Atrial Fibrillation Revisited —With a Special Reference to Primary Prevention—

Atrial fibrillation (AF) is common arrhythmia and results in a rapid and irregular rhythm. Patients with this arrhythmia may be asymptomatic but AF often causes palpitation or chest discomfort especially when it develops in its paroxysmal form and patients might develop fatigue easily or reduced working capacity. Because of a loss of atrial contribution to ventricular filling, AF results in a decrease of cardiac output by 15% at rest and up to 30% upon exercise. Long-standing tachycardia leads to cardiac dysfunction known as tachycardia-induced cardiomyopathy and AF can be the cause of such cardiomyopahty and results in atrial stunning. The prevalence of AF increases with advanced age: 0.4% in the general population but less than 6% in those >80 years and the elder patients are prone to develop heart failure. Rarely, AF can be fatal in WPW syndrome when rapid ventricular activation occurs via the Kent bundle. In addition to such morbidity, AF is the major cause of stroke and is associated with increased mortality and morbidity. For stroke in patients with AF, several risk factors have been established and in animal model, altered gene expression predisposing to coagulation was confirmed in the endocardium of the paced-atrium. To reduce stroke, efficacy of anticoagulant therapy by Warfarin is well established. Aspirin seems to be inefficacious especially in Japan to prevent stroke due to AF. For AF, antiarrhythmic drugs are prescribed to prevent recurrence but with limited efficacy. The best result in preventing the recurrence of AF is that reported by CTAF using amiodarone, wherein the AF free rate was 60% at the 600th day of therapy. However, the drug might be withdrawn because of side effects and paroxysmal AF progresses eventually to chronic AF over time. Recently, catheter ablation has been established as a new promising therapy to prevent the recurrence of AF but it would be difficult to apply catheter ablation to every patient because of the large number of patients. For these reasons, we have to seek other possibilities and the prevention of the occurrence of AF in the general population is very important. We hereby, review the epidemiology and the underlying diseases of AF from the point of view of primary prevention of AF.