[Atrial fibrillation and stroke].
Atrial fibrillation (AF) is the most common cardiac arrhythmia. The prevalence of AF is 0.4% in the general population and increases with age up to 6-8% in octogenarians. In Switzerland, approximately 68,000 persons are in atrial fibrillation, and in the EU countries 3.5 millions. Atrial fibrillation disturbs synchronous mechanical atrial activity and impairs the haemodynamics. This can give rise to thrombus formation, mostly in the left atrial appendage, and embolism to the systemic circulation. Clinical manifestations are most often neurological such as transient ischaemic attacks or ischaemic strokes, on average 5% per year. Of all strokes, one in every six occurs in patients with AF. Antiarrhythmic therapy is useful to improve cardiac rate and function in AF. However, to reduce first or recurrent emboli, antithrombotic therapy is of paramount importance. Adjusted-dose warfarin reduces first or recurrent strokes by about 60%. When patients with non-valvular AF are anticoagulated, the odds against ischaemic stroke and intracranial bleeding favour an INR between 2.0 and 3.0. Acetylsalicylic acid is less efficacious than warfarin in AF patients, reducing the risk of stroke by about 20%. Therefore, anticoagulation is the current treatment modality in AF patients at high or intermediate risk, i.e. patients with history of transient ischaemic attack or stroke, those aged > 65 years, those with a history of hypertension, diabetes, heart failure or structural heart disease, valvular disease or significant systolic dysfunction. Antiplatelet agents should be used only for young (< 65 years) AF patients at low risk.