Abstract 10073: Characteristics of Very Late Stent Thrombosis Assessed by Coronary Angioscopy and Histopathology of Aspirated Thrombus

Abstract

Background: The mechanisms of very late stent thrombosis (VLST) have not been fully elucidated and may involve multiple factors. The aim of this study was to evaluate characteristics of VLST based on angioscopy and histopathology of aspirated thrombus. Methods: Coronary angioscopy was performed in all stent thrombosis cases to evaluate the culprit lesion. The mechanisms of VLST were divided according to two factors by angioscopic findings such as uncovered struts and neoatherosclerosis. Uncovered struts were defined as stent struts uncovered by neointima. Neoatherosclerosis was defined as stent struts covered by yellow neointima. Furthermore, aspirated material was collected for assessment of atherothrombotic characteristics in all cases. Results: From February 2011 to April 2015, emergency PCI for acute myocardial infarction was performed in 336 patients, with 13 of these cases due to stent thrombosis. Clinical characteristics of VLST patients are shown in Figure. In uncovered struts, all 3 cases were not on any antiplatelet therapy prior to VLST, whereas patients with neoatherosclerosis were taking at least one antiplatelet agents except for one case. In the presence of neoatherosclerosis, thrombus with atheroma material was aspirated in 5 of 10 cases despite there was no atheroma material in patients with uncovered strut. The time period of occurrence of VLST was significantly shorter in patients with uncovered strut compared with neoatherosclerosis (48.6±12.5 month vs. 84.3±6.9 month, p=0.03) In 13 case of VLST, peri stent contrast staining (PSS) was found in 1 case of each neoatherosclerosis and uncovered strut at the time of follow-up angiography. Conclusions: Discontinuation of dual anti platelet therapy was an important predictor for VLST, especially in patients with uncovered struts. However, most VLST weredue to neoatherosclerotic plaque rupture assessed by coronary angioscopy, which were also confirmed by histopathology of aspirated thrombus.