Short-term DAPT linked to more heart attacks than extended treatment

Long-term dual antiplatelet therapy (DAPT) should remain the standard of care following implantation of drug-eluting stents, suggests research presented March 12 at the American College of Cardiology’s annual scientific session and published simultaneously online in The Lancet.

Principal investigator Hyeon Cheol Gwon, MD, and colleagues studied outcomes in 2,712 South Korean patients—75 percent male; average age 63—who were randomized to DAPT for at least 12 months or DAPT for six months followed by aspirin treatment alone. While the combined rate of death, heart attack and stroke weren’t significantly different between the two groups, those in the six-month DAPT group demonstrated more than double the risk of myocardial infarction (MI) within 18 months.

"Based on our findings, we can't say that short-term DAPT is safe in patients with ACS (acute coronary syndrome) who have received drug-eluting stents," Gwon, director of the cardiac center at Samsung Medical Center in Seoul, South Korea, said in a press release. "We conclude that current guidelines that recommend prolonged DAPT in patients with ACS who are not at excessive risk for bleeding should continue to be followed."

The trial is the largest so far to address the optimal length of DAPT—a combination of aspirin and a P2Y12 inhibitor—in patients with ACS. It was designed to show noninferiority of short-term DAPT versus long-term DAPT. The duration of this treatment course has been debated in previous reports as clinicians try to balance the benefits of antiplatelet therapy with their penchant for increased bleeding risk.

A total of 63 patients in the short-term group met the primary endpoint of all-cause death, MI and stroke at 18 months compared to 56 patients in the long-term DAPT group (4.7 versus 4.2 percent). This difference wasn’t statistically significant, in contrast to the heart attack rates.

MIs occurred in 1.8 percent of patients in the six-month DAPT group and 0.8 percent of patients in the 12-month or longer DAPT group—a 2.4-fold difference. Notably, after the short-term DAPT patients transitioned to aspirin alone (six to 18 months), they showed a 5.1-fold risk of heart attack compared to those receiving DAPT for at least a year.

The risk of meeting the primary endpoint was also 69 percent higher for short-term DAPT patients during that period, suggesting the nonsignificant overall trend toward more all-cause deaths, strokes and MIs was driven by the timeframe after the treatments diverged.

Limitations of the study include the lack of blinding of both patients and doctors, as well as the absence of a placebo group. Gwon said the researchers plan to follow these patients for an additional 18 months to reach three total years of follow-up.