Six months of dual antiplatelet therapy (DAPT) was found to be non-inferior in ST-elevation myocardial infarction (STEMI) patients to the internationally recommended 12-month regimen in a pioneering trial presented at the 29th annual Transcatheter Cardiovascular Therapeutics (TCT) conference in Denver.

The study, authored by Elvin Kedhi, MD, PhD, and colleagues, was the first of its kind to evaluate the outcomes of shorter DAPT therapies in STEMI patients. The American Heart Association, American College of Cardiology and European Society of Cardiology have all published guidelines encouraging a one-year minimum for DAPT after primary percutaneous coronary intervention (PCI) with drug-eluting stents, because longer-duration therapy reduces the risk of ischemic events in vulnerable STEMI patients. However, longer DAPT treatment also increases the risk of major bleeding events in these individuals, which can lead to complications and fatalities.

DAPT STEMI was a prospective, randomized trial that ultimately enrolled 870 STEMI patients who had undergone primary PCI with a second-generation zotarolimus-eluting stent and were event-free six months after surgery. Second-generation stents have lower stent thrombosis risks than their first-generation counterparts, according to the research, possibly lowering the harmful risks of shorter-duration DAPT.

The trial initially employed 1,100 subjects across the Netherlands, Switzerland, Poland and Norway, Kedhi said at a press conference Wednesday, but the pool was narrowed when a handful of subjects had either experienced an adverse event by the six-month mark or withdrew their consent to participate in the study. Kedhi said it was difficult for his team to enroll patients in a trial that negated established recommendations.

“Having to change this mentality, it was almost impossible to convince people to go for six months of DAPT,” he said, though “the bleeding risk was very low” for six-month therapy.

Remaining patients were randomized to either single antiplatelet therapy (SAPT) or DAPT, with both cohorts well-matched in baseline characteristics. The groups saw similar results after 12 and six months, respectively, suggesting a six-month DAPT regimen was non-inferior to a yearlong one.

The study’s primary endpoints included all-cause mortality, any myocardial infarction, any revascularization, stroke or thrombolysis in myocardial infarction. Rates of mortality differed the most—0.7 percent in SAPT patients versus 1.4 percent in DAPT patients—but all other endpoints were nearly identical in outcome.

“For the first time in the modern drug-eluting stent era, this trial indicates that STEMI patients, similar to stable angina patients, may not benefit from prolonged DAPT therapy beyond six months as currently recommended,” Kedhi said in a TCT release. “This sets the stage for further dedicated research on this important topic.”

Kedhi said he is part of a team working on a follow-up study known as Onyx ONE, which will aim to explore the results of one-month DAPT treatment in a large, global patient population.