Cobalt-chromium everolimus-eluting stents show lowest thrombosis rates at two years


A meta-analysis published online in The Lancet and presented at the American College of Cardiology’s (ACC) 61st Annual Scientific Session in Chicago, USA, shows that cobalt-chromium (Co-Cr) everolimus-eluting stents (Xience, Abbott Vascular) 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, 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 Tulio Palmerini, Istituto di Cardiologia, Policlinico S Orsola, Bologna, Italy, and 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.

“The relative safety of drug-eluting stents and bare metal stents, especially with respect to stent thrombosis, continues to be debated. In view of the overall low frequency of stent thrombosis, large sample sizes are needed to accurately estimate treatment differences between stents. We compared the risk of thrombosis between bare-metal and drug-eluting stents,” the authors wrote.

Forty nine trials involving 50,844 patients were analysed, the largest study to date of the relative safety of drug-eluting and bare metal stents from randomised trials. One-year definite stent thrombosis was 77% lower with cobalt-chromium everolimus eluting stents than with bare metal stents. The significant difference in stent thrombosis between CoCr-everolimus-eluting stent and bare metal stents was evident as early as 30 days (a 79% lower risk) and was also significant between 31 days and one year (73% lower risk).

CoCr-everolimus-eluting stents were also associated with rates of one-year definite stent thrombosis that were 72% lower compared with paclitaxel-eluting stents (Taxus, Boston Scientific), 59% lower compared with permanent polymer-based sirolimus-eluting stents (Cypher, Cordis), 79% lower than for phosphorylcholine-based zotarolimus-eluting stents (Medtronic), and 86% lower than for Resolute zotarolimus-eluting stents (Medtronic).

At two-year follow-up, CoCr-everolimus-eluting stents 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 two-year follow-up.

Currently, drug-eluting stents are used in 40–95% of patients, depending on the country, with CoCr-everolimus-eluting stents 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-everolimus-eluting stents compared with bare-metal stents at one-year and two-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.”

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

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