Clinical Efficacy of Polymer-Based Paclitaxel-Eluting Stents in the Treatment of Complex, Long Coronary Artery Lesions From a Multicenter, Randomized Trial
Support for the Use of Drug-Eluting Stents in Contemporary Clinical Practice
Background— Intracoronary polymer-based stent delivery of paclitaxel has been shown to be effective in reducing restenosis in simple coronary lesions, but the evidence base for contemporary use in longer, more complex coronary stenoses is lacking.
Methods and Results— TAXUS VI is a prospective, multicenter, double-blind, randomized trial assessing clinical and angiographic outcomes of the TAXUS Moderate Release paclitaxel-eluting stent in the treatment of long, complex coronary artery lesions. Four hundred forty-eight patients at 44 sites were randomized (1:1) between a drug-eluting TAXUS Express2 and an uncoated Express2 control stent. Per protocol, the 9-month follow-up included an angiographic reevaluation in all patients. The primary end point was the rate of target-vessel revascularization 9 months after the study procedure; secondary end points included the rate of target-lesion revascularization and binary restenosis at follow-up. Mean lesion length in the study was 20.6 mm, with a mean stent-covered length of 33.4 mm. Of all lesions, 55.6% were classified as complex lesions (type C of the AHA/ACC classification). At 9 months, target-vessel revascularization was 9.1% in the TAXUS group and 19.4% in the control group (P=0.0027; relative reduction, 53%). Target-lesion revascularization was reduced from 18.9% to 6.8%, respectively (P=0.0001). The incidence of major adverse cardiac events was similar in the 2 groups, 16.4% and 22.5% in TAXUS and control, respectively (P=0.12), including comparable rates for acute myocardial infarction. Binary restenosis in the stented area was reduced from 32.9% in the control group to 9.1% in the TAXUS patients (P<0.0001).
Conclusions— The finding that the TAXUS Moderate Release stent system is safe and effective in the treatment of long, complex coronary artery lesions provides the evidence base for the more widespread use of drug-eluting stents in contemporary clinical practice.
Received March 28, 2005; revision received July 20, 2005; accepted July 22, 2005.
Percutaneous intervention with intracoronary stents is now the most common procedure used in the invasive treatment of the patient with coronary heart disease. In previously published randomized clinical studies evaluating simple de novo coronary artery lesions, drug-eluting stents providing local drug delivery at the time of stent implantation reduced indices of restenosis, including the need for reintervention, compared with bare metal stents.1–9
Because of these promising results, paclitaxel- and sirolimus-eluting stents have become widely used in clinical practice, expanding beyond the simple lesions evaluated in clinical studies to more complex lesions and procedures. Contemporary use of this new technology in the treatment of the long, complex coronary stenoses commonly seen in clinical practice is lacking an evidence base. This randomized study was specifically designed to assess the safety and efficacy of the polymer-based paclitaxel-eluting stents in patients with longer lesions often requiring the implantation of longer or multiple overlapping stents.
Paclitaxel-Eluting Stent System
The TAXUS stent consists of a balloon-expandable Express2 stent with a triblock copolymer coating containing paclitaxel (1 μg/mm2 of paclitaxel [loaded drug/stent surface area]). The Translute polymer coating poly(styrene-b-isobutylene-b-styrene) serves as a carrier to provide uniform and controlled biphasic release of the drug into the vessel wall once the stent is deployed. Slow- and moderate-release (MR) formulations of the polymer have been under investigation. The slow-release formulation is currently commercially available. The MR polymer formulation used in this study produces a paclitaxel release rate approximately threefold higher than the slow-release formulation on the basis of in vivo preclinical measurements. The TAXUS MR stent is premounted on a high-pressure monorail delivery catheter. An uncoated Express2 stent (hereafter referred to as the control stent) served as the control in the study.
Patients, who had to be at least 18 years of age, provided written informed consent and had to have evidence of myocardial ischemia and be eligible for percutaneous coronary intervention and acceptable candidates for coronary artery bypass grafting. Angiographic inclusion criteria included a de novo target lesion located within a single native coronary vessel with a reference vessel diameter between 2.5 and 3.75 mm, a cumulative target-lesion length of 18 to 40 mm, and a diameter stenosis ≥50%. Target lesions randomized to treatment with the study device had to be completely coverable by up to 2 study stents (maximum allowable stent length, 48 mm). Only 1 target lesion could be randomized and treated with a study stent(s) during the study procedure. To ensure a more “real-world” patient population, the study also allowed inclusion of patients with successful treatment of an additional uncomplicated nonstudy lesion located in a nontarget vessel before randomization during the same procedure.
Important exclusion criteria included recent acute myocardial infarction, poor left ventricular function, left main coronary artery disease, an ostial target-lesion location, total occlusion, or involvement of a bifurcation with a side branch diameter >2.0 mm. Treatment with additional devices (eg, cutting balloons, directional/rotational atherectomy) was not permitted.
The study was approved by the local medical ethics committees at each of the investigation sites. Patients who met the study entry criteria were randomized to receive treatment with the TAXUS stent or the control stent using an interactive voice response system. Randomization schedules using a pseudorandom number generator were stratified by clinical site and by the presence or absence of medically treated diabetes mellitus. Within each stratum, eligible patients were randomized in a 1:1 ratio to receive either the TAXUS stent or the control stent. Study devices were packaged and labeled appropriately to maintain double-blind treatment assignments.
Patients were pretreated with aspirin 75 mg and clopidogrel 300 mg (at least 2 hours earlier). A dose of intravenous unfractionated heparin was administered that was sufficient to maintain the activated coagulation time ≥250 seconds. Intracoronary nitrates (glyceryl trinitrate or isosorbide dinitrate) were given before the baseline and final angiograms were recorded. Percutaneous intervention was undertaken by use of standard techniques; balloon predilatation before stent insertion was mandated. Intracoronary stents were implanted according to the manufacturer’s instructions for use. Angiographic images were recorded according to the protocol of the angiographic core laboratory. A predischarge ECG was obtained, and cardiac enzyme estimations were taken 12 to 24 hours after stent placement. Aspirin ≥75 mg/d and clopidogrel 75 mg/d were continued for a minimum of 6 months after the procedure. Glycoprotein IIb/IIIa inhibitors were used at the discretion of the physician.
All enrolled patients were evaluated at 1, 3, 6, and 9 months after the stent implantation procedure; follow-up at 1, 2, 3, 4, and 5 years after the study procedure is planned. At the 9-month follow-up, an ECG was recorded, and an assessment was made of drug compliance, together with repeat coronary angiography. The study was considered complete (with regard to the primary end point) after all enrolled patients had completed the 9-month angiographic follow-up.
Site monitoring and data management and analysis were undertaken by an independent organization (PPD Development, Nuernberg, Germany); after unblinding, the investigators had unrestricted access to the data. An independent core angiographic laboratory (Brigham and Women’s Hospital Angiographic Core Laboratory, Boston, Mass) analyzed the angiograms without knowledge of the patient allocation. All major adverse cardiac events were reviewed and adjudicated by an independent committee whose members were unaware of the patients’ treatment allocation. A Data Monitoring Committee periodically reviewed blinded safety data.
Study End Points
The primary end point of the study was the rate of target-vessel revascularization (TVR) 9 months after the study procedure. Secondary end points included the rates of clinical procedural success, composite major adverse cardiac events (MACE) (death, myocardial infarction, or target-lesion revascularization [TLR] and TVR) at 1, 3, 6, and 9 months after the study procedure and annually for 5 years, the target-vessel failure rate, and the stent thrombosis rate. Myocardial infarctions were categorized as Q-wave and non–Q-wave; Q-wave infarction was defined as the development of new pathological Q waves in 2 or more leads lasting 0.4 seconds or more with postprocedure creatine kinase (CK)-MB levels elevated above normal; non–Q-wave infarction was defined as the presence of postprocedure CK levels >2.0 times normal with positive CK-MB.
Quantitative Coronary Angiographic Analysis
Angiographic variables derived from 9-month restudy included absolute lesion length, stent length, reference vessel diameter, minimum lumen diameter, percent diameter stenosis, binary restenosis rate, acute gain, late loss, loss index, and the patterns of recurrent restenosis, including the edge effect (ie, measurements of the in-stent segment and the analysis segment, that is, the in-stent segment plus 5 mm at either end).
The primary objective of the study was to evaluate the clinical safety and efficacy of the TAXUS stent in reducing the rate of ischemia-driven TVR in patients with de novo coronary lesions at 9 months. The null hypothesis was that the TVR rate in the treatment group would be equal to the TVR rate in the control group (H0: Pe−Pc=0), where Pe and Pc are the 9-month TVR rates for the treatment and control groups, respectively. The alternative hypothesis was that the TVR rate in the treatment group would be different from the TVR rate in the control group (H1: Pe−Pc≠0). The calculation of the sample size (n=448) was based on a z test of equal proportions (normal approximation to binomial) at the 2-sided 5% significance level and 80% power. A 50% treatment effect was determined to be clinically significant assuming a control rate of 20%.
All analyses were based on the intention-to-treat principle. For continuous variables, differences between the treatment groups were evaluated by ANOVA or Wilcoxon’s rank-sum test, as appropriate. For discrete variables, differences were expressed as counts and percentages and were analyzed with Fisher’s exact test. Revascularization of the target lesion or vessel and the composite of major adverse cardiac events were also analyzed by the Kaplan-Meier method. Differences between the event-free survival curves for the 2 groups were compared with the use of log-rank tests.
Between May and December 2002, 448 patients were enrolled at 44 sites in 15 European countries. Two patients who were treated with study stents without randomization (because of technical problems with the interactive voice-response randomization system) were excluded from the intent-to-treat analysis. Four hundred forty-six patients were randomized to receive a paclitaxel-eluting TAXUS Express2 (n=219) or an uncoated bare-metal Express2 control stent (n=227) (Figure 1). Patients were well matched for baseline demographics (Table 1) and lesion and vessel characteristics (Table 2) between the 2 groups. The mean lesion length was 20.6 mm, and the mean stent-covered length was 33.4 mm. Complex (American College of Cardiology/American Heart Association [ACC/AHA] type C) lesions were present in 55.6% of lesions, small-vessel (<2.5 mm in diameter) disease was present in 27.8%, overlapping stents were used in 27.8% of patients, and additional non–target-vessel percutaneous coronary intervention with a nonstudy stent was undertaken in 23.5% of patients.
The primary end point for the study was met in that the rate of TVR at 9 months was reduced from 19.4% (44 of 227) in the control group to 9.1% (20 of 219) in the TAXUS group (relative reduction, 53%; P=0.0027) (Figure 2). TLR was reduced from 18.9% (43 of 227) in the control group to 6.8% (15 of 219) in the TAXUS group (relative reduction, 64%; P=0.0001). The TLR benefit with TAXUS was independent of the classic risk factors for restenosis; in small vessels (<2.5 mm in diameter), 29.7% and 5.0% (relative reduction, 83%; P=0.0003); in long lesions (≥26 mm), 26.3% and 4.4% (relative reduction, 83%; P=0.0097); in diabetics, 22.0% and 2.6% (relative reduction, 88%; P=0.0103); and in patients with multiple, overlapping stents, 23.0% and 1.6% (relative reduction, 93%; P=0.0002) for the control and TAXUS groups, respectively.
Stent thrombosis occurred in 3 of 227 patients (1.3%) in the control group and 1 of 219 patients (0.5%) in the TAXUS group (P=NS) during the 9-month study period. No patient suffered a stent thrombosis in the 3-month period after cessation of the 6-month therapy with clopidogrel and the 9-month follow-up. Overall MACE (death, acute myocardial infarction, TVR) at 9 months was similar in the 2 groups at 22.5% and 16.4% in the control and TAXUS groups, respectively (P=0.12). The components of MACE and other clinical outcomes are detailed in Table 3.
Follow-up 9-month angiography was available in 417 patients (93.5%), 210 of 219 (95.9%) of the TAXUS group and 207 of 227 (91.2%) of the control group (Table 4). Binary restenosis (rate of patients with % diameter stenosis in-stent >50% at follow-up) was reduced from 32.9% in the control group to 9.1% in the TAXUS patients (relative reduction, 72%; P<0.0001) (Figure 3, A–C). The TAXUS benefit in binary restenosis was independent of the classic risk factors for restenosis; in small vessels (<2.5-mm diameter) 40.4% and 7.3% (relative reduction, 82%; P<0.0001), in long lesions (≥26-mm), 50.0% and 7.0% (relative reduction, 86%; P<0.0001), in diabetics 40.5% and 8.1% (relative reduction, 80%; P=0.0015), and in patients with multiple, overlapping stents 45.5% and 4.8% (relative reduction, 89%; P<0.0001) for the control and TAXUS groups, respectively.
Late lumen loss (reduction in minimum lumen diameter from after the procedure to follow-up) was reduced from 0.99±0.59 to 0.39±0.56 mm (P<0.0001) in stent and from 0.66±0.62 to 0.24±0.57 mm in the analysis segment (including the stented area plus the proximal and distal 5-mm edge, P<0.0001). Details of the continuous and binary 9-month quantitative angiographic results are presented in Table 4.
The length of in-stent restenosis in the TAXUS group was significantly shorter than in the control group at 10.8±6.05 and 17.7±9.72 mm, respectively (P=0.0048), with a significant shift to more focal restenosis in the TAXUS patients. At 9-month angiographic follow-up, late acquired aneurysms (defined as vessel distension ≥1.2 times reference vessel diameter present at follow-up but not after the procedure) were observed in 1 control patient (0.5%) and 3 TAXUS patients (1.4%) (P=0.62).
The impact of coronary heart disease on the health economy is profound, and percutaneous coronary techniques have become the dominant treatment option, particularly because the advent of intracoronary stents has resulted in a predictably low periprocedural complication rate. The Achilles heel of bare-metal stent implantation has been the development of angiographic in-stent restenosis. After implantation of a bare-metal stent, there are a number of established predictors of restenosis, particularly lesion length and complexity, vessel diameter, and the presence of diabetes mellitus.10 This prospective, multicenter, double-blind, randomized trial provides, for the first time, the evidence base for the treatment of patients with these risk factors. The population evaluated in this study is representative of patients presenting in current clinical practice and is the most challenging so far treated with drug-eluting stents, with lesion lengths >20 mm, implanted stent covered length 33.4 mm, overlapping stents used in 27.8%, complex (ACC/AHA type C) lesions present in 55.6% of lesions, small-vessel (<2.5-mm diameter) disease in 27.8%, and medically treated diabetes in 17.8%.
In this high-risk group, superior and concordant results were found for the TAXUS stent for clinical and angiographic measures of restenosis compared with the control bare stent. In-stent binary restenosis was reduced in the TAXUS group to 9.1% from 32.9% in the control patients (P=0.0001; relative reduction, 72%). Published trials assessing the angiographic response to bare-metal stents implanted in long lesions predict a binary restenosis rate of 39% to 45%,11,12 comparable with bare-metal stents used in the control limb of the other published drug-eluting stent trials of simple lesions, for example, 36.7% in the RAVEL trial,5 35.4% in the SIRIUS trial,6 and 42.3% in the E-SIRIUS trial.7
Despite the already favorable angiographic result with the control (Express2) stent, there was an additional 53% reduction in TVR (the primary end point of the study) from 19.4% to 9.1% in the TAXUS group compared with control (P=0.0027). Thus, direct patient benefit for the reduced need for either redo percutaneous or surgical revascularization as a consequence of ischemia-driven restenosis of the study vessel is demonstrated for the TAXUS MR stent.
Safety in terms of MACE at 9 months was statistically similar in the 2 groups (16.4% and 22.5% in the TAXUS and control groups, respectively, P=0.12), Non–Q-wave myocardial infarction trended numerically higher in the TAXUS group at 9 months, reflecting the in-hospital non–Q-wave myocardial infarction rate associated with the index procedure (in-hospital non–Q-wave infarction 5.9%, 13 of 219; and 3.1%, 7 of 227, P=0.17, in the TAXUS group and control patients, respectively). In that lesion complexity in the 2 groups was well matched, the cause of this discrepancy remains unclear; possible explanations include an increase in side-branch compromise because of the (thicker) polymer-coated stent struts, a polymer-induced local response, and microembolization, among others.
Previous concerns relating to the possible association between thrombosis and drug-eluting stents have not been realized, with only a single stent thrombosis in the TAXUS group (0.5%) and 3 stent thromboses in the control group (1.3%) at 9 months (P=NS). Importantly, no stent thrombosis occurred in the 3-month period after clopidogrel had been discontinued when patients were maintained on low-dose aspirin alone, although this trial was not powered to investigate prospectively the incidence of stent thrombosis, which, with a frequency of ≈1%, would require a randomized trial of 10 000 to 20 000 patients.
Late-acquired aneurysms were not found significantly more frequently in the TAXUS group compared with control patients (1.4%, 3 of 209, versus 0.5%, 1 of 207, respectively; P=0.62), despite the higher local paclitaxel release from the TAXUS MR stent used in this trial compared with the TAXUS SR stent that has been assessed in earlier studies.1–4 Further insights into aneurysm formation (including the question of inadequate or incomplete healing) are likely to be realized in the Taxus VI intravascular ultrasound substudy (n=179), which will be reported in detail elsewhere.
When the data become available, a comparison of the outcomes from the TAXUS V trial (using the SR formulation) will allow a detailed analysis of the efficacy and effect of the 2 paclitaxel dose formulations in similar patient subsets.
There was no deleterious “edge” effect in the TAXUS group, such that the relative reduction in binary restenosis was similar within the in-stent and the analysis segments (Figure 3).
The results of treatment in the predefined diabetic subgroup of 89 were very gratifying, with a reduction of in-stent binary restenosis from 40.5% in the control group to 8.1% in the TAXUS group (P=0.0015; relative reduction, 80%), which was consistent across the various diabetic subgroups regardless of medication, glycemic control, or severity of the disease.
Taken together, these findings support the National Institute for Clinical Excellence (NICE) guidance in the United Kingdom in relation to the clinical and cost effectiveness of stents (including drug-eluting stents),13 who base their recommendations on angiographic indices, namely, a target-vessel diameter of <3.0 mm and a target-lesion length of >15 mm for the use of drug-eluting stents. It was suggested that these higher-risk lesion subsets may be present in one third of patients; more recent evidence shows that these characteristics are present in 77% of a population undergoing percutaneous treatment in a typical UK referral center.14
Before the advent of drug-eluting stents, operators used the shortest possible stents to treat the lesion (so called “spot” stenting) because of awareness that the likelihood of restenosis was related to the implanted stent length. This study confirms the applicability of “stenting long” with a lesion-to-stent ratio of 1:1.7, thus stenting back to angiographically “normal” vessel on either side of the lesion without the penalty of late in-stent restenosis. In patients who did develop in-stent restenosis, the lesions were significantly shorter and more focal in the TAXUS group, thus facilitating further treatment with conventional percutaneous techniques.
Limitations of the study include the possibility of increasing the likelihood of developing in-stent restenosis in the control patients as a result of using a “stenting long” strategy. Also, although a clinical assessment of patient status was made before undertaking the 9-month angiogram, the “oculostenotic reflex” may have affected the TLR rate.
This study extends the applicability of drug-eluting stents beyond proof of concept studies15 evaluating single, discrete lesion stenting by confirming the safety and efficacy of the TAXUS MR stent system in the treatment of long, complex coronary artery lesions, including small vessel diameter and multiple overlapping stents. Since the commercial availability of drug-eluting stents in Europe in 2002, percutaneous intervention has become the most frequently used revascularization option; this study makes the decision making all the more rational.
This study was supported by Boston Scientific Corp.
Dr Keith D. Dawkins and Dr Eberhard Grube, as principal investigators, were responsible for the conception, design, and execution of the study, the analysis and interpretation of the data, and the writing of the manuscript. Drs Giulio Guagliumi, Adrian Banning, Krzysztof Zmudka, Antonio Colombo, Leif Thuesen, Karl Hauptman, Jean Marco, William Wijns, and Jeffrey J. Popma participated substantially in the enrollment of patients, execution of the study, and the review of the manuscript. Mary E. Russell and Joerg Koglin participated in the design and execution of the study, the analysis of the data, and the writing of the manuscript. All authors approved the final version of the report. Please see the Data Supplement for a list of recruiting centers and the members of the Clinical Events Committee and Data Safety Monitoring Board.
The study sponsor, Boston Scientific Corp, Natick, Mass, supported the design of the study and the collection and analysis of the data and participated in the writing of the report. Dr Dawkins is a consultant to Boston Scientific Corp, and Drs Russell and Koglin are employees and stockholders of Boston Scientific Corp, the sponsor of the study. Dr Guagliumi also has a consulting agreement with Boston Scientific. No other conflict of interest was declared by any coauthor of this article.
Guest Editor for this article was James T. Willerson, MD.
The online-only Data Supplement, which lists study recruiting centers as well as members of the Clinical Events Committee and Data Safety and Monitoring Board, can be found at http://circ.ahajournals.org/cgi/content/full/CIRCULATIONAHA.105.552190/DC1.
Grube E, Silber S, Hauptmann KE, Mueller R, Buellesfeld L, Gerckens U, Russell ME. TAXUS I: six- and twelve-month results from a randomized, double-blind trial on a slow-release paclitaxel-eluting stent for de novo coronary lesions. Circulation. 2003; 107: 38–42.
Colombo A, Drzewiecki J, Banning A, Grube E, Hauptmann K, Silber S, Dudek D, Fort S, Schiele F, Zmudka K, Guagliumi G, Russell ME, TAXUS II Study Group. Randomized study to assess the effectiveness of slow- and moderate-release polymer-based paclitaxel-eluting stent for coronary artery lesions. Circulation. 2003; 108: 788–794.
Stone GW, Ellis SG, Cox DA, Hermiller J, O’Shaughnessy C, Tift Mann J, Turco M, Caputo R, Bergin P, Greenberg J, Popma JJ, Russell ME, for the TAXUS-IV Investigators. A polymer-based, paclitaxel-eluting stent in patients with coronary artery disease. N Engl J Med. 2004; 350: 221–231.
Stone GW, Ellis SG, Cox DA, Hermiller J, O’Shaughnessy C, Tift Mann J, Turco M, Caputo R, Bergin P, Greenberg J, Popma JJ, Russell ME for the TAXUS-IV Investigators. One-year clinical results with the slow-release, polymer-based, paclitaxel-eluting stent: the TAXUS-IV trial. Circulation. 2004; 109: 1942–1947.
Morice M-C, Serruys PW, Sousa JE, Fajadet J, Ban Hayashi E, Perin M, Colombo A, Schuler G, Barragan P, Guagliumi G, Molnar F, Falotico R, RAVEL Study Group. A randomized comparison of a sirolimus eluting stent with a standard stent for coronary revascularization. N Engl J Med. 2002; 346: 1773–1780.
Moses JW, Leon MB, Popma JJ, Fitzgerald PJ, Holmes DR, O’Shaughnessy C, Caputo RP, Kereiakes DJ, Williams DO, Teirstein PS, Jaeger JL, Kuntz RE, SIRIUS Investigators. Sirolimus-eluting stents versus standard stents in patients with stenosis in a native coronary artery. N Engl J Med. 2003; 349: 1315–1323.
Schofer J, Schlüter M, Gershlick AH, Wijns W, Garcia E, Schampaert E, Breithardt G, for the E-Sirius investigators. Sirolimus-eluting stents for the treatment of patients with long atherosclerotic lesions in small coronary arteries: double-blind, randomised controlled trial (E-SIRIUS). Lancet. 2003; 362: 1093–1099.
Gershlick A, De Scheerder I, Chevalier B, Stephens-Lloyd A, Camenzind E, Vrints C, Reifart N, Missault L, Goy J-J, Brinker JA, Raizner AE, Urban P, Heldman AW. Inhibition of restenosis with a paclitaxel-eluting, polymer-free coronary stent: the European evaluation of paclitaxel eluting stent (ELUTES) trial. Circulation. 2004; 109: 487–493.
Ho KKL, Senerchia C, Rodriguez O, Chauhan MS, Kuntz RE. Predictors of angiographic restenosis after stenting: pooled analysis of 1197 patients with protocol mandated angiographic follow-up from five randomized stent trials. Circulation. 1998; 98: 362–368.
Hoffmann R, Herrmann G, Silber S, Braun P, Werner GS, Hennen B, Rupprecht H-J, vom Dahl J, Hanrath P, for the Impact Upon Long lesion Stenting Study Group (IMPULSE). Randomized comparison of success and adverse event rates and cost effectiveness of one long versus two short stents for treatment of long coronary narrowings. Am J Cardiol. 2002; 90: 460–464.
Oemrawsingh PV, Mintz GS, Schalij MJ, Zwinderman AH, Wouter Jukema J, van der Wall EE. Intravascular ultrasound guidance improves angiographic and clinical outcome of stent implantation for long coronary artery stenoses: final results of a randomized comparison with angiographic guidance (TULIP study). Circulation. 2003; 107: 62–67.
Guidance on the Use of Coronary Artery Stents. Technology Appraisal No. 71 (October 2003). National Institute for Clinical Excellence (NICE). http://www.nice.org.uk/pdf/TA71_coronaryarterystents_fullguidance.pdf.
Wells T, Dawkins KD. Drug eluting stents: NICE guidelines and the reality. 2005. Br J Cardiol. 2005; 12: 45–48.