How do you treat mitral stenosis?

It depends on cause. Mitral stenosis may be mild and not require specific therapy. For more significant mitral stenosis, treatment is either catheter-based or surgical. Catheter-based therapies involve feeding a balloon-tipped catheter through a large blood vessel in the groin into the heart and across the narrowed mitral valve. The balloon is inflated with relief of stenosis. Surgery involves repair or replacement.
Meds, surgery. A good article on mitral valve stenosis is on mayoclinic.Com. Treatments are medications: 'water pills' (loop diuretics), blood pressure pills (beta blockers or calcium channel blockers) and possibly 'blood thinners'. You may have to treat a heart rhythm called 'atrial fibrillation'. 2 procedures are done to repair mitral valve stenosis :valvotomy or valve replacement. The cardiologist will help.