A 28-year-old woman from rural India presents with dyspnea on exertion and orthopnea for 3 months. On examination, she has an opening snap, diastolic murmur at the apex, and signs of pulmonary edema. Chest X-ray shows cardiomegaly and pulmonary congestion. Echocardiography confirms mitral stenosis with a valve area of 1.2 cm² and moderate left atrial enlargement. She is currently on diuretics and digoxin. What is the most appropriate next step in management?