A 28-year-old woman from rural Maharashtra presents with progressive dyspnea on exertion and palpitations for 6 months. She has a history of acute rheumatic fever at age 12. On examination, she is in sinus rhythm with a pulse of 88/min and BP 118/76 mmHg. Auscultation reveals a loud S1, an opening snap 80 ms after A2, and a low-pitched diastolic murmur at the apex. Chest X-ray shows straightening of the left heart border and pulmonary edema. Echocardiography demonstrates a mitral valve area of 1.2 cm². What is the most appropriate next step in management?