Bioresorbable Scaffolds

ioresorbable scaffolds (BRSs) were designed to reduce adverse events related to permanent metallic stents by providing temporal mechanical support and subsequent complete resorption. The BRS hypothesis was built on the assumption that the absence of metallic caging would facilitate full restoration of vasomotion, induce luminal enlargement and plaque burden reduction, and, most important, mitigate lesion-related events compared with permanent metallic drug-eluting stents (DESs). Although a total of 8 BRSs have entered clinical evaluation, the Absorb BVS is the only one that was extensively tested. A decade ago, Ormiston et al 1 reported the results of the first-in-human ABSORB cohort A study using the Absorb BVS 1.0 polymeric BRSs. Reinforcement of the mechanical performance and prolongation of its mechanical integrity for a longer period of time led to second-generation Absorb BVS 1.1, which was approved in Europe in 2011 and subsequently in the United States in 2016. To date, the Absorb BVS has been compared with newer generation metallic everolimus-eluting stents in 10 000 patients from 9 randomized controlled trials covering a wide range of patient subsets (ie, all-comer population, 2 ST-segment-elevation myocardial infarction [STEMI], 3 complex lesions 4 ). The initial expectation of being on par with metallic DES before complete degradation was not fulfilled. A detailed patient-level synthesis including 3389 study participants with follow-up of 3 years (ie, before complete degradation) reported an increased risk of target vessel myocardial infarction and target lesion revascularization (TLR) and concerning hazards of device thrombosis occurring early and late after device implantation. 5 These findings were confirmed by a large all-comers trial at a follow-up of 3 years. 2 Although the risk of TLR was subsequently much improved by a rigorous implementation of all the lessons learned (eg, avoiding small vessels and applying BVS-specific implantation protocols with routine predilatation and postdilatation) in the ABSORB IV trial 6 and the COMPARE-ABSORB trial 4 (ABSORB Bioresorbable Scaffold vs Xience Metallic Stent for Prevention of Restenosis in Patients at High Risk of Restenosis), the concerns about device thrombosis continued. It is disappointing that other prophecies beyond the failed mitigation of device-related events could not be confirmed. Vasoreactivity was not different between Absorb BVS and the metallic counterpart at 3 years, 7 and in the same study, late lumen enlargement was limited to 25% of lesions 8 and to 6.4% in the ABSORB Japan trial. he increased hazards for device thrombosis are attributable to various BVSspecific properties, including less radial force, expansion limits, thicker struts, limited biocompatibility of poly-l-lactic acid and the extensive time until degradation, leading to new resorption-related failure mechanisms such as scaffold dismantling (Figure).