EuroPCR 2017: Status of bioresorbable scaffold technologies for clinical use
At the onset of EuroPCR, Robert Byrne, reporting on behalf of the ESC-EAPCI Task Force (formed in 2013), shared an evaluation of the current state of BRS and their use, stressing that the current evidence base is insufficient. For the basis of its report, the Task Force reviewed the rationale and unmet needs for BRS and established a “comprehensive” list of all BRS with CE mark or in clinical testing.The Task Force then undertook a systematic review of all published randomised controlled trials evaluating BRS up to October 2016, and invited the principal investigators of ongoing randomised controlled trials to share any upcoming data with the Task Force under a non-disclosure agreement. Proposals for evaluation and approval of BRS were then made.
R. Byrne noted that only one BRS has clinical outcome data from randomised controlled trials—the Absorb BRS (Abbott)—and that while “we are in a good place” when it comes to one-year outcomes for target lesion revascularisation, concerns remain regarding long-term performance and stent thrombosis, which the six Absorb randomised controlled trials showed to be twice as high as with conventional stents.
“Until these concerns can be assuaged, current-generation BRS should not be preferred to drug-eluting stents in routine practice,” R. Byrne said. He continued, suggesting that for those patients already treated with polymeric BRS, prolonged dual antiplatelet therapy (DAPT) should be considered (possibly out until the time of scaffold reabsorption). In addition, the Task Force came to the conclusion that there is currently insufficient data to make any recommendations on magnesium alloy BRS, and therefore further study of these devices is required.
Co-chair Jean Fajadet discussed the use and performance of BRS from a clinical perspective, analysing the randomised controlled trials on BRS and suggesting that the weaknesses of these trials are to blame for the lack of reliable BRS data. He told the audience that when using BRS, “We must respect the rules of patient selection, vessel sizing, systematic pre-dilatation, proper delivery of the scaffold, and systematic post dilatation. We also recommend long duration DAPT, even though there is no hard proof for it, and intra-coronary imaging evaluation, although this is optional.”
J. Fajadet noted that these rules were not frequently met in the BRS randomised controlled trials, hence the paucity of good-quality data. For example, in the pooled Absorb BRS data, full post dilatation was only performed in 10.4% of patients treated and high-pressure post dilatation was only performed in 12.8%. These failings, he said, could explain the high rate of scaffold thrombosis—two-year scaffold thrombosis rate for patients with full post-dilatation was 0.7% compared with 1.9% for not full post-dilatation—an adverse event which “is certainly amplified by the meta-analysis”. The rate could be reduced by “respecting the rules for optimal scaffold implantation, by applying strict procedural methodology, by employing DAPT for longer periods of time, and by the introduction of a new generation of BRS devices, with thinner struts, reduced footprint and polymer load,” J. Fajadet suggested.
Co-chair William Wijns then took to the stage to deliver PCR’s summary statements. “The concept that a stent does its job and disappears is a valuable long-term goal to pursue, especially in young patients with prolonged life expectancy,” Wijns said. “The currently available BRS are first-generation devices and show mechanical limitations when compared to current thin strut metallic drug-eluting stents. Only one BRS (Absorb) has been evaluated by randomised controlled trials up to medium-term follow-up, and mechanical limitations impose a restricted selection of lesion/vessel characteristics and demanding procedural techniques, infrequently applied in early trials and registries.”
“Clinical outcomes are inferior to results obtainable with state-of-the-art drug-eluting stents, with significantly increased risk of early and late definite and probable scaffold thrombosis. Post-hoc analysis according to vessel size and adequate procedural technique shows mitigation of scaffold thrombosis, while the potential protective role of prolonged DAPT is debated.”
W. Wijns concluded with a call to the interventional community to “protect the future of this technology by providing careful evaluation of next-generation devices by high-quality trials and registries”.