Non–Polymer-Based Paclitaxel-Coated Coronary Stents for the Treatment of Patients With De Novo Coronary Lesions

TAXUS VI final 5-year results: a multicentre, randomised trial comparing polymer-based moderate-release paclitaxel-eluting stent with a bare metal stent for treatment of long, complex coronary artery lesions

AIMS

To assess the long-term safety and efficacy of the paclitaxel-eluting TAXUS moderate-release (MR) investigation-only stent for the treatment of long, complex coronary artery lesions.

METHODS AND RESULTS

TAXUS VI was a prospective, double-blind, multicentre trial wherein 446 patients were randomised between a TAXUS Express MR stent and an uncoated Express Control stent. At 5-years, the overall rate of major adverse cardiac events (MACE) was similar in the two groups at 27.8% in control and 31.3% in TAXUS (P = 0.61), including similar rates for stent thrombosis. The target vessel revascularisation (TVR) rate was 23.7% in control and 22.2% in TAXUS (P = 0.45) with a non-target lesion revascularisation (non-TLR) rate of 5.1% in control and 10.9% in TAXUS (P = 0.0274) and a TLR rate of 21.4% in control and 14.6% in TAXUS (relative reduction, 32%; P = 0.0325). Furthermore, subgroup analysis revealed that the TLR benefit of TAXUS was preserved among study groups including small vessels, long lesions and patients receiving multiple overlapping stents.

CONCLUSIONS

Treatment of complex coronary lesions with the TAXUS MR stent demonstrated similar MACE, similar TVR, and reduced TLR rates compared with control through five years. Based on these positive results, the aetiology of increased non-TLR TVR rate in TAXUS remains unclear.

The evolution of cardiovascular stent materials and surfaces in response to clinical drivers: a review

This review examines cardiovascular stent materials from the perspective of a range of clinical drivers and the materials that have been developed in response to these drivers. The review is generally chronological and outlines how stent materials have evolved from initial basic stainless steel devices all the way through to the novel biodegradable devices currently being explored. Where appropriate, pre-clinical or clinical data that influenced decisions and selections along the way is referenced. Opinions are given as to the merit and direction of various ongoing and future developments.

Experience with paclitaxel-eluting Infinnium coronary stents

To investigate the safety and efficacy of the Infinnium Paclitaxel-eluting stents in the treatment of coronary artery lesions, 196 patients with symptomatic coronary disease who received 202 stents at our center from January 2004 to November 2005 were studied prospectively. The primary study endpoint was the incidence of abnormalities on exercise electrocardiograms or cardiac single-photon emission tomography at 6 months, as a noninvasive index of stent reocclusion. Secondary endpoints were the rates of major adverse cardiac events at 1, 3, 6, 9, and 12 months. Stent deployment was successful in 98% of patients. Cumulative major adverse cardiac event rates at the end of 12 months were: cardiac death 1%, myocardial infarction 5% (Q-wave 2.5%, non-Q-wave 2.5%), and repeat revascularization of the stented lesion 3%. The overall major adverse cardiac event rate was 8.1%. There were 6 (3%) stent thromboses; all occurred late after the procedure. In patients with symptomatic ischemic heart disease, the low-cost Infinnium stent proved both effective and safe, with an acceptably low major adverse cardiac event rate.

Strut fracture: a further concern with drug-eluting stents

A potential cause of drug-eluting stent restenosis is strut fracture. To date, few cases have been reported in the available literature and a best treatment method has not been established. We describe two cases of sirolimus-eluting stent fracture combined with focal restenosis and also review those previously reported.

Effect of a novel drug-eluted balloon coated with genistein before stent implantation in porcine coronary arteries

BACKGROUND

The major drawback of stent implantation in native human coronary vessels is the occurrence of restenosis. Drug-eluting stents significantly reduce restenosis after percutaneous coronary intervention (PCI), but may be associated with persistent local inflammation involved in the restenosis mechanisms. In this setting coating coronary devices with anti-inflammatory agents represents an intriguing alternative to stent-based local drug delivery. The aim of the present study was to test in a porcine model the safety and efficacy of a novel Genistein-eluting balloon preceding coronary stenting.

DESIGN

Female piglets underwent PCI in a randomized fashion with either a Genistein-eluting or a standard balloon angioplasty, followed in all vessels by bare-metal stent implantation. Pigs were sacrificed at different time points to appraise safety (i.e. endothelialization) and efficacy (i.e. anti-inflammatory and anti-proliferative effects): 1, 4, and 6-8 weeks following PCI.

RESULTS

Overall analysis was conducted on 14 piglets. Twenty-five bare-metal stents were implanted preceded by angioplasty with a conventional balloon in 13 vessels and by the Genistein-eluted balloon in 12. No untoward effects were reported in either group. Healing and endothelialization appeared universal within 4 weeks. The Genistein-eluted balloon group disclosed a significant reduction, at four weeks from implantation, of the peri-stent inflammatory cells count (mononucleocytes 39 +/- 32 Vs. 96 +/- 29 per square millimetre, P = 0.019). This effect did not clearly translate into a trend towards a reduced neointimal hyperplasia at 6-8 weeks (0.13 +/- 0.11 Vs. 0.14 +/- 0.09, P = 0.835).

CONCLUSION

This study provides the first in vivo demonstration of the anti-inflammatory effects of a Genistein-eluting balloon in PCI, warranting further research including the combination of a Genistein-eluting balloon with standard drug-eluting stent.

Effect of abciximab on clinical and angiographic restenosis in patients with non-ST-segment elevation acute coronary syndromes

The ISAR-REACT 2 trial was designed to assess the effect of abciximab in patients with acute coronary syndromes undergoing percutaneous coronary intervention after a 600-mg loading dose of clopidogrel. The aim of the present study was to investigate the impact of abciximab on clinical and angiographic restenosis after coronary stenting in patients with acute coronary syndromes. The angiographic substudy included 1,544 patients from the ISAR-REACT 2 trial randomly assigned to abciximab (771 patients) or placebo (773 patients). All patients were scheduled for routine angiographic follow-up at 6 to 8 months after intervention. The primary end point was incidence of angiographic in-segment binary restenosis. The secondary end point was 1-year incidence of target-lesion revascularization. Binary restenosis was observed in 21.9% of patients in the abciximab group and 24.5% of patients in the placebo group (p=0.29). Percentages of in-stent (29+/-22% vs 33+/-24%; p=0.02) and in-segment (35+/-20% vs 38+/-21%; p=0.04) diameter stenoses were significantly lower in the abciximab group than the placebo group. There was a strong trend toward lower 1-year incidence of target-lesion revascularization in patients treated with abciximab than in patients treated with placebo (13.6% vs 16.8%; p=0.08). In conclusion, in patients with non-ST-segment elevation acute coronary syndromes undergoing early percutaneous coronary intervention with stenting after a 600-mg loading dose of clopidogrel, abciximab therapy may have a slight positive impact on the prevention of restenosis.

Current Status of Off-Pump Coronary Artery Bypass Surgery

The expanding indications for angioplasty coupled with the successful short and mid-term results of randomized controlled trials of drug-eluting stents have already had an unquestionable impact on the practice of coronary revascularization operations. However, coronary artery bypass grafting remains a major mode of therapy for coronary artery disease. It is likely that surgery will continue to be preferred for more complex subsets and that surgeons will have to continue to maintain good results in patients with more complex problems. Concerns regarding morbidity associated with conventional surgical myocardial revascularization on cardiopulmonary bypass have led to a resurgence of interest in off-pump bypass surgery during the last decade, with the expectation that it would be safer if cardiopulmonary bypass could be avoided. This review summarizes the impact of off-pump bypass surgery in reducing the morbidity and mortality associated with conventional coronary artery bypass on cardiopulmonary bypass by evaluating the current best-available evidence from randomized controlled trials and meta-analyses comparing off-pump surgery with conventional bypass grafting.

Are "treatment" bare metal stents superior to "control" bare metal stents? A meta-analytic approach

BACKGROUND

It has been suggested that the benefits of drug-eluting stents compared to bare metal stents (BMS) have been overestimated in part because target lesion/vessel revascularization (TLR/TVR) rates in the BMS control group of these trials were spuriously high.

METHODS

We used meta-analytic techniques to systematically compare clinical event rates among patients treated with BMS in trials where BMS were the experimental (BMS(experimental)) rather than the control (BMS(control)) intervention. MEDLINE searches were performed to identify eligible randomized trials comparing either drug-eluting stents with BMS(control) or BMS(experimental) with balloon angioplasty in patients with nonacute coronary artery disease. Trial characteristics and 6- to 12-month rates for death, myocardial infarction, TLR/TVR, and major adverse cardiac events were extracted and assessed.

RESULTS

Eligible trials yielded 50 BMS cohorts: 19 in the BMS(control) group (4046 patients) and 31 in the BMS(experimental) group (5068 patients). Summary death and infarction rates did not differ between groups. The summary TLR/TVR rates were 16.2% (95% CI 13.5-19.3) versus 13.8% (95% CI 12.0-15.7) in BMS(control) versus BMS(experimental) groups, respectively (P = .15). Among 39 BMS cohorts with < or = 250 patients, TLR/TVR rates were significantly higher in BMS(control) versus BMS(experimental) groups (18.9% [95% CI 16.0-22.2] vs 13.7% [95% CI 11.5-16.3], P = .01). There were no between-group differences among larger BMS cohorts (P = .98).

CONCLUSIONS

Although overall clinical event rates did not differ in the BMS(control) and the BMS(experimental) groups, a higher rate of TVR/TLR was seen in the BMS(control) group among smaller trials.

Drug-eluting stents - what should be improved?

Despite the success of drug-eluting stents (DES) in reducing restenosis and the need for target vessel revascularization, several deficiencies have been unraveled since their first clinical application including the risk of stent thrombosis, undesired effects due to the stent polymer as well as the stent itself, and incomplete inhibition of restenosis (especially in complex lesions). Several novel stent systems are being investigated in order to address these issues. In second-generation DES, the rapamycin analogues zotarolimus and everolimus (and more recently biolimus) have been most extensively studied. Furthermore, special stent-coatings to actively promote endothelial healing (in order to reduce the risk of stent thrombosis) and to further reduce restenosis have been employed. To avoid undesirable effects of currently applied (durable) polymers, biocompatible and bioabsorbable polymers as well as DES delivery systems without the need for a polymer have been developed. Bioabsorbable stents, both polymeric and metallic, were developed to decrease potential late complications after stent implantation. Although most of these innovative novel principles intuitively seem appealing and demonstrate good results in initial clinical evaluations, long-term large-scale studies are necessary in order to reliably assess whether these novel systems are truly superior to first-generation DES with respect to safety and efficacy.

The cell cycle: a critical therapeutic target to prevent vascular proliferative disease

Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle.

Understanding the drug-eluting stent trials

The advent of intravascular stenting dramatically reduced the incidence of restenosis among patients undergoing percutaneous transluminal coronary angioplasty. However, a substantial percentage of patients, particularly those with risk factors such as diabetes mellitus or complicated lesions, remain at risk for restenosis. Drug-eluting stents overcome this problem by releasing bioactive agents from a polymeric coating directly into the vessel wall, inhibiting the cellular mechanisms of restenosis while avoiding systemic toxicity. Recent data indicate that local targeting of the proliferative process with drug-eluting stents dramatically reduces the risk for restenosis, even among high-risk patients. A range of bioactive coatings are currently available or in late clinical trials. Both sirolimus- and paclitaxel-eluting stents have demonstrated efficacy in a broad range of patient types; early data from clinical trials of second-generation stent coatings, such as everolimus and ABT-578 (zotarolimus), suggest that these agents are also effective in preventing restenosis. This article reviews the pathophysiology of in-stent restenosis and surveys recent key clinical trials of drug-eluting stents.

A comparison of mortality, myocardial infarction, and repeated revascularization for sirolimus-eluting and paclitaxel-eluting coronary stents

BACKGROUND

Drug-eluting stents are now used in most percutaneous coronary interventions. There are only 2 approved devices: sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). Only a few population-based studies have compared their patient outcomes.

METHODS

All New York State patients undergoing SES or PES in nonfederal hospitals in the state between April 1 and December 31, 2004, except those with a previous revascularization, left main coronary artery disease, or a recent myocardial infarction (MI) or shock (4867 patients with PES and 6914 with SES) were followed up through the end of 2005. We compared SES and PES with respect to inhospital and 18-month mortality, 18-month mortality/MI, and subsequent target vessel and target lesion revascularization (TVR and TLR) after adjusting for differences in patient risk factors.

RESULTS

By 18 months after receiving a PES, 4.0% of the patients died compared with 4.1% for SES patients, 5.9% of PES patients experienced mortality/MI compared with 6.3% of SES patients, 6.8% of the PES patients had a subsequent TVR within 18 months compared with 7.8% for SES patients, and 4.5% of the PES patients had a subsequent TLR within 18 months compared with 5.3% for SES patients. The respective adjusted hazards ratios (PES/SES) for these adverse outcomes were 1.02 (95% CI 0.82-1.26, P = .86), 0.94 (95% CI 0.78-1.13, P = .52), 0.89 (95% CI 0.75-1.06, P = .20), and 0.86 (95% CI 0.70-1.05, P = .14).

CONCLUSIONS

Patients receiving PES and SES do not have significantly different 18-month mortality, mortality/MI, subsequent TVR, or subsequent TLR rates.

Meta-analysis comparing clinical effectiveness of drug-eluting stents, bare metal stents and coronary artery bypass surgery

Objective  To compare clinical outcomes among patients receiving drug-eluting stents, bare metal stents, or coronary artery bypass grafting surgery (CABG) to treat coronary artery disease. Data sources  Randomised controlled trials were systematically selected from electronic database for head-to-head comparisons. The results from these head-to-head comparisons were used for an adjusted indirect comparison. Methods  Published randomised controlled trials were reviewed for outcome data in patients treated for coronary artery disease with drug-eluting stents, bare metal stents, or CABG. Head-to-head comparisons were conducted for drug-eluting stents versus bare metal stents and for CABG versus bare metal stents. Adjusted indirect comparison was used to compare drug-eluting stents and CABG. Mid-term clinical outcomes (range: 6-12 months) were investigated and included rates of mortality, myocardial infarction, thrombosis, target lesion revascularisation, target vessel revascularisation, restenosis and major adverse cardiac events. Results  Systematic literature search identified 23 randomised controlled trials (15 for drug-eluting stents vs. bare metal stents, 8 for CABG vs. bare metal stents). Head-to-head comparisons for both single and multiple vessel disease demonstrated that compared with bare metal stents, drug-eluting stents had better outcomes for target lesion revascularisation, target vessel revascularisation, restenosis and major adverse cardiac events. Except target lesion revascularisation, data were similarly favourable for CABG when compared with bare metal stents. Adjusted indirect comparison between drug-eluting stents and CABG in single vessel disease failed to detect significant differences in any of the measured outcomes. Multiple vessel disease data analysis demonstrated that target vessel revascularisation (odds ratio 3.41 [95% CI 2.29-5.08]) and major adverse cardiac events (1.89 [1.28-2.79]) were superior to drug-eluting stents in patients undergoing CABG. Conclusions  Drug-eluting stents and CABG were superior to bare metal stents in terms of target lesion revascularisation (drug-eluting stents only), target vessel revascularisation, restenosis and major adverse cardiac events. There was no difference in clinical outcomes when comparing CABG and drug-eluting stents in patients with single vessel disease, and CABG may be superior to drug-eluting stents for target vessel revascularisation and major adverse cardiac events in patients with multiple vessel disease. However, results may vary between subpopulations with different clinical or socioeconomic differences.

Meta-analysis of angiographic versus intravascular ultrasound parameters of drug-eluting stent efficacy (from TAXUS IV, V, and VI)

Both quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS) are currently used to assess in-stent restenosis. This study aimed to use standardized imaging and clinical follow-up to compare QCA parameters with several IVUS parameters to evaluate their strengths and weaknesses for detecting in-stent restenosis in a drug-eluting stent population. A subset of patients from the TAXUS IV, V, and VI studies was evaluated. The subset, which included 216 TAXUS-treated patients and 191 bare-metal stent-treated patients, had complete IVUS and QCA performed at baseline and follow-up. As expected, all QCA and IVUS parameters were consistent with less intimal hyperplasia in TAXUS patients than controls. The overall incidence of QCA binary restenosis was 14.0%, which was 9.3% in TAXUS-treated patients and 19% in bare-metal stent-treated patients (p = 0.0008). Regression analysis showed that QCA late lumen loss and percentage of diameter stenosis correlated only moderately with the various IVUS measures of neointimal hyperplasia for the combined group of patients (TAXUS + bare-metal stent), as well as for the TAXUS-treated and bare-metal stent-treated patients separately. However, in general, correlations within the control (bare-metal stent) group tended to be stronger than within the TAXUS group. The strongest correlation was between QCA percentage of diameter stenosis and IVUS percentage of intimal hyperplasia in the overall group and the control group. The strongest IVUS predictor of QCA binary restenosis at 9 months was maximum percentage of intimal hyperplasia, with an overall C = 0.91 and p <0.001. In conclusion, the QCA and IVUS parameters used to evaluate drug-eluting stent efficacy showed a moderate correlation with IVUS percentage of intimal hyperplasia, reliably predicting QCA binary in-stent restenosis.

Stent fracture associated with drug-eluting stents: clinical characteristics and implications

OBJECTIVE

To evaluate the clinical characteristics and implications of stent fracture in drug-eluting stents.

BACKGROUND

Approximately 2.5 million drug-eluting stents are implanted every year worldwide. In 10 randomized controlled trials involving 2,602 patients, no incidence of stent fracture was recognized or reported.

METHODS

From April 2003 to December 2005, 2,728 patients underwent drug-eluting stenting. The angiograms of all 530 patients who underwent repeat angiography were analyzed to identify the presence of stent fracture. We then documented the incidence of adverse events associated with drug-eluting stent fracture and systematically analyzed the clinical, procedural, and structural factors, which might predispose to stent fracture.

RESULTS

Stent fracture was identified in 10 patients. None of these fractures were detectable at the time of stent placement. The median time interval from stent implantation to detection of fracture at repeat angiography was 226 days (range, 7-620 days). Adverse clinical outcomes associated with stent fracture occurred in 7 patients (6 patients had binary restenosis and 1 patient had stent thrombosis), all necessitating repeat intervention. Analysis of potential predisposing clinical, procedural, and structural factors revealed that 4 patients had excessive tortuosity in the proximal segment, and overlapping stents were used in 5 cases. All fractures occurred in sirolimus-eluting stents.

CONCLUSIONS

Stent fracture may represent a new potential mechanism of restenosis and stent thrombosis in drug-eluting stents. Predisposing clinical and procedural factors may be vessel tortuosity and use of overlapping stents. The most important predisposing factor, however, may be stent structure, since all fractures occurred in sirolimus-eluting stents.

Drug delivery via nano-, micro and macroporous coronary stent surfaces

Drug-eluting stents (DESs) have revolutionized the treatment of occlusive coronary artery disease via marked reduction of in-stent restenosis. One critical feature for successful DESs is the sustained release of drugs, which is achieved using a polymer coating in the present generation of DESs. However, recent studies have raised a concern that polymers may trigger allergic reactions and/or prolonged inflammation in some patients. These untoward reactions may eventually lead to undesirable clinical events, including stent thrombosis and sudden cardiac death. A new drug delivery technology, using a porous stent surface, may offer desirable drug elution properties without the use of polymers, and may translate into an improved safety profile for the next-generation DESs.

Does the use of paclitaxel or rapamycin-eluting stent decrease further need for coronary-artery bypass grafting when compared with bare-metal stent?

CONTEXT AND OBJECTIVE

The safety and efficacy of drug-eluting stents reduce the need for surgical revascularization. The objective of the present study was to investigate whether paclitaxel or rapamycin-eluting stent are effective in avoiding the need for coronary-artery bypass grafting.

METHODS

This was a systematic review of the literature using the methodology of the Cochrane Collaboration. The type of study considered was controlled randomized trials; the type of intervention was drug-eluting or bare-metal stents; and the main outcome investigated was coronary-artery bypass grafting.

RESULTS

The ten studies included in this systematic review did not show any statistically significant difference between the drug-eluting stents and the bare-metal stents with regard to the outcome of coronary-artery bypass grafting (confidence interval: 0.31 to 1.42).

CONCLUSION

The surgical revascularization rate was not reduced by the use of drug-eluting stents.

Intravascular drug release kinetics dictate arterial drug deposition, retention, and distribution

Millions of patients worldwide have received drug-eluting stents to reduce their risk for in-stent restenosis. The efficacy and toxicity of these local therapeutics depend upon arterial drug deposition, distribution, and retention. To examine how administered dose and drug release kinetics control arterial drug uptake, a model was created using principles of computational fluid dynamics and transient drug diffusion-convection. The modeling predictions for drug elution were validated using empiric data from stented porcine coronary arteries. Inefficient, minimal arterial drug deposition was predicted when a bolus of drug was released and depleted within seconds. Month-long stent-based drug release efficiently delivered nearly continuous drug levels, but the slow rate of drug presentation limited arterial drug uptake. Uptake was only maximized when the rates of drug release and absorption matched, which occurred for hour-long drug release. Of the two possible means for increasing the amount of drug on the stent, modulation of drug concentration potently impacts the magnitude of arterial drug deposition, while changes in coating drug mass affect duration of release. We demonstrate the importance of drug release kinetics and administered drug dose in governing arterial drug uptake and suggest novel drug delivery strategies for controlling spatio-temporal arterial drug distribution.

Abciximab offers greater benefits to insulin-dependent diabetic patients undergoing coronary stent implantation

INTRODUCTION AND OBJECTIVES

Abciximab use does not exceed 25% in most of the studies on diabetic patients undergoing stent implantation. The aim of this study was to evaluate whether abciximab could be more beneficial in different subgroups such as insulin-dependent (ID) patients and whether its use could provide additional benefits to those afforded by drug-eluting stents in these patients.

PATIENTS AND METHODS

A total of 373 consecutive diabetics [223 non-insulin-dependent (NID) and 150 ID patients] who had undergone stent implantation were examined with a follow-up of 25.6+/-16.2 months. Abciximab was used in 21.7%.

RESULTS

The abciximab-treated group had a lower rate of revascularization (26.8% vs. 15.8%. P=.02). The results by subgroups were as follows: NID nonabciximab, 23.5%; NID abciximab, 19% (P=NS); ID nonabciximab, 32.7%; ID abciximab, 12.2% (P=.05). In multivariate analysis, the restenosis predictors were insulin dependency (OR, 2.7), abciximab use (OR, 0.18), stent diameter (OR, 0.18).

CONCLUSIONS

Abciximab use in diabetics with stent implantation has a favorable effect by reducing the need for new revascularization. This benefit is more evident in ID patients; the negative prognosis effect of being insulin-dependent is eliminated, and the percentage of events in this population over a long follow-up period is equal to those in NID patients.

Drug-eluting stent: a review and update

The development of stent has been a major advance in the treatment of obstructive coronary artery disease since the introduction of balloon angioplasty. However, neointimal hyperplasia occurring within the stent leading to in-stent restenosis is a main obstacle in the long-term success of percutaneous coronary intervention (PCI). The recent introduction of drug-eluting stents (DES) contributes a major breakthrough to interventional cardiology. Many large randomized clinical trials using DES have shown a remarkable reduction in angiographic restenosis and target vessel revascularization when compared with bare metal stents. The results of these trials also appear to be supported by evidence from everyday practice and noncontrolled clinical trials. However, the expanded applications of DES, especially in treating complex lesions such as left main trunk, bifurcation, saphenous vein graft lesions, or in-stent restenosis, are still under evaluation with ongoing studies. With the availability of different types of DES in the market, the issue of cost should not be a deterrent and DES will eventually be an economically viable option for all patients. The adoption of DES in all percutaneous coronary intervention may become a reality in the near future. In this review article, we summarize the recent development and progress of DES as well as compare and update the results of clinical trials.

Drug-Eluting Stents

The introduction of percutaneous transluminal coronary angioplasty has revolutionized the field of cardiology by providing patients with coronary artery disease immediate and effective therapy. Overshadowing the early success of angioplasty was the high rate of angiographic restenosis and recurrent symptoms at 6 months. The use of stents reduced the incidence of restenosis; however, the rise in the number of patients undergoing percutaneous interventions produced a new problem of restenosis occurring within the stent: in-stent restenosis (ISR). Mechanical approaches, including directional and rotational atherectomy and systemic pharmacotherapy, have failed to demonstrate a reduction in ISR in randomized clinical trials. Intravascular brachytherapy is currently the only approved therapy for ISR, although this treatment has numerous unresolved questions and is not effective in a large percent of patients. Drug-eluting stents have reduced the incidence of restenosis by providing localized therapy to the targeted lesion without systemic toxicity. The purpose of this review is to synthesize data from major clinical trials involving the 2 most successful agents used in the prevention of restenosis: sirolimus and paclitaxel. The cellular and molecular mechanisms of both ISR and restenosis postangioplasty derived from animal models will be introduced. Second, an overview of 3 alternate interventions that attempt to reduce the rates of restenosis is presented. Finally, the major randomized, controlled trials involving sirolimus and paclitaxel are described, and their clinical implications and use as a possible solution in the prevention of restenosis is discussed.

Two-Year Follow-Up of the Quantitative Angiographic and Volumetric Intravascular Ultrasound Analysis After Nonpolymeric Paclitaxel-Eluting Stent Implantation

OBJECTIVES

This study used serial angiographic and intravascular ultrasound (IVUS) analysis to evaluate the long-term efficacy of a nonpolymeric, paclitaxel-eluting stent coating on intimal hyperplasia (IH) 2 years after implantation.

BACKGROUND

Long-term efficacy of patients treated with nonpolymeric paclitaxel-eluting stents beyond 1 year has not been well determined.

METHODS

Patients were randomized to placebo or 1 of 2 doses of paclitaxel (low dose, 1.28 microg/mm2; high dose, 3.10 microg/mm2). Complete after-procedure, 6-month, and 2-year angiographic and IVUS data were available in 53 patients (17, 17, and 19 patients, respectively).

RESULTS

Baseline characteristics were similar among the 3 groups. Although 6-month minimal luminal diameter (MLD) was significantly smaller in placebo compared with paclitaxel-eluting stent patients (1.9 +/- 0.6 mm in placebo, 2.5 +/- 0.6 mm in low-dose, and 2.6 +/- 0.5 mm in high-dose patients, p = 0.004), the MLDs at 2 years were similar (2.3 +/- 0.6 mm, 2.3 +/- 0.7 mm, and 2.0 +/- 0.8 mm, respectively, p = 0.4). Despite a stepwise reduction in IH accumulation at 6 months (23 +/- 18 mm3 in placebo, 14 +/- 11 mm3 in low-dose, and 10 +/- 12 mm3 in high-dose, p = 0.017), the increase of IH volume from 6 months to 2 years was significantly greater in the high-dose patients (13 +/- 14 mm3 in high-dose vs. 4 +/- 7 mm3 in low-dose patients, p = 0.074; and vs. 1 +/- 13 mm3 in placebo, p = 0.019). Late target lesion revascularization (beyond 1 year) was performed in 2 high-dose patients.

CONCLUSIONS

Despite the suppression of IH after non-polymeric paclitaxel-eluting stents compared with bare-metal stents at 6 months, a "late catch-up" IH growth was found in the high-dose patients at 2-year follow-up.

The exclusion of patients with chronic kidney disease from clinical trials in coronary artery disease

Chronic kidney disease (CKD) is associated with a high risk of death from coronary artery disease and may modify the response to standard cardiovascular therapies. Treatment of subjects with CKD should ideally be based on evidence from randomized, clinical trials, but how often subjects with CKD have been excluded from these trials is uncertain. We undertook this study in order to quantify how often subjects with moderate to advanced CKD were excluded from large cardiovascular trials. MEDLINE and the reference list of selected articles were searched in order to identify large, randomized, controlled trials of five different coronary artery disease therapies published between 1998 and 2005. Exclusion criteria and reported clinical characteristics of subjects were abstracted. Rates of exclusion and reporting of baseline characteristics of study participants were compared for CKD, diabetes, history of smoking, and hypertension. Eighty-six trials randomizing 411 653 patients were identified. More than 80% of trials excluded subjects with end-stage renal disease and 75.0% excluded patients with CKD. Subjects with diabetes, hypertension, or a history of smoking were excluded less than 4% of the time. Baseline renal function of study participant was reported in only 7% of trials. Patients with CKD are frequently excluded from coronary artery disease trials and renal function of randomized subjects is rarely reported. These findings reinforce the notion that available data on the treatment of coronary artery disease in subjects with CKD have significant limitations and should be generalized to the treatment of subjects with CKD cautiously.

A New and Rapid Scoring System to Assess the Scientific Evidence from Clinical Trials

Guidelines are based on a scientific analysis from existing data of randomized controlled trials (RCTs), registry trials, simple registries, case reports, and the personal experience of the task force members. Furthermore, meta-analyses and subgroup analyses are used to derive the strengths of recommendations. Fortunately, the major cardiac societies, i.e., the American College of Cardiology (ACC), the American Heart Association (AHA), and the European Society of Cardiology (ESC), are essentially using the same definitions for the levels of recommendations. In the expanding field of cardiology, however, the overwhelming and increasing number of clinical studies reveals the limitations of the traditional ranking of these studies: Applying the standard definitions of the ACC/AHA/ESC criteria for the levels of recommendation, almost every PCI procedure would easily reach the level of evidence A, even with two small, underpowered studies and a surrogate endpoint. Although meta-analyses are important tools for creating an overview of major diagnostic or treatment modalities, they are bound to severe limitations. The compilation of several underpowered, small trials can generate a statistically artificial "significant" result. This is especially important because only two meta-analyses containing almost identical studies could easily yield an evidence level A. RCTs are usually designed and conducted according to a power calculation, for which a primary clinical or surrogate endpoint can be chosen. Surrogate endpoints, however, do not necessarily correlate with the clinical outcome. The history of medicine is full of errors introduced by underpowered studies with surrogate endpoints. Many investigators and companies attempt to tease out treatment effects in specific subpopulations of patients. These subgroup analyses are usually underpowered. Another major limitation of the ACC/AHA/ESC scoring system is that neither the power of a study nor the choice of a primary clinical endpoint is included in their definitions. Yet another limitation of the ACC/AHA/ESC grading system is that two "simple" registries may already lead to a level of evidence B. A new scoring system is presented addressing most of these limitations: a primary clinical endpoint receives three points, whereas all of the following receive one point: double-blind design, evaluation interval of primary endpoint > or = 6 months, multicenter (at least three centers), independent data and safety monitoring, power of > or = 80% for primary endpoint achieved, and follow-up > or = 80% for a surrogate primary endpoint or follow-up of > or = 95% for a clinical primary endpoint. Thus, the maximum achievable points is 10. This scoring system can also be applied for high-quality registry controlled trials using a predefined control group and power calculation. For simple registry studies and subgroup analyses, a modified scoring system has been developed (maximum achievable points is 5). The advantage of the suggested new scoring system is its transparency, reproducibility, and ease of use by quickly answering the key quality questions for clinical trials. The new scoring system suggested here should help make decisions regarding which treatment to use and stimulate discussions.

Angioscopic evaluation of neointima coverage: sirolimus drug-eluting stent versus bare metal stent

BACKGROUND

The process of neointima formation after bare metal stent (BMS) implantation has been previously elucidated by angioscopic observations; however, that after drug-eluting stent (DES) implantation has not been clarified. Therefore, we compared the angioscopic appearance of neointima over DESs with that over BMSs 6 months after implantation.

METHODS AND RESULTS

Patients who received an implantation of a BMS (n = 13) or a sirolimus DES (n = 24) were included in this study. Angiographic and angioscopic examinations were performed at 6 months. The color of the stented lesion (white or yellow), coverage of stent by neointima (not covered, covered by a thin layer, or buried under neointima), and thrombus at the stented lesion (presence or absence) were angioscopically evaluated. Of the 24 lesions in which a DES was implanted, 11 (46%) had a part where the stent strut had no coverage, 21 (88%) had a part where it was covered by a thin layer, and 11 (46%) had a part where it was buried under neointima. Of the 13 lesions in which a BMS was implanted, 1 (8%) lesion had a part where the stent strut had no coverage, 4 (31%) lesions had a part where it was covered by a thin layer, and 13 (100%) lesions had a part where it was buried under neointima. The prevalence of a stent buried under neointima (46% vs 100%, P = .001) was lower and that of thrombus (42% vs 8%, P = .03) was higher in DES-implanted lesions as compared with BMS-implanted lesions. The prevalence of thrombus (64% vs 17%, P = .005) was higher in the yellow area than in the white area when a DES was implanted.

CONCLUSION

Sirolimus DESs, as compared with BMSs, were poorly covered by neointima and were accompanied by thrombus especially when there was a yellow plaque under the stents. Thus, the thrombogenic potential in DES-implanted lesions may be sustained by the inhibition of neointima formation over thrombogenic plaques.

Efficacy and Safety of Drug-Eluting Stents: Current Best Available Evidence

The development of drug-eluting coronary stents has proved to be a quantum advance in interventional cardiology, rivaling the impact of stenting itself. Drug-eluting coronary stents deliver effective local concentrations of antiproliferative drugs (thus avoiding systemic toxicities), without substantially modifying the technique of percutaneous coronary intervention. Studies involving several different stent platforms and antiproliferative drug coatings have recently demonstrated dramatic reductions in restenosis rates, compared to conventional bare metal stents. Although the clinical benefits of drug-eluting stents are increasingly evident, important concerns about their long-term safety and costs have been raised. Furthermore, drug-eluting stents are being claimed to replace coronary artery bypass surgery in the near future. This review article evaluates the current best available evidence on the efficacy and safety of drug-eluting stents with a focus on the impact of this "revolutionary" new technology on the practice of coronary artery bypass surgery.

Progressive stent technologies: new approaches for the treatment of cardiovascular diseases

The CYPHER (Cordis, Johnson & Johnson) sirolimus-eluting stent and the TAXU (Boston Scientific) paclitaxel-eluting stent have been extensively evaluated and have been proven to be significant novel tools for the treatment of coronary artery disease. Several sirolimus derivatives have already emerged, receiving CE Mark approval. However, in the future, it is likely that drugs presently under investigation will address additional mechanisms associated with neointimal formation, either as single agents or in combination with antiproliferative compounds. Concurrently, alterations on stent platform design (helicoidal, open-closed cell), coatings (biodegradable, bioabsorbable, nanoporous) and polymers are being explored.

Polymer-based paclitaxel-eluting stents are superior to nonpolymer-based paclitaxel-eluting stents in the treatment of de novo coronary lesions

Although polymer coating of coronary stents enables sufficient loading and release of incorporated drugs, it has also been associated with potentially negative effects. This study compared the clinical, angiographic, and intravascular ultrasound (IVUS) outcomes of patients treated with polymer- versus nonpolymer-based paclitaxel-eluting stents (PESs). Sixty-five consecutive patients (70 de novo lesions) treated with polymer-based PESs (TAXUS, 1 microg/mm2 of paclitaxel; Boston Scientific Corp.) and 65 consecutive patients (65 de novo lesions) treated with nonpolymer-based PESs (V-Flex Plus, 2.7 microg/mm2 of paclitaxel; Cook, Inc.) were enrolled in the study. Six-month angiographic follow-up was performed on 54 lesions of the polymer-based PES group and 51 lesions of the nonpolymer-based PES group. IVUS at angiographic follow-up was performed in 61 of the first 70 included lesions. At 6-month IVUS follow-up, mean intimal hyperplasia cross-sectional area was 2.36 +/- 1.60 mm2 in the nonpolymer-based PES group versus 0.62 +/- 0.41 mm2 in the polymer-based PES group (p = 0.003). Implantation of polymer-based PESs resulted in significantly lower in-stent late lumen loss (0.22 +/- 0.27 vs 0.74 +/- 0.61 mm, respectively, p <0.001). In-stent binary restenosis rate was 5% versus 20%, respectively (p <0.001). Target lesion revascularization rate was 9% after implantation of polymer-based PES versus 18% (p = 0.128) after implantation of nonpolymer-based PES, and the major adverse cardiac event rate was 9% versus 23%, respectively (p = 0.032). In conclusion, polymer-based PESs result in superior angiographic and IVUS follow-up findings compared with nonpolymer-based PESs.

Coronary artery restenosis: vascular biology and emerging therapeutic strategies

Percutaneous coronary intervention with drug-eluting stents is currently the preferred approach to the treatment of obstructive coronary stenoses. Large, randomized trials have demonstrated a significant reduction in the incidence of restenosis after drug-eluting stent placement compared with balloon angioplasty or bare metal stents across a wide range of lesions. Furthermore, these stents have appeared to be effective in maintaining the luminal patency at follow up for up to 2-4 years. Concerns regarding the potential adverse effects of drug-eluting stents, such as aneurysm formation in arteries secondary to drug toxicity or hypersensitivity, as well as the overdependence on antiplatelet therapy for a protracted period to prevent subacute thrombosis, have been raised. However, evidence from large studies has not demonstrated any significant increase in the incidence of such adverse events. Future approaches to treating coronary stenoses involve technical modifications, such as direct stenting, accelerating endothelialization with gene delivery of nitric oxide donors, smooth muscle cell growth inhibitors after stent placement, biodegradable stents and concurrent use of local molecule delivery and oral chemotherapy. Ongoing large-scale postmarketing surveillance studies are expected to provide credible answers to the concerns regarding the safety of these stents.

Implantation of paclitaxel-eluting stents in saphenous vein grafts: clinical and angiographic follow-up results from a multicentre study

OBJECTIVE

To define the clinical and angiographic follow-up results after implantation of paclitaxel-eluting stents (PESs) in stenotic saphenous vein grafts (SVGs).

DESIGN

Prospective multicentre study. Comparison with a control group.

METHODS

60 consecutive patients with 65 lesions located in 65 SVGs (mean (SD) age of vein grafts 11.3 (5.7) years) treated with PES (V-Flex Plus, 2.7 microg/mm(2) paclitaxel, Cook) and 60 patients with 60 SVG lesions treated with bare metal stent (BMS) were included. Lesions had to be <20 mm in length and in grafts of 2.75-3.5 mm diameter. The 6 month angiographic follow-up was obtained on 51 lesions (79%) of the PES group and on 51 lesions (85%) of the BMS group.

RESULTS

Baseline clinical and angiographic characteristics were comparable between both groups. At angiographic follow-up, three vein grafts in the PES group and five vein grafts in the BMS group were occluded. In-stent late lumen loss was lower in PES than in BMS (0.61 (0.81) vs 1.06 (0.72) mm, respectively; p = 0.021). In-stent binary restenosis rates were 12% vs 33%, respectively, (p = 0.012). Linear regression analysis showed BMS to be the only factor with an effect on late lumen loss (p = 0.011). Target-vessel failure rates were 18% in the PES group and 41% in the BMS group (p = 0.019), whereas major adverse cardiac event (MACE) rates at 180 days were 15% and 37%, respectively (p = 0.014).

CONCLUSIONS

Implantation of non-polymer-based PES in SVG lesions is associated with a lower late lumen loss and restenosis rate than those of BMS. There remains a substantial target-vessel failure rate and MACE rate even at 6 months owing to graft occlusion or new lesions in the graft.

Neointima Inhibition: Comparison of Effectiveness of Non–Stent-based Local Drug Delivery and a Drug-eluting Stent in Porcine Coronary Arteries

PURPOSE

To compare the inhibition of neointimal proliferation by using non-stent-based local drug delivery and a drug-eluting stent in porcine coronary arteries.

MATERIALS AND METHODS

Experiments were conducted with permission of the animal protection committee of the local government. Paclitaxel was either dissolved in a nonionic contrast medium or coated on balloons. Stents were crimped on the coated balloons. Effectiveness was tested in 22 pigs. Two coronary stents were placed in each pig, and slight overstretch was applied. The animals were treated as follows: group A (control group), uncoated balloons, bare stents, and "plain" contrast medium; group B, same treatment as group A, but with paclitaxel in the contrast medium; group C, paclitaxel-coated balloons, with premounted bare stents and plain contrast medium; and group D, sirolimus-eluting stents, noncoated balloons, and plain contrast medium. Stenosis was assessed 4 weeks later at angiography and histomorphometry. For exploratory purposes, continuous variables of quantitative coronary angiography and histomorphometry were compared by using analysis of variance.

RESULTS

Results at follow-up angiography indicated a mean of 1.00 mm +/- 0.18 (standard deviation) lumen diameter loss in the control group and 0.14 mm +/- 0.18 loss in the group treated with the paclitaxel-coated balloon (group C; P < .001). Findings at histomorphometry confirmed the effectiveness of drug delivery, with the most impressive inhibition of neointimal proliferation from coated balloons-the neointimal area was 2.4 mm2 +/- 0.3 (P < .01 vs all other groups), compared with 5.2 mm2 +/- 0.3 in group A (control group), 4.3 mm2 +/- 0.3 in group B, and 3.8 mm2 +/- 0.3 in group D.

CONCLUSION

In spite of the short intima contact time, paclitaxel coated on the balloon inhibits neointimal formation in the porcine model of coronary stent placement.