Atrial fibrillation is the most serious disorder of atrial electrical activity in which regular and orderly atrial electrical activity is lost and replaced by rapid and disordered fibrillation waves. The loss of effective contraction and diastole by disordered atrial fibrillation, the deterioration or loss of atrial pumping function, and the decremental conduction of the atrioventricular node to rapid atrial excitation cause an extremely irregular response of the ventricles. Thus, ventricular rhythm (rate) disturbances, impaired cardiac function, and atrial appendage thrombosis are the main pathophysiological features of patients with atrial fibrillation. Why do strokes occur in patients with atrial fibrillation? The formation of thrombus is associated with the loss of rhythmic mechanical contraction of the atria during atrial fibrillation, resulting in slowed blood flow to the left ear and blood stagnation. How high is the risk of stroke in patients with atrial fibrillation? The risk of cerebral embolism is 5.6 times higher in patients with atrial fibrillation than in those without atrial fibrillation. The incidence of embolism is higher in older patients with atrial fibrillation, with an annual incidence of stroke due to atrial fibrillation of 1.5% in patients aged 50-59 years, but rising to 23.5% in those aged 80-89 years. Which patients with atrial fibrillation are more likely to have a stroke? Patients with atrial fibrillation with hypertension, diabetes mellitus, heart failure, previous strokes, and those over 65 years of age are more likely to have a stroke.