Three-year follow-up of the randomised comparison between an everolimus-eluting bioresorbable scaffold and a durable polymer everolimus-eluting metallic stent in patients with ST-segment elevation myocardial infarction (TROFI II trial)

Introduction Previous midterm follow-up reports after implantation of the Absorb™ everolimus-eluting bioresorbable scaffold (BRS; Abbott Vascular, Santa Clara, CA, USA) in stable coronary artery disease and acute coronary syndrome have shown an increase of scaffold thrombosis leading to an excess of the device-oriented composite endpoint (DOCE: a composite of cardiac death, target vessel myocardial infarction [TVMI], and clinically driven target lesion revascularisation [CD-TLR])1. In contrast, in the six-month primary report of ABSORB STEMI: the TROFI II Study (NCT01986803)2, which randomised patients with ST-elevation myocardial infarction (STEMI) to receive either the Absorb BRS or the XIENCE metallic everolimus-eluting stent (EES; Abbott Vascular), optical frequency domain imaging (OFDI)-derived healing score was comparable between the BRS arm and the EES arm. The aim of this report was to present the three-year clinical outcome results of the BRS and the metallic EES at the time when full resorption of the scaffold device can be expected. Methods The trial design and methods, as well as the study population, have been described in previous reports2. Follow-up information at three years was available in 100% of the study population (Figure 1). All clinical events were adjudicated by an independent clinical events adjudication committee. Time-to-event variables were compared by log-rank test. Results Clinical outcomes at three years are tabulated in Table 1. At three years, the rates of DOCE were 5.3% (5/95) in the BRS arm and 3.1% (3/96) in the EES arm without a statistically significant difference (p=0.465). There were two cardiac deaths (2.1%) in the BRS arm: one was adjudicated as cardiac death on day 280 since no information was available as the patient died overseas. The autopsy of the second patient who died on day 999 revealed no evidence of scaffold thrombosis. There were no cardiac deaths in the EES arm. Discussion Three years after implantation of BRS or EES, in the setting of primary PCI, the rates of DOCE and ST were low and not significantly different between both arms. It is of note that there were no cases of ST after two years, while most of the patients in both arms discontinued dual antiplatelet therapy between one and two years (Supplementary Table 1). The three-year clinical results are in line with the comparable OFDI-derived healing scores2 and neointimal quality3 at six months. In addition, the recent report in the subpopulation of the current cohort showed a better vasomotion in BRS than in EES and similar microcirculatory function as well as healing score at three years4. Although routine thrombectomy is not recommended in the recent guidelines, in treating STEMI patients with BRS, thrombectomy could facilitate better scaffold sizing to achieve better long-term outcome. In the substudy of the present trial4, intraluminal dismantling was observed by OCT in 26.3%. However, the fact that the substudy only included event-free patients precludes the understanding of the clinical implication of intraluminal dismantling. Limitations The trial was not powered to evaluate clinical endpoints. The implantation technique reflects the state of the art at the time of enrolment in 2014 and did not take into account the more recent findings on BRS usage in terms of size selection, lesion preparation and deployment technique. It remains to be elucidated whether the comparative clinical outcomes in this study performed in STEMI patients will be maintained after three years. Conclusions Three years after implantation of BRS or EES, in the setting of primary PCI, the rates of DOCE and ST were low and not significantly different between both arms. The three-year clinical results are in line with the comparable healing scores observed at six months. However, the study was not powered to assess clinical endpoints.