Mechanisms of Very Late Bioresorbable Scaffold Thrombosis: The INVEST Registry

Background Very late scaffold thrombosis (VLScT) occurs more frequently after bioresorbable scaffold (Absorb BVS 1.1, Abbott Vascular, Santa Clara, California) implantation than with metallic everolimus-eluting stents. Objectives The purpose of this study was to elucidate mechanisms underlying VLScT as assessed by optical coherence tomography (OCT). Methods The INVEST (Independent OCT Registry on Very Late Bioresorbable Scaffold Thrombosis) registry is an international consortium of investigators who used OCT to examine patients with VLScT. Results Between June 2013 and May 2017, 36 patients with 38 lesions who had VLScT underwent OCT at 19 centers. VLScT occurred at a median of 20 months (interquartile range: 16 to 27 months) after implantation. At the time of VLScT, 83% of patients received aspirin monotherapy and 17% received dual-antiplatelet therapy. The mechanisms underlying VLScT were (in descending order) scaffold discontinuity (42.1%), malapposition (18.4%), neoatherosclerosis (18.4%), underexpansion or scaffold recoil (10.5%), uncovered struts (5.3%), and edge-related disease progression (2.6%). Discontinuity (odds ratio [OR]: 110; 95% confidence interval [CI]: 73.5 to 173; p < 0.001), malapposed struts (OR: 17.0; 95% CI: 14.8 to 19.7; p < 0.001), and uncovered struts (OR: 7.3; 95% CI: 6.2 to 8.8; p < 0.001) were more frequent in the thrombosed than the nonthrombosed scaffold regions. In 2 of 16 patients with scaffold discontinuity, intercurrent OCT before VLScT provided evidence of circularly apposed scaffold struts with minimal tissue coverage. Conclusions The leading mechanism underlying VLScT was scaffold discontinuity, which suggests an unfavorable resorption-related process, followed by malapposition and neoatherosclerosis. It remains to be determined whether modifications in scaffold design and optimized implantation can mitigate the risk of VLScT.