No Risk in Stopping DAPT at Six Months: Endeavor

October 21, 2011

October 21, 2011 (Atlanta, Georgia) — An analysis of patients treated with the zotarolimus-eluting stent (Endeavor, Medtronic) suggests there is no increased risk of death, myocardial infarction, stroke, or stent thrombosis when stopping dual antiplatelet therapy (DAPT) with aspirin and thienopyridine therapy at six months [1].

"The majority of evidence suggests a consistent message that continuing DAPT beyond the initial six months of PCI does not prevent against the risk of stent thrombosis, which has been by far the major driver of extending DAPT to 12 months, if not a perception of lifetime commitment," lead investigator Dr David Kandzari (Piedmont Heart Institute, Atlanta, GA) stated in an email to heartwire .

The results, published October 20, 2011 in the Journal of the American College of Cardiology Interventions, are based on an analysis of 2032 patients undergoing PCI with the zotarolimus-eluting stent in the Endeavor clinical trials program. After three years of follow-up, the adjusted risk of individual ischemic events--death, myocardial infarction, stroke, and stent thrombosis--did not significantly differ between patients treated with DAPT for six months, more than 12 months, or more than two years. In addition, the composite risk of ischemic events did not statistically differ between treatment durations. Treatment with DAPT for six months was not associated with a higher risk of thrombotic events compared with patients treated for longer durations. Bleeding risks were similar across treatment durations and considered negligible.

"These data, along with additional recent trials evaluating differential DAPT durations, indicate that abbreviated DAPT duration may be safe and that inability to comply with 12 months of DAPT should not be considered an absolute contraindication to PCI with drug-eluting stents," according to Kandzari.

In an accompanying editorial [2], Drs Adnan Kastrati, Robert Byrne, and Stefanie Schulz (Deutsches Herzzentrum, Munich, Germany) state these data are consistent with previous observational studies, and suggest that a six-month duration of DAPT might be safe in certain patients treated with some drug-eluting stents. They point out, however, that such studies are limited in that they were not specifically designed to assess optimal DAPT duration and, as a result, are unable to guide clinical practice given the limitations of nonrandomized studies. While ongoing randomized clinical trials might provide some guidance in defining the optimal duration of DAPT, these studies are also unlikely to provide definitive recommendations for all patients.

"Optimal DAPT duration after drug-eluting stents will still be guided by a careful assessment of the balance between the risk of stent thrombosis and the likelihood of bleeding events at an individual patient level," write the editorialists.

The Dual Antiplatelet Therapy (DAPT) trial, which is currently under way, is comparing 12 vs 30 months of DAPT among 15 000 patients treated with drug-eluting stents. Led by Dr Laura Mauri (Harvard Clinical Research Institute, Boston, MA) and Dr Dean Kereiakes (Christ Hospital Heart and Vascular Center, Cincinnati, OH), the trial is powered to assess the primary efficacy end points of differences in stent-thrombosis rates and major adverse cardiovascular/cerebrovascular events (MACCE). The primary safety end point is major bleeding. An additional 5000 patients treated with bare-metal stents will also be enrolled.

To heartwire , Kandzari said he believes clinicians are not as interested in these longer durations as much as when it would be safe to stop thienopyridine therapy earlier in the course of treatment. He noted, however, that one of the ironies of the trial is that many clinicians who, after enrolling patients in DAPT, do not wish to take their eligible patients off dual therapy after one year. "This issue is the biggest one confronting not only interventional cardiologists, but many other healthcare practitioners, and yet it is one that has been most challenging to find support for study," Kandzari said.

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