Alternate-day dosing of aspirin in atrial fibrillation

Background In inhibiting platelet function, aspirin seems to reduce the risk of cerebrovascular accidents, death, and acute coronary events in patients with nonrheumatic atrial fibrillation. Aspirin given on alternate days might have the advantage of not hindering prostacyclin synthesis. Thus a study was performed to evaluate whether aspirin used in this way might improve the results reported with daily treatment. Methods To test this hypothesis 285 patients (age range 40 to 82 years) with primary atrial fibrillation were randomly allocated in an open multicenter trial to 3 groups: (1) group A1, treated with 125 mg aspirin daily (n = 104); (2) group A2, treated with 125 mg aspirin on alternate days (n = 90), (3) group C (controls), who were not treated with anticoagulants or platelet inhibitors (n = 91). Results Inclusion took place from January 1990 to July 1994, and follow-up ended in May 1996 (range 1 to 62 months). Sudden cardiac death in association with heart failure or angina was the most common final event: 4.8%, 1.1%, and 6.6% in groups A1, A2, and C, respectively. Both cardiovascular mortality rate and the incidence of main events were reduced, in relative terms, by 80% (1.1% in group A2 vs 6.6% in group C). The differences were smaller between group A1 and C but did not reach statistical significance. The reduction of main cardiovascular events between groups A1 and A2 was statistically significant (7.7% vs 2.2% = 5.5%; 95% confidence limits 1%, 11%; P < .05). The difference did not reach statistical significance when other end points were analyzed. Conclusion In this trial low-dose aspirin given on alternate days seemed to be an efficient intervention in preventing major cardiovascular events. Regarding strokes, however, aspirin was less efficient. Mortality rate in the 3 groups as a whole was associated with heart failure and the development of ischemic heart disease. (Am Heart J 1999;138:137-43.)