WASHINGTON, D.C.--"We don’t know when it is safe to stop dual-antiplatelet therapy after drug-eluting stent (DES) implantation," said Laura Mauri, MD, of Brigham and Women’s Hospital in Boston, during a Feb. 6 presentation at the Cardiovascular Research Technologies (CRT) meeting.

“Since we don’t know when it’s safe, there is a broad variation in practice,” she added, “even among physicians within the same country.”

To get a more definite answer, Mauri reviewed some recent data:

• The TIMI-TRITON 38 substudy, which assessed the utilization of dual-antiplatelet therapy (DAPT) beyond 12 months, found that it was highly variable across different geographies. Specifically, in North America, the study found that more than 50 percent of patients are treated with DAPT beyond 12 months, and 50 percent are treated with DAPT for less than 12 months. “Outside of North America, it is more common to administer a shorter duration [of DAPT], but even that has variation across countries,” she said.
• The Duke Registry, a single-center landmark analysis of a relatively small number of patients, found that in DES patients, there was a lower risk of death and MI associated with longer clopidogrel use at 24 months, compared with 12 months. “While this is observational data, which cannot be seen as conclusive, these data suggest that there could be a benefit to longer therapy,” Mauri said.

To truly compare retrospective DAPT, researchers must consider the goals for the patients associated with that comparison, according to Mauri, who noted the balance of ischemic and bleeding risks. “We know that stent thrombosis is a rare event when DES is used, but it does have a profound significance, with a high mortality rate.” 

The data required to understand stent thrombosis are not available in registries, and the “presence of even a small confounder in observational studies can result in really biased results because it’s such a rare event,” she said. “As a result, large and inclusive, randomized trials have been needed to better understand what the correct dual-antiplatelet is following the implantation of a DES.”

One study, the DAPT trial, on which Mauri is the principal investigator, includes patients who have either received a DES or a bare-metal stent, and are followed for one year. Unless otherwise contraindicated, the patients will be randomized to receive 12 months or 30 months of DAPT. The primary endpoints are stent thrombosis and the composite of death, MI or stroke. In addition, there is a powered safety endpoint to assess bleeding. The DAPT trial, which is currently enrolling 26,000 participants, is on track to reveal its results in 2014.

Until these results emerge, the current guidelines, issued by the American College of Cardiology, the American Heart Association and the Society for Cardiac Angiography and Interventions, suggest that 12 months of DAPT is “very reasonable,” Mauri concluded.