T he advent of coronary stents in conjunction with potent adjunctive medical treatment has resulted in substantial improvements in the efficacy and safety of percutaneous coronary interventions (PCIs).1 Although infrequent, stent thrombosis remains an important concern because of its sequelae, including myocardial infarction and death in up to 80%. 2,3 Early stent thrombosis is largely independent of stent type and mainly related to procedural variables, including major edge dissections and stent underexpansion. 4 Conversely, the mechanisms underlying very late stent thrombosis (VLST), occurring beyond 1 year after drug-eluting stent (DES) implantation, remain poorly defined, and the translation of mechanistic insights into therapeutic approaches is unsatisfactory. Despite an attenuation of the risk for VLST with the use of newer-generation DES, which is similar to that of bare metal stents, the accumulated long-term risk is still notable. Clinical Perspective on p 660Because of its high resolution (10-20 μm), optical coherence tomography (OCT) has become the imaging modality of choice for the in vivo assessment of stent failures, including VLST. 5 As a result of the infrequent encounter of this Background-The pathomechanisms underlying very late stent thrombosis (VLST) after implantation of drug-eluting stents (DES) are incompletely understood. Using optical coherence tomography, we investigated potential causes of this adverse event. Methods and Results-Between August 2010 and December 2014, 64 patients were investigated at the time point of VLST as part of an international optical coherence tomography registry. Optical coherence tomography pullbacks were performed after restoration of flow and analyzed at 0.4 mm. A total of 38 early-and 20 newer-generation drug-eluting stents were suitable for analysis. VLST occurred at a median of 4.7 years (interquartile range, 3.1-7.5 years). An underlying putative cause by optical coherence tomography was identified in 98% of cases. The most frequent findings were strut malapposition (34.5%), neoatherosclerosis (27.6%), uncovered struts (12.1%), and stent underexpansion (6.9%). Uncovered and malapposed struts were more frequent in thrombosed compared with nonthrombosed regions (ratio of percentages, 8.26; 95% confidence interval, 6.82-10.04; P<0.001 and 13.03; 95% confidence interval, 10. 13-16.93; P<0.001, respectively). The maximal length of malapposed or uncovered struts (3.40 mm; 95% confidence interval, 2.55-4.25; versus 1.29 mm; 95% confidence interval, 0.81-1.77; P<0.001), but not the maximal or average axial malapposition distance, was greater in thrombosed compared with nonthrombosed segments. The associations of both uncovered and malapposed struts with thrombus were consistent among early-and newer-generation drug-eluting stents. Conclusions-The leading associated findings in VLST patients in descending order were malapposition, neoatherosclerosis, uncovered struts, and stent underexpansion without differences between patients treated with early-and new...

Background-Biodegradable polymers for release of antiproliferative drugs from drug-eluting stents aim to improve vascular healing. We assessed noninferiority of a novel ultrathin strut drug-eluting stent releasing sirolimus from a biodegradable polymer (Orsiro, O-SES) compared with the durable polymer Xience Prime everolimus-eluting stent (X-EES) in terms of the primary end point in-stent late lumen loss at 9 months. Methods and Results-A total of 452 patients were randomly assigned 2:1 to treatment with O-SES (298 patients, 332 lesions) or X-EES (154 patients, 173 lesions) in a multicenter, noninferiority trial. The primary end point was in-stent late loss at 9 months. O-SES was noninferior to X-EES for the primary end point (0.