Patients who have a stent implanted to open a blocked coronary artery face dual risks of developing blood clots and of having excessive bleeding in the months following the procedure. While routine treatment with aspirin plus a second anti-clotting drug, known as dual antiplatelet therapy (DAPT), can prevent blood clots, these drugs may increase risk for bleeding, especially among patients who are older or in poorer health. For patients at either high or low risk of bleeding, the optimal duration of treatment to prevent blood clots without increasing bleeding risk following stent implantation has not been clear.
In a new study presented at the American College of Cardiology's Annual Scientific Session (ACC.25), South Korean researchers report that for patients at high risk for bleeding following stent implantation, three months of DAPT was better than one month at reducing heart attacks, strokes and other adverse events without increasing bleeding risk. For patients with a low risk for bleeding, the study found that three months of DAPT was comparable to 12 months for reducing adverse events and better than 12 months for reducing bleeding risk.
Ours is the first study to examine the question of the optimal DAPT duration in patients at both high and low risk of bleeding."
Hyo-Soo Kim, MD, PhD, professor of internal medicine at Seoul National University Hospital in South Korea and study's principal investigator
"Patients with high bleeding risk who received three months of DAPT experienced fewer deaths, heart attacks, blood clots in stents and strokes, with no increase in bleeding episodes, than patients who received one month of dual antiplatelet therapy," Kim said. "For patients with low bleeding risk, three months of dual antiplatelet therapy resulted in similar rates of adverse events and significantly fewer bleeding events compared with 12 months of therapy."
The trial, known as HOST-BR, enrolled 4,900 patients in South Korea, one-third of whom had high bleeding risk (HBR) and two-thirds of whom had low bleeding risk (LBR). In the HBR group, patients' average age was 73 years and 77% were men, while in the LBR group the average age was 63 years and 80% were men. All patients underwent a procedure to implant one or more stents in narrowed coronary arteries to prevent the arteries from becoming blocked. After stent implantation, the patients were randomly assigned to different durations of DAPT: one or three months in the HBR group and three or 12 months in the LBR group.
The study was designed with three primary endpoints that were assessed in the following order: first, all deaths, heart attacks, blood clots in stents, strokes and major bleeding episodes; second, deaths from heart disease or stroke, heart attacks, definite or probable blood clots in stents and strokes caused by a blockage of blood flow to the brain; and third, any episode of bleeding that needed medical attention. Patients were followed for 12 months.
At 12 months, in the HBR group, patients who received three months of DAPT did better on the first and second components of the primary endpoint than those who received one month of therapy (14.4% vs. 18.4%, respectively, for the first component; 6.4% vs. 10.3%, respectively, for the second component). Bleeding episodes (the third component) were not significantly different whether patients received one or three months of treatment (15.6% vs. 17.9%, respectively).
In the LBR group, outcomes were similar for patients in the three months and 12 months of treatment groups on the first and second components of the primary endpoint (4% vs. 5.7%, respectively, for the first component; 2.5% vs. 2.8%, respectively, for the second component). Patients receiving three months of treatment had significantly fewer bleeding episodes (the third component) than those who received 12 months of treatment (9.2% vs. 13.7%, respectively).
The researchers will continue to follow the patients in the study for up to three years to identify any long-term differences associated with different durations of DAPT.
The study is limited in that it was conducted entirely in South Korea. In addition, about 80% of patients in the study received clopidogrel as their second anti-clotting drug, which is the standard regimen in East Asia, Kim said. Previous randomized clinical trials have shown that patients in East Asia had better outcomes when treated with clopidogrel than with ticagrelor, a newer and more potent medication in the same class as clopidogrel that is used in other regions. These findings may not be applicable to all ethnic groups. Nevertheless, Kim said, the optimal duration of DAPT derived from this study might be applied to patients regardless of the drug type.
The study was funded by Medtronic, Inc., and Abbott Vascular, Inc.
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