[Isolated atrial fibrillation. The risk of embolism and its prevention].

Whether or not atrial fibrillation is alone, if not idiopathic, is difficult to determine. The risk of embolization in lone atrial fibrillation is distinctly higher in healthy subjects over 60 years of age when the left atrium is dilated. In chronic atrial fibrillation this risk is higher than in paroxysmal fibrillation, especially within the year following the onset of the arrhythmia. In most patients anticoagulant therapy is effective in the primary or secondary prevention of embolic accidents. In subjects older than 75 aspirin given in daily doses of 325 mg seems to give similar results. The risk of antithrombosis therapy must not be underevaluated. The alternative is to maintain or restore the sinus rhythm, even at an advanced age, if the arrhythmia is recent and the left atrium is moderately dilated.