The story behind most referrals for mitral valve surgery differs but often begins with either symptoms or an "incidental" finding of a murmur during a routine physical exam. The first issue to understand is what the mitral valve is and what does it do? The mitral valve sits between two chambers of the heart, the left atrium and the left ventricle. Blood filed with oxygen (oxygenated) flows into the left atrium from the lungs ready to go out to the body. It then gets pumped from the left atrium into the left ventricle which then squeezes which raises the pressure in the ventricle. This causes the mitral valve to shut tight and the aortic valve to open, releasing the oxygenated blood into the body via the aorta. The heart then relaxes and the mitral valve opens again, ready to do its job of keeping blood moving forward toward the body and not backward towards the lungs.
The second issue to appreciate is what can go wrong with the mitral valve? Basically two broad categories of problems can occur: regurgitation (leaky valve in which it allows blood to go backwards toward the left atrium and lungs) and stenosis (narrowed valve than makes it difficult for blood to get from the left atrium to the ventricle). Underlying causes of these conditions include: myxomatous disease, fibroelastic deficiency, rheumatic disease (caused by untreated strep throat during childhood), heart attacks (myocardial infarction), heart failure (enlarged failing heart), and others.
Patients fall into two basic categories: symptomatic and asymptomatic (without symptoms). Symptoms commonly associated with mitral valve disease include: shortness of breath, fatigue, leg swelling, rapid or irregular heart beat (atrial fibrillation), chest pain, and others. Of course these symptoms can be associated with other medical conditions as well.
The American College of Cardiology and American Heart Association have convened committees to publish guidelines on valve disease evaluation and treatment to include the mitral valve. In general, most patients with symptoms should have surgery if they are good candidates from a risk standpoint. Repair is preferred when possible as this has been associated with better outcomes. There are several different surgical approaches: full sternotomy (breastplate division), partial sternotomy, right thoracotomy (incision under right breast), robotic approaches including right thoracotomy and totally endoscopic approaches. For every way of performing mitral valve surgery, I can name a surgeon I would trust my family with. However, the operation with the smallest incisions that I am aware of is the totally endoscopic robotic approach. There are some evolving (currently experimental) catheter based approaches but these are early in their evolution and are likely to be limited to high-risk patients in the near future.
With regard to who should do your mitral valve surgery, experience matters. I believe that mitral valve surgery, especially repair, is becoming a subspecialty that is best performed by cardiovascular surgeons who are focused on it and have special training in repair techniques. Although most mitral valve surgery in the US is performed by surgeons who do less than 10 cases per year, I do not feel this is ideal (my opinion). Ask your surgeon about his / her volume of experience before making this important decision.