treat SES, than BMS restenosis. These results might affect the mid-term clinical outcomes of re-intervention with SES.

Comparison of vascular response to zotarolimus-eluting stent vs paclitaxel-eluting stent implantation: pooled IVUS results from the ZoMaxx I and II trials

BACKGROUND

The ZoMaxx I and II trials were randomized controlled studies of the zotarolimus-eluting, phosphorylcholine-coated, TriMaxx stent for the treatment of de novo coronary lesions. The aim of this study was to compare the vessel response between zotarolimus- (ZES) and paclitaxel-eluting stents (PES) using intravascular ultrasound (IVUS).

METHODS AND RESULTS

Data were obtained from the ZoMaxx I and II trials, in which a standard IVUS parameter was available in 263 cases (baseline and 9-months follow up). Neointima-free frame ratio was calculated as the number of frames without IVUS-detectable neointima divided by the total number of frames within the stent. While an increase in vessel and plaque was observed in PES from baseline to follow up, there was no significant change in ZES. At follow up, % neointimal obstruction was significantly higher (15.4 ± 8.8% vs 11.3 ± 9.7%), and minimum lumen area at follow up was significantly smaller in ZES compared to PES. However, the incidence of IVUS-defined restenosis (maximum cross-sectional narrowing >60%) was similar in the 2 groups (3.2% vs 6.7%). Neointima-free frame ratio was significantly lower in ZES. There were 5 cases of late incomplete stent apposition in PES and none in ZES.

CONCLUSIONS

These IVUS results demonstrate a similar incidence of severe narrowing between these 2 DES. There was a moderate increase in neointimal hyperplasia that was associated with a greater extent of neointimal coverage in ZES compared with PES.

Coronary bare metal stent implantation in homozygous LDL receptor deficient swine induces a neointimal formation pattern similar to humans

INTRODUCTION

To date, most of all new developments in stent technologies are tested in normal animals. Although invaluable in the evaluation of device safety, the juvenile domestic swine (DS) do not follow the biological healing response occurring in humans following coronary stent implantation. By using a novel swine breed afflicted with familial hypercholesterolemia (FHS), we aimed to analyse the vascular response occurring following bare metal stent (BMS) implantation by comparing in vivo endovascular imaging and histological data.

METHODS

A total of 26 swine were included in this study (12 FHS and 14 DS). Sixty eight BMS (FHS=28 versus DS=40) were implanted using a 10% overstretch ratio. Imaging evaluation (IVUS and OCT) was conducted in all animals at 30 (n=14) or 90 (n=12) days following stent implantation. After imaging, the stented coronary segments were harvested for histological evaluation.

RESULTS

At 30 days, the degree of neointimal formation analysed by OCT (%AS=DS 21.9 ± 10% versus FHS 25.4 ± 12%; p=0.18) and histology (DS 24.6 ± 10% versus FHS 23.58 ± 10%; p=0.8) was similar between both animal groups. At 90 days, the degree of neointimal formation in the DS group decreased in all analysed variables (-40% in IVUS neointimal volume, -57% in OCT %AS, and -30% in %AS by histology) compared to the progression of neointimal formation observed in the FHS group (+29% in IVUS neointimal volume, +27% in OCT %AS and +43% in %AS by histology).

CONCLUSION

The pattern of neointimal formation following BMS implantation in the FHS follows a progressive course that does not occur in the DS. Therefore, by providing a progressive neointimal biological response to BMS implantation, the FHS could serve as an ideal efficacy model for the validation of drug eluting stent technologies.

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.

Optical coherence tomography assessment of in vivo vascular response after implantation of overlapping bare-metal and drug-eluting stents

OBJECTIVES

We designed a randomized trial exploiting optical coherence tomography (OCT) to assess coverage and apposition of overlapping bare-metal stents (BMS) and drug-eluting stents (DES) in human coronary arteries.

BACKGROUND

Overlapping DES impair healing in animals. Optical coherence tomography allows accurate in vivo assessment of stent strut coverage and apposition.

METHODS

Seventy-seven patients with long coronary stenoses were randomized to overlapping sirolimus-eluting stents (SES), paclitaxel-eluting stents (PES), zotarolimus-eluting stents (ZES), or BMS. The primary goal of the study was to determine the rate of uncovered/malapposed struts in overlap versus nonoverlap segments, according to stent type, at 6-month follow-up with OCT.

RESULTS

A total of 53,047 struts were analyzed. The rate of uncovered/malapposed struts was 1.5 +/- 3.4% and 0.6 +/- 2.7% in overlap versus nonoverlap BMS (p = NS), respectively, and 4.3 +/- 11% and 3.6 +/- 8% in overlap versus nonoverlap DES (p = NS), respectively. There were no differences in the rates of uncovered/malapposed struts between overlapping BMS and DES, likely due to low frequency of uncovered/malapposed struts in ZES (0.1 +/- 0.4%), which offset the higher rates observed in SES (6.7 +/- 9.6%) and PES (6.7 +/- 16.5%, p < 0.05). Overlap segments showed greater neointimal volume obstruction versus nonoverlap segments in all DES (p < 0.05 for all DES types). Strut-level neointimal thickness at overlap and nonoverlap segments were lowest in SES (0.16 +/- 0.1 mm and 0.12 +/- 0.1 mm, respectively) compared with PES (0.27 +/- 0.1 mm and 0.20 +/- 0.1 mm, respectively), ZES (0.40 +/- 0.16 mm and 0.33 +/- 0.13 mm, respectively), and BMS (0.55 +/- 0.31 mm and 0.53 +/- 0.25 mm, respectively, p < 0.05).

CONCLUSIONS

As assessed by OCT the impact of DES on vascular healing was similar at overlapping and nonoverlapping sites. However, strut malapposition, coverage pattern, and neointimal hyperplasia differ significantly according to DES type. (Optical Coherence Tomography for Drug Eluting Stent Safety [ODESSA]; NCT00693030).

Interventional cardiology: does stent overlap make a difference to clinical outcome?

The impact of overlap of drug-eluting stents on clinical and angiographic outcomes is controversial. Individuals with long coronary lesions requiring implantation of multiple stents are an important patient subgroup for whom careful evaluation and decision-making with optimal stent deployment is needed to ensure the best possible short-term and long-term results.

High incidence of intramural thrombus after overlapping paclitaxel-eluting stent implantation: angioscopic and histopathologic analysis in porcine coronary arteries

BACKGROUND

Systematic analysis of in vivo angioscopy and postmortem histopathology for paclitaxel-eluting stents (PES) has not been previously reported. We assessed 1-month angioscopic and histopathologic sequelae of overlapping PES in pig coronary arteries.

METHODS AND RESULTS

Overlapping PES and bare-metal stents (BMS; n=9, one pair per pig) were implanted, and animals were euthanized at 1 month. Late lumen loss was reduced in PES compared with BMS (0.46+/-0.63 mm versus 1.30+/-0.50 mm; P=0.01). Angioscopically, PES stent struts were clearly visible and accompanied by substantial red material indicating mural thrombi. In contrast, stent struts and mural thrombi were barely visible in BMS (P<0.001 versus PES). Macroscopically, mural thrombi were abundant but distributed irregularly throughout the PES, with greater concentration in overlapping segments. Only occasional mural thrombi were noted for BMS. Microscopically, neointima of BMS was fibrocellular and mature, whereas only a thin layer of immature neointima was seen in PES. Neointimal thickness was less in PES than BMS (0.11+/-0.07 mm versus 0.33+/-0.12 mm; P=0.018). Additionally, extensive para-strut and intramural thrombi, red blood cell debris, and minute luminal thrombi were observed in PES. Despite normal angioscopic appearance of both proximal and distal nonstented reference segments, endothelium-dependent relaxation to substance P was notably diminished (PES, 0+/-7% versus BMS, 10+/-6%; P=0.007), whereas nitroglycerin response was preserved (PES, 9+/-5% versus BMS, 12+/-7%; P=0.34).

CONCLUSIONS

In the porcine coronary model, overlapping PES is associated with marked intramural thrombi, which was accurately detected on angioscopy at 1 month. Moreover, despite normal luminal angioscopic appearance, adjacent nonstented reference segments demonstrated impaired endothelium-dependent vasoreactivity.