Because rheumatic fever is the primary cause of mitral stenosis, secondary prophylaxis against group a beta-hemolytic streptococcus is recommended. The recommended regimen for prevention of recurrent rheumatic fever is an intramuscular injection of 1,200,000 units of benzathiazine penicillin every 4 weeks for most patients and every 3 weeks in populations in which the incidence of rheumatic fever is very high. Penicillin V 250 mg twice daily or sulfadiazine 500 mg to 1,000 mg once daily dependent on weight may be used. For penicillin-allergic persons, a narrow-spectrum oral cephalosporin, oral clindamycin, or various oral macrolides or azalides should be used. Prophylaxis should continue until at least age 40 and perhaps for life in persons with increased exposure to streptococcal infections. Prophylaxis should continue even after valve surgery. The current American Heart Association guidelines no longer recommend routine bacterial endocarditis prophylaxis for persons with rheumatic mitral stenosis. For the patients with rheumatic heart disease in whom infective endocarditis prophylaxis remains recommended such as patients with prosthetic valves or prosthetic material used in valve repair, a drug other than penicillin is recommended to prevent infective endocarditis in patients receiving penicillin for rheumatic fever prophylaxis. Patients with mitral stenosis in sinus rhythm with exertional symptoms occurring with high ventricular rates should be treated with a beta blocker, verapamil, or diltiazem. Dietary sodium restriction and diuretic therapy should be used to treat symptoms due to pulmonary congestion. Reduction of preload by oral nitrates may also be beneficial. Prolongation of the diastolic filling time by beta blockers can reduce left atrial pressure. Treatment of an acute episode of atrial fibrillation with a rapid ventricular rate consists of anticoagulation with heparin and reduction of the ventricular rate by intravenous beta blockers, diltiazem, or verapamil and with amiodarone if these drugs cannot be used. If there is hemodynamic instability, the patient should be treated with directcurrent cardioversion immediately with intravenous heparin administered before, during, and after the procedure. The ventricular rate in patients with atrial fibrillation should be controlled long-term by use of beta blockers, verapamil, diltiazem, amiodarone, or digoxin. Class I indications for use of oral warfarin in patients with mitral stenosis are paroxysmal or chronic atrial fibrillation or a prior thromboembolic event in a patient with sinus rhythm with an International Normalized Ratio (INR) maintained between 2.0 to 3.0 or a left atrial thrombus with the INR maintained between 2.5 to 3.5 . The novel anticoagulant drugs such as dabigatran, rivaroxaban, and apixaban are not approved for treatment of atrial fibrillation associated with valvular heart disease.