Since the introduction of coronary drug-eluting stents in 2002, the platform has steadily improved, from refinements in durable polymers and drug delivery methods, to improvements in stent architecture and strut thickness, all of which have led to enhanced clinical outcomes. Despite initial concerns about increased rates of late and very late stent thrombosis with drug-eluting stent use in STEMI patients, clinical evidence supporting the use of DES mounted, culminating with the adoption of DES in STEMI in the clinical practice guidelines in 2014.
Recently, even newer generation of stents have been introduced. This includes the Osiro (Biotronik, Burach, Switzerland) drug-eluting stent, which features an ultrathin metallic strut (60 mm at sizes £ 3.0 mm diameter and 80 mm at sizes > 3.0 mm diameter) and an absorbable poly-L lactate polymer and the anti-proliferative drug sirolimus. The Osiro stent was previously tested in the BIOSCIENCE trial, which was an all-comers trial of PCI. Although clinical outcomes were similar between the two groups, a subgroup analysis of the BIOSCIENCE trial suggested that STEMI patients treated with Osiro had reduced target lesion failure.
The BIOSTEMI trial was a single-blind trial of patients with STEMI (including cardiogenic shock and cardiac arrest) randomized to primary PCI with the Osiro stent or Xience (Abbott Vascular) DES. Patients and treating physicians were aware of treatment allocation, but outcomes reviewers were blinded to treatment group. The primary endpoint was target lesion failure, a composite of cardiac death, target vessel myocardial infarction, and clinically indicated target vessel revascularization. The authors used an advanced Bayesian methodology to estimate events rates based on the historical data from the BIOSCIENCE study, allowing for a smaller sample size in BIOSTEMI In all, 1,300 patients were randomized: 649 to Osiro and 651 to Xience DES.
The 2-year results of the BIOSTEMI are largely consistent with the 1-year results (Iglesias JF et al., Lancet, Sept. 2019), demonstrating a lower incidence of target lesion failure in the Osiro group (5.1%) versus the Xience group (8.1%; RR 0.58 [95% CI 0.40-0.84], Bayesian posterior probability, 0.998). The difference in TLR was driven primarily by a lower incidence of clinically indicated target lesion revascularization in the Osiro group versus the Xience group (2.5% versus 5.1%, respectively; RR 0.52 [95% CI 0.30-0.87], posterior probability 0.993). There was no significant difference in cardiac death (3.2% versus 2.9%), target vessel myocardial infarction (2.0% versus 1.5%) or stent thrombosis between the Xience and Osiro groups, respectively.
Taken together, these results suggest that the ultra-thin strut Osiro bioabsorbable polymer drug-eluting stent is at least as efficacious, or perhaps superior, to durable polymer DES in patients with STEMI. Some interventionalists may interpret these results with caution, however. First, the authors used a complex statistical methodology, incorporating historical data in a Bayesian analysis to reduce enrollment size while avoiding type 1 error. The statistical methods will be unfamiliar to the majority of readers. Second, the lack of blinding of treatment group to the patient and treating physician is a subtle, yet meaningful limitation, especially given that the difference in primary endpoint was driven mostly by target lesion revascularization, a softer endpoint than cardiac death or target vessel myocardial infarction.These limitations aside, it is remarkable that, given the excellent performance of contemporary drug-eluting stents, the Osiro bioabsorbable polymer demonstrated a better clinical performed than Xience, especially given the low background rate of follow up events after DES implantation for patients with STEMI.