FOCUS ISSUE: DRUG-ELUTING STENTS: TAXUS-IV
Outcomes of paclitaxel-eluting stent implantation in patients with stenosis of the left anterior descending coronary artery
George Dangas, MD, PhD, FACC*,
Stephen G. Ellis, MD, FACC ,1,
Richard Shlofmitz, MD, FACC ,
Stanley Katz, MD, FACC ,
David Fish, MD, FACC||,
Steven Martin, MD, FACC¶,
Roxana Mehran, MD, FACC*,
Mary E. Russell, MD#,2,
Gregg W. Stone, MD, FACC*,1,* TAXUS-IV Investigators
* Columbia University Medical Center and Cardiovascular Research Foundation, New York, New York
Cleveland Clinic Foundation, Cleveland, Ohio
St. Francis Hospital, Roslyn, New York
North Shore University Hospital, Manhasset, New York
|| St. Luke’s Episcopal Hospital, Houston, Texas
¶ Nebraska Heart Institute, Lincoln, Nebraska
# Boston Scientific Corp., Natick, Massachusetts.
Manuscript received June 28, 2004;
revised manuscript received October 22, 2004,
accepted October 25, 2004.
* Reprint requests and correspondence: Dr. Gregg W. Stone, Cardiovascular Research Foundation, 55 East 59th Street, 6th Floor, New York, New York 10022. (Email: gstone{at}crf.org).
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Abstract
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OBJECTIVES: We sought to examine the efficacy of paclitaxel-eluting stent implantation in the left anterior descending coronary artery (LAD).
BACKGROUND: Restenosis and recurrent cardiac events after percutaneous intervention are more common for lesions in the LAD than other native coronary arteries, and often necessitate bypass surgery. Drug-eluting stents may improve the long-term prognosis of this high-risk group.
METHODS: In the TAXUS-IV trial, 1,314 patients with single de novo coronary lesions were assigned to implantation of the slow-release, polymer-based, paclitaxel-eluting TAXUS stent or an identical bare-metal stent; 536 (41%) randomized patients had LAD lesions.
RESULTS: Baseline characteristics of patients with LAD lesions were well-matched between the randomized groups. Late lumen loss at nine months after paclitaxel-eluting and control stent implantation were 0.28 ± 0.51 mm and 0.54 ± 0.57 mm, respectively (p = 0.0004), and binary restenosis rates were 11.3% and 26.9%, respectively (p = 0.004). At one year, major adverse cardiac events (MACE) occurred in 13.5% of TAXUS-treated patients versus 21.2% treated with the control stent (p = 0.01). The need for bypass surgery at one year was reduced among patients randomized to the TAXUS stent (2.6% vs. 6.3%, p = 0.02). In the proximal LAD subgroup (n = 126), the one-year target vessel revascularization rate was 7.9% with the TAXUS stent and 18.6% with the bare-metal stent (p = 0.009).
CONCLUSIONS: Compared to bare-metal stents, implantation of polymer-based, paclitaxel-eluting stents in LAD lesions is safe, and reduces angiographic restenosis and MACE one year. Notably, the need for bypass graft surgery due to restenosis is reduced after TAXUS stent implantation in LAD lesions.
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Abbreviations and Acronyms
| | CI = confidence interval | | HR = hazard ratio | | LAD = left anterior descending coronary artery | | LCX = left circumflex coronary artery | | MACE = major adverse cardiac event | | OR = odds ratio | | PCI = percutaneous coronary intervention | | RCA = right coronary artery | | TLR = target lesion revascularization | | TVR = target vessel revascularization |
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The implantation of drug-eluting coronary stents significantly reduces angiographic restenosis and recurrent cardiac events compared to bare-metal stents, which are, in turn, superior to balloon angioplasty alone (1–5). One of the predictors of angiographic restenosis after balloon angioplasty and bare-metal stent implantation is the location of the target lesion in the left anterior descending coronary artery (LAD) (5–11). Numerous studies have investigated the outcomes of percutaneous coronary intervention (PCI) and bypass surgery in patients with LAD stenosis (12–20). In most of these studies, the long-term rates of survival free from re-infarction have been similar after the two revascularization techniques; the biggest differences noted have been a greater rate of recurrent target lesion revascularization (TLR) and target vessel revascularization (TVR) after PCI compared to surgery. Moreover, a recently published report found LAD bypass grafting to be the best predictor of event-free survival at three years after bypass graft surgery (20), underlining the importance of sustained LAD patency.
Importantly, drug-eluting stents were used in none of the above-mentioned comparative studies. The specific results with these bioactive devices in the LAD, and their potential impact in improving long-term outcomes after PCI, have not been examined. The present study represents a pre-specified, secondary analysis from the TAXUS-IV trial (1), examining early and late outcomes of patients randomized to the slow-release, polymer-based, paclitaxel-eluting stent to PCI with bare-metal stents as a function of epicardial target lesion location.
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Methods
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TAXUS-IV study design.
The study population, design, and overall conduct of the TAXUS-IV randomized trial have been published in detail elsewhere (1). In brief, the TAXUS study enrolled patients with stable or unstable angina or provokable ischemia undergoing PCI of a single de novo lesion in a native coronary artery. Angiographic inclusion required the presence of a single, non-ostial, target lesion with visually estimated reference vessel diameter  2.5 to  3.75 mm and lesion length 10 to 28 mm coverable by a single study stent. Telephone randomization was performed before pre-dilatation, stratified by the presence of medically treated diabetes and vessel size. Patients were equally assigned in a double-blind fashion using random serial numbers to treatment with either the slow rate-release, polymer-based, paclitaxel-eluting EXPRESS stent (the TAXUS stent, Boston Scientific Corp., Natick, Massachusetts) or a visually indistinguishable bare-metal EXPRESS stent.
Patients were pretreated with aspirin, and a 300-mg oral loading dose of clopidogrel was recommended. Unfractionated heparin was administered per standard practice, and glycoprotein IIb/IIIa inhibitor use was at the operator’s discretion. After mandatory pre-dilatation, an appropriate-sized stent (approximately 2 to 4 mm longer than the lesion with a stent-to-distal reference vessel diameter ratio of 1 to 1.1:1) was implanted at 12 atm. Stents were available in lengths of 16, 24, and 32 mm, and in diameters of 2.5, 3.0, and 3.5 mm. Additional study stents were permitted for edge dissections greater than or equal to type B or otherwise suboptimal results, and post-dilatation was at the operator’s discretion.
After PCI, patients were maintained on aspirin 325 mg daily indefinitely and clopidogrel 75 mg daily for at least six months. Clinical follow-up was scheduled at one, four, and nine months, and yearly thereafter for five years. Angiographic follow-up was pre-specified in a subgroup of 732 patients at nine months.
Details of trial management have been previously reported, as have the study end points (1). All major adverse cardiac events (MACE) were adjudicated by an independent committee blinded to treatment allocation after review of original source documentation. Independent core angiographic laboratory analysis was performed blinded to clinical outcomes using validated quantitative methods (21,22). Measures were reported separately within the stent, within 5 mm proximal and distal to each edge, and over the entire analysis segment.
Statistical methods.
Categorical variables were compared by the Fisher exact test for two-way comparisons or the chi-square test for trend for three-way comparisons. Continuous variables are presented as mean ± 1 SD or median with interquartile ranges, and were compared by the Wilcoxon two-sample test. The influence of baseline variables on one-year categorical end points was evaluated with logistic regression. Survival estimates were created using Kaplan-Meier methodology, and compared with the log-rank test. Independent determinates of event-free survival were identified with Cox proportional hazards regression. Candidate variables for multivariate analyses included: randomization arm, age, female gender, current smoker, any diabetes, LAD location, previous myocardial infarction, hypertension, hyperlipidemia, left ventricular ejection fraction, unstable angina, bailout stent used, non-study stents used, total stent length, maximum device pressure, maximum device diameter, balloon-to-artery ratio, stent-to-lesion-length ratio, creatinine clearance, ostial location, arterial tortuosity, calcification, lesion length, baseline reference vessel diameter, and baseline minimal luminal diameter. Epicardial vessel was forced into the equations. The Breslow-Day test for homogeneity was used to test for the presence of specific interaction between randomization arm and epicardial vessel on clinical and angiographic outcome variables. All p values are two-sided.
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Results
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Of 1,314 patients enrolled in the TAXUS-IV trial, the target lesion was in the LAD in 536 patients (40.8%), in the left circumflex (LCX) in 364 patients (27.7%), and in the right coronary artery (RCA) in 414 patients (31.5%).
Baseline features and procedural outcomes in the LAD subgroup.
Of the 536 patients in the LAD subgroup, 264 patients were randomized to receive a paclitaxel-eluting stent, and 272 patients to a bare-metal stent. Baseline characteristics were well matched between the two groups, with a non-significant trend toward larger reference vessel diameter present in the paclitaxel-eluting stent group (Table 1). The number of stents implanted per patient, mean stent length, diameter, and deployment parameters were similar between the paclitaxel and control stent groups (Table 2). Acute angiographic results were comparable between the two study cohorts.
Clinical and angiographic outcomes in the LAD subgroup.
As shown in Table 3, death, myocardial infarction, and stent thrombosis rates occurred with similarly low frequency in the two treatment groups throughout the one-year follow-up period. Implantation of the paclitaxel-eluting stent compared to bare-metal stenting reduced the one-year rates of TLR and TVR by 69% and 62%, respectively, and the MACE rate by 61%. Of note, the need for bypass graft surgery due to TVR was significantly reduced among patients randomized to the TAXUS stent.
Repeat catheterization was completed in 223 of 298 patients (75.3%) in the 9-month follow-up angiography group. Compared to bare-metal stenting, patients randomized to the paclitaxel-eluting stent had less late loss and a lower loss index, resulting in greater luminal dimensions and a lower diameter stenosis at follow-up (Table 4). Accordingly, the binary restenosis rate was reduced by 64% within the stent, and by 58% in the analysis segment. Moreover, restenosis, when it did occur after paclitaxel-eluting stent placement, was significantly shorter in length and less frequently diffuse than restenosis after bare-metal stent implantation.
Outcomes of lesions in the proximal LAD location.
The target lesion was located in the proximal LAD segment in 236 patients (44% of the overall LAD group); 126 were assigned to paclitaxel and 110 to bare-metal stent implantation. The results in the proximal LAD subgroup were, in general, concordant to these observed in the overall LAD cohort (Table 5).
Relative outcomes in the LAD, LCX, and RCA.
In patients randomized to the bare-metal stent, the rates of restenosis and adverse events during the follow-up period were similar after treatment of lesions in all three coronary arteries. However, the likelihood of requiring bypass graft surgery for TVR was significantly higher after bare-metal stenting of the LAD than the RCA or LCX (Table 6). In contrast, though late loss tended to be slightly higher after paclitaxel-eluting stent implantation in the LAD compared to the RCA and LCX vessels, the one-year rates of TLR and TVR, including bypass graft surgery, were similar in all three coronary arteries after TAXUS stent implantation (Table 7).
By multivariate analysis, among patients with LAD lesions, randomization to the TAXUS stent was a significant independent predictor of freedom from one-year TVR (hazard ratio [HR] = 0.44 [95% confidence interval (CI) 0.26 to 0.75], p = 0.002) and analysis segment restenosis (odds ratio [OR] = 0.42 [95% CI 0.20 to 0.89], p = 0.02). Similarly, among patients with stenoses in the LCX or RCA, randomization to the TAXUS stent was a significant predictor of freedom from one-year TVR (HR = 0.36 [95% CI 0.22 to 0.58], p < 0.0001) and analysis segment restenosis (OR = 0.12 [95% CI 0.05 to 0.27], p < 0.0001). No significant interaction was present between randomization arm and epicardial vessel (LAD vs. non-LAD) on either the rate of TVR at one year or analysis segment restenosis (p = 0.95 and 0.16, respectively).
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Discussion
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The present substudy of the TAXUS-IV trial demonstrates that the slow-release, polymer-based, paclitaxel-eluting stent, when implanted in single de novo LAD lesions of moderate complexity, markedly reduces recurrent clinical events and angiographic restenosis compared to use of an identical bare-metal stent. Moreover, when restenosis did occur with the TAXUS stent, the length of the restenotic segment was shorter, and its pattern more focal. As a result, randomization to the TAXUS stent rather than the bare-metal stent significantly reduced the need for subsequent bypass graft surgery, in addition to repeat PCI (21). Moreover, use of the paclitaxel-eluting stent was safe, with similarly low rates of cardiac death and myocardial infarction over the one-year follow-up period after both paclitaxel-eluting and bare stents in this important patient cohort.
Some variability in the absolute and relative reductions in the clinical and angiographic event rates after TAXUS stenting was observed across the three major epicardial coronary arteries, possibly due to differences in vessel size, lesion length, and diabetes. Nonetheless, randomization to the TAXUS stent was an independent determinate of freedom from restenosis and TVR among both patients with LAD and non-LAD lesions. The fact that no specific interaction between randomization arm and epicardial vessel on either clinical or angiographic measures of restenosis was identified suggests that the efficacy of the TAXUS stent is independent of epicardial lesion location.
The one-year rates of TVR (8.4%) and MACE (13.5%) observed after paclitaxel-eluting stent placement in the LAD from the current study is similar to the reported 5% to 8% TVR and up to 15% MACE rates at 6 to 12 months after surgical revascularization of the LAD (12,13,16,17). Importantly, similar results were obtained with the TAXUS stent after implantation in lesions located in the proximal LAD, a location that, in prior studies, has tended to benefit from bypass graft surgery rather than PCI (14,18). Again, the results observed with the paclitaxel-eluting stent in the present analysis are very similar to that observed after surgical revascularization of isolated proximal LAD lesions in these earlier studies. The validity of this observation is reinforced by the similar clinical event rates in the bare-metal stent arms of the TAXUS-IV trial and the previous stent study (14), which, in turn, was more favorable than the earlier study with balloon angioplasty of the proximal LAD (18).
Therefore, on the basis of the above findings, paclitaxel stent implantation appears both safe and efficacious for treatment of LAD stenoses, and may approach the efficacy of surgical revascularization with a left internal mammary artery graft to the LAD. Of note, however, the enrollment criteria in the current study limited the lesion types studied. Furthermore, whether contemporary PCI with drug-eluting stents and optimal pharmacotherapy results in similar survival in diabetic patients as does bypass surgery is also unknown (18). Prospective, randomized trials comparing drug-eluting stents to bypass graft surgery are required to properly examine clinical outcomes after these two forms of revascularization.
Limitations and clinical perspectives.
Although the present report represents a pre-specified analysis, subgroup analyses inherently demonstrate selection bias and typically lack adequate statistical power for robust comparisons among modest-sized cohorts. Ostial narrowings and bifurcation stenoses are examples of critical LAD lesions that were excluded from randomization. The results contained in the present report also cannot be generalized to other drug-eluting stent systems. Despite these caveats, the results from the present study demonstrate that, compared to bare-metal stents, the paclitaxel-eluting TAXUS stent significantly enhances event-free survival in all three coronary arteries. Longer-term follow-up data, further experience in lesions not enrolled in the TAXUS-IV trial, and direct comparisons with bypass graft surgery are required to completely characterize the relative benefits of this device in patients with coronary atherosclerosis (23–25).
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Footnotes
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1 Drs. Ellis and Stone have served as consultants for Boston Scientific 
2 Dr. Russell is an employee of and equity holder in Boston Scientific.
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Abstract
Methods