Level 2: Mid-level evidence

Dual antiplatelet therapy (DAPT) is recommended for at least 12 months in patients having a percutaneous coronary intervention with a drug-eluting stent to reduce the risk of restenosis (Circulation. 2011;124[23]:e574-e651).

Extending the duration of DAPT may decrease the risk of stent thrombosis, but evidence on the efficacy of DAPT for greater than one year has been inconsistent (Am J Cardiol. 2014;114[2]:236; Am J Cardiol. 2013;111[4]:486). A recent randomized trial compared 12 versus 30 months of treatment with thienopyridine (clopidogrel or prasugrel) plus aspirin in 9,961 patients (mean age, 62 years; 75% male) having drug-eluting stent implantation (N Engl J Med. 2014;371[23]:2155).

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All patients were treated with DAPT for 12 months before being randomized to thienopyridine versus placebo for an additional 18 months, while aspirin therapy was continued indefinitely. Between study months 12 and 30, extended 30-month DAPT was associated with reduced stent thrombosis (0.4% vs. 1.4%; P<0.001; NNT 100) and reduced major adverse cardiovascular and cerebrovascular events (4.3% vs. 5.9%; P<0.001; NNT 63), compared with standard 12-month DAPT. Extended 30-month DAPT was not without risks, however, as extended DAPT was associated with increased risk of moderate-to-severe bleeding (2.5% vs. 1.6%; P=0.001; NNH 111).

On further analysis, an increased risk of bleeding was observed for moderate bleeding only, with no significant differences in severe bleeding between groups. All-cause mortality during the 18-month randomization period was 2% in patients with extended DAPT versus 1.5% with placebo (P=0.05). Increased risk of stent thrombosis and myocardial infarction were observed for the first three months after thienopyridine discontinuation, regardless of treatment duration.

This trial suggests that increasing the duration of DAPT to 30 months after implantation of a drug-eluting stent decreases the risk of stent thrombosis, as well as major cardiovascular and cerebrovascular events.

Extended DAPT therapy was associated with a small increase in all-cause mortality, but this finding was driven by an increase in cancer-related deaths in patients with a cancer diagnosis before randomization. The difference in all-cause mortality between groups was no longer significant when patients with cancer diagnoses before randomization were excluded from analysis.

Alan Ehrlich, MD, is a deputy editor for DynaMed, in Ipswich, Mass., and assistant clinical professor in Family Medicine, University of Massachusetts Medical School in Worcester.

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