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J Am Coll Cardiol, 2007; 49:1043-1051, doi:10.1016/j.jacc.2007.01.015
(Published online 23 February 2007). © 2007 by the American College of Cardiology Foundation |
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* The Cleveland Clinic, Cleveland, Ohio
Columbus Hospital, Milan, Italy
Heart Center Siegburg, Siegburg, Germany
Brigham and Womens Hospital, Boston, Massachusetts
|| Boston Scientific Corporation, Natick, Massachusetts
¶ Southampton University Hospital, Southampton, United Kingdom
# Columbia University Medical Center and the Cardiovascular Research Foundation, New York, New York.
Manuscript received July 26, 2006; revised manuscript received January 2, 2007, accepted January 9, 2007.
* Reprint requests and correspondence: Dr. Stephen G. Ellis, Department of Cardiovascular Medicine, The Cleveland Clinic, 9500 Euclid Avenue, F25, Cleveland, Ohio 44195. (Email: elliss{at}ccf.org).
Data presented in part at the Transcatheter Cardiovascular Therapeutics Conference, October 23 to 27, 2005, Washington, DC, and the American College of Cardiology Foundation Annual Scientific Session, March 11 to 14, 2006, Atlanta, Georgia.
| Abstract |
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Background: The incidence and timing of stent thrombosis after drug-eluting stent placement compared with bare-metal stent implantation remain unsettled, with consequent uncertainty about risk stratification and long-term recommendations for antiplatelet medications.
Methods: This study used a patient-based meta-analysis using the 4 principal TAXUS randomized trials (3,445 patients) with a follow-up duration of
1 year.
Results: Cumulative stent thrombosis occurred in 1.28% ± 0.31% in the Taxus group and 0.76% ± 0.23% in the bare-metal stent group at 3 years (hazard ratio 1.51 [95% confidence interval 0.73 to 3.14], p = 0.26). Hazard ratios (per 100 patients per 6 months) were similar between the Taxus stent group (0.59 [95% confidence interval 0.22 to 0.95]) and the bare-metal stent group (0.64 [95% confidence interval 0.26 to 1.02]) through 6 months during the prescribed clopidogrel period. However, from 6 months to 3 years there were more stent thromboses in the Taxus group (hazard ratio 0.19 [95% confidence interval 0.06 to 0.32] vs. 0.02 [95% confidence interval 0.00 to 0.07], p = 0.049). Of 8 patients with Taxus-related thrombosis after 6 months, 0 were taking clopidogrel and 2 were not taking aspirin consistently. No Taxus-related stent thrombosis occurred after 2 years (922 patients thus far followed up for 3 years). Independent correlates of stent thrombosis were nonuse of clopidogrel, male gender, smoking, and possibly use of multiple nonoverlapping stents.
Conclusions: Approximately 0.8% of Taxus patients have stent thrombosis in the first 6 months after stent implantation, similar to bare-metal stents. However, a modest increase in risk is present with Taxus stents beyond 6 months, possibly because of inadequate antiplatelet drug therapy.
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| Methods |
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75 mg (
324 mg in TAXUS IV and V) daily was recommended indefinitely, and clopidogrel 75 mg daily was recommended for at least 6 months. Characteristics of the individual trials are provided in Table 1. Follow-up is currently available through 3 years for TAXUS II and IV, through 2 years for TAXUS VI, and through 1 year for TAXUS V. One patient randomized to the control arm of TAXUS VI and who had a stent thrombosis on day 21 did not receive a study stent and therefore is excluded from this analysis.
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30 days) or late (>30 days). In addition, the late cases were subdivided into a very late category (>180 days), which corresponds to the period beyond the protocol-mandated duration of clopidogrel use.
Statistical methodology.
Data are presented as mean ± standard deviation. Between-group comparisons of event rates were made using the Fisher exact test. Data for the slow- and moderate-release formulations of the Taxus stent were tested for between-group differences and were combined for comparison with BMS when no apparent differences (p > 0.10) were observed. Time-to-event data were calculated with Kaplan-Meier methodology and compared with the log-rank test. Independent predictors of stent thrombosis were determined using multivariate Cox proportional hazard regression models. Adjustments for baseline characteristics were made. Subjects who were alive at the start of each time interval (defined for early stent thrombosis as
30 days, late stent thrombosis as 30 to 180 days, and very late stent thrombosis as >180 days) were included in the analysis group. Patients were not censored from inclusion in the later time periods if they had earlier stent thrombosis, but stent thromboses were counted only once during each of the 3 time periods. Candidate variables are listed in the footnote of Table 5. A 2-sided p value < 0.05 was considered statistically significant. All modeling analyses were performed using SAS version 9.1 (SAS Institute Inc., Cary, North Carolina).
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| Results |
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Correlates of stent thrombosis. A comparison of baseline demographics, lesion characteristics, and treatments rendered between patients with (n = 30) and without (n = 3,415) stent thrombosis is provided in Table 3. Patients with stent thrombosis were more likely to be male, to have multiple nonoverlapping stents implanted, to smoke, and to initially present with unstable angina. As noted in Table 4, clopidogrel or ticlopidine use at 1 month was less frequent in patients with versus in those without stent thrombosis (88.5%, 23 of 26 vs. 98.8%, 3,343 of 3,384, respectively, p = 0.004). Reasons for not taking thienopyridines at 30 days in patients with stent thrombosis were protocol violation (n = 1), and diagnosis of gastric carcinoma shortly after the index procedure (n = 1) and emergency colectomy at day 30 (n = 1), both of which required antiplatelet therapy withdrawal. In these 3 patients, stent thrombosis occurred on days 0, 5, and 38, respectively. Conversely, stent thrombosis developed in 3 of 43 patients (6.98%) who were not taking clopidogrel or ticlopidine at 1 month, compared with 23 of 3,366 patients (0.68%) who were taking clopidogrel or ticlopidine at 1 month (p = 0.004).
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Univariate correlates of stent thrombosis during the 3-year follow-up period were nonuse of clopidogrel/ticlopidine at hospital discharge, smoking, male gender, multiple nonoverlapping stents, age, and unstable angina at initial presentation (Table 5). Multivariate regression analysis identified clopidogrel/ticlopidine nonuse, male gender, and smoking at the time of stent implantation, but not Taxus stent implantation, as significant correlates for stent thromboses occurring during the 3-year period. Notably, clopidogrel/ticlopidine nonuse, smoking, and multiple nonoverlapping stents were significant predictors for early (
30 days) stent thrombosis.
The only independent correlate of late stent thrombosis (>30 days) was a major adverse cardiac event (MACE) occurring within 30 days of the original procedure (1 Taxus patient with stent thrombosis on day 408 had a Q-wave myocardial infarction on day 0, and a second Taxus patient with stent thrombosis on day 519 had a Q-wave myocardial infarction on day 1). A weak trend was present toward Taxus stent use as an independent predictor of late stent thrombosis (hazard ratio 2.89 [95% confidence interval 0.78 to 10.69], p = 0.11).
Considering very late stent thrombosis (6 months to 3 years), however, use of a Taxus stent was correlated with excess risk (hazard ratio 8.09 [95% confidence interval 1.01 to 64.67], p = 0.021). No Taxus-related thrombosis occurred in the 922 patients followed up beyond 2 years thus far.
Clinical consequences of early and late stent thrombosis occurring up to 6 months after stenting. Early stent thrombosis resulted in 30-day rates of death in 29.4% (5 of 17) of patients, myocardial infarction in 76.5% (13 of 17), and target vessel revascularization (TVR) in 70.6% (12 of 17). The overall mortality of patients with early stent thrombosis was 41.2% (7 of 17), with a median follow-up duration after stent thrombosis of 6.2 months versus 3.2% (108 of 3,428) in patients without stent thrombosis (median follow-up duration of 25.9 months).
The clinical correlates, timing, aspirin and clopidogrel use, and consequences of the 20 stent thromboses that occurred <180 days after stent implantation are listed in Table 6. There were 2 BMS patients and 2 Taxus patients with stent thrombosis between 30 days and 6 months after stenting. Of these 4 patients, 2 patients (50.0%) died, 3 patients (75.0%) had a myocardial infarction, and 1 patient (25.0%) had a TVR. A 66-year-old man who received a BMS died suddenly 75 days after stent implantation. Because no autopsy was performed, the occurrence of stent thrombosis was presumed by the clinical events committee. A 51-year-old male Taxus slow-release patient who had a Q-wave myocardial infarction and angiographically confirmed stent thrombosis 38 days after the index procedure died during attempted TVR. Both aspirin and clopidogrel therapy had been discontinued for 4 days before the stent thrombosis for planned surgery.
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| Discussion |
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The incidence of Taxus-related early stent thrombosis in this study perhaps is modestly higher than, but generally in line with, that found by Moreno et al. (11) in their meta-analysis of DES. This difference likely reflects the considerably longer lesions and increased complexity in patients enrolled in the Taxus V and VI studies (which were not included in the review by Moreno et al. [11]) (16,17), and possibly differences in the definition of stent thrombosis between studies (15,18). The modest number of patients (n = 9) with very late (>6 months) stent thrombosis makes assessment of correlations difficult, and the results should be considered speculative and hypothesis generating. Certainly, the absence of clopidogrel therapy in all patients developing very late stent thrombosis is notable. However, it should be noted that the frequency of aspirin and clopidogrel use was not collected in patients without MACE after 9 months; as such, determination of the exact relationship between late antiplatelet agent usage and late stent thrombosis is not possible from this study. Patients surviving stent thrombosis also may have had their duration of therapy extended in attempt to prevent further events. The possible etiologic role of antiplatelet agent hyporesponsiveness in stent thrombosis also is not addressed by the present report. In this regard, studies relating patient "resistance" to aspirin and/or clopidogrel are provocative, but not yet definitive (7,19).
The results of the present study are important to consider in light of 2 recent reports. The BASKET-LATE (BAsel Stent Kosten Effektivitäts Trial—Late Thrombotic Events) randomized trial of drug-eluting stents versus BMS showed that for 746 patients who were MACE-free at 6 months, the incidence of late stent thrombosis between 6 and 18 months tended to be greater in patients assigned to sirolimus-eluting or paclitaxel-eluting stents rather than to BMS (2.6% vs. 1.3%, p = 0.23) (20). Secondly, investigators from the multicenter observational PREMIER (Prevention of Myocardial Infarction Early Remodeling) registry documented that 13.6% of 500 patients receiving DES discontinued clopidogrel within 30 days, a finding associated with a 10-fold increase in mortality at 1 year (21). These 2 studies suggest that the frequency of premature thienopyridine discontinuation and subsequent stent thrombosis may be even more prevalent in an unregulated, real-world environment than in highly controlled, randomized, clinical trials.
The devastating complications of stent thrombosis (1,2), together with the possible correlation of very late stent thrombosis with the absence of dual antiplatelet therapy, might make one consider prolonging the routine duration of poststent clopidogrel. However, that consideration must be balanced against the lack of firm knowledge, the bleeding risks (22), and the costs associated with clopidogrel use. Platelet hyper-reactivity in the setting of hyperadrenergic states may also contribute to stent thrombosis. In this regard, antiplatelet agents were forced to be discontinued in some patients because of the need for surgery or hemorrhagic complications, after which stent thrombosis occurred. It is not clear that such situations could be avoided by recommendation of universal prolonged usage of a dual antiplatelet regimen. Clearly, more research is necessary to understand the relationship between aspirin and clopidogrel use, antiplatelet agent hyporesponsiveness (resistance), and the risk of stent thrombosis.
The rate of stent thrombosis is dependent on the definitions used. The current definitions might overestimate stent thrombosis as far out as 30 days and underestimate stent thrombosis after 30 days. Moreover, varying definitions of stent thrombosis have been used in studies evaluating other (non–paclitaxel-based) DES, and as such, comparison of these results with other trials is difficult. An optimized industry-standard definition is urgently needed. Nonetheless, it is of note that an excess rate of very late stent thrombosis of approximately 0.5% through 3 years has also been reported with the sirolimus-eluting stent compared with its bare metal equivalent in a similar meta-analysis of 4 pivotal trials with that device, at least using some definitions (23).
This analysis is principally limited by the modest number of patients with stent thrombosis, uncertainties regarding drug treatment beyond 1 year after stenting for patients without stent thrombosis, and lack of definite dates of antiplatelet agent discontinuation. The results from randomized trials also do not apply to all real-world applications, even when increasingly complex patients and lesions are included, as in the present study. Additionally, the hazard ratio for very late stent thrombosis (6 months to 3 years) for the Taxus stent, 8.09 [95% confidence interval 1.01 to 64.67, p = 0.049], was calculated with the deaths before 6 months (n = 33) removed from the risk set, those lost to follow-up before 6 months (n = 36) removed from the data set, and the patients with treated stent thrombosis before 6 months (n = 21) retained in the data set. Thus, this hazard ratio and its associated p value were not based on the full randomization groups and should be interpreted as approximate.
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2 Drs. Ellis, Stone, and Dawkins are on the Boston Scientific Consultant/Advisory Board; ![]()
3 Dr. Koglin holds Boston Scientific ownership interest/stock; and Dr. Koglin is employed by Boston Scientific. ![]()
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