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Although drug-eluting stents (DES) are associated with lower restenosis rates after percutaneous coronary intervention (PCI) than are bare-metal stents (BMS), concerns about risk for late thrombosis with DES have prompted multiple studies designed to assess their pros and cons.
Two studies showed that, once clopidogrel was discontinued, late-thrombosis rates were higher in DES patients than in BMS patients. In one study, clopidogrel was discontinued at 6 months in 746 patients who received DES or BMS. Overall, rates of myocardial infarction and death were similar in the two groups at 18 months. However, between months 7 and 18, significantly more MIs and deaths (4.9% vs. 1.3%) and late thromboses associated with death or MI (2.6% vs. 1.3%) occurred in the DES group. In another study, 4666 patients who received stents were studied. Among patients without major adverse events at 6 months, discontinuing clopidogrel therapy was a predictor of both death or MI and all-cause death at 24 months for DES patients but not for BMS patients (Journal Watch Jan 4 2007).
In a third study, researchers followed more than 8000 patients for 3 years after they received DES. Angiographically proven stent thrombosis occurred in 1.1% of patients within 30 days and in 0.6 per 100 person-years thereafter. Most late thromboses occurred after clopidogrel was discontinued (Journal Watch Mar 20 2007).
In response to these data, experts from multiple groups issued a clinical advisory stating that premature discontinuation of dual antiplatelet therapy after DES placement is associated with increased risk for stent thrombosis; they recommended that patients with DES and low risk for bleeding should receive at least 12 months of dual antiplatelet therapy (followed by lifelong aspirin therapy). They also recommended that any elective surgery that is associated with substantial risk for bleeding be postponed until dual antiplatelet therapy is complete — i.e., 1 month for BMS and 12 months for DES patients (Journal Watch Feb 15 2007).
Five studies of DES, both sirolimus-eluting (SE) and paclitaxel-eluting (PE), were published simultaneously in March 2007. Three groups pooled data from randomized trials of SE and PE stents versus BMS. Overall mortality and MI rates were similar for DES and BMS patients, but late stent thromboses were more common with both drug-eluting DES than with BMS, although event numbers were small. A fourth group reported pooled stent thrombosis data from 14 trials of DES and BMS; overall, thrombosis rates were similar for DES and BMS. However, rates were higher for DES after 1 year. Finally, in a registry study of almost 20,000 stent recipients, adjusted 6-month mortality was significantly higher with DES than with BMS (Journal Watch Mar 1 2007).
These studies all confirmed that repeat revascularization of the target vessel was less common after DES placement. More recent data from a meta-analysis of more than 18,000 patients in 38 DES versus BMS trials showed that short-term mortality was similar in all groups (hazard ratios, 1 for SE stents vs. BMS and 1.03 for PE stents vs. BMS). However, SE stents fared better than PE stents for preventing MI, target-vessel revascularization, and late thrombosis (Journal Watch Oct 23 2007).
Studies of “real-world” stent use suggest that off-label use of DES is so common that data from trials might not be representative. In two studies, 47% and 55% of DES were used in off-label situations. The rate of in-hospital and 1-year complication rates for off-label use was roughly twice those seen for approved uses (Journal Watch May 15 2007).
What should we make of all this? This year’s studies have not put the controversy of DES versus BMS to rest. Risk for late thrombosis with DES, although low, is real, which prompted the recommendation for extending dual antiplatelet therapy. The optimal duration remains unknown. In general, DES are preferable in situations where their beneficial effects on restenosis outweigh their thrombosis risk, but, practically, stent choice is made on an individual patient basis, taking into account diverse factors such as patient and lesion characteristics, drug adherence, and need for surgical procedures.