Rheumatic Heart Disease

In chronic rheumatic mitral stenosis, which histological change in the valve leaflet is responsible for the 'fish-mouth' appearance seen on gross examination?

Which valve is most commonly affected in acute rheumatic fever, and what is the characteristic pathological lesion seen on the valve surface?

A 35-year-old man with a history of acute rheumatic fever (ARF) 15 years ago presents with palpitations and dyspnea. Echocardiography shows moderate aortic regurgitation (AR) with a regurgitant jet width of 8 mm and aortic root diameter of 50 mm. Left ventricular ejection fraction (LVEF) is 50%. He is currently on no cardiac medications. What is the most appropriate next step in management?

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. She is currently on diuretics and digoxin. What is the most appropriate next step in management?

Which structural feature best distinguishes acute rheumatic carditis from chronic rheumatic heart disease in a patient with a history of group A streptococcal infection?