[Epidemiology and nosology of atrial fibrillation].

Atrial fibrillation (AF) is the most commonly encountered arrhythmia in clinical practice. It presents as chronic AF (duration > 7 days) or paroxysmal AF with intermittence of sinus rhythm giving rise to different clinical patterns which require classification. The prevalence of AF depends on the age and health of the population under consideration. The arrhythmia is exceptional in children, uncommon in young adults, but 3 to 4% of subjects over 60 years of age. Underlying cardiac disease is present in nearly 80% of cases. Valvular heart disease, though decreasing in frequency, represented 23% of cases in our hospital series. Coronary artery disease is commonly associated with AF especially in cases with left ventricular dysfunction. The relations between hypertension and AF is not clear. This relationship is more significant in the presence of left ventricular hypertrophy. Myocardial disease (hypertrophic or dilated cardiomyopathy) often underlies AF but the prognosis does not seem to be influenced by the arrhythmia. After valvular disease, cardiac failure is the most significant predictive factor of AF. Atrial fibrillation doubles the mortality and carries à 3-6% risk of systemic embolism per year, usually as a cerebrovascular accident. This risk is influenced by age, the presence of valvular disease, hypertension, previous history of myocardial infarction or cardiac failure. Idiopathic AF is a common entity (about 20% of cases in hospital series) and carries an embolic risk of 2 to 5% per year. These observations are essential for appropriate therapeutic strategy for this arrhythmia which is less benign than previously thought.