Vascular pathology of drug-eluting stents

Polymer-based sirolimus- (Cypher) and paclitaxel-eluting stents (Taxus), so-called drug-eluting stents (DES), have become the treatment of choice for patients with symptomatic coronary artery disease undergoing percutaneous coronary revascularization (PCI). While these stents have reduced rates of restenosis and late lumen loss compared to bare-metal stents (BMS), late thrombosis, a life-threatening complication of this technology, has emerged as a major concern. Our understanding of the pathophysiology of late DES thrombosis is derived from animal and human pathologic samples taken after implantation of these devices. These data indicate that the DES cause substantial impairment in arterial healing characterized by lack of complete reendothelialization and persistence of fibrin when compared to BMS. This so-called delayed healing is "identified as" the primary substrate of an underlying cause of late DES thrombosis at autopsy. Several additional risk factors for late stent thrombosis include penetration of necrotic core, malapposition, overlapping stent placement, excessive stent length, and bifurcation lesions. These represent additional barriers to healing and should be avoided if DES are to be used in order to minimize the late thrombotic risks of these devices. Since the time course of complete healing with DES is unknown, the optimal duration of antiplatelet treatment remains to be determined.