Why does atrial fibrillation increase the risk of stroke?
Each year there are 150,000 strokes in the UK. Nearly one in five (18%) of the people presenting with a stroke are in atrial fibrillation (AF) at the time of presentation, and one in six strokes are directly attributable to AF.
The risk of stroke in AF is reduced by two-thirds with oral anticoagulation, while antiplatelet therapy reduces stroke by one-fifth. The reduction with antiplatelet therapy is broadly consistent with the stroke reduction seen with this therapy in patients with vascular disease or risk factors, and, given that AF largely coexists with vascular disease, the effect of antiplatelet therapy would probably reflect this. The risk of stroke is similar with paroxysmal or permanent AF, in the presence of associated risk factors.