Evaluate efficacy and safety of Indobufen v. Aspirin in preventing thromboembolic events in patients at high risk of CV events such as patients suffering from nonrheumatic atrial fibrillation.

Inclusion Criteria:

• Chronic or paroxysmal non rheumatic atrial fibrillation with cardioembolic risk factors: hypertension, ischemic cardiopathy, Congestive Heart Failure, diabetes mellitus

Exclusion Criteria:

• Clinically relevant organ disease
• creatinine clearance < 30 ml/min
• gastric or duodenal ulcer
• severe anaemia or poliglobulia