Signs and symptoms of mitral valve prolapse are due to the amount of blood leaking backward through the valve. Mitral valve prolapse symptoms can vary widely from one person to another. Many people with mitral valve prolapse don't have noticeable symptoms. Other people may have mild symptoms that develop gradually. Symptoms of mitral valve prolapse may include: 
A racing or irregular heartbeat (arrhythmia)
Dizziness or lightheadedness
Difficulty breathing or shortness of breath, especially during exercise or when lying flat
Fatigue
