and Medicine for Seniors
Stent Patients Suffer Fewer Heart Attacks if
Anti-Clotting Meds Extended
Benefits extended if taken for more than standard
12 months - patients average age 62
Nov. 17, 2014 - Patients - average age 62 - who took
two anti-clotting medications beyond the standard 12 months after
stent placement were significantly less likely to develop blood
clots within their stents or to have a heart attack than those whose
treatment followed the 12-month protocol, according to
late-breaking clinical trial research presented at the American Heart
Association’s Scientific Sessions 2014.
“We know that dual antiplatelet therapy is essential for
all patients receiving coronary stents to prevent blood clots within the
stents (in-stent thrombosis). This study showed that the preventive
benefit continues when the medications can be taken for more than one
year,” said the study’s principal investigator and lead author, Laura
Mauri, M.D., M.Sc.
Investigators found that study participants who took
aspirin plus another type of anti-clotting medication (clopidogrel or
prasugrel) – for 30 rather than 12 months after stent placement:
● were .5 times less likely to develop in-stent
thrombos is than patients who received dual therapy for 12 months,
followed by aspirin plus placebo for 18 months (placebo group) and
● had about half the risk of having new heart attacks
compared to the placebo group.
“Overall the benefits of longer therapy were very
consistent throughout the types of patients we studied, and outweighed
the risks,” she said. The average age of patients in the study was 62.
A stent is a thin, wire-mesh tube inserted into a
blocked coronary artery to hold it open and restore blood flow. Although
infrequent, one of the most serious risks after stent placement is the
formation of a blood clot, either within the stent or in another blood
“The DAPT (Dual Antiplatelet Therapy) Study was the
first and only study comparing durations of treatment with antiplatelet
therapy that was adequately powered to detect a benefit on stent-related
heart attacks,” said Mauri, who is an interventional cardiologist at
Brigham and Women’s Hospital, associate professor of medicine at Harvard
Medical School and Chief Scientific Adviser at the Harvard Clinical
Research Institute in Boston, Massachusetts.
To prevent blood clots, standard post-stent treatment
involves dual treatment with aspirin and another anti-clotting
medication. European guidelines call for six to 12 months of this
treatment and U.S. guidelines recommend it for 12 months after the
What was unclear until now was whether extending this
combined treatment for longer than 12 months could decrease the risk of
in-stent thrombosis or whether it would prevent heart attack or stroke.
The safety of longer-term treatment was also assessed in this trial.
Although moderate to severe bleeding was more common
among the medication group than the placebo group in the study, fatal
bleeding was rare among both groups of patients.
While overall stroke rates and death rates were not
reduced by extending the combined treatment, the investigators noted in
a secondary analysis, including data beyond the time point after all
patients had stopped the study drug (to 33 months), that death from any
cause was 0.8 percent higher (2.3 percent vs, 1.5 percent) among the
medication group compared to those on placebo.
The study results were tracked during the study by a
data safety monitoring committee, but this difference in risk was not
evident until the end of the study, Mauri said.
A secondary analysis revealed that the higher death rate
was attributable to trauma and cancer.
“However, there was no difference in the occurrence of
new cancers,” Mauri said. “In retrospect, it appears that there may have
been an imbalance between the groups in the number of patients with
known cancer before enrollment in the study.
Taken together with results
from many other large studies of these medications, enrolling over
60,000 subjects worldwide, that show no difference in mortality, it
seems likely that this finding was related to a chance imbalance between
the groups studied in the trial.”
Prevention of heart attack and blood clots in stents
with longer antiplatelet therapy was consistent in all patient groups,
drug and stent types studied, Mauri noted, but “physicians should
consider individual patient risks in prescribing dual anti-clotting
therapy. In particular, the trial excluded patients with a history of
major bleeding either before the stent procedure or within the first
year of treatment.”
DAPT was a five-year, international study of 25,682
patients. 22,866 received drug-eluting stents, and of these 9,961
patients (average age 62, about 25 percent female, and mostly from the
United States) were randomized in the primary analysis.
investigators randomly assigned patients to one of the two groups, and
neither investigators nor patients knew who was receiving medication
versus placebo. The study took place from August 2009, to June 2014, at
more than 450 sites in the United States, Canada, Europe, Australia, and
Limitations of the study include the fact that it only
included patients who were known to have tolerated anti-clotting
medication for a year; and follow-up ended after 33 months, even though
the study data suggest that a longer course of treatment may provide
Co- principal investigator Dean Kereiakes, M.D., will
present the results comparing subjects treated with drug-eluting and
bare metal stents in a Clinical Science Special Report session (abstract
20113) on Tuesday, Nov. 18, 2014 at the Scientific Sessions.
Other authors and author disclosures are on the
manuscript. The Harvard Clinical Research Institute and the following
stent and pharmaceutical companies supported the study: Abbott; Boston
Scientific Corporation; Cordis Corporation; Medtronic, Inc.;
Bristol-Myers Squibb Company/Sanofi Pharmaceuticals Partnership; Eli
Lilly and Company; and Daiichi Sankyo Company Limited.