MVP in males is worse than in females, as the disease progresses quicker in males--so he will need to have regular follow-up, but the timing for surgery is not for MVP, but when there is a lot of regurgitation of that valve. Not sure why the doctor put him on atenolol, unless his symptoms were of palpitations and were becoming more frequent--is he seeing a cardiologist or a primary physician? If he is now tired all the time, it is probably from the atenolol, and the doctor may wish to try another medication.
The diagnosis 20 years ago for MVP was almost a guess, to be honest--a person (especially a lady) would come into the office, complain of chest pain or palpitations, the doctor may think he hears a click and bingo--a diagnosis is made. Even 10 years ago, the echocardiographic machines were fairly unreliable and difficult to show MVP or lack of MVP. Today with improved echo machines--the diagnosis is much more accurate, so I often send patients who have been told for years they have MVP for an echo to confirm or eliminate that diagnosis.