Introduction: Anticoagulants appear to be more effective than aspirin in preventing thromboembolism in patients with atrial fibrillation (AF), with no increase in the risk of bleeding. Despite the evidence for the limited efficacy and poor safety of aspirin, as well as for the diminished role of aspirin in recent guidelines, it is still commonly used in AF patients. (1-3) Our aim was to assess the association of aspirin therapy with the prevalence of left atrial thrombosis (LAT) in patients with AF.

Patients and Methods: We performed an observational study involving 131 patients with AF who underwent transesophageal echocardiography in our institution during the period from January 2011 until January 2015, and who were not on any form of anticoagulation therapy. According to history of aspirin therapy, we divided them into two groups: Group 1 (patients on aspirin) and Group 2 (patients without aspirin). The presence of LAT was evaluated in both groups. We also analyzed thromboembolic risk according to the CHA2DS2-Vasc score system.

Results: Out of 131 patients, 51 (38.9%) were on aspirin. The prevalence of LAT in the Group 1 as compared to the Group 2 was 6/51 vs. 5/80, respectively, p=0.43. The two groups did not differ in the proportion of intermediate to high thromboembolic risk patients according to the CHA2DS2-Vasc score system 44/51 vs. 67/80, respectively, p=0.59.

Conclusion: Our study shows that therapy with aspirin is not associated with less prevalence of LAT in patients with AF in comparison to patients who were not on any anticoagulation/antiplatelet therapy. Therefore, we believe that aspirin should not be the drug of choice for prevention of thromboembolic events in patients with AF. Due to the small number of patients, our study was underpowered, but our results correlate with larger studies and recent guidelines recommendations.