Varying Safety, Efficacy of Approved Stents

June 01, 2012

June 1, 2012 (New York, New York) — A comprehensive meta-analysis of randomized, clinical trials that tested approved drug-eluting stents (DES) against each other or bare-metal stents (BMS) has shown that DES are highly effective in reducing target vessel revascularization (TVR) compared with BMS and are not associated with an increased risk of adverse outcomes, including stent thrombosis [1].

Overall, there is large difference in the performance of the DES types, with the everolimus-eluting stent (EES), sirolimus-eluting stent (SES), and the newest-generation zotarolimus-eluting stent (ZES) being the most efficacious, and the everolimus-eluting stent having the lowest rates of myocardial infarction and stent thrombosis compared with BMS.

"In terms of safety, stent thrombosis is definitely on the top of the list, but death and myocardial infarction are also on it as well," lead investigator Dr Sripal Bangalore (New York University School of Medicine) told heartwire . "The analysis was interesting in that we showed none of the currently approved DES have safety concerns. There was no increased stent thrombosis when compared with BMS. What was surprising to us was the fact that the EES actually decreased the risk of stent thrombosis when compared with BMS."

Dr Sunil Rao (Duke University Medical Center, Durham, NC), an interventional cardiologist who was not involved in the analysis, told heartwire that the results confirm the clinical opinions of the majority of practicing physicians that the everolimus-eluting Xience V (Abbott) and zotarolimus-eluting Resolute (Medtronic) are highly efficacious stents, but noted that safety is what really interests operators given previous concerns of stent thrombosis and mortality with DES. "It's refreshing to see that the newer platforms and continued iterations of these devices have translated not only into improved efficacy, but also safety," he said.

Large meta-analysis with significant patient–years

The meta-analysis included 76 randomized, controlled trials with 117 762 patient–years of follow up. Of these studies, 60 trials used clopidogrel for at least six months and mean duration of follow up was 2.1 years. The six stent types studied included BMS, which was used as the reference, SES, paclitaxel-eluting stents (PES), EES, and the older- and newer-generation ZES.

In evaluating the short-term efficacy of the stents over less than one year, all of the DES reduced TVR from 39% to 61% compared with BMS, with the magnitude of reduction varying by stent type. SES, EES, and the newest-iteration ZES (Resolute) each reduced the risk of TVR by 74%, 72%, and 69%, respectively, and PES and the older ZES reduced TVR by 53% and 52%, respectively. These results were largely similar when target lesion revascularization was the clinical outcome assessed.

"In terms of efficacy, we had a sort of three-way tie between the SES, EES, and the newer Resolute stent," said Bangalore. "Again, it's an interesting finding as the SES — the Cypher stent — is no longer going to be on the market. Johnson & Johnson decided they aren't going to pursue working on it, but even though it's a first-generation stent, it has stood the test of time and shown that it is as comparable as other stents in terms of efficacy."

Compared with BMS, there was no increased risk of death with any of the DES: the median short-term mortality rate was < 0.3% for all stents. For all the DES, there were significant reductions in risk of myocardial infarction compared with BMS, although no reduction was observed with PES. Compared against BMS, there was no increased risk of stent thrombosis with any of the stents. In contrast, EES reduced the risk of stent thrombosis by 56% compared with BMS, and also decreased the risk of stent thrombosis compared with SES, PES, and ZES. The median stent thrombosis rate for any stent was < 0.2%, including 0.18% with BMS and < 0.10% with EES.

"In terms of safety with stents, as of now, the benchmark has been BMS," said Bangalore. "These results suggest we might have to rethink what our benchmark should be in terms of safety in future clinical trials. Perhaps it might be the everolimus stent." Rao agreed, telling heartwire he believes that if a new stent emerges it should be able to prove that it is at least as safe as the EES.

Long-term analysis

In long-term analyses, defined as greater than one year, mortality and myocardial infarction findings were similar to those observed in the short term. Long term, there was a significant 18% to 37% reduction in risk of myocardial infarction with all DES compared with BMS, with the exception of PES. Overall, EES had the lowest myocardial infarction rate. Regarding the long-term safety of the stents, 'any' stent thrombosis rates were similar for DES compared with BMS, with the exception of EES which showed a significant 49% reduction in the risk of stent thrombosis. For between-stent comparisons, SES had lower rates of stent thrombosis than PES, and EES was superior to SES, PES, and the older ZES.

Rao said that the study also underscores the fact that the risk of late stent thrombosis is not zero with BMS. The analysis by Bangalore and colleagues, which Rao praised for being well conducted and evaluated, was basically an "all-comers" study and would likely include a lower-risk population than physicians might see in clinical practice. "Even if we're going to use BMS, we do have to be cognizant of the fact that there is a risk associated with those devices," said Rao. He pointed out that the Xience V stent recently received CE Mark approval as a stent that requires only three months of dual antiplatelet therapy, suggesting that some stent-thrombosis panic is starting to be dialed down a little bit.

Overall, Bangalore said the results provide a "scorecard" for physicians evaluating safety and efficacy of the stents for specific patients and would allow them to select a stent that best fits their patients' risk profile. He noted that previous studies, including registry data from Europe, have suggested a reduction in stent thrombosis among those treated with EES. He believes that the reduction in risk might be a combination of the stent characteristics, including improved biocompatibility, as well as an increased awareness of the need for dual antiplatelet therapy.

Bangalore and Rao report no conflicts of interest.