Could a heart valve repair itself?

No: If a heart valve is leaky or stenotic these conditions do not generally improve without intervention. This is due to the fact that once abnormal mechanical forces start they can begin a cycle of negative effects. The rate of progression varies tremendously, often related to the root cause. Many people, for example, with trivial leaky valves live normally without ever having any problems.

No: A heart valve problem is either synoptic (tight), or regurgitate (loose). Once that has occurred, that damage is done. Medical therapy can help with some of the effects, but the valve will only be repaired if someone' repairs it.