A meta-analysis published by The Lancet shows that cobalt-chromium everolimus-eluting stents have much lower short-term and long-term stent thrombosis rates than both bare metal stents and all other drug-eluting stents.

While drug-eluting stents outperform bare metal stents in terms of efficacy (fewer re-narrowings), the cobalt-chromium everolimus-eluting stent is the first to have lower thrombosis rates than bare metal stents during follow-up.

The authors, led by Professor Gregg W Stone (Columbia University Medical Center/ New York-Presbyterian Hospital and the Cardiovascular Research Foundation, New York, NY, USA) say that the results, if confirmed in future studies, could result in a paradigm shift in how we view the safety of drug-eluting stents.

Stents are inserted into an artery when patients have suffered a cardiovascular event such as a heart attack or stroke.

They are metallic tubes that allow blood flow to return to normal in that blood vessel. However, blood clots can quickly or gradually build up within the stent (thrombosis), which frequently causes a heart attack and may even be fatal. The relative safety of drug-eluting stents and bare-metal stents, especially with respect to stent thrombosis, continues to be debated.

Ever since drug-eluting stents were approved for use in patients, the belief was that they were not as safe as bare metal stents. However, in view of the overall low frequency of stent thrombosis, large sample sizes are needed to accurately estimate treatment differences between stents. Thus the authors compared the risk of thrombosis between bare-metal and drug-eluting stents.

49 trials involving some 50,000 patients were analysed, the largest study to date of the relative safety of drug-eluting and bare metal stents from randomized trials. 1-year definite stent thrombosis was 77% lower with cobalt-chromium everolimus eluting stents (CoCr-EES) than with bare-metal stents. The significant difference in stent thrombosis between CoCr-EES and bare-metal stents was evident as early as 30 days (a 79% lower risk) and was also significant between 31 days and 1 year (73% lower risk).

CoCr-EES were also associated with rates of 1-year definite stent thrombosis that were 72% lower compared with paclitaxel-eluting stents, 59% lower compared with permanent polymer-based sirolimus-eluting stents, 79% lower than for phosphorylcholine-based zotarolimus-eluting stents, and 86% lower than for Resolute zotarolimus-eluting stents.

At 2-year follow-up, CoCr-EES were associated with 65% lower rates of definite stent thrombosis than were bare metal stents and 66% lower rates than in paclitaxel-eluting stents. No other drug-eluting stent had lower definite thrombosis rates compared with bare-metal stents at 2-year follow-up.

Currently, drug-eluting stents are used in 40-95% of patients, depending on the country, with CoCr-EES the most widely used drug-eluting stent. But many other drug-eluting stents are also used in tens of thousands of patents, and the relative safety and efficacy of them is hotly debated.

The authors say: “Potentially the most important and unexpected finding of this study is the significantly lower risk of stent thrombosis with CoCr-EES compared with bare-metal stents at 1-year and 2-year follow-up. Although drug-eluting stents are more effective than bare-metal stents in reducing restenosis, their safety has continued to be questioned in view of the ongoing propensity of first-generation drug-eluting stents for very late stent thrombosis.”

They conclude: “The finding that CoCr-EES also reduced stent thrombosis compared with bare-metal stents, if confirmed in future randomised trials, represents a paradigm shift.”

In a linked Comment, Dr John A Ormiston, Mercy Hospital, Auckland, New Zealand, and Dr Mark W I Webster, Auckland City Hospital, Auckland, New Zealand, say: “The low rate of stent thrombosis in the first 2 years after deployment of CoCr-EES is very reassuring. On this basis, CoCr-EES should 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.”

Source: The Lancet