How does atrial fibrillation increase the risk of stroke?

Atrial fibrillation (AF) significantly increases the risk of stroke primarily due to its role in promoting the formation of blood clots within the heart. In AF, the atria (the upper chambers of the heart) experience chaotic electrical signals, which leads to ineffective contractions and can cause the blood to pool. Particularly, the left atrial appendage is a common site for thrombus (blood clot) formation. When blood pools and clots form, these clots can dislodge and travel through the bloodstream, eventually reaching the brain, where they can block blood flow and result in a stroke.

This mechanism is critical to understanding the importance of anticoagulation therapy in patients with atrial fibrillation, as reducing the risk of clot formation directly impacts the prevention of strokes. In contrast to this, while other factors like high blood pressure and weakened heart muscle can contribute to cardiovascular diseases, they are not the primary reasons for the increased stroke risk specifically associated with atrial fibrillation. Additionally, while AF may alter blood flow dynamics, it does not intrinsically reduce blood flow to the brain as a direct consequence of the arrhythmia itself, making the formation of clots the key factor in the stroke risk associated with this condition.