Atrial fibrillation is the most common type of arrhythmia in patients with mitral stenosis of rheumatic heart disease. Enlargement of the left atrium due to increased left atrial pressure and fibrosis of the atrial wall are the pathologic basis for the persistence of atrial fibrillation. It may begin as frequent atrial premature beats, then progress to paroxysmal AF, then to persistent AF, and then to permanent AF as the condition prolongs. The incidence of AF increases with left atrial enlargement and age. Patients with rheumatic heart disease who develop atrial fibrillation should have their ventricular rate controlled and use anticoagulants such as warfarin to prevent thrombosis. For severe mitral stenosis, balloon dilatation or prosthetic valve replacement may be an option. Patients with rheumatic heart disease should seek timely medical attention, and under the guidance of the doctor should actively treat the primary disease to prevent complications.