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Compared with bare metal stents (BMS), drug-eluting stents (DES) reduce rates of restenosis and repeat procedures in the target vessel after percutaneous coronary intervention (PCI). However, there is growing concern that DES may be associated with higher risks for late thrombosis, which can lead to myocardial infarction or death. Two observational studies provide new insights.
The first study included 746 patients from a randomized trial of DES and BMS. Patients who survived 6 months without major events were enrolled in a longer-term follow-up study after clopidogrel was discontinued at 6 months. The overall rates of cardiac death and MI were similar in DES and BMS patients at 18 months, but the rates from months 7 through 18 were higher in DES than in BMS patients (4.9% vs. 1.3%). Documented late thrombosis and associated death or MI occurred in 2.6% of DES patients and 1.3% of BMS patients. Conversely, restenosis requiring target-vessel revascularization remained less common in DES patients than in BMS patients (hazard ratio, 0.52).
The second study included 4666 patients receiving stents (about one third drug-eluting). In DES patients who had no major events during the first 6 months, longer-term use of clopidogrel was associated with significantly lower rates of death (2.0% among those still using clopidogrel vs. 5.3% among those not using it) and the combined endpoint of death or MI (3.1% vs. 7.2%) at 24 months. In contrast, longer-term clopidogrel therapy was not associated with reduced event rates in BMS patients. Event rates were lowest in patients receiving DES and clopidogrel.
Pfisterer M et al. Late clinical events after clopidogrel discontinuation may limit the benefit of drug-eluting stents: An observational study of drug-eluting versus bare-metal stents. J Am Coll Cardiol 2006 Dec 19; 48:2584-91.
Eisenstein EL et al. Clopidogrel use and long-term clinical outcomes after drug-eluting stent implantation. JAMA 2006 Dec 5; [Epub ahead of print]. (http://dx.doi.org/10.1001/jama.297.2.joc60179)
Harrington RA and Califf RM. Late ischemic events after clopidogrel cessation following drug-eluting stenting: Should we be worried? J Am Coll Cardiol 2006 Dec 19; 48:2592-5.
Comment
Taken together, these observational studies suggest that late thrombosis may be more common in patients who receive drug-eluting stents than in those who receive bare metal stents after clopidogrel is discontinued, and that continuing clopidogrel therapy may reduce rates of death or MI. However, as editorialists note, given the relatively small numbers of events involved and the limitations of observational data, a randomized study will likely be required to provide definitive answers concerning the risk for late thrombosis and the optimal duration of clopidogrel therapy.