How could mitral stenosis be complicated by pulmonary fibrosis?

Can't fix it: The two conditions are separate but both lead to similar symptoms. So fixing the mitral valve might not resolve the symptoms as anticipated. Fixing the valve is also made riskier by the lung problem. So one complicates the other.

Pulmonary HTN: Mitral stenosis makes it difficult for blood to return from the lungs to the left heart. This in turn raises the pressure in the pulmonary circulation, which causes pulmonary hypertension. Over time, this may cause scarring in the lungs, although typically it results in right heart failure instead.