Thin- versus thick-strut polymer-free biolimus-eluting stents: the BioFreedom QCA randomised trial

Evolution of Coronary Stent Platforms: A Brief Overview of Currently Used Drug-Eluting Stents

Cardiovascular disease, including ischemic heart disease, is the leading cause of death worldwide, and percutaneous coronary interventions (PCIs) have been demonstrated to improve the prognosis of these patients on top of optimal medical therapy. PCIs have evolved from plain old balloon angioplasty to coronary stent implantation at the end of the last century. There has been a constant technical and scientific improvement in stent technology from bare metal stents to the era of drug-eluting stents (DESs) to overcome clinical challenges such as target lesion failure related to in-stent restenosis or stent thrombosis. A better understanding of the underlying mechanisms of these adverse events has led DESs to evolve from first-generation DESs to thinner and ultrathin third-generation DESs with improved polymer biocompatibility that seems to have reached a peak in efficiency. This review aims to provide a brief historical overview of the evolution of coronary DES platforms and an update on clinical studies and major characteristics of the most currently used DESs.

Comparison of 1-Month and 12-Month Vessel Responses Between the Polymer-Free Biolimus A9-Coated Stent and the Durable Polymer Everolimus-Eluting Stent

BACKGROUND

A polymer-free biolimus A9-coated stent (PF-BCS) may achieve better arterial healing than a durable polymer drug-eluting stent owing to its polymer-free feature.

METHODS AND RESULTS

This multicenter, prospective, observational study enrolled 105 patients (132 lesions) who underwent PF-BCS (51 patients, 71 lesions) or durable polymer everolimus-eluting stent (DP-EES, 54 patients, 61 lesions) implantation. Serial coronary angioscopy (CAS) and optical coherence tomography (OCT) examinations were performed at 1 and 12 months, and the serial vessel responses were compared between PF-BCS and DP-EES. The primary outcome measure was the incidence of subclinical intrastent thrombus on CAS. The secondary outcome measures were: adequate strut coverage (≥40 μm) on OCT and maximum yellow color grade on CAS. The incidence of thrombus was high at 1 month (100% vs. 93%, P=0.091), but decreased at 12 months (18% vs. 25%, P=0.56), without a significant difference between PF-BCS and DP-EES. The adequate strut coverage rate was significantly higher (84±14% vs. 69±22%, P<0.001) and yellow color was significantly less intense (P=0.012) at 12 months in PF-BCS than in DP-EES; however, they were not significantly different at 1 month (adequate strut coverage: 47±21% vs. 50±17%, P=0.40; yellow color: P=0.99).

CONCLUSIONS

Although the thrombogenicity of PF-BCS was similar to that of DP-EES, the adequate coverage and plaque stabilization rates of PF-BCS were superior to those of DP-EES at 12 months.

Polymer-free biolimus-coated stents versus ultrathin-strut biodegradable polymer sirolimus-eluting stents: two-year outcomes of the randomised SORT OUT IX trial

BACKGROUND

For patients with high bleeding risk, the BioFreedom stent is safer and more effective than a bare metal stent. However, at the one-year follow-up of the SORT OUT IX trial, the BioFreedom stent did not meet the criteria for non-inferiority for target lesion failure (TLF) when compared with the Orsiro stent and had a higher incidence of target lesion revascularisation (TLR).

AIMS

The aim of the study was to compare the two-year outcomes following coronary implantation of the BioFreedom or the Orsiro stents in all-comer patients.

METHODS

The Scandinavian Organization for Randomized Trials with Clinical Outcome (SORT OUT) IX trial is a prospective, multicentre, randomised clinical trial comparing the BioFreedom and the Orsiro stents. The primary endpoint, TLF, was a composite of cardiac death, myocardial infarction (MI; not related to other lesions) and TLR.

RESULTS

A total of 1,572 patients were randomised to treatment with the BioFreedom stent and 1,579 patients with the Orsiro stent. At two-year follow-up, TLF was 7.8% in the BioFreedom and 6.3% in the Orsiro stent groups (rate ratio [RR] 1.23, 95% confidence interval [CI]: 0.94-1.61). Risks of cardiac death, MI and definite stent thrombosis did not differ significantly between the groups, whereas more patients in the BioFreedom group had TLR (5.1% vs 2.6%; RR 1.98, 95% CI: 1.26-2.89) attributable to a higher risk of TLR within the first year (3.5% vs 1.3%; RR 2.77, 95% CI: 1.66-4.62).

CONCLUSIONS

At two years, there were no significant differences between the BioFreedom and Orsiro stents for TLF. TLR was significantly higher with the BioFreedom stent due to higher risk of TLR within the first year.

Overcoming challenges in refining the current generation of coronary stents

INTRODUCTION

Late stent thrombosis caused by delayed vascular healing and prolonged local inflammation were major drawbacks of 1^st generation drug-eluting stents (DES). Strut design, biocompatibility of polymer, and drug-release profiles were improved in 2^nd and 3rdgeneration DES. Accordingly, the indications for percutaneous coronary intervention with DES have been expanded to more complex patients and lesions. Despite these improvements, significant barriers such as greater flexibility in the duration of dual-antiplatelet therapy (DAPT) as well as reducing long-term stent-related events remain. To achieve ideal short- and long-term results, these existing limitations need to be overcome.

AREAS COVERED

We will discuss the current limitations of coronary DES and how they might be overcome from pathological and clinical viewpoints.

EXPERT OPINION

Optimizing DAPT duration after stent implantation and prevention of in-stent neoatherosclerosis are two major issues in current DES. Overcoming these drawbacks is a prerequisite toward achieving better short- and long-term clinical outcomes. New technologies including platform design, polymer types, and anti-proliferative agent itself might lead to further improvements. Although the initial experience with bioresorbable scaffold/stents (BRS) was disappointing, positive results of clinical studies regarding novel BRS are raising expectations. Overall, further device innovation is desired for overcoming the limitations of current DES.