(Circulation. 2007;115:2352-2357.)
© 2007 American Heart Association, Inc.
Special Reports |
From the University of New Mexico Medical School (W.K.L.), Albuquerque; Baylor University Medical Center (C.W.Y.), Dallas, Tex; and Beth Israel Deaconess Medical Center, Harvard Medical School (W.H.M.), Boston, Mass.
Correspondence to Dr William H. Maisel, MD, MPH, Beth Israel Deaconess Medical Center, Cardiovascular Division, 185 Pilgrim Road, Baker 4, Boston, MA 02215. E-mail wmaisel{at}bidmc.harvard.edu
Key Words: restenosis stents thrombosis
| Introduction |
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Presentations at national and international meetings in 2006 suggested that DES use may be associated with an increase in late (
1 year after implantation) stent thrombosis (ST). Other studies suggested that there may be a significant increase in the combined end point of death and myocardial infarction (MI) compared with BMS. In response to these safety concerns, the US Food and Drug Administration (FDA) convened a meeting of the Circulatory System Medical Devices Advisory Panel. Advisory Panels make nonbinding recommendations to the FDA.
| Definitions |
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To address the shortcomings of the ST definitions, an Academic Research Consortium (ARC) composed of clinical investigators, industry representatives, and regulatory authorities (including the FDA) has proposed new definitions for ST (Table 1) in an attempt to establish uniformity in the industry and to improve sensitivity for the diagnosis of ST. For the purposes of the panel meeting, the FDA believed that the ARC definitions were acceptable and requested that sponsors and investigators apply these definitions to their data sets when possible. The FDA also recognized that other definitions of ST may be appropriate and proposed for use in clinical studies. A majority of the panel agreed that, among the ARC categories, "definite" and "probable" are most useful, although the true sensitivity and specificity have not been determined; the "possible" category, which lacks specificity, was least useful and was likely to lead to overestimates of the true ST frequency. Not all panel members, however, felt that the ARC definitions should be used for future studies, and several felt it was inappropriate to readjudicate (even blindly) results of prior studies. A number of panel members felt that it was more appropriate to use the "on-protocol" ST definitions. Some felt that a process independent of industry input would be preferable and that ST definitions should be readdressed by previously established entities, such as the American College of Cardiology or American Heart Association.
| On-Label Drug-Eluting Stent Use |
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| Long-Term Follow-Up of Pivotal DES Trials |
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4 years of follow-up in 94% of the 1058 study patients. Long-term effectiveness of SES compared with BMS was demonstrated with significant sustained reductions in the rate of target vessel failure. No significant differences were observed in mortality, MI, or on-protocol ST between SES and BMS (Table 3). Similarly, data from TAXUS IV compares PES to BMS with >95% follow-up available at 3 years for the 1314 patients. Significant sustained reductions in TVR were observed in PES patients compared with BMS patients with no significant difference in cardiac mortality, MI, or on-protocol stent thrombosis (Table 3).
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Pooled analyses and meta-analyses of patient-level data from both the pivotal and additional randomized, blinded, controlled DES trials were also presented. These analyses demonstrated no significant differences in the rate of death, MI, or death/nonfatal MI for either SES (follow-up
4 years) or PES (mean follow-up 3.2 years) when compared with BMS.
Similarly, the cumulative incidence of ST at 4 years was not significantly different between SES and BMS either by the protocol-defined ST definition (SES 1.2% versus BMS 0.6%, P=NS) or by the ARC ST definition (with categories of definite and probable) (SES 1.5% versus BMS 1.8%, P=NS) (Table 4). Patient-level pooled analysis of the PES trial experience similarly confirmed the absence of a statistically significant difference in the cumulative ST rate at 4 years (protocol definition: PES 1.3% versus BMS, 0.9%, P=NS; ARC definition categories definite and probable: PES 1.9% versus BMS 1.5%, P=NS) (Table 4). The panel, however, recognized that the studies were underpowered to detect even moderate clinically significant differences in the rate of rare events like ST.
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Despite the absence of a significant overall difference in the rate of ST, the time distribution of events appeared different for BMS compared with DES. Specifically, there were numerically more BMS ST in the 30-day to 1-year time period (late), and numerically more DES ST in the >1-year time period (very late). The pooled analysis of the 4 randomized, blinded, controlled, SES stent trials demonstrated a protocol-defined ST rate beyond 1 year of 0.6% (5 of 848 cases) in the SES arm and 0% (0 of 843 cases) in the BMS control arm (P<0.05), and a numerical, nonstatistically significant increase in the number of ARC definite and probable ST in the SES group (Table 4). A similar analysis of PES randomized controlled trials also demonstrated a significant increase in the protocol-defined rate of very late ST (>1 year) in the PES group compared with BMS and a numerical, nonstatistically significant increase in the ARC rate of definite and probable ST in the PES group (Table 4). An additional, patient-level, pooled analyses of the PES randomized controlled trial data set reported a small but statistically significant increased risk (0.21% per patient per year) of late (>6 months) ST with the ARC definitions of definite and probable (DES 0.25 per 100 patient-years of follow-up versus BMS 0.04 per 100 patient-years, P=0.007).
For on-label use, the panel felt that, in total, the data were consistent with a numerical increase in very late (>1 year after implant) ST associated with DES use compared with BMS use, but that the true magnitude of the risk and the duration of the risk were uncertain. Given the convincing and persistent reduction in target vessel failure and TVR with DES, as well as evidence that indicates that mortality and MI rates are not different between DES and BMS patients, the panel unanimously agreed that, when used in accordance with their labeled indications, both the Cypher SES and the Taxus PES are safe and effective.
| Antiplatelet Therapy |
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The ideal duration of dual antiplatelet therapy for patients who receive on-label DES is unknown and the panel acknowledged that currently available data are insufficient to support a specific duration of dual antiplatelet therapy for all patients. The panel discussed the current (2005) American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions Guidelines for the Treatment of Patients Undergoing Percutaneous Coronary Intervention, which recommend thienopyridine treatment (75 mg clopidogrel daily), in addition to aspirin, ideally for up to 12 months after DES in patients at low risk for bleeding. Ultimately, the panel recommended addition of a synopsis of these guidelines to the current product label.
| Off-Label Drug-Eluting Stent Use |
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The panel reviewed data from a number of "real-world" stent registries (periapproval, single-center, multicenter, United Statesbased, and international) to assess the safety and effectiveness of DES. A summary of selected registries is displayed in Table 5. Data from FDA-mandated, postapproval, single-arm DES registries from Cordis (1 year follow-up) and Boston Scientific (2 year follow-up) were presented. Other registries were used to make outcome comparisons between DES and BMS, although it should be noted that the patients in these registries were not randomized, and the choice of stent was at the discretion of the treating physician. Therefore, it is uncertain whether observed differences between the 2 types of stents were caused by a true difference in the performance of the stents, or caused by other confounding factors (such as physician preference in the selection of a specific stent).
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Nevertheless, certain observations were consistent among the registries presented: 1) DES use results in a reduction in the need for TLR and TVR, and this benefit appears to persist for at least several years; 2) compared with on-label use, off-label DES use (like off-label BMS use) is associated with an increased risk of adverse events, such as death or the combined end point of death or nonfatal MI, which likely reflects the increased complexity of the patients and the lesions as noted above; 3) data are currently inadequate to assess the relative benefit of DES compared with BMS or DES compared with coronary artery bypass surgery in the off-label population. In particular, it is uncertain whether multivessel DES or coronary artery bypass grafting is the preferred approach for patients with multivessel disease. Data from several large-scale nonrandomized registries suggest that historical long-term survival with coronary artery bypass grafting may be better than multivessel stenting in selected patients, but again confounding factors may have contributed to these observations. The preferred treatment approach for these patients is unlikely to be established until the completion of prospective, randomized, controlled trials of cardiac surgery versus DES in the setting of multivessel disease.
The majority of registries suggested that no significant mortality difference existed between patients who received DES and those who received BMS. Similarly, data from the >19 000 patients in the Swedish Coronary Angiography and Angioplasty Registry with complete long-term follow-up for death and MI were presented, and the data demonstrated no significant difference between DES and BMS for death/MI (relative risk, 1.04; 95% confidence interval, 0.95 to 1.15) at 2.5 years of follow-up. Further analysis demonstrated an increased mortality risk after 6 months for DES compared with BMS (relative risk, 1.2; 95% confidence interval, 1.05 to 1.37), which was not observed in the first 6 months postimplantation (relative risk, 0.94; 95% confidence interval, 0.83 to 1.06). Importantly, this was a post hoc analysis not prespecified by design. In addition, because of the lack of randomization and potential differences in the DES versus BMS patient populations, the validity of these findings is uncertain.
| Stent Thrombosis and Dual Antiplatelet Therapy in the Off-Label Population |
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The ideal duration of dual antiplatelet therapy for off-label DES patients is unknown. For example, 1 report from the Northern California and Colorado Kaiser Permanente organization suggested that no additional protective effect of clopidogrel existed beyond 9 months of treatment for SES or 12 months of treatment for PES. Premature discontinuation, however, of dual antiplatelet therapy after DES implantation does appear to be associated with an increased risk of ST, death, and MI. These risks may be even higher in the off-label compared with the on-label use of DES. The panel highlighted the need for improved physician and patient education about this important issue and discussed methods to better inform the public about the risks of premature discontinuation of antiplatelet therapy.
In weighing the risks and benefits of extended dual antiplatelet therapy, the panel recognized that for some patients the increased risk of bleeding may be of the same or greater magnitude as the risk of stent thrombosis itself (
1% to 2%). Issues that affect medical compliance (eg, psychosocial, economic, and demographic) were also discussed. Most panelists agreed that dual antiplatelet therapy for at least 12 months should be advised for patients who receive DES in an off-label setting and who are not at high risk of bleeding, which is consistent with the current American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions Guidelines for the Treatment of Patients Undergoing Percutaneous Coronary Intervention. Patients who are unable to take dual antiplatelet therapy or who are not expected to adhere to uninterrupted dual antiplatelet therapy should be considered for alternative treatment strategies. Additional clinical studies to determine the ideal duration of antiplatelet therapy after DES implantation should be performed.
| Limitations of Registries |
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| Conclusions |
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| Acknowledgments |
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Dr Maisel is the chair and Dr Yancy is a member of the Circulatory System Devices Advisory Panel. Dr Laskey served as the previous chair of the Circulatory System Devices Advisory Panel and is a US Food and Drug Administration consultant. Dr Yancy has received research support from GlaxoSmithKline, Medtronic, and Scios Inc; and honoraria from GlaxoSmithKline, Novartis, Nitromed, and Scios Inc. He has served on the Speakers Bureau for GlaxoSmithKline and Novartis and as a consultant or advisory board member for GlaxoSmithKline and Nitromed.
| Footnotes |
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*A full transcript of the panel meeting may be found at http://www.fda.gov/ohrms/dockets/ac/cdrh06.html#circulatory. ![]()
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