The concept of a coronary-artery stent that could “fade away” after achieving its “mission” is extremely attractive, particularly in view of the longer term complications associated with intracoronary stents, including in-stent restenosis and endothelial dysfunction affecting coronary vasomotion which may impair clinical outcomes after PCI. In the past few years, two bioresorbable stents developed with the aim of improving long term outcomes, have received CE-mark approval i.e. the everolimus-eluting Absorb vascular scaffold system (Abbott Vascular) and the novolimus-eluting DESolve bioresorbable coronary scaffold system (Elixir Medical). A recent study by Ellis et al in the NEJM (1) reports on the efficacy of the Absorb scaffold system compared with the Xience (Abbott Vascular) conventional metallic everolimus-eluting stent, in 2008 patients with stable or unstable angina pectoris. In this large, multicenter, randomized trial, the primary end point, which was tested for both noninferiority and superiority, was target-lesion failure defined as cardiac death, target-vessel myocardial infarction, or ischemia-driven target-lesion revascularization, at 1 year. In the intention-to-treat analysis, the authors report a rate of the primary outcome of 7.8% in the Absorb group versus 6.1% in the Xience group, for a difference of 1.7 percentage points (95% confidence interval, −0.5 to 3.9; P=0.007 for noninferiority). Device thrombosis within 1 year occurred in 1.5% of patients in the Absorb group and in 0.7% of patients in the Xience group (P=0.13). Based on these results the authors concluded that the Absorb scaffold system was noninferior to the conventional drug-eluting metallic Xience system. The results are certainly of interest in relation to the future development of resorbable systems but several issues remain unresolved as highlighted in an editorial article also published in the NEJM (2). Cardiodebate has asked interventional cardiology expert Edoardo Camenzind, to comment on the clinical implications of the Ellis’ study (1).
References
- Ellis S et al for the ABSORB III Investigators, October 12, 2015DOI: 10.1056/NEJMoa1509038
- Byrne RA. October 12, 2015DOI: 10.1056/NEJMe1512331
Bio-resorbable vascular scaffold: the cornerstone of future coronary intervention landscape
Despite the improvement achieved with the use of newer generations of drug eluting stents (DES), some important issues remained unsolved such as persistent inflammation, loss of the normal vessel curvature, impaired vasomotion, and progression of atherosclerosis. The advent of bio-resorbable vascular scaffold (BVS) with its promise of anatomical and functional vascular restoration that should avoid the situation created by the current use of conventional stents that transform the coronary artery into a “stiff tube” encased by persistent metallic struts. Although this latter concept is intuitively attractive, promise alone is not enough to convince the interventional cardiology community.
Early clinical trials using first generation of BVS showed satisfactory efficacy and safety outcomes in comparison with best-in-class second generation DES. In a large multicenter randomized trial, Ellis et al. (1) compared the 1-year clinical outcome in patients with stable and unstable angina undergoing percutaneous coronary intervention (PCI) with everolimus-eluting Absorb vascular scaffold system (Abbott Vascular) vs. everolimus eluting cobalt chromium Xience (Abbott Vascular). In the intention-to-treat analysis, the authors report a rate of the primary outcome (target lesion failure) of 7.8% in the Absorb group versus 6.1% in the Xience group, for a difference of 1.7 percentage points (95% confidence interval, −0.5 to 3.9; p=0.007 for noninferiority). However, definite or probable stent thrombosis at 1 year was about twice as likely in Absorb patients compared with those receiving Xience stent. The issue of relatively high rates of scaffold thrombosis has also been reported in theliterature (2,3).
We believe that BVS will change the landscape of PCI in the future with the prediction that more than 50% of implanted stents will be BVS before 2020. However, further technical improvement and exhaustive clinical research trials are both still required. The reduction in strut thickness afforded by BVS could reduce flow disturbance and this may in turn reduce stent thrombogenicity. Furthermore, more favourable results could be obtained with the optimization of the implantation technique through the wider use of intracoronary imaging modalities. Needless to say that the issue of what would represent optimal anti-platelet therapy in the setting of BVS implantation has still to be determined. Finally, the encouraging results of the initial trials, if confirmed by currently ongoing clinical trials, are likely to extend BVS indications to different clinical settings and coronary lesion subsets.
References
- Ellis SG, Kereiakes DJ, Metzger DC, et al. Everolimus-Eluting Bioresorbable Scaffolds for Coronary Artery Disease. N Engl J Med. 2015 Nov 12;373(20):1905-15.
- Capodanno D, Gori T, Nef H, et al. Percutaneous coronary intervention with everolimus-eluting bioresorbable vascular scaffolds in routine clinical practice: early and midterm outcomes from the European multicentre GHOST-EU registry. EuroIntervention. 2015 Feb;10(10):1144-53.
- Sabaté M, Windecker S, Iñiguez A, et al. Everolimus-eluting bioresorbable stent vs. durable polymer everolimus-eluting metallic stent in patients with ST-segment elevation myocardial infarction: results of the randomized ABSORB ST-segment elevation myocardial infarction-TROFI II trial. Eur Heart J. 2015 Sep 23. pii: ehv500.
