ESC 2019: Ultrathin strut Orsiro better than thin strut Xience for STEMI patients

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Thomas Pilgrim

One-year data from the BIOSTEMI study, simultaneously published in The Lancet and presented at the European Society of Cardiology Congress (ESC 2019; 31 August–4 September, Paris, France), indicate that patients with ST-segment elevation myocardial infarction (STEMI) who undergo percutaneous coronary intervention (PCI) with an ultrathin, sirolimus-eluting stent with a biodegradable polymer (Orsiro, Biotronik) have a significantly lower rate of target lesion failure than those who undergo PCI with a thin strut everolimus-eluting stent with a durable polymer (Xience, Abbott).

Writing in the Lancet, Juan F Iglesias (Division of Cardiology, Geneva Hospitals, Geneva, Switzerland) and colleagues report that a prespecified subanalysis of the BIOSCIENCE trial suggested a benefit of sirolimus-eluting biodegradable polymer stents over durable polymer everolimus-eluting stents They add: “The prothrombotic and inflammatory milieu in patients with acute STEMI poses particular challenges to vascular healing and stent-related clinical outcomes after primary PCI and might reveal the differences among stent platforms.”

According to Iglesias et al, to their knowledge, “there are no dedicated randomised controlled trials comparing newer-generation drug-eluting stents in the setting of acute STEMI”. Therefore, the aim of BIOSTEMI was to compare the biodegradable polymer stent Orsiro with the durable polymer Xience stent.

In the study, patients who had been referred for primary PCI for the management of acute STEMI were randomised to undergo PCI with Orsiro (649) or to Xience (651). The primary endpoint was target lesion failure (a composite of cardiac death, target vessel myocardial reinfarction and clinically indicated target lesion revascularisation) within one year of the index procedure.

The BIOSTEMI trial used a Bayesian approach, including information from the pre-specified STEMI subgroup enrolled into the BIOSCIENCE trial as a prior. While this approach reduced the number of study participants required to maintain appropriate power, study author Thomas Pilgrim (Department of Cardiology, Inselspital, University of Bern, Bern, Switzerland) told Cardiovascular News that “the Bayesian approach increases power provided that the findings in the patients recruited in the BIOSTEMI trial are consistent with the prior information from the BIOSCIENCE STEMI subgroup, but does not increase the likelihood of a positive outcome in case the null hypothesis is true that there is no real difference between stents.”

At one year, data were available for 614 patients who received Orsiro and for 626 patients who received Xience. The rate of the primary endpoint was 4% for the Orsiro group and 6% for the Xience group. The authors state: “The prespecified criterion for superiority of ultrathin strut biodegradable polymer sirolimus-eluting stents compared with thin strut durable polymer everolimus-eluting stents was met.” They add that this finding was “largely driven” by a lower rate of clinically-driven target revascularisation in the Orsiro group, noting that there were no differences in the rate of myocardial infarction between groups. By contrast, myocardial infarction drove the difference in target lesion failure between Orsiro and Xience in the BIOFLOW-V study. “The absence of a robust difference in the incidence of the incidence of target vessel myocardial infarction between the two treatment groups in our study might be explained by the difficultly in detection of periprocedural myocardial infarction in the setting of acute STEMI,” Iglesias et al comment.

They speculate that the difference in target lesion failure between the devices may relate to Orisro having a biodegradable polymer and/or because it has thinner stent struts (60μm vs. 81μm for Xience). “A reduction in strut thickness has been shown to mitigate inflammation, vessel injury, neointimal proliferation, and thrombus formation. These findings are particularly relevant in the inflammatory milieu of acute STEMI and might explain the differences we observed in the incidence of target lesion failure,” Iglesias et al state.

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