Hello. I'm Dr. Christensen.
I'm sorry your mother is having problems. Regarding her upcoming surgery, the most important considerations are getting her blood pressure under better control and making certain she does not have endocarditis, which is an infection (usually bacterial) on the interior surface of a person's heart (typically on a valve). Symptoms of endocarditis can be subtle -- fatigue, for example -- or they can be more obvious: chest pain, fever, night sweats or shortness of breath. In addition, bacteria from an infected valve can travel to other areas of the body, causing serious or even life-threatening complications: sepsis ("blood poisoning") or abscesses in the brain, spleen, kidneys or other organs.
Individuals with endocarditis shouldn't undergo joint replacement until the endocarditis is treated, because bacteria from the infected area of the heart could enter the bloodstream and infect a new joint prosthesis. Further evaluation (blood tests and possibly a trans-esophageal echocardiogram) may be needed to determine if your mother has endocarditis. If so, IV antibiotics might be needed to treat this condition.
Your mother's high blood pressure could be the result of her congenital kidney anomaly. Our kidneys play a major role in controlling our blood pressure, and any problems with kidney function can lead to high blood pressure. Further consultation with a cardiologist and/or a nephrologist (a kidney specialist) may be warranted in your mother's case. While people with high blood pressure often undergo surgery, it's best to have this problem under control if at all possible. (By the way, people with high blood pressure frequently exhibit reduced left ventricular compliance on an echocardiogram.)
As far as the mitral valve prolapse (MVP) is concerned, this is a common condition, and your mother's MVP is mild. Mild MVP does not prevent someone from undergoing surgery, and in most cases doesn't even require treatment. In fact, people with mild MVP typically don't even have any symptoms, so you don't necessarily need to watch for problems arising from this condition.
In summary, you should ask your mother's doctors what needs to be done to make sure she doesn't have endocarditis, and someone -- a cardiologist or nephrologist (or both) -- should review her medications to determine if anything else can be done for her high blood pressure.
I hope that answers your questions. I'll be available if you have additional concerns, but I suggest you call your mother's doctor(s) before you make a 1200-mile trip with the expectation that she'll be having her surgery soon. It sounds like there's some work to be done before she has her knees replaced.
Good luck!

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Your mother's elevated ESR could be due to endocarditis, but there are many other possible causes; anything that triggers inflammation can cause your ESR to rise. Given the findings of your mother's echocardiogram, though, endocarditis is the first thing that needs to be ruled out. Blood cultures and trans-esophageal echocardiography are the next steps in that evaluation.
The vast majority of patients who undergo knee replacement surgery are much improved once they get through the post-operative rehabilitation period, which can be quite painful. (Your mother will probably need help for at least 4 to 6 weeks.) As with any surgical procedure, complications do occasionally occur with knee replacements: problems with anesthesia, bleeding, blood clots, post-op infections, implant failure, etc. However, such problems only occur in about 1 in 50 operations. When a person can no longer perform his or her daily activities due to severe knee arthritis, replacing the joints typically restores a good level of function.

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