incidence of late stent thrombosis after successful cypher stent implantation

Stent thrombosis is a rare but devastating complication of coronary stent implantation. Coronary stent deployment is associated with a low incidence of acute and sub-acute thrombosis. However, late stent thrombosis has been recognized clinically. The aim of this prospective study was to evaluate the incidence of late stent thrombosis in patients receiving sirolimus-eluting stents. One hundred patients [132 lesions] who underwent implantation of sirolimus eluting stents were selected. All patients were pre-medicated with 325 mg of aspirin, which was continued indefinitely. Anti-thrombotic regimens, including intravenous heparin and a loading dose of clopidogrel [300 mg] were given in the catheterization laboratory and clopidogrel 75 mg/day was continued for at least 6 months. In patients allergic to clopidogrel, ticlopidine at a dose of 250 mg twice daily was prescribed as a substitute. Late stent thrombosis was defined as myocardial infarction characterized by anginal symptoms with ST-elevation on the electrocardiogram and creatine kinase-MB elevation > 3 times the upper limit of normal with angiographic documentation of partial or total stent occlusion more than 30 days after sirolimus eluting stent implantation [while the stented segment was the culprit lesion]. Complete 2 year follow-up was available for all patients. Between 30 days to 2 years after sirolimus-eluting stent implantation, 2 patients [2%] experienced late stent thrombosis at a mean time of 420 days [range 360 to 480]. This study reports a very late stent thrombosis after 20 months of sirolimus eluting stent implantation and 15 months after cessation of clopidogrel treatment, despite continued aspirin administration. This study also implies the possible need for long term antiplatelet therapy among patients receiving sirolimus eluting stents