It depends on the patient and the condition - whether the valve is stenotic (not opening fully) or incompetent (not closing fully).
Initially the doctors will work with medication to mitigate the symptoms. If this is successful, the patient will be placed on longterm drug therapy. This will not fix the problem, but it may make it liveable.
If medication is not effective on its own, then surgery becomes necessary to replace the diseased valve. The replacement options are either tissue (made from porcine or bovine tissue) which will last for about 15 years and then need to be replaced again, or mechanical, steel and titanium which last for a lifetime, but carry a 1-2% chance per year of stroke
or leakage and require anticoagulant
(blood thinner) therapy for the rest of the patient's lifespan.
If this is for your own health or that of a loved one, best of luck.