Optimal antiplatelet regimen in ‘bi-risk’ ACS?

The high bleeding risk criteria were female gender, iron deficiency anemia, stroke, taking a type 2 diabetes medication, and chronic kidney disease.

The high ischemic risk criteria included troponin-positive ACS, previous stent thrombosis, previous CV events (MI, stroke, peripheral artery disease [PAD], percutaneous coronary intervention [PCI]), on a type 2 diabetes medication, chronic kidney disease, and certain lesion characteristics.

The patients had a mean age of about 65 years and 41% were female. 

About half (52%) had type 2 diabetes, 18% had previous MI, and 15% had previous ischemic stroke. The ACS was mainly unstable angina (62%), followed by NSTEMI (17%) or STEMI (21%).

The patients had a mean high ischemic risk criteria of 3.2 and a mean high bleeding risk criteria of 1.4.

The initial DAPT treatment was aspirin and clopidogrel in three quarters of the patients and aspirin and ticagrelor in the remaining patients.

At 9 months, the primary endpoint of BARC type 2-5 bleeding occurred in 2.5% of patients in the clopidogrel plus placebo group and in 3.3% of patients in the clopidogrel plus aspirin group (hazard ratio, 0.75; 95% confidence interval, 0.57-0.97, P = .03).

“The bleeding results are not surprising,” Dr. Lopes said. Monotherapy vs. DAPT will cause less bleeding, Dr. Han agreed.

At 9 months, MACCE occurred in 2.6% of patients in the clopidogrel plus placebo group and in 3.5% of patients in the clopidogrel plus aspirin group (HR, 0.74; 95% CI, 0.57-0.96, P = .02).

Interpreting this latter finding as “reduced risk” of MACCE “is a stretch,” Dr. Lopes cautioned.

A potential explanation for this finding in the trial is that in the comparison group (aspirin plus clopidogrel), when patients had bleeding, they might have stopped all antiplatelet therapy, and this may have led to more ischemic events, he speculated.

“The observed reduction in MACCE is plausible,” Dr. Han said. “However, according to study protocol, we assumed that clopidogrel monotherapy would be noninferior to DAPT on the risk of MACCE. The superiority of clopidogrel alone vs. DAPT on MACCE should therefore be hypothesis-generating.”

“The increased rate of MACCE in the clopidogrel plus aspirin group was surprising,” she said in a press release from the ESC, “and may be because hemorrhagic events, which are more common with ongoing DAPT, could be associated with an adrenergic state with increased platelet aggregation due to hypotension, remedial procedures to treat bleeding, and the cessation of anti-ischemic medications.”
 

A low-risk subset of bi-risk patients, commonly seen in clinical practice

At the time of the index ACS, more than 60% of the patients had unstable angina, Dr. Lopes observed, “and we know these patients are lower risk.” Also, more than 1,000 of the patients did not have at least one high-risk factor for bleeding or ischemia. Moreover, these patients had not had any clinical events in the past 9-12 months on DAPT, “so they were not truly high risk when they were randomized.

“Patients aged 75 years and above are definitely bi-risk (even without any bleeding/ischemic criteria), especially post ACS, according to much literature,” Dr. Han said.

“Although patients met the bi-risk criteria for increased ischemia and bleeding at the time of index ACS and PCI, they were free from major events for at least 6 months on DAPT, thus constituting a relatively low-risk subset of bi-risk patients,” she conceded.

“Nonetheless, these patients (mean age nearly 65 years, 41% female, 52% diabetes, 18% MI history and 15% ischemic stroke history in bi-risk study) represent a large cohort seen in clinical practice,” she said. And “according to a real-world, nationwide registry from China (the OPT-CAD study), unstable angina accounted for about 50% of all ACS patients.”

There have been more data with shorter times for stopping aspirin, so it’s difficult to reconcile those studies with data from OPT-BIRISK, according to Dr. Lopes.

For example, the 2019 TWILIGHT study in patients undergoing PCI at high risk for bleeding showed that it seems to be safe to stop aspirin after 3 months and continue ticagrelor, without an increase in ischemic events.

“The question is almost in the wrong time,” he said, noting that the field is moving in the direction of stopping aspirin earlier, according to five or six recently published trials.

It is hard to generalize from an Asian population, he agreed. “In the U.S., we have other data that suggests that for high-risk patients, you can stop aspirin earlier than 9 months. That’s what most practices are doing.”

“When you look at different drugs, different doses, different duration,” Dr. Lopes summarized, “you have thousands of different permutations,” for antiplatelet therapy strategies. “Every time we have some data in large studies it adds a piece to the puzzle.”

The study was funded by the National Key Research and Development Project in China, and by a grant from Sanofi-Aventis. Dr. Han reports no relevant financial relationships. Disclosures for the other coauthors can be found with the original article.

A version of this article first appeared on Medscape.com.