Study Supports Use of Low-Dose Aspirin After Acute MI

Most patients undergoing stenting for acute MI in the United States receive high-dose aspirin at discharge despite this strategy being associated with higher rates of bleeding but no accompanying reduction in MACE compared with a lower dose. The bleeding difference is driven by minor events not requiring hospitalization, according to a study published online May 20, 2015, ahead of print in Circulation.

“Collectively, these findings provide empiric support for the current AHA/ACC guideline recommendations of aspirin 81 mg in preference to higher maintenance doses after PCI in the setting of an acute MI,” write Ying Xian, MD, PhD, of the Duke Clinical Research Institute (Durham, NC), and colleagues.

The researchers looked at data from the TRANSLATE-ACS study, which includes patients with STEMI or NSTEMI who undergo PCI during the index hospitalization and are treated with ADP receptor antagonists. The analysis included 10,213 patients (51.9% with STEMI) treated at 228 US hospitals between April 2010 and October 2012. Most (62.6%) received high-dose aspirin (325 mg/day) at discharge, with the rest receiving a low dose (81 mg/day).

In the first 6 months after discharge, MACE (death, MI, stroke, or unplanned revascularization) occurred with similar frequency in the high- and low-dose aspirin groups, but overall BARC-defined bleeding events, predominantly minor BARC type 1 or 2 bleeds not requiring hospitalization, were more common with high-dose aspirin (table 1). Results were unchanged after inverse probability-weighted propensity adjustment.

A substantial proportion of patients who received high-dose aspirin at discharge switched to a low dose by 6 weeks (19.2%) or 6 months (34.9%). The corresponding percentages of patients who switched from a low to a high dose were 7.8% and 7.9%, respectively, at the 2 time points. The main findings of the study were unchanged in landmark analyses that adjusted for these shifts.

The results also were generally consistent across subgroups defined by age, sex, home aspirin use, and type of ADP receptor antagonist used as part of the dual antiplatelet therapy regimen. However, the risks of any or minor BARC-defined bleeds associated with high-dose aspirin use were slightly greater in younger patients, men, those using aspirin before admission, and those prescribed prasugrel or ticagrelor (vs clopidogrel) at discharge.

No Added Benefit, Potential Harm From High-Dose Aspirin

Although high-dose aspirin is commonly prescribed in contemporary practice in the US, studies addressing the best maintenance dose after stenting are limited, the authors note.

In the CURRENT OASIS 7 trial, outcomes were similar regardless of aspirin dose, although follow-up was limited to 1 month. In addition, post hoc analyses of the CURE and CHARISMA trials showed similar reductions in cardiovascular events with high- or low-dose aspirin and similar or greater risks of bleeding with a high dose.

Based on those data, the American Heart Association and American College of Cardiology have modified their recommendations in recent years to support low rather than high aspirin doses as maintenance therapy after an acute MI.

Despite changes to the guideline recommendations, high-dose aspirin is still frequently used in US practice, the authors observe, noting that “there are few comparative data evaluating aspirin dose and long-term outcomes among contemporary MI patients—especially those who are concurrently treated with more potent ADP receptor inhibitors such as prasugrel and ticagrelor.” There were only 315 ticagrelor-treated patients in the current study, the authors note.

“Nonetheless, our data suggest no added benefit and potential harm of bleeding events associated with high-dose aspirin, regardless of whether clopidogrel or a more potent ADP receptor inhibitor was used,” they write. “In light of these results, low-dose aspirin appears to be a reasonable option for long-term maintenance therapy following PCI for all patients treated with clopidogrel, prasugrel, or ticagrelor.”

Xian Y, Wang TY, McCoy LA, et al. The association of discharge aspirin dose with outcomes after acute myocardial infarction: insights from the TRANSLATE-ACS study. Circulation. 2015;Epub ahead of print.

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