Analyzing contemporary dosing patterns after a myocardial infarction (MI), new research suggests that a low-dose aspirin is safer and provide similar efficacy compared to a high-dose aspirin. Published Aug. 12 in Circulation: Cardiovascular Quality and Outcomes, and shepherded by Hurst Hall, MD, Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, the study challenged U.S. guidelines which have historically viewed higher doses of aspirin more favorably than the country's international counterparts.

Gathering data from 221,199 patients with MI – 40.2 percent of which endured ST-segment-elevation MI – from 525 hospitals enrolled in the ACTION Registry – GWTG, the investigation defined high-dose aspirin as 325 mg and low dose as 81 mg. Spanning 2007 to March 2011, 60.9 percent of patients with acute MI were discharged on high-dose aspirin, while 35.6 percent were on low-dose aspirin, and 3.5 percent were on other doses. Of patients treated with percutaneous coronary intervention, 44.6 percent were managed medically, while 73 percent were prescribed high-dose aspirin at discharge.

Performing an observational analysis, results showed no significant difference in efficacy for low-dose aspirin (less than or equal to 100 mg) compared to high-dose aspirin (equal or greater than 200 mg), but an increase in bleeding complications with high-dose aspirin. These findings were similar among patients prescribed aspirin monotherapy compared to dual antiplatelet treatment with aspirin and clopidogrel. Looking at major adverse cardiac events between patients with acute coronary syndrome randomized to high- (300-325 mg) vs. low-dose (75-100 mg) aspirin also revealed no significant differences, though there was a higher incidence of gastrointestinal bleeding with high-dose aspirin compared with low-dose aspirin.

The most comprehensive analysis of U.S. practice patterns of aspirin dosing following MI, Hall and his colleagues' hospital analysis suggest that local and institutional practice habits play a substantial role in high-dose aspirin use, with a surprisingly large variation in aspirin dosing from hospital to hospital. Hall et al. observed a 25-fold variance among hospitals in the proportion of patients discharged on high-dose aspirin, with some facilities discharging less than 10 percent of high-dose aspirin and others discharging 100 percent of patients on high-dose aspirin. Based on these findings, moving forward, the authors recommend redesigning hospital-based treatment pathways and suggest adding aspirin dosing to hospital-based quality reports so that they are more strategically aligned to current practice patterns and guideline recommendations.

Keywords: Registries, Myocardial Infarction, Acute Coronary Syndrome, Ticlopidine, Habits, Hemorrhage, Percutaneous Coronary Intervention, National Cardiovascular Data Registries, ACTION Registry