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

Neointimal coverage on drug-eluting stent struts crossing side-branch vessels using optical coherence tomography

The status of neointimal coverage on the drug-eluting stent (DES) struts, which are placed across the side-branch vessels, remains unclear. The degree of neointimal coverage of stent struts crossing the side-branch vessel was evaluated according to the different types of DESs. Follow-up optical coherence tomography images at 9.3 months after the index procedure were identified in 51 patients who had undergone DES (sirolimus-eluting stents [SESs] in 22 patients, paclitaxel-eluting stents [PESs] in 15, and zotarolimus-eluting stents [ZESs] in 14) implantation with crossover of the side-branch vessels (size >2.0 mm). The enrolled patients were classified as a covered group if every unapposed strut showed neointimal coverage or an uncovered group if any struts lacked neointimal coverage. The neointimal hyperplasia thickness was also measured. The number of patients in the covered group was 15 (29%), with 36 patients in the uncovered group. Significant differences were found in the proportion of the covered group among the 3 DES types (6 [27%] of 22 with SESs, 1 [7%] of 15 with PESs, and 8 [57%] of 14 with ZESs; p = 0.011). The percentage of neointimal coverage in the overall stent struts was also significantly different among the 3 DES types (65% of 356 struts, 20% of 165 struts, and 83% of 143 struts for the SESs, PESs, and ZESs, respectively; p<0.001). The neointimal hyperplasia thickness in the PES group was significantly smaller than those of the ZES and SES groups (0.02 +/- 0.02 mm vs 0.08 +/- 0.06 mm and 0.04 +/- 0.03 mm, respectively; p = 0.002). In conclusion, different patterns of neointimal coverage of the stent struts crossing the side branch vessels were observed according to the type of DES.

Effects of combined therapy with ezetimibe plus simvastatin after drug-eluting stent implantation in a porcine coronary restenosis model

The aim of this study was to examine the anti-proliferative and anti-inflammatory effects of ezetimibe/simvastatin (E/S) after drug-eluting stent (DES) implantation in a porcine coronary restenosis model. Pigs were randomized into two groups in which the coronary arteries (23 pigs) had DES. Stents were deployed with oversizing (stent/artery ratio 1.3:1) in porcine coronary arteries. Fifteen pigs were taken 10/20 mg of E/S and eight pigs were not taken E/S. Histopathologic analysis was assessed at 28 days after stenting. In neointima, most inflammatory cells were lymphohistiocytes. Lymphohistiocyte count was not different between two groups (337+/-227 vs. 443+/-366 cells, P=0.292), but neointima area was significantly smaller (1.00+/-0.49 mm(2) vs. 1.69+/-0.98 mm(2), P=0.021) and percent area stenosis was significantly lower (23.3+/-10% vs. 39+/-19%, P=0.007) in E/S group compared with control group. There were no significant differences in fibrin score (1.99+/-0.79 vs. 1.81+/-0.88, P=0.49), endothelial score (1.75+/-0.66 vs. 1.80+/-0.59, P=0.79), and the percent of endothelium covered lumen (43+/-21% vs. 45+/-21%, P=0.84) between E/S group and control group. Combined therapy with ezetimibe and simvastatin inhibits neointimal hyperplasia, but does not inhibit inflammatory infiltration and arterial healing after DES implantation in a porcine coronary restenosis model.

Emerging drugs for coronary restenosis: the role of systemic oral agents the in stent era

Introduction of drug eluting stents (DES) during percutaneous coronary interventions significantly reduces the rate of angiographic restenosis, target lesion and vessel revascularization. In spite of these benefits, other clinical hard end points such as death or myocardial infarction were not reduced and, furthermore, new concerns associated with the presence of late and very late stent thrombosis have been raised. The requirement of long-term dual antiplatelet therapy is another limitation associated with DES. Conversely, in this decade, other options to DES have been simultaneously discussed in observational and randomized studies. Several registries and randomized trials using the systemic approach with anti-inflammatory, immunosuppressive or antiplatelet therapies have been identified and discussed in this manuscript. In spite of all randomized studies with oral therapies in the bare metal stent (BMS) era demonstrating positive reductions in coronary restenosis, this practice has not been introduced clinically. Furthermore, a recent randomized trial comparing oral sirolimus plus BMS versus DES demonstrated that the first approach was cost saving and of comparable efficacy to DES. Conclusive evidence of high incidence of late and very late stent thrombosis with DES, together with clinical limitations for its widespread use, has opened up a large opportunity to search for alternative therapies in coronary restenosis prevention.

The effects of vinblastine on smooth muscle cells in vitro: evaluation of a therapeutic window for the treatment of restenosis

The development of drug-eluting stents (DES) to combat the problem of in-stent restenosis has revolutionized interventional cardiology. However, concerns have emerged about the risk of late angiographic stent thromboses associated with DES. The evaluation and width of the therapeutic window of a particular DES system is of huge importance to its safety and efficacy. In this study, the effects of vinblastine, an antimitotic drug, on smooth muscle cells in vitro is analyzed. The change in levels of proliferation, activity, migration, and viability in human coronary artery smooth muscle cells was measured at a range of concentrations and over a number of time points. These findings were then compared with those of a previous study on the effects of vinblastine on endothelial cells, and an optimum working concentration range was evaluated. This study suggests that the concentration of vinblastine most appropriate in restenosis treatment would be between 0.1 and 1 nM. At this concentration, vinblastine exerts a distinct effect on smooth muscle cell proliferation without detrimental effects on endothelial cell viability. It was also found that vinblastine affects certain cellular activities such as migration in a threshold-independent manner, suggesting that very low doses could be active against the processes of restenosis.

Analysis of the long-term effects of drug-eluting stents on coronary arterial wall morphology as assessed by virtual histology intravascular ultrasound

BACKGROUND

Animal models show impairment of arterial healing after drug-eluting stents (DES) compared with bare-metal stents (BMS). Virtual histology intravascular ultrasound (VH-IVUS) offers an opportunity to assess lesion morphology in vivo.

METHODS

We used VH-IVUS in 80 patients to assess long-term (median = 10 months) native artery vascular responses after 76 implantations of DES compared with 32 BMS. The presence of "necrotic core abutting the lumen" was evaluated at baseline and follow-up.

RESULTS

At baseline, necrotic core abutting the lumen through the stent struts was observed in 76% of DES and 75% of BMS. Although the percentage of necrotic core within the plaque behind the stents did not change during follow-up in DES (23% [18%, 28%] to 22% [17%, 27%], P = .57) or BMS (22% [19%, 27%] to 20% [12%, 26%], P = .29), necrotic core abutting the lumen through the stent struts decreased more in BMS (75% to 19%, P < .001) than DES (76% to 61%, P = .036) because of the lack of an overlying, protective neointima in DES-treated lesions. Furthermore, within the adjacent reference segments, the incidence of necrotic core abutting the lumen decreased in BMS-treated lesions (proximal 23% to 0%, P = .023; distal 21% to 0%, P = .023), but not in DES (proximal 22% to 17%, P = .48; distal 23% to 21%, P = .82).

CONCLUSIONS

Serial VH-IVUS analysis of DES-treated lesions showed a greater frequency of unstable lesion morphometry at follow-up compared with BMS. The apparent mechanism was a suppression of the protective neointimal hyperplasia layer coupled with a lack of vulnerable plaque resolution at reference segments in DES compared with BMS.

Intracoronary optical coherence tomography: a comprehensive review clinical and research applications

Cardiovascular optical coherence tomography (OCT) is a catheter-based invasive imaging system. Using light rather than ultrasound, OCT produces high-resolution in vivo images of coronary arteries and deployed stents. This comprehensive review will assist practicing interventional cardiologists in understanding the technical aspects of OCT based upon the physics of light and will also highlight the emerging research and clinical applications of OCT. Semi-automated imaging analyses of OCT systems permit accurate measurements of luminal architecture and provide insights regarding stent apposition, overlap, neointimal thickening, and, in the case of bioabsorbable stents, information regarding the time course of stent dissolution. The advantages and limitations of this new imaging modality will be discussed with emphasis on key physical and technical aspects of intracoronary image acquisition, current applications, definitions, pitfalls, and future directions.

Stent choice in primary percutaneous coronary intervention: drug-eluting stents or bare metal stents?

The controversial choice between bare metal stents and drug-eluting stents (DES) in primary percutaneous coronary intervention (PCI) seems to be driven by a growing body of evidence. Although evidence supporting the use of DES in the setting of ST-segment elevation myocardial infarction (STEMI) has been demonstrated, including a lower target vessel revascularization (TVR) rate without increased mortality, at present the proportion of DES implants in STEMI patients is low. This may be due to higher costs of DES, cultural issues, lack of concerns about restenosis in STEMI, lack of information on patient bleeding risk and the need for surgery within a limited time. In addition, initial enthusiasm about the efficacy of DES in reducing restenosis is now decreasing as a result of the safety concerns regarding in-stent thrombosis. Moreover, DES requires long-term dual antiplatelet therapy (DAT), which may pose problems in patients prone to bleeding or in candidates for elective surgery. Nevertheless, benefits associated with use of DES include significantly lower TVR rates without remarkable adverse effects in terms of death and myocardial infarction. Data about the efficacy of DES are still limited to 1-year follow-up in most trials. Uncoated stents permit early arterial wall healing, requiring a shorter duration of DAT and are potentially associated with a reduced risk of thrombus formation at long-term follow-up. Importantly, however, this potential late threat has not been confirmed in recent data from the limited number of studies with longer than 2-years follow-up. Anatomical features and individual risk profiles can sometimes help in the choice of the most suitable type of stent. In conclusion, stent choice in primary PCI cannot be standardized for all patients and appears to be influenced by various factors that need to be considered to provide better revascularization in terms of both efficacy and safety.

Preclinical Models of Restenosis and Their Application in the Evaluation of Drug-Eluting Stent Systems

Coronary arterial disease (CAD) is the leading cause of death in the United States, the European Union, and Canada. Percutaneous coronary intervention (PCI) has revolutionized the treatment of CAD, and it is the advent of drug-eluting stent (DES) systems that has effectively allayed much of the challenge of restenosis that has plagued the success of PCI through its 30-year history. However, DES systems have not been a panacea: There yet remain the challenges associated with interventions involving bare metallic stents as well as newly arisen concerns related to the application of DES systems. To effectively address these novel and ongoing issues, animal models are relied on both to project the safety and efficacy of endovascular devices and to provide insight into the pathophysiology underlying the vascular response to injury and mechanisms of restenosis. In this review, preclinical models of restenosis are presented, and their application and limitation in the evaluation of device-based interventional technologies for the treatment of CAD are discussed.

Coronary angioscopic evaluation for serial changes of luminal appearance after pharmacological and catheter interventions

Although preventive pharmacological therapies effectually reduce the risk of cardiovascular events, acute coronary syndrome (ACS) remains a leading cause of morbidity and mortality in our country, Japan. Disruption of atherosclerotic vulnerable plaques and flow-limiting thrombus formation in non-stent segments of native coronary arteries are considered a main mechanism of ACS. In addition, stent thrombosis originating from implanted metallic coronary stents, so-called vulnerable stents, occasionally appears as ACS in the clinical settings. Coronary angioscopy is a unique imaging modality permitting direct visualization of luminal structures, such as atherosclerotic plaque, thrombus, stent struts, and proliferating neointima. On the basis of accumulated angioscopic findings, intense yellow plaques and stents without neointimal coverage are considered vulnerable plaques and vulnerable stents, respectively. In contrast, morphological disappearance of vulnerable plaques or vulnerable stents by pharmacological and trans-catheter therapies imply stabilization of the plaques or stents. Hence, angioscopic assessment for vulnerability (or stability) of atherosclerotic plaques and implanted stents might be useful for risk classification in the future events of ACS. To evaluate serial changes of coronary lumen after pharmacological and catheter interventions using angioscopy might also provide important information on potential benefits and surrogate endpoints of the therapies and on patients' management.

Luminal flow amplifies stent-based drug deposition in arterial bifurcations

BACKGROUND

Treatment of arterial bifurcation lesions using drug-eluting stents (DES) is now common clinical practice and yet the mechanisms governing drug distribution in these complex morphologies are incompletely understood. It is still not evident how to efficiently determine the efficacy of local drug delivery and quantify zones of excessive drug that are harbingers of vascular toxicity and thrombosis, and areas of depletion that are associated with tissue overgrowth and luminal re-narrowing.

METHODS AND RESULTS

We constructed two-phase computational models of stent-deployed arterial bifurcations simulating blood flow and drug transport to investigate the factors modulating drug distribution when the main-branch (MB) was treated using a DES. Simulations predicted extensive flow-mediated drug delivery in bifurcated vascular beds where the drug distribution patterns are heterogeneous and sensitive to relative stent position and luminal flow. A single DES in the MB coupled with large retrograde luminal flow on the lateral wall of the side-branch (SB) can provide drug deposition on the SB lumen-wall interface, except when the MB stent is downstream of the SB flow divider. In an even more dramatic fashion, the presence of the SB affects drug distribution in the stented MB. Here fluid mechanic effects play an even greater role than in the SB especially when the DES is across and downstream to the flow divider and in a manner dependent upon the Reynolds number.

CONCLUSIONS

The flow effects on drug deposition and subsequent uptake from endovascular DES are amplified in bifurcation lesions. When only one branch is stented, a complex interplay occurs - drug deposition in the stented MB is altered by the flow divider imposed by the SB and in the SB by the presence of a DES in the MB. The use of DES in arterial bifurcations requires a complex calculus that balances vascular and stent geometry as well as luminal flow.

Genous endothelial progenitor cell capturing stent vs. the Taxus Liberte stent in patients with de novo coronary lesions with a high-risk of coronary restenosis: a randomized, single-centre, pilot study

Aims

The purpose of this study was to evaluate the Genous^TM endothelial progenitor cell capturing stent vs. the Taxus Liberté paclitaxel-eluting stent in patients with de novo coronary lesions with a high-risk of coronary restenosis.

Methods and results

We randomly assigned 193 patients with lesions carrying a high risk of restenosis to have the Genous stent or the Taxus stent implanted. Lesions were considered high risk of restenosis if one of the following applied: chronic total occlusion, lesion length >23 mm, vessel diameter <2.8 mm, or any lesion in a diabetic patient. At 1-year, the rate of the primary end point, target vessel failure (TVF), was 17.3% in the Genous stent group when compared with 10.5% in the Taxus stent group [risk difference (RD) 6.8%, 95% CI −3.1 to 16.7%], a difference predominantly due to a higher incidence of repeat revascularization in patients treated with the Genous stent. In contrast, no stent thrombosis was observed in the Genous stent group compared to 4 stent thromboses in the Taxus stent group (RD −4.2%; 95% CI −10.3 to 0.3%). Repeat angiography between 6 and 12 months in a subgroup of patients showed a significantly higher late loss in the Genous stent compared with the Taxus stent (1.14 ± 0.64 and 0.55 ± 0.61 mm).

Conclusion

In patients with lesions carrying a high risk of restenosis, the Genous stent resulted in a non-significant higher rate of TVF compared with the Taxus stent mainly due to more repeat revascularizations in the Genous stent group. There were four stent thromboses with Taxus stent, none with the Genous stent.

Clinical outcomes after sirolimus-eluting, paclitaxel-eluting, and bare metal stents (from the first phase of the prospective multicenter German DES.DE Registry)

The prospective multicenter German Drug-Eluting Stent (DES.DE) registry is an observational study to analyze and evaluate the therapeutic principle of the differential drug-eluting stents (sirolimus- and paclitaxel-eluting stents) and bare metal stents under real world conditions in the context of the German healthcare system. The baseline clinical and angiographic characteristics and follow-up events for 1 year were recorded for all enrolled patients. In addition, a health economics assessment was performed at 3, 6, 9, and 12 months after initial stent placement. The composite of death, myocardial infarction, and stroke, defined as major adverse cardiac and cerebrovascular events, and target vessel revascularization were used as the primary objectives. From October 2005 to October 2006, 6,384 patients were enrolled (sirolimus-eluting stents, n = 2,137; paclitaxel-eluting stents, n = 2,740; bare metal stents, n = 485) at 98 Deutsches Drug-Eluting Stent Register sites. With similar baseline clinical and descriptive morphology of coronary artery disease between both drug-eluting stent groups, no differences were present at 1 year of follow-up in the rates of overall mortality (3.8% vs 4.1%), target vessel revascularization (10.4% vs 10.4%), overall stent thrombosis (3.6% vs 3.8%), and major adverse cardiac and cerebrovascular events (8.1% vs 8.0%). Compared with the bare metal stent group, patients treated with drug-eluting stents had significantly lower rates of myocardial infarction (3.2% vs 6.0%; p <0.01), stroke (1.2% vs 2.7%; p <0.05), and target vessel revascularization (10.4% vs 14.9%; p <0.01) without any difference in the stent thrombosis rate (3.7% vs 4.3%; p = 0.57) or mortality rate (4.0% vs 5.2%; p = 0.21). In conclusion, the data generated from the German Drug-Eluting Stent registry revealed no differences between patients receiving a paclitaxel-eluting stent and sirolimus-eluting stent in a "real-world" setting with regard to the clinical outcomes at 1 year.

Next generation drug-eluting stents: focus on bioabsorbable platforms and polymers

The success of drug-eluting stents in preventing restenosis has shifted the focus of new stent development toward enhancing long term safety and efficacy of these devices, while simultaneously eliminating the need for indefinite dual antiplatelet therapy. A technical advance fulfilling these aims would hold tremendous potential to reduce morbidity, mortality and economic costs associated with the percutaneous treatment of coronary artery disease. An attractive approach is the use of bioabsorbable stent designs. These may include stents with different bioabsorbable drugs, bioabsorbable polymers or even bioabsorbable metallic backbones. A device that could achieve excellent acute and long-term results, but disappear completely within months (thereby avoiding the need for prolonged dual antiplatelet therapy), would be a tremendous advance. Too good to be true? We explore here the scientific rationale and prospects for success with this exciting concept.

Design and rationale of the TRI-stent adjudication study (TRIAS) program

BACKGROUND

In the treatment of coronary artery disease, a "pro-healing" approach for prevention of in-stent restenosis and late stent thrombosis is intuitively favored over the use of cytotoxic or cytostatic drugs released from a drug-eluting stent (DES). Promoting accelerated endothelial coverage of the stent surface, the endothelial progenitor cell (EPC) capturing stent has shown its safety and efficacy in the HEALING observational studies; however, randomized trials evaluating the device are lacking.

METHODS

The multicenter, randomized, controlled, 2-armed TRIAS program aims to include a total of 2560 patients. In the TRIAS Low Risk trial, a total of 1300 patients with lesions carrying a low risk of restenosis are randomized between the EPC capturing stent and a bare metal stent, assuming superiority in the incidence of target lesion failure (TLF) at 1 year. In the TRIAS High Risk trial, 1260 patients with lesions carrying a high risk of restenosis are randomized, assuming the noninferiority in TLF at 1 year of the EPC capturing stent as compared to DES. TLF is defined as the composite of cardiac death, myocardial infarction, and clinically driven target lesion revascularization. In addition, the duration of clinical follow-up is extended to 5 years to capture late events. Angiographic follow-up at 13 months is performed as part of the TRIAS Program ancillary study.

IMPLICATION

The results of the TRIAS Program will provide information on a relevant patient population with coronary artery lesions, comprising the full spectrum of low risk and high risk of restenosis treated with a novel stent technology in a randomized, controlled manner (TRIAS Low Risk trial: ISRCTN 47701105 and TRIAS High Risk trial: ISRCTN 74297220).

Differential healing after sirolimus, paclitaxel, and bare metal stent placement in combination with peroxisome proliferator-activator receptor gamma agonists: requirement for mTOR/Akt2 in PPARgamma activation

RATIONALE

Sirolimus-eluting coronary stents (SESs) and paclitaxel-eluting coronary stents (PESs) are used to reduce restenosis but have different sites of action. The molecular targets of sirolimus overlap with those of the peroxisome proliferator-activated receptor (PPAR)gamma agonist rosiglitazone (RSG) but the consequence of this interaction on endothelialization is unknown.

OBJECTIVE

Using the New Zealand white rabbit iliac model of stenting, we examined the effects of RSG on SESs, PESs, and bare metal stents endothelialization.

METHODS AND RESULTS

Animals receiving SESs, PESs, or bare metal stents and either RSG (3 mg/kg per day) or placebo were euthanized at 28 days, and arteries were evaluated by scanning electron microscopy. Fourteen-day organ culture and Western blotting of iliac arteries and tissue culture experiments were conducted. Endothelialization was significantly reduced by RSG in SESs but not in PESs or bare metal stents. Organ culture revealed reduced vascular endothelial growth factor in SESs receiving RSG compared to RSG animals receiving bare metal stent or PESs. Quantitative polymerase chain reaction in human aortic endothelial cells (HAECs) revealed that sirolimus (but not paclitaxel) inhibited RSG-induced vascular endothelial growth factor transcription. Western blotting demonstrated that inhibition of molecular signaling in SES+RSG-treated arteries was similar to findings in HAECs treated with RSG and small interfering RNA to PPARgamma, suggesting that sirolimus inhibits PPARgamma. Transfection of HAECs with mTOR (mammalian target of rapamycin) short hairpin RNA and with Akt2 small interfering RNA significantly inhibited RSG-mediated transcriptional upregulation of heme oxygenase-1, a PPARgamma target gene. Chromatin immunoprecipitation assay demonstrated sirolimus interferes with binding of PPARgamma to its response elements in heme oxygenase-1 promoter.

CONCLUSIONS

mTOR/Akt2 is required for optimal PPARgamma activation. Patients who receive SESs during concomitant RSG treatment may be at risk for delayed stent healing.

Comparison of long versus short ("spot") drug-eluting stenting for long coronary stenoses

We compared spot drug-eluting stenting (DES) to full stent coverage for treatment of long coronary stenoses. Consecutive, consenting patients with a long (>20 mm) coronary lesion of nonuniform severity and indication for percutaneous coronary intervention were randomized to full stent coverage of the atherosclerotic lesion with multiple, overlapping stenting (full DES group, n = 90) or spot stenting of hemodynamically significant parts of the lesion only (defined as diameter stenosis >50%; spot DES group, n = 89). At 1-year follow-up, 14 patients with full DES (15.6%) and 5 patients (5.6%) with spot DES had a major adverse cardiac event (MACE; p = 0.031). At 3 years, MACEs occurred in 18 patients with full DES (20%) and 7 patients (7.8%) with spot DES (p = 0.019). Cox proportional hazard model showed that the risk for MACEs was almost 60% lower in patients with spot DES compared to those with full DES (hazard ratio 0.41, 95% confidence interval 0.17 to 0.98, p = 0.044). This association remained even after controlling for age, gender, lesion length, and type of stent used (hazard ratio 0.42, 95% confidence interval 0.17 to 1.00, p = 0.05). In conclusion, total lesion coverage with DES is not necessary in the presence of diffuse disease of nonuniform severity. Selective stenting of only the significantly stenosed parts of the lesion is an appropriate therapeutic alternative in this setting, offering a favorable clinical outcome.

Durability of antirestenotic efficacy in drug-eluting stents with and without permanent polymer

OBJECTIVES

We sought to assess changes in antirestenotic efficacy of drug-eluting stents (DES) by restudying subjects at 2 time points after coronary stenting (6 to 8 months and 2 years) and to compare differences in time courses of late luminal loss (LLL) between 3 different DES platforms in use at our institution.

BACKGROUND

DES therapy is associated with low levels of LLL at 6 to 8 months. The temporal course of neointimal formation after this time point remains unclear.

METHODS

This prospective, observational, systematic angiographic follow-up study was conducted at 2 centers in Munich, Germany. Patients underwent stenting with permanent-polymer rapamycin-eluting stents (RES), polymer-free RES, or permanent-polymer paclitaxel-eluting stents (PES). The primary end point was delayed LLL (the difference in in-stent LLL between 6 to 8 months and 2 years).

RESULTS

Of 2,588 patients undergoing stenting, 2,030 patients (78.4%) had 6- to 8-month angiographic follow-up and were enrolled in the study. Target lesion revascularization was performed in 259 patients; these patients were not considered for further angiographic analysis. Of 1,771 remaining patients, 1,331 had available 2-year reangiographic data (75.2%). Overall mean (SD) delayed LLL was 0.12 +/- 0.49 mm (0.17 +/- 0.50 mm, 0.01 +/- 0.42 mm, and 0.13 +/- 0.50 mm in permanent-polymer RES, polymer-free RES, and permanent-polymer PES groups, respectively [p < 0.001]). In multivariate analysis, only stent type (in favor of polymer-free RES) predicted delayed LLL.

CONCLUSIONS

Ongoing erosion of luminal caliber beyond 6 to 8 months after the index procedure is observed following DES implantation. Absence of permanent polymer from the DES platform seems to militate against this effect.

Comparison of inflammatory response after implantation of sirolimus- and paclitaxel-eluting stents in porcine coronary arteries

BACKGROUND

Although both sirolimus (CYPHER) and paclitaxel (TAXUS) drug-eluting stents have demonstrated efficacy and safety in clinical trials, human autopsy data have raised concerns about long-term healing and the potential for local inflammatory reactions.

METHODS AND RESULTS

Overlapping stents (CYPHER drug-eluting stents, Bx SONIC bare metal stents, TAXUS drug-eluting stents, and Liberté bare metal stents) were implanted in noninjured coronary arteries of 58 domestic swine. Histopathological evaluation of proximal, overlapped, and distal stented segments was determined with emphasis on inflammation at 30, 90, and 180 days. Circumferential granulomatous inflammation in all stented segments was defined as inflammation consisting of macrophages, multinucleated giant cells, lymphocytes, and granulocytes, including many eosinophils, adjacent to almost all struts. Circumferential granulomatous inflammation was more prevalent in CYPHER (9 of 23, 39%) compared with TAXUS (1 of 21, 5%; P=0.01) and control bare metal stents (0 of 44) in the combined 90- and 180-day cohorts. Only CYPHER specimens showed marked adventitial inflammation (P=0.0025) and fibrosis (P=0.0055) accompanied by extensive remodeling. Fibrin deposition within neointima and medial smooth muscle cell death were greater (both P<0.001) in TAXUS than CYPHER at 30 days, with more fibrin in TAXUS than CYPHER through 90 days (P<0.05).

CONCLUSIONS

Although these data cannot be directly extrapolated to humans, the high prevalence in this porcine model of diffuse granulomatous inflammation seen with CYPHER stents, persisting at 180 days and associated with extensive remodeling of the artery, and persistent para-strut fibrin deposition with TAXUS stents emphasize the need for further investigation of biocompatibility with these and other novel combination drug/polymer drug-eluting stents.

The "crush" technique for coronary artery bifurcation stenting: insights from micro-computed tomographic imaging of bench deployments

OBJECTIVES

This study provides insights into "crush" coronary bifurcation stenting through imaging of bench deployments.

BACKGROUND

Although the strategy of provisional side-branch stenting is widely accepted for suitable bifurcation lesions, there is no consensus on the best option for elective stenting with 2 stents. The crush technique has the potential to scaffold and apply the drug to the side-branch ostium where restenosis is most common.

METHODS

Sequential steps of crush stent deployment and post-dilation were undertaken in silicone phantoms and recorded on cine angiography and microcomputed tomography. We assessed the effect of deployment strategies, post-dilation strategies, and cell size on side-branch ostial area.

RESULTS

Side-branch ostial coverage by metal struts was 53% (95% confidence interval [CI]: 46 to 59) after 1-step kissing post-dilation and was reduced by 2-step kissing post-dilation to 33% (95% CI: 28 to 37; p < 0.0001). Although the residual stenosis after the classical crush strategy was 47% (95% CI: 39 to 53), it was 36% (95% CI: 31 to 40; p = 0.002) after mini-crush deployment. Stents with larger cell size (>3.5 mm diameter) had a residual stenosis of 37% (95% CI: 32 to 42) after crush deployment that was less than the residual stenosis for stents with smaller cell size (52%; 95% CI: 44 to 60; p < 0.0001).

CONCLUSIONS

Side-branch ostial stenosis after crush stenting was minimized by mini-crush deployment, 2-step kissing post-dilation, and the use of stents with larger cell size. It is unknown if optimizing stent deployment at bifurcation lesions will reduce clinical stent thrombosis and restenosis.

Comparative healing response after sirolimus- and paclitaxel-eluting stent implantation in a pig model of restenosis

OBJECTIVE

We compared local vessel healing and inflammatory responses associated with nonoverlapping sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES).

BACKGROUND

Sirolimus and paclitaxel may have different effects on vascular healing. In the present study, we analyzed the local histologic effects of drug-eluting stents (DES).

METHODS

We placed 43 stents (22 PES and 21 SES) in 16 Yucatan minipigs. Stents were randomly assigned and placed in the left anterior descending, circumflex, or right coronary arteries (one stent per artery), covering a region previously injured by balloon angioplasty.

RESULTS

Histopathologic analysis showed that the distribution of injury scores was similar between the two stent groups, reflecting the homogeneity of coronary injury secondary to balloon overstretch. Electron microscopy showed complete endothelialization in most cases. Incomplete endothelialization was present in 12.5% of PES and almost 20% of SES at 30 days. In the PES group, moderate to severe inflammation was found in eight arteries, whereas only one vessel had moderate inflammation in the SES group. Severe inflammation was observed significantly more often in the PES than in the sirolimus group (P = 0.006). With the PES group, stent struts overlying side branches had a significantly higher frequency of poor endothelialization scores than did stent struts that did not overlay side branches (P = 0.006).

CONCLUSIONS

In this preclinical study in a pig model of in-stent restenosis, implantation of nonoverlapping DES was associated with local inflammatory reactions and decreased endothelial repair. Impaired endothelialization was visualized in the struts overlying side branches.

Time dependent vascular and myocardial responses of a second generation, small vessel, paclitaxel-eluting stent platform

OBJECTIVES

The purpose of this study was to evaluate the time-dependent vascular and myocardial responses to a second-generation, small vessel (< or =2.5 mm) paclitaxel-eluting stent (PES) platform.

BACKGROUND

Small caliber coronary vessels present complex challenges for percutaneous coronary intervention (PCI) and are associated with lower technical success and inferior long-term efficacy. A next-generation, highly deliverable PES may improve clinical outcomes in small vessels.

METHODS

Sixty single stents were implanted in noninjured coronary arteries in 30 domestic swine (one TAXUS Liberté small vessel PES (svPES) and one Liberté small vessel bare metal stent (svBMS) in each animal). Ten animals each were allocated to 30-, 90-, and 180-day follow-up groups; final quantitative angiography and necropsy were performed. Samples of myocardium, liver, and kidney were processed and evaluated for pathology. Radiography and either histopathology or scanning electron microscopy were performed on all the explanted stented vessels.

RESULTS

There were no stent-related deaths or downstream myocardial pathology. Both the svPES stent and its svBMS control demonstrated complete strut tissue coverage and complete endothelialization at all timepoints, and there was no evidence of macro- or microscopic thrombus or stent fracture. Medial smooth muscle cell content was markedly reduced in all the svPES groups compared with that in the svBMS controls.

CONCLUSIONS

The small diameter paclitaxel-eluting TAXUS Liberté stent has a safe and predictable biologic vascular response in the noninjured swine model. This device warrants further investigation targeting the currently poorly met clinical need for small vessel PCI.

Six-month comparison of coronary endothelial dysfunction associated with sirolimus-eluting stent versus Paclitaxel-eluting stent

OBJECTIVES

This study was designed to investigate whether endothelial dysfunction is related to drug-eluting stent (DES) implantation at 6 months after stenting.

BACKGROUND

Current available DES could delay vessel healing and subsequently impair endothelial function.

METHODS

Endothelial function was estimated at 6-month follow-up in 75 patients (31 men, mean age 62.1 years) with a DES (39 sirolimus-eluting stents [SES], 36 paclitaxel-eluting stents [PES]), and 10 patients with a bare-metal stent (BMS) to the left anterior descending artery, by incremental acetylcholine (Ach) infusion (20 microg/min, 50 microg/min, 100 microg/min) and nitrate (200 microg/min) into the left coronary ostium. Vascular responses were quantitatively measured in arterial segments 5 mm proximal and distal to DES and compared with corresponding segments in the BMS group and midsegments in the left circumflex artery as a reference nonstented artery. All antianginal agents were withheld for at least 72 h before coronary angiography.

RESULTS

Greater vasoconstriction to Ach was observed in both the SES and PES groups than in the BMS group or control segments of left circumflex artery. Vasoconstriction to Ach was more prominent in arterial segments distal to stents in both SES and PES groups compared with those in the BMS group (p < 0.001). The degree of vasoconstriction to Ach was similar between the SES and PES groups. Endothelium-independent vasodilatation to nitrate did not differ significantly between the study groups.

CONCLUSIONS

Abnormal vasoconstriction to Ach was found in the SES and PES groups, especially in arterial segments distal to DES at 6 months after stenting, which suggests that DES has a potential long-term adverse effect on local coronary endothelial dysfunction.

Serial intravascular ultrasound analysis of peri-stent remodeling and proximal and distal edge effects after sirolimus-eluting or paclitaxel-eluting stent implantation in patients with diabetes mellitus

Patients with diabetes have an increased risk of in-stent restenosis after coronary stent implantation. Serial intravascular ultrasound was used to study chronic arterial responses and edge effects after implantation of Cypher (Cordis, Johnson & Johnson, Miami Lakes, Florida) or Taxus (Boston Scientific, Maple Grove, Minnesota) stents in diabetic patients. Seventy-four diabetic patients were randomly assigned to Cypher or Taxus stent implantation. Intravascular ultrasound of 5-mm long segments immediately proximal and distal to the stent was performed after the procedure and at the 8-month follow-up. The increase in peri-stent external elastic membrane (EEM) volume was more pronounced in the Taxus group (292.4 +/- 132.6 to 309.5 +/- 146.8 mm(3)) than in the Cypher group (274.4 +/- 137.2 to 275.4 +/- 140.1 mm(3); p = 0.005). Peri-stent plaque volume increased in the Taxus group (152.5 +/- 73.7 to 166.1 +/- 85.1 mm(3)), but was unchanged in the Cypher group (153.5 +/- 75.5 to 151.5 +/- 75.8 mm(3); p = 0.002). In proximal and distal reference segments, mean lumen area decreased within the entire 5-mm edge segment (proximal and distal) because of plaque progression (distal, 5.5 +/- 3.6 to 5.8 +/- 3.7 mm(2); p = 0.097; proximal, 8.1 +/- 2.7 to 8.7 +/- 2.9 mm(2); p = 0.006) without remodeling (change in EEM) in the Taxus group. Conversely, there were no significant changes in reference-segment EEM or plaque areas in the Cypher group. In conclusion, in diabetic patients, Taxus stent implantation was associated with increased (1) peri-stent EEM volume and peri-stent plaque, and (2) stent edge plaque progression accompanied by lumen reduction without remodeling. These findings were not seen in Cypher stents.