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Thrombosis
Volume 2012 (2012), Article ID 608593, 16 pages
http://dx.doi.org/10.1155/2012/608593
Review Article

Pathologic Etiologies of Late and Very Late Stent Thrombosis following First-Generation Drug-Eluting Stent Placement

Department of Cardiovascular Pathology, CVPath Institute Inc., 19 Firstfield Road, Gaithersburg, MD 20878, USA

Received 10 September 2012; Accepted 23 October 2012

Academic Editor: Karin Przyklenk

Copyright © 2012 Fumiyuki Otsuka et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Several randomized and observational studies have reported steady increase in cumulative incidence of late and very late ST (LST/VLST) following first-generation drug-eluting stents (DES: sirolimus-(SES) and paclitaxel-(PES)) up to 5 years. Pathologic studies have identified uncovered struts as the primary substrate responsible for LST/VLST following DES, where delayed arterial healing is associated with stent struts penetrating into the necrotic core, long/overlapping stents, and bifurcation stenting especially in flow divider region. Grade V stent fracture also induces LST/VLST and restenosis. Hypersensitivity reaction is exclusive to SES as an etiology of LST/VLST, whereas malapposition secondary to excessive fibrin deposition is associated with PES. Uncovered struts can be identified in SES and PES with duration of implant beyond 12 months, particularly in stents placed for “off-label” indications. Neoatherosclerosis is another important contributing factor for VLST in DES and bare metal stents (BMS); however, DES shows rapid and more frequent development of neoatherosclerosis than BMS. Future pathologic studies should address the long-term safety of newer generation DES including zotarolimus- and everolimus-eluting stents in terms of the improvement in reendothelialization, decreased inflammation and fibrin deposition as well as a lower incidence of stent fracture-related adverse events, and reduced neoatherosclerosis, which likely contribute to the decreased risk of LST/VLST and better patient outcomes.