Meta-Analysis: Cobalt-Chromium EES Cut Stent Thrombosis Compared with BMS, Other DES

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Cobalt-chromium everolimus-eluting stents (EES) achieve a lower risk of stent thrombosis at 2 years after implantation than not only other drug-eluting stents (DES) but also bare-metal stents (BMS), according to a meta-analysis published online March 23, 2012, ahead of print in the Lancet.

Gregg W. Stone, MD, of Columbia University Medical Center (New York, NY), and colleagues conducted a network meta-analysis of 49 randomized controlled trials (n = 50,884) comparing different DES or DES vs. BMS. Follow-up durations varied, with 24 studies assessing definite stent thrombosis through 2 years (n = 26,156). All stent designs included in the analysis are currently approved by the US Food and Drug Administration:

  • Cypher sirolimus-eluting stents (Cordis, Miami Lakes, FL)
  • Taxus Express and Liberté paclitaxel-eluting stents (Boston Scientific, Natick, MA)
  • Cobalt-chromium EES, marketed as Xience V (Abbott Vascular; Santa Clara, CA) and Promus (Boston Scientific)
  • Promus Element platinum-chromium EES (Boston Scientific)
  • Endeavor phosphorylcholine-based zotarolimus-eluting stents (Medtronic, Santa Rosa, CA)
  • Resolute zotarolimus-eluting stents (Medtronic)

Among the various devices, cobalt-chromium EES had the lowest risk of Academic Research Consortium (ARC)-defined definite stent thrombosis, even compared with BMS. The advantage over BMS was apparent at 30 days and lasted through 2 years. Cobalt-chromium EES also outperformed other DES (tables 1 and 2).

Table 1. Risk of Definite Stent Thrombosis: Cobalt-Chromium EES vs. BMS

 

OR

95% CI

30 Days

0.21

0.11-0.42

31 Days-1 Year

0.27

0.08-0.74

1 Year

0.23

0.13-0.41

2 Years

0.35

0.17-0.69

 
Table 2. Risk of Definite Stent Thrombosis: Cobalt-Chromium EES vs. Other DES

 

OR

95% CI

1 Year
Cypher
Taxus
Endeavor
Resolute

0.41
0.28
0.21
0.14

0.24-0.70
0.16-0.48
0.10-0.44
0.03-0.47

2 Years
Taxus

0.34

0.19-0.62


“The concept of a polymer-coated drug-eluting stent being safer than a bare-metal stent represents a paradigm shift,” the authors write, noting that cobalt-chromium EES are “characterized by thin struts coated with a durable, fluorinated, thromboresistant polymer,” qualities that may reduce stent thrombosis.

If the advantage is confirmed, ideally in an adequately powered large-scale randomized trial, it “would have profound clinical implications for patients with coronary artery disease,” they say.

Cautious Optimism

Asked whether the observed reductions in stent thrombosis are clinically relevant since the event is so rare, David E. Kandzari, MD, of the Piedmont Heart Institute (Atlanta, GA), was unequivocal. “Given that stent thrombosis is almost uniformly associated with death and/or MI, any opportunity to reduce its occurrence is meaningful,” he told TCTMD in an e-mail communication.

An editorial by John A. Ormiston, MB, ChB, of Mercy Hospital (Auckland, New Zealand), and Mark W.I. Webster, MD, of Auckland City Hospital, notes that cobalt-chromium EES “should [now] be regarded as the standard against which future design improvements are compared. These findings might also give pause to those who are developing stents with resorbable coatings with the thought that a so-called bare-metal-equivalent stent would be less thrombogenic.”

But like any meta-analysis, the current study should be regarded as hypothesis generating only, Drs. Ormiston and Webster stress.

They point out that ARC-defined definite stent thrombosis can underestimate the true incidence because of the need for angiographic or pathological confirmation. Because the event often presents as death or MI, they note, “[i]t would be reassuring if the differences between stents found in this study persisted” when using a composite endpoint.

Dr. Kandzari reported being “less certain regarding the suggestion that everolimus-eluting stents have a lower stent thrombosis rate than BMS, as this observation may be ‘assisted’ by other variables including evolution in technique (compared with more historical trials that incorporated BMS) and practice (namely, extended prescription of dual antiplatelet therapy [DAPT]).” He added that the advantage held by cobalt-chromium EES “does not appear unique” among DES, with Endeavor also showing lower stent thrombosis rates than BMS at 5 years in other studies.

Nor did the meta-analysis “include the longest duration of follow-up across trials. In many recent instances, it has been through long-term follow-up that differences, particularly in stent thrombosis, have emerged,” Dr. Kandzari commented. “For example, in SCAAR, significantly higher stent thrombosis was observed with Cypher at 3 years compared with Endeavor. Similarly, significant differences in very late stent thrombosis and cardiac/death MI were identified over 5-year follow-up in the ENDEAVOR IV trial. These data were not represented in this analysis.”

Both Dr. Kandzari and the editorial predict that a randomized controlled trial comparing cobalt-chromium EES and BMS is unlikely. “The only possible (but still unlikely) exception would be STEMI, given that there is still some perception of equipoise for this indication within the interventional community,” he said, mentioning an indication also proposed by the study authors. “Instead, it is likely more focus will be dedicated toward examining abbreviated durations of DAPT, and I believe these data, in addition to numerous observational studies with DES and variable DAPT durations, support such study.”

Note: Dr. Stone is a faculty member of the Cardiovascular Research Foundation (CRF), which owns and operates TCTMD. CRF also funded the research.

 


Sources:
1. Palmerini T, Biondi-Zoccai G, Della Riva D, et al. Stent thrombosis with drug-eluting and bare-metal stents: Evidence from a comprehensive network meta-analysis. Lancet. 2012;Epub ahead of print.

2. Ormiston JA, Webster MWI. Stent thrombosis: Has the firestorm been extinguished? Lancet. 2012;Epub ahead of print.

 

 

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Disclosures
  • Dr. Stone reports serving as a consultant for, receiving honoraria from, and holding stock or stock options from numerous drug and device companies.
  • Dr. Ormiston reports serving on advisory boards for and receiving honoraria from Abbott Vascular and Boston Scientific as well as receiving research funding from Abbott Vascular, Atrium Medical, Boston Scientific, Elixir Medical, Maya Medical, and Micell Technologies.
  • Dr. Webster reports receiving research funding from Abbott Vascular, Atrium Medical, Boston Scientific, Elixir Medical, Maya Medical, and Micell Technologies.
  • Dr. Kandzari reports receiving consulting fees, honoraria, and/or research support from Abbott Vascular, Boston Scientific, Cordis, Covidien, Medtronic, Micell Technologies, and Terumo Medical.

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